Angioscopy

0039--:6109/92 $0.00 + .20

ENDOVASCULARSURGERY

ANGIOSCOPY Geoffrey H. White, MB BS, FRACS

Angioscopy is the process of endoscopic examination of the vascular system. Angioscopy first became practical as a regular technique in vascular surgical practice only in the mid-1980s and has since become an accepted intraoperative and percutaneous procedure in peripheral vascular surgery and vascular interventional radiology and, to a lesser extent, in interventional cardiology and cardiac surgery. Acceptance of the value of angioscopy and widespread usage came with the advent of miniaturized fiberoptic catheters of acceptable flexibility and high resolution and sterilizable video cameras with reliable optical qualities. Similar equipment and techniques have found application in inspection of the biliary, renal, and gynecologic tracts. To date, there are no absolute indications for angioscopy. The precise definition of the best applications varies somewhat according to the experience of particular vascular units and local conditions of cost, equipment availability, patient referral patterns, and so on. Nevertheless, there is generalized agreement that familiarity with angioscopic equipment and techniques is a necessary part of any major vascular practice and vascular surgery training schemes. Usage in interventional radiology has also gradually increased, and angioscopy has been of particular value in monitoring the newer forms of endovascular surgical procedures, demonstrating the mechanisms of action and effects on the vascular wall of many of the new interventional devices. HISTORY OF VASCULAR ENDOSCOPY

Attempts were made to perform endoscopy of the cardiac chambers with rigid tubes in the early 1900s-this is recognized as the first serious trial of cardiovascular endoscopy and a precursor of modern angioscopic techniques. 3, 9 In 1957, Brock commented on the intraluminal views of the aortic arch obtained using a rigid endoscope during surgery for aortic valve disease. 5 In From the Department of Surgery, Royal Prince Alfred Hospital, University of Sydney, Sydney, New South Wales, Australia

SURGICAL CLINICS OF NORTH AMERICA VOLUME 72 • NUMBER 4 • AUGUST 1992

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1966, Greenstone and colleagues described the clear views obtained of the vascular lumen of vessels in live dogs and cadaveric aortas using a 7-mm forward-viewing, flexible fiberoptic irrigating choledochoscope. '4 Vollmar began studies of vascular endoscopy in 1966 using both a rigid Hopkins endoscope (external diameter 6.3 mm) and a flexible endoscope similar to the one used by Greenstone and associates. An early report of this work in 1969 described the use of a straight rigid endoscope introduced through the femoral artery to inspect the results of semiclosed loop endarterectomy. 41 In 1974, the experience of Vollmar's group was reported in the English-language literature, including the statement that a significant impetus for endoscopy of the peripheral vascular system came from the development of indirect therapeutic techniques such as balloon or ring thromboendarterectomy.42 Vollmar suggested the use of either clamps or a balloon catheter to achieve proximal blood flow control and of an infusion of saline to overcome collateral inflow. Although the three-dimensional representation obtained by angioscopy was considered to have added considerably to the single-plane view of angiography, technical failure in this early experience occurred in 15% and vessel rupture in 9%, and there was a 7% incidence of septicemia. 42 Infective complications were eliminated with the introduction of a closed perfusion system. Crispin and Van Baarle reported the use of a fiberoptic endoscope for monitoring semiclosed thromboendarterectomy and concluded that "fiberoscopy provides visual control and the opportunity to correct some hitherto invisible faults."8 Crispin later described the value of angioscopy in directing the removal of retained thrombotic debris using biopsy and brushing forceps.7 Olinger, in 1977, investigated carotid artery endoscopy in postmortem studies in an attempt to correlate different carotid lesions with clinical syndromes. 32 He was able to demonstrate a variety of carotid pathology angioscopically in patients with normal angiograms and felt that the study provided significant insight into the relation of disease of the carotid bifurcation and the clinical picture of stroke. In 1977, Towne and Bernhard reported on a prospective evaluation of endoscopy for a variety of arterial reconstructions including carotid endarterectomy, profunda endarterectomy and patch angioplasty, arterial anastomosis, and graft thrombectomy.3' They concluded that angioscopy allowed detection of technical errors that could be repaired at the initial operation so as to prevent subsequent failure. These workers used mainly rigid endoscopes, as did most investigators up to this time, apart from the occasional use of larger choledochoscope-style endoscopes. These techniques remained investigational because of perceived difficulties with the use of the rigid endoscopes in fragile vessels. Tanabe and colleagues reported a 12-year experience of cardiac and peripheral endoscopy in 1980. 38 In conjunction with Olympus Corporation, they developed a 4-mm fiberoptic instrument with a tip that could be angled either up or down. Further studies of the use of fiberoptic endoscopes within the vascular system were reported by Itoh and Hori20 and Moser and Shure and their associates. 30,35 Shure et al demonstrated the superior accuracy of endoscopy in the diagnosis of pulmonary emboli in a dog model. 35 The 1980s have seen the emergence of small-diameter fiberoptic angioscopes with better resolution and video camera adaptation to provide magnification and projection of a greatly improved image. Angioscopes with diameters as small as 0.2 mm are currently under evaluation. Accompanying this improvement in technology has come a broadening of experimental and clinical applications and the evolution of percutaneous techniques. 10, 36, 37 The last decade has seen the increasing use of a variety of techniques proposed to permit

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"closed" recanalization of atherosclerotic and thrombosed vessels. The efficacy of many of these techniques is not yet substantiated, and angioscopy has a valuable role in the validation process. APPLICATIONS OF ANGIOSCOPY

Specific and theoretical applications of endoscopy have been described for the coronary, peripheral, carotid, visceral, and pulmonary arteries and for the venous system. These applications can be defined as diagnostic or therapeutic (Table 1). Diagnostic use includes identification of luminal and surface disorders such as thrombus, plaque, hemorrhage, ulceration, atherosclerotic occlusion, or embolus. It is possible that new syndromes will be identified by further recognition of the roles of these various factors in the pathogenesis of cardiovascular diseases. Endoscopic biopsy of atheromatous lesions may come to playa role in determining prognosis and appropriate treatment, including drug selection. 4 Angioscopy also is being used for validation of other imaging techniques such as intravascular ultrasound, duplex Doppler scanning, and magnetic resonance imaging. Therapeutic applications in clinical practice include the monitoring of many intravascular procedures performed at a remote site within the vessel. Angioplasty, laser angioplasty, atherectomy, and stent placement are prime examples of this capability. Direct information may be collected regarding the immediate and long-term effects of various instruments on the arterial lumen and intima. This may allow comparison of new techniques and permit immediate correction of visualized faults or complications. EQUIPMENT FOR ANGIOSCOPY

The conditions necessary for vascular endoscopy are temporary interruption of blood flow; replacement of blood by a transparent medium; use of a sterilized endoscope of suitable length and of good optical quality; provision of high-intensity, cold-light illumination; a process of magnification; perseverance; patience; and care in manipulation. Angioscopy is currently performed Table 1. APPLICATIONS OF ANGIOSCOPY

Diagnosis Assessment of angiogram findings Differentiation of thrombus from atherosclerotic occlusion Evaluation of aortic and arterial dissections Intraoperative evaluation of vascular reconstruction Assessment of extent of intimal injury due to trauma Identification of site of venous valves and major tributaries during in situ bypass Assessment of coronary artery disease Diagnosis of pulmonary embolism Monitoring vascular therapies Thromboembolectomy and venous thrombectomy Division of venous valves (in situ bypass) Laser angioplasy, rotational atherectomy, and transluminal angioplasty Infusion of thrombolytic agents, vasodilators Endarterectomy and carotid endarterectomy

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by indirect video endoscopy techniques, with the image being conveyed from the fiberoptic angioscope catheter through an adapter to a video camera attachment,25,54 The components of a typical angioscope system are: L 2, 3, 4, 5,

Angioscope catheter-a flexible fiberoptic multichannel endoscope; Video adapter with image focusing and magnification capability; Video camera and television monitor; High-intensity light source; Fluid irrigation pump system,

In some of the newer instrument systems, several of these components are integrated into a single unit (Fig, 1). For endoscopy of the peripheral vascular system, the most suitable angioscope catheters have an integrated channel for irrigation of the vessel lumen with saline to clear blood from the field of view. Adequate irrigation is vital to successful visualization, and failure to achieve a sufficient flow of clear fluid to the area of vessel to be examined is the principal reason for failed endoscopy. Pressurized bags of heparinized saline, connected to the angioscope's internal channel by intravenous tubing sets, are often used but sometimes do not provide adequate rates of fluid flow. Automatic roller-pump systems solve many of these problems by providing reliable and adequate constant flow rates, with the provision for rapid bolus infusion when needed. The optical fiber bundles, including the light source fibers bringing illumination to the tip of the angioscope, usually require at least 1 mm of catheter diameter, and the addition of the fluid channel and protective cladding generally increases the diameter of the multilumen endoscope to between 2 and 3 mm (Fig. 2). This size is suitable for iliac, femoral, popliteal, and carotid vessels, as well as the saphenous vein in most patients. For smaller vessels, angioscopes between 1 and 2 mm external diameter are available. These smaller endoscopes do not have a fluid channel, so that use in the coronary or tibial vessels requires an alternative method of blood-flow clearance, wlUally via a coaxial catheter. Ultrafine angioscope instruments with external diameters as small as 0.2 mm are being used in investigational studies (Fig. 3). More detailed information on commercial angioscopy systems and equipment is available elsewhere. 45 Several commercial companies are now marketing disposable endoscope catheters designed for single use only (Fig. 4). These are less expensive but are more easily damaged than the multiuse angioscope catheters. TECHNIQUES OF ANGIOSCOPY

The angioscope and video camera are set out on a sterile field before the start of the operation or endovascular procedure, and the fluid irrigation system (pressure bag or pump) and tubing are positioned nearby. The television monitor should be placed opposite the surgeon so that the image can be seen eaSily without having to turn around during the procedure. Correct focusing of the optics is checked before inserting the endoscope into the blood stream. Intraoperative Angioscopy

Lower-extremity Vascular Operations

Access is usually obtained via a longitudinal incision into the common femoral artery or other site according to the operation planned. Transverse

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Figure 1. Equipment required for vascular endoscopy. A, A fine, flexible angioscope catheter (A) is attached to the sterilizable video camera (C) via an adapter (a). A highintensity light source (L) is needed because of the small diameter of the fiberoptics. Fluid irrigation may be provided by a simple pressure-bag system (F) or by a roller pump. B, Angioscope catheter (arrows) with incorporated light source cable and optics. This angioscope is sterilized between uses by cold ethylene oxide gas sterilization in the storage tray illustrated.

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Figure 2. An intravascular view of the tip of the angioscope, demonstrating the two lumens for light source fiberoptics and image optical bundle, as well as an open channel for fluid irrigation. Guidewires and microinstruments may be introduced via this working channel. The tip has relatively atraumatic beveled edges and contacts the artery wall only along a small segment of its perimeter.

arteriotomy incisions usually are avoided when angioscopy is planned, because the angioscope may tend to lift the intima of the downstream side of a transverse opening. An incision made over the bifurcation facilitates inspection of the profunda femoris artery as well as the superficial femoral artery. Femoral Arteries. We have found that the profunda femoris artery will usually quite easily accommodate angioscopes of diameters from 1.5 to 2.8 mm; often, inspection of this artery can be carried out to a distance of 20 to 25 cm.

Figure 3. An ultrafine endoscope catheter (arrow) of O.8-mm diameter protruding from the lumen of an angioscopic delivery catheter designed for percutaneous use (peripheral vessels or coronary arteries). Inflation of the balloon positioned near the tip of the delivery catheter is used for occlusion of blood flow while irrigation fluid is run through the lumen.

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Figure 4. Percutaneous angioscopy system. The delivery catheter (d) has a distal occlusion balloon (closed arrow; shown inflated in Figure 3) and two proximal ports: one for attachment of a syringe (s) for balloon inflation and the second for attachment of an irrigation line and hemostatic valve (v) to allow flushing of the vessel without excessive leakage around the angioscope (open arrows).

Orifice stenosis or multiple distal stenotic lesions, which are often encountered in diabetic patients, may make endoscopy more difficult. Collateral flow from one or two major branches usually temporarily clouds the view within a short segment several centimeters above the branch, and it is necessary to allow 5 to 30 seconds for the flush solution to overcome this blood flow. The profunda is usually relatively spared by atherosclerotic disease except for the first few centimeters of its course, even in patients who have severe disease elsewhere. Angioscopy of the profunda usually is not of particular practical importance, except after thromboembolectomy or as a method of assessing the severity of disease involvement prior to use of the profunda as the outflow artery for a bypass procedure. The superficial femoral artery is one of the easiest vessels to examine intraoperatively, as its relatively large caliber accepts most flexible angioscopes and because in the patient group undergoing surgery, there is often a distal occlusion or severe stenosis of this vessel, limiting backflow. Angioscopy of this artery is of most value after thromboembolectomy (Fig. 5) or endovascular surgery. 56 Diagnostic application is limited to differentiation of thrombosis from atheromatous occlusion or to selected cases of vascular trauma. 50 Popliteal Artery. The diagnostic and therapeutic applications of angioscopy in the popliteal artery are similar to those described for the superficial femoral artery. During femoropopliteal bypass operations, the popliteal artery may be inspected at the proposed site of anastomosis via the arteriotomy made for that purpose. The angioscope may then be introduced down the outflow vasculature to the proximal segments of the tibial arteries if there is not a significant size discrepancy between the lumen of the tibial artery and the diameter of the angioscope. Angioscopy may be used to determine if the segment of popliteal artery above the knee, not well outlined on preoperative angiography, is of

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Figure 5. Intraoperative technique for angioscopic monitoring of femoropopliteal arterial thromboembolectomy. The angioscope may be used to monitor the complete procedure with the embolectomy catheter passed simultaneously beside the angioscope or may be passed after the removal of thrombus to check on the completeness of the procedure and to exclude complications. (From White GH, White RA, Kopchok GE, et al: Angioscopic thromboembolectomy: Preliminary observations with a recent technique. J Vasc Surg 7:318, 1988; with permission.)

suitable quality and caliber for bypass or if it would be more judicious to extend the bypass graft to the below-knee position. Tibial Arteries. Angioscopy of the narrow tibial vessels requires an endoscope of the size usually reserved for use in the coronary arteries, with a diameter from 0.75 to 1.5 mm. Experience has shown that the tibial and peroneal vessels are likely to go into spasm during angioscopy with larger catheters, although this seems to be reversed with infusion of papaverine. There is also a greater potential for causing intimal trauma in these smaller vessels. Aortoiliac Segment Angioscopy of the iliac arteries and distal aorta may be achieved from the femoral approach by the method illustrated in Figure 6 involving proximal inflow control with a large occlusion balloon. In practice, we have found this technique to be unsatisfactory at times because of high rates of collateral blood flow from the internal iliac and lumbar arteries. Exceptions to this arise when

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Figure 6. Technique of angioscopy "upstream" by inflation of a balloon catheter proximal to the segment of vessel to be examined. This technique is particularly useful for inspection of an iliac artery or graft via the femoral approach. (From White GH, White RA, Kopchok GE, et al: Angioscopic thromboembolectomy: Preliminary observations with a recent technique. J Vasc Surg 7:318, 1988; with permission.)

thrombotic occlusion of the inflow has occurred or when angioscopy is performed within a prosthetic aortobifemoral graft limb, where there are no collateral branches. For example, the thoroughness of a graft thrombectomy may be confirmed if the graft is occluded at its bifurcation by the balloon. In this situation, large amounts of thrombus often remain adherent to the wall. 55 If the aorta and iliac arteries have been exposed at laparotomy, angioscopy may be carried out after proximal and distal clamping. Practical applications seem unlikely, however, except perhaps to monitor the results of segmental endarterectomy.42 Autogenous and Prosthetic Grafts

Recent studies indicate that significant abnormalities of autogenous veins, which may compromise subsequent bypass patency, can be revealed by angioscopic examination even though the external appearance of the vein is normal. Such abnormalities include sclerotic and recanalized segments, giving the internal appearance of fibrinous strands, webs, or flaps.28 Inspection of the anastomoses of a vein graft, especially the distal anastomosis, may be performed to exclude technical errors such as misplaced sutures and intimal flaps or tears. The absence of debris, embolus, or thrombus within the anastomotic site may also be confirmed. Angioscopy within an autogenous vein graft may be complicated by spasm, intimal trauma, and trauma to the valves. These dangers are more pronounced when the vein is less than 4 mm in diameter. Special applications of angioscopy during the preparation of veins for in situ bypass are presented below. Angioscopic inspection of the interior of prosthetic grafts is facilitated by

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the absence of side branches and the relative ease of control of backflow. Apart from inspection of anastomoses, the body of the graft is examined to exclude kinks or twists of its wall. The most frequent indication for angioscopy of a prosthetic graft is during thrombectomy. In these cases, the thrombus tends to become tightly adherent to the graft wall and may not be removed adequately by balloon catheters (see Fig. 5). Removal by forceps, brushes, or curettes can be monitored and quickly checked for completeness. '6 , 55 In our experience, this is one of the most valuable applications of angioscopy (see below). Venous Angioscopy

Angioscopy within the venous system is complicated by several difficulties. First, there is a danger of trauma to the fragile structure of the valves, with progress of an angioscope catheter possible in only one direction. Second, the large capacity and multiple tributaries of the venous system make it difficult to clear blood completely from the lumen in vivo; as fluid irrigant is infused, it tends to dilate the venous walls, producing hemodilution but not clearing. In most cases, therefore, patience in technique and large amounts of flush solution are required unless venous obstruction is present. Percutaneous Angioscopy

Percutaneous angioscopy can be performed as a diagnostic investigation (in conjunction with arteriography) or as a monitoring method for percutaneous endovascular surgery.l3, 53 The techniques of percutaneous angioscopy are similar to the intraoperative techniques described above but with several differences. The angioscope is inserted through a percutaneous vascular sheath, which has a hemostatic valve. The sheath should not occlude the flow of blood down the femoral artery, so more vigorous fluid irrigation is required to replace the blood in the field of view with transparent fluid. Backflow of blood from distal and collateral vessels is often significant during percutaneous endoscopy; this may be controlled more easily if a blood pressure cuff is placed around the leg just below the knee and inflated to a pressure above the systolic blood pressure at the appropriate time during angioscopy. Use of a roller pump to enhance the fluid irrigation rate is valuable for percutaneous examinations. Percutaneous angioscopy requires special techniques and delivery catheters. Percutaneous access is initially achieved by the Seldinger needle technique. A guidewire is then inserted and a dilatation catheter used to widen the arteriotomy sufficiently for insertion of an 8-Fr introducer sheath, which has a hemostatic valve around the entry port (for entry of the guidewire, balloons, endovascular instruments, or angioscope) and a side arm for infusion of irrigation fluid or contrast medium. An ultrathin angioscope catheter may be advanced to the site of interest within a delivery catheter of 6-Fr or 7-Fr size. The delivery catheter has an inflatable occlusion balloon positioned close to the tip. The position of the tip of the angioscope may be monitored by fluoroscopy. Once it is positioned satisfactorily, the occlusion cuff is inflated if necessary. Several designs of intraoperative multichannel angioscopes of 2.3 mm diameter will pass through an 8-Fr percutaneous sheath and are quite suitable for percutaneous angioscopy, without the requirement for a delivery catheter. Visualization is practical only when the angioscope is inserted and advanced in an antegrade direction within the peripheral arteries. A steady,

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profuse flow of flush is required; this is provided most efficiently by an irrigation pump. The bulk of the 8-Fr access sheath sometimes acts as a significant impediment to inflow of blood down the superficial femoral artery, so that a good view may be obtained without inflation of the balloon. A useful method to decrease collateral or retrograde blood flow is to have an assistant compress the popliteal artery just below the knee or at other sites or to inflate a blood pressure cuff at the same level. With this maneuver and with use of a roller pump, visualization of these arteries is achieved in 80% to 90% of examinations. In the minority of cases, a satisfactory view is not obtained because of an inability to overcome local blood flow, especially after successful treatment of a stenotic or occluding lesion. INTERPRETATION OF THE ANGIOSCOPIC IMAGE

As with any imaging technique, interpretation of the observed endoscopic findings and determination of which of these require intervention will be somewhat subjective and dependent on the experience of the angioscopist. The image projected on the video monitor is a relative field, with size changes being dependent on the distance of a lesion from the objective lens (Fig. 7). A minor abnormality examined from a distance of just a few millimeters therefore may be distorted out of proportion. Many investigators have reported a high incidence of retained fragments and debris, intimal fibrinous strands, and webs within peripheral arteries, especially after endarterectomy, thrombectomy, or angioplasty.15, 39, 55 The true clinical significance of these findings often is unclear. Perhaps no intervention is indicated, although such observations often lead to revision of the vascular 120

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Figure 7. Relation between apparent object size and distance from the lens of the angioscope. The perceived size of an object is much greater when its distance from the lens is 5 mm or less, (From Spears JR, Spokogny AM, Marais HJ: Coronary angioscopy during cardiac catheterization. J Am Coli Cardiol 6:93, 1985; reprinted with permission from the American College of Cardiology,)

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procedure or further attempts at improving the result. Accurate interpretation of the observed abnormal angioscopic findings and correct management will depend on careful recording of a large experience objectively correlated with early and late outcomes. Angioscopy will likely be shown to have a prognostic role, with specific visual appearances correlating with an unsatisfactory result or early failure. Spectroscopic analysis of light reflected from atherosclerotic lesions may provide more complex data. USE OF ANGIOSCOPY IN VASCULAR BYPASS OPERATIONS

During bypass procedures using vein or prosthetic grafts, angioscopy may be used to confirm the severity and distribution of disease, particularly in the outflow segment. If there is concern about the possibility of inflow stenosis in the iliac artery, this vessel may also be inspected by first proximally inflating a large Fogarty balloon (Baxter-Edwards, Santa Ana, California). Video angioscopy has been used as an alternative or adjunctive to intraoperative angiography of the distal anastomosis and outfloW. '5, 16, 25 In 15% to 30% of vascular operations, angioscopy reveals clinically relevant information that is not apparent by external visualization, flow studies, or angiography. 18, 25 Grundfest et at'7 reported that routine use of angioscopy led to revision of 25% of grafts based on technical faults detected on the angioscopic image. In a later report, the rate of revision fell to 13%,'6 suggesting that minor defects may have been overtreated in the initial experience. By contrast, in our prospective comparison of angioscopy with arteriography in 24 patients, no anastomotic faults warranting revision were detected. 54 Misplaced sutures, intimal flaps, thrombus, or debris within the anastomosis may be rapidly excluded. Inspection is limited to the distal anastomosis and a short segment of the outflow artery. Examination of Veins Harvested for Use as Bypass Conduits

Angioscopic inspection of saphenous veins and other veins excised for use as bypass grafts may reveal unfavorable features that are not obvious on external examination of the vessel. These features, which may cause early or late graft failure, include sclerotic or thickened segments of vein wall, regions of previous recanalized thrombus (leaving residual webs, bands, or strands), fibrotic valves, and segments with a very narrow lumen. 28 In one report, unsuspected primary pathology was detected in 22 of 53 vein grafts examined endoscopically.28 In Situ Saphenous Vein Bypass

Angioscopy has great appeal during in situ bypass because of the desire to achieve precise complete disruption of the venous valves without causing damage to the adjacent sections of the vein wall or to vein tributaries. These are problems that may hinder the results of this procedure when it is performed by blind instrumentation. Visual monitoring assures satisfactory disruption, while the stream of irrigant fluid simulates blood flow and gives a functional evaluation of possible retained valve cusps. 11,24

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Venous tributaries may be identified by the site of their orifices into the main channel and by the back flow of blood at this site. Some surgeons use these factors to help plan small skin incisions over these points for ligation of the major tributaries, rather than exposing the entire length of vein. 6 It is possible that the process of preparation of the vein for in situ bypass may soon be performed entirely by endovascular angioscopic methods, with skin incisions required only at the anastomoses. To this end, experimental techniques of endovascular occlusion of the tributaries are being researched. 33 Irrigation of the vein for angioscopic examinations may be carried out effectively by several methods. It usually is preferable to use a relatively narrow angioscope (without an incorporated fluid channel). A separate irrigating catheter can be inserted from the proximal end of the vein, via a sizeable tributary, or via the divided distal end of the vein (Fig. 8). For large-diameter veins, an angioscope of diameter sufficient to include a fluid channel is acceptable in some cases. There have been numerous reports demonstrating that angioscopic examination of in situ vein bypass grafts readily identifies retained competent valves. 6, 11, 28 There are two main techniques for angioscopic monitoring, In the first of these, the valvulotomy instrument is passed through all of the valves blindly, and the angioscope is then passed down the vein from its proximal end to inspect the lumen in a search for undivided valve cusps and to exclude damage to the endothelial surface or tears of the vein walL The second technique involves the use of the angioscope to monitor and control the process directly by positioning it within the vein just above the valve as the valvulotome is drawn down retrograde (Figs. 9 and 10). This can be done with a Mills valvulotome hook (Pilling, Fort Washington, Pennsylvania) introduced through a large or medium-diameter tributary29 or with specially designed long valvulotomes developed by Mehigan and OlcotF5 and Miller and associates. 28 As each successive valve is encountered, the valvulotome is used to divide the cusps; both the angioscope and the valvulotome are then advanced to the next valve. The entry points of venous tributaries are noted as they are viewed internally. Even with the whole length of vein surgically exposed, a significant number of tributaries may remain undetected because they enter the vein from its deep aspect. Carefully performed angioscopic inspection reveals these. When all valves have been divided and all tributaries ligated, the proximal and distal anastomoses are completed. Miller and coworkers 28 have reported that by adopting this latter technique of direct visual control of the complete intraluminal procedure, they were able to reduce the incidence of retained valve leaflets from 18.9% (when using the blind technique) to O. At the same time, the incidence of observed valvulotome injury to the vein wall was decreased from 85% during the blind technique to 15.6% by the angioscopic technique. With the cylindric internal-cutting valvulotomy instruments of Leather or Lemaitre (Vascutech, Andover, Massachusetts), the angioscopic view is obscured during valvulotomy, so use of the angioscope is restricted to evaluation of the valves before and after the valvulotomy procedure, as in the blind technique described above. The narrow diameter of the saphenous vein around the knee in some patients and distally near the ankle in most can cause difficulties with angioscopic monitoring, because all but the narrowest of angioscopes will be a tight fit, increasing the possibility of intimal trauma.51 Vein stenosis may theoretically result from intimal injury after angioscopy but has been reported only rarely31 and does not seem to be a significant

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Figure 8. Use of angioscopic monitoring in bypass procedures. A, Monitoring of valve division during preparation of the saphenous vein for in situ bypass. Fluid irrigation may be via a cannula inserted through a tributary vein or via an internal channel of the larger angioscopes. The angioscopic view inside the vein is represented within the circle and photographed in Figure 9A. (From Mehigan JT, Olcott C: Video angioscopy as an alternative to intraoperative arteriography. Am J Surg 152:739, 1986; with permission.) B, Monitoring of valve division during in situ bypass. The angioscope catheter (a) has been inserted through the proximal end of the saphenous vein to monitor the position of the blade of the valvulotome (v), which has been fed retrograde via a large tributary.

problem. Hashizume et aP9 simulated angioscopic injury to the endothelium in a laboratory model and found very little evidence of injury and nO functional decrease in prostacyclin production. Multiple passes with intentional injury produced anatomic and physiologic abnormalities, which recovered well within several weeks. 19 It seems likely, therefore, that with careful technique, little damage is caused to the healthy endothelium by passage of the angioscope

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Figure 9. Direct angioscopic monitoring of valvulotomy. A, Angioscopic view of the cutting blade of a Mills valvulotome correctly positioned for division of the valve cusp. B, A torn valve cusp that has not been adequately divided by the valvulotome.

Figure 10. View of the valve after division of one cusp (at the site of the arrow), with the other cusp remaining intact.

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during these operations. The evidence cited above suggests that overall endothelial damage is, in fact, reduced by angioscopically directed valvulotomy. The correctable causes of bypass graft failure that may be identified by early angioscopy can be summarized as residual or incompletely divided valve leaflets, vein graft stenosis or sclerosis, vein webs or thrombus, graft twists or kinks, technical errors at the anastomosis, and severe disease of the outflow artery.26

Endarterectomy

Angioscopy has been advocated for monitoring and checking the result of extended endarterectomy of the aortoiliac and femoral arteries, especially by Vollmar, who has used vascular endoscopes of various designs since 1969. 42 ,43 Semiclosed procedures may be performed with the knowledge that lumen irregularities, intimal flaps and dissections, residual atherosclerotic plaque, thrombus, and inadequate or raised end-points may all be detected immediately and corrected while the vessels are still open." It is interesting to speculate that the abandonment of closed endarterectomy with ring strippers and related instruments in many vascular units may have been the result of poor results associated with technical defects that could have been avoided by endoscopic monitoring. Perhaps the initial success of endovascular surgical procedures will result in a re-evaluation of the older techniques of semiclosed endarterectomy.

Carotid Angioscopy

Endoscopic inspection after endarterectomy has been used in several centers for immediate assessment of the technical results of carotid endarterectomy operations as an alternative or adjunct to completion angiography and ultrasound evaluation. Routine use of intraoperative angiograms in this setting in some series has revealed a high incidence of technical flaws, but this technique is not widely used because of the potential complications and the time or equipment requirements. In 1977, Towne and Bernhard reported the findings obtained with a rigid rod-lens system in a series of 35 carotid endarterectomies. 40 In the external carotid artery, abnormalities at the end-point or lumen were detected in 25 of 35 patients (71 %)-the identified problems were mainly raised intimal flaps or free embolic debris. In 13 patients in this series, the internal carotid artery was also examined after removal of the shunt and partial closure of the arteriotomy.4o Significant intimal shreds were revealed in two patients. Angioscopy of the carotid artery after endarterectomy was revived by Mehigan and Olcott following the introduction of flexible fiberoptic endoscopes narrow enough to be inserted through an opening in the almost completed suture line.25 In a series of 63 carotid endarterectomies, surface irregularities including short strands adherent to the wall were consistently found. The proximal common carotid end-point required revision in two patients, and the internal carotid artery had spiral intimal flaps in five patients. The force of the irrigant stream directed against this end-point clearly established whether the intima was fixed.

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ANGIOSCOPIC MONITORING OF EMBOLECTOMY AND THROMBECTOMY

Balloon catheter thromboembolectomy is conventionally performed by a semiclosed blind technique. In our experience, the opportunity to convert this blind procedure into a visual procedure is one of the most compelling indications for the use of angioscopy in vascular surgical practice, with applications in the arterial system, prosthetic bypass grafts, vein, and hemodialysis access shunts. 44,55 Angioscopy provides direct inspection of the vessels containing thrombus or embolic debris, a visual monitor of the embolectomy procedure, and examination of the lumen after instrumentation. The technique serves both as a diagnostic aid and a therapeutic adjunct (Table 2). We have found that the ability to monitor visually the placement, inflation, and retraction of balloon catheters has resulted in more thorough clearance of occluded vessels or grafts, and that the technique is more convenient and faster than intraoperative arteriograms. 55 Unless the whole length of the vessel is occluded, the angioscope may initially be introduced through the arteriotomy to inspect the lumen and define the exact site and extent of thrombosis or embolism and to determine if there is pre-existing atherosclerotic disease. Fogarty catheters may then be passed beside the angioscope if the arterial lumen is large enough, Balloon inflation, detachment and retraction of clot, and removal of debris are then visually monitored. The ability to observe the inflation of the balloon is valuable, as it allows direct determination of the amount of inflation necessary to function adequately without causing overinflation-related injury or perforation. We find that the balloon catheter slides over thrombus, which is adherent to the wall, surprisingly frequently, leaving large fragments that mayor may not be removed with repeated passes. The limitations of balloon embolectomy are plainly revealed by the ability to observe such intraluminal events, When thromboembolectomy is considered complete, a final inspection is made. On-table angiography of the smaller run-off vessels may be performed by injection of contrast medium through the fluid channel of the angioscope without the requirement to close the vessel. One of the great advantages of this approach is that complications and technical faults can be corrected while the artery is still open. The angiogram usually fails to demonstrate the smaller irregularities of the wall caused by partially attached intimal flaps and adherent clot and may underestimate larger lesions as well. These aspects are obvious on the three-dimensional endoscopic view. When adherent thrombus is observed, we usually make further attempts to retrieve it by positioning the balloon just distal to the clot and then oscillating Table 2. ADVANTAGES OF ANGIOSCOPIC THROMBOEMBOLECTOMY Accurate localization and dermination of etiology of obstruction Guided pOSitioning of thrombectomy catheters Visual calibration of balloon inflation Immediate detection of retained thrombus Immediate, accurate detection of complications Assessment of underlying atherosclerotic disease Reduction of angiographic contrast and radiation exposure Selective cannulation of major arterial branches Observation of effects of alternative instruments, devices Faster and more convenient than operative angiography

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the balloon back and forth to dislodge the clot. If this procedure is not successful, the surgeon may attempt extraction by other instruments such as guidewires, flexible grasping forceps, rotary atherectomy devices, or vascular brushes." A further possible alternative is the intraoperative use of fibrinolytic agents." Experience with angioscopy in more than 160 cases of thromboembolectomy has revealed some residual thrombus after passage of the balloon catheter in almost every treated vessel or graft. 46 This was an unexpected finding, because on-table angiograms have often appeared relatively normal. In many cases, the missed clot is quite small and probably would not significantly jeopardize the outcome. This is most likely with soft mural thrombus, which is closely attached to the wall and not stenotic. In such instances, the balloon catheter has been observed to pass between the vessel wall and the clot without dislodging it. Angioscopy overcomes some of the limitations of arteriography and gives a clear three-dimensional view of the vascular tree. Angioscopy, in our experience, is also faster and more convenient than intraoperative angiography and reduces exposure to radiation and contrast medium. In some patients, visually guided selective cannulation of the tibial arteries avoids the necessity to expose surgically the distal popliteal or tibial vessels to complete the thrombectomy. 55 ANGIOSCOPIC MONITORING OF ENDOVASCULAR PROCEDURES

Angioscopy can be used for precise monitoring of endovascular surgical procedures in both the research and the clinical setting. It was originally envisioned that angioscopy would be valuable for controlling and guiding laser, atherectomy, and other endovascular angioplasty devices within the vascular lumen. However, the working channel of currently available angioscopy catheters is not large enough to admit devices larger than guidewires or optical fibers, and it becomes very difficult to irrigate the vessel with any of these instruments occupying the channel. To be practical, this technique would preferably make use of an endoscope with two internal channels. This means that, in most situations, direct visual monitoring of the endovascular procedure is limited to passage of an angioscope beside the device, with the possible exception of direct application of laser energy via an optical fiber in the fluid channel. In our experience, angioscopy is most valuable for examining the arterial lumen immediately after angioplasty, laser application, or atherectomy to inspect for complications such as intimal flaps, dissection, or thrombosis and to judge the outcome of the intervention precisely. Angioscopic examination reveals the extent of intimal injury after angioplasty and demonstrates the mechanisms and effects of instrumentation by various endovascular devices. The angioscopic appearance of the arterial wall and lumen can be used to determine whether an arterial stent should be placed to prevent early occlusion or to salvage various complications. There are increasing numbers of reports describing new applications of angioscope-assisted intraluminal instrumentation (Table 3).

Endoscopic Intravascular Surgery We have investigated the concept of endoscopically guided intravascular removal of intimal flaps, dissections, and thrombus using flexible grasping

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Table 3. REPORTED APPLICATIONS OF ANGIOSCOPE-ASSISTED INTRALUMINAL INSTRUMENTATION

Source

Procedure

Vollmar 42 . 43

Aortoiliac endarterectomy

Towne & Bernhard 39 Mehigan & Olcott25

Carotid endarterectomy Carotid endarterectomy

White et al 56

Arterial thromboembolectomy

Crispin et aV Vollman & Storz42

Thrombectomy Venous thrombectomy

Grundfest et al'· Fleischer et al"

Bypass operation In situ bypass

White et al 49 Lee et al 22 Abela et al' White et al 56 Ahn et al 2

In situ bypass Coronary laser irradiation Laser angioplasty Embolectomy Atherectomy

Pigott et al 33

In situ bypass

Endoscopic Manipulation Semiclosed ring disobliteration performed via aortic and iliac vessels Revision of end-point Removal of retained intimal shreds with forceps Removal of residual thrombus with forceps Vascular brush technique Iliac vein thrombectomy with ring stripper Revision of anastomosis Angioscopically monitored valvulotomy Laser venous valvulotomy Aiming of laser fibers Guidance of laser fibers Selective vessel cannulation Control of atherectomy in femoral areries Catheter occlusion of venous tributaries

forceps and other instruments. 56 This may be achieved in selected patients during percutaneous interventions or intraoperatively. The advent of vascular endoscopy has introduced the possibility of such intravascular interventions under direct vision, providing immediate assessment of the result. Removal of thrombogenic arterial dissections and flaps of the iliac, femoral, and popliteal arteries by flexible forceps, introduced remotely via the femoral artery under angioscopic control, has been performed in nine patients with traumatic intimal flaps (five iatrogenic and four as a result of external trauma).56 This technique was successful in complete or partial removal of the flaps or dissection planes in the femoropopliteal position in six patients, with only one reocclusion in early follow-up (Fig. 11). In two other patients, the damage observed to the intimal surface was considered too severe, and immediate bypass was performed instead of attempting intravascular repair. Five iatrogenic injuries causing thrombosis of the iliac artery were treated successfully by similar methods. In addition, tightly occlusive arterial thrombi were removed with flexible biopsy forceps in 17 of 154 patients (11 %) who had angioscopic monitoring of thromboembolectomy of native arteries or bypass grafts.

Laser Angioplasty and Atherectomy

Angioscopy may be used in a similar fashion for monitoring intraoperative laser or atherectomy procedures. I. 2, 47, 52 The diseased vessel is inspected before angioplasty to determine the severity, distribution, and character of the occluding or stenotic lesion. In selected cases, the laser or atherectomy drill or bur may be observed during its action and aimed or controlled by the visual image. 52

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Figure 11. Angioscopic monitoring for endovascular removal of thrombus and intimal flaps. A, Thrombus within a popliteal artery after external trauma. A Fogarty catheter has been passed through this segment of vessel, leaving a significant amount of thrombus in the traumatized area. B, Flexible biopsy forceps (arrow) being used to remove remaining thrombus and underlying intimal shreds. C, Several shreds of intimal flap remain within the lumen. D, After further removal of debris with the biopsy forceps under endoscopic control, a relatively clear arterial lumen was achieved.

The postprocedural inspection of the recanalized artery to assess the lumen caliber for residual stenosis is of particular interest and value. Angioscopy is also an effective method of inspection of the laser- or atherectomy-treated vessel for the presence of complications including plaque dissection, intimal flap, vessel perforation, thrombosis, or embolus (Fig. 12). This capability for immediate three-dimensional assessment of vessel morphology allows rapid correction of defects while the access to the vessel is maintained and may lead to repeat procedure or alternative therapy by atherectomy or balloon angioplasty if the results of the laser procedure are judged to be inadequate. The most valuable use for angioscopy would be as a replacement for fluoroscopy during intraoperative laser angioplasty performed by surgical exposure of the vessel. In this setting, the radiologic monitoring is often limited by inadequate equipment; the possibility of contaminating sterile fields; the need to minimize the X-ray exposure of the patient, surgeon, and operating room personnel; and the requirement for contrast medium that may cause nephrotoxic or anaphylactic responses.

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Figure 12. Angioscopic monitoring of endovascular surgery. Typical angioscopic appearance of an occluded segment of femoral artery after laser-assisted balloon angioplasty. Partial recanalization of the arterial lumen (L) is revealed, in association with cracking of atherosclerotic plaque (small closed arrow), and there is evidence of laser damage to other segments of the arterial wall (open arrow).

In 1982, Lee and coworkers studied the feasibility of precise delivery of laser energy to atherosclerotic plaque by simultaneous angioscopic visualization and intravascular irradiation with bare-tip argon lasers. 22,23 Abela and associates! reported the application of vascular endoscopy in conjunction with metal-tip thermal laser probes of 2 mm diameter to position the probe tip precisely and to observe the process of recanalization of occluded superficial femoral arteries. The role of angioscopic monitoring and aiming in the control of laser intervention in the vascular system was investigated in our research laboratory in 48 vessels in 33 dogs, and the techniques were then applied to 20 patients undergoing intraoperative or percutaneous laserprobe angioplastyY These studies, in summary, gave the following results. Experimental bare argon-fiber laser application in 20 normal canine arteries in vivo demonstrated that small fibers fed through the internal channel of a 2.S-mm angioscope could be aimed grossly by manipulations of the angioscope, but this process was clumsy and did not prevent perforation of the undiseased arterial wall by laser energy. Adapting similar techniques to intraoperative laser angioplasty in atherosclerotic human arteries produced several difficulties. In patients with long or multisegmental arterial occlusions, proximal stenosis or tapering in the superficial femoral artery prevented the 2.8-mm angioscope from reaching the site of occlusion in a high proportion of cases. With shorter occlusions or stenotic lesions and with the use of a 2.3-mm angioscope (which may also be used percutaneously via an 8-Fr access sheath), postprocedural angioscopy is successful in 80% to 90% of cases and reveals wall thermal damage, fragmentation, and mural thrombus. These findings are particularly prevalent in previously occluded segments of arteries. Postprocedural inspection is valuable for immediate detection of inadequate recanalization or complications and may provide prognostic information. In a further research project, angioscope guidance of metal-tip laserprobes was used for division of 82 valve cusps in preparation for in situ bypass in 28 canine and 1 human veins, with satisfactory aiming and monitoring achieved expeditiously by manipulations of the angioscope. 49 Ahn et aP have described techniques and results of angioscopic monitoring of rotary atherectomy. Gehani and associates!2 found percutaneous angioscopy

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to be a valuable tool for assessing the result of atherectomy procedures and reported the invariable occurence of intimal flaps following the activation of one type of atherectomy device inside arteries. Angioscopy was also used to prove that atherectomy devices have only a limited ability to maintain a coaxial or self-centering position within the arterial lumen. 13 In a more recent study,53 the value of angioscopic monitoring for angioplasty and endovascular surgical procedures in iliac, femoral, and popliteal arteries was prospectively studied in 194 patients undergoing laser-assisted balloon angioplasty (n = 124), percutaneous transluminal balloon angioplasty (n = 52), or rotary atherectomy (n = 18). Thermallaserprobes were used for laser angioplasty in this study. Inspections were made with angioscopes of diameter 0.8 to 2.8 mm inserted percutaneously (n = 119) or intraoperatively (n = 75). Unsuspected fresh thrombus was detected preprocedure in nine patients (4.6%) and managed by surgical thromboembolectomy or percutaneous aspiration. Postprocedural angioscopic assessment was successful in 96% of the intraoperative and 82% of the percutaneous procedures. Longitudinal dissections of the intimal surface were common after laser or balloon angioplasty, being more frequent in complex lesions and those longer than 2 cm. These deep wall cracks were rarely observed after atherectomy, whereas smaller intimal fronds or flaps were equally common after each of the three techniques. Debulking of lesions was less with percutaneous transluminal angioplasty than with laser or rotary atherectomy and was overestimated on the radiologic image compared with the angioscopic inspection for all three techniques. The angioscopic image suggested that atherectomy devices resulted in a greater dilatation effect than actual extraction of tissue. False channels were common after laser recanalization of arterial occlusions longer than 6 cm, particularly in the iliac and femoral arteries, and were associated with inability to direct the probe away from the path of least resistance. Thermal charring damage was observed in 78% of the laser-treated arteries and did not result in early failure. A grading system for the endoscopic features of the arterial wall after endovascular interventions has been developed (Table 4). Specific angioscopic features that were predictive of poor outcome were: (1) large fragment flaps and dissections; (2) fresh thrombus; (3) narrow channel diameters; and (4) perforation of a false channel (Fig. 13). Immediate detection of defects allowed correction by either retrieval of thrombus, repeat dilatation, or placement of an arterial stent. The complications included creation of new intimal flaps by the angioscope in regions of arterial dissection in six patients (3%). Angioscopy was most valuable in the postprocedural inspection of recanalized arterial obstructions, with particular benefits being accurate evaluation Table 4. ANGIOSCOPIC GRADING SYSTEM FOR POSTANGIOPLASTY APPEARANCE OF INTIMAL SURFACE OF AN ARTERY Grade 0 Grade 1

Grade 2

Grade 3

Normal artery Mild changes Mild intimal strands Soft, nonstenotic mural thrombus Moderate changes Moderate intimal flap, mural cracking, or dissection plane Moderate amounts of thrombus or atheromatous debris Severe changes Large flaps, mural cracking, or dissections Large amounts of thrombus or atheromatous debris

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Figure 13. An angioscopic grading system for the arterial lumen after angioplasty or endovascular recanalization. A, Grade 1. Minor arterial wall changes after balloon angioplasty of a stenotic lesion. This minor degree of surface irregularity and associated small intimal flaps (f) are rarely hemodynamically significant on subsequent Duplex doppler ultrasound scanning, and the prognosis for long-term patency is good. B, Grade 2. Moderate wall changes after laser-assisted balloon angioplasty of an occluded superficial femoral artery. The resultant lumen area is less than 50%, and there is moderate plaque cracking, thrombus, and mural hemorrhage. The prognosis for longterm patency is variable, and our current data suggest that this appearance may be an indication for placement of an arterial stent. C, Grade 3. Severe wall damage, residual plaque and debris (arrow), and an inadequate lumen (probably less than 25% recanalization) after laser angioplasty of this superficial femoral artery. Early thrombosis or re-occlusion is very likely unless the situation can be salvaged by stent placement or more extensive removal of atheromatous tissue and debris.

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of the degree of residual stenosis, detection and characterization of complications, and assessment of resultant luminal architecture.

Vascular Stent Insertion

Angioscopy can be a valuable adjunct in the decision about whether a vascular stent is indicated after endovascular recanalization, especially in the femoral artery. When the lumen is seen to be severely compromised by residual atheroma or by dissection, intimal flaps, debris, or thrombus (grade 2 or 3 angioscopic appearance, as detailed in Table 4), placement of an expandable stent may prevent early reocclusion of the artery. After placement of the stent, angioscopic inspection can be used to ensure that the stent is fully expanded and is retaining the dissection planes against the arterial wall.

EXAMPLES OF APPLICATIONS AND VALUE OF ANGIOSCOPY IN CLINICAL PRACTICE Case 1: Angioscopic Assessment of Reversed-Vein Bypass Graft, Anastomosis, and Run-off Artery

A 72-year-old female diabetic patient had a femoropopliteal bypass using reversed saphenous vein, with the distal anastomosis sewn to the infrageniculate popliteal artery with a continuous 6-0 Prolene suture. After completion of the distal anastomosis, a 2.5-mm multichannel angioscope was passed down the saphenous vein from the groin end of the graft before completion of the proximal anastomosis to the common femoral artery. The interior of the saphenous vein was inspected, revealing five normal-appearing, competent valves along the length of the vein. The valves opened as the angioscope approached because of the flow of heparinized saline through the angioscope's internal channel. There were no significant kinks or sclerotic segments in the graft. The intimal surface of the vein appeared relatively normal, with several regions demonstrating fine intimal strands. The distal anastomosis was then inspected, revealing no technical faults. The Prolene sutures were seen to be placed uniformly, with no intimal flaps and no embolic material, thrombus, or debris within the anastomotic segment. A vascular clamp on the distal popliteal artery was then released and the run-off artery inspected to a distance of 10 cm, at which point, the angioscope's diameter would not permit further safe advancement. The lumen of this run-off vessel had a moderate degree of smooth plaque along the posterior wall. The angioscope was then slowly withdrawn, giving an excellent view of the lumen of artery and vein graft as the catheter was retracted. No intraoperative angiogram was performed. Angioscopy may be performed in 5 to 10 minutes during vascular bypass operations. The absence of collateral blood flow in reversed-vein or prosthetic grafts makes endoscopic inspection of these conduits quite simple. Technical errors in vein selection and graft placement can be excluded. Inspection of the anastomosis is often quite difficult because of the acute angle of entry of the graft to the distal artery and the lack of a full 360-degree view of the anastomosis because of its width. In our experience, technical errors at the anastomosis are rare, and most examinations reveal no significant abnormality. 54

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Case 2: Angioscopic Monitoring of In Situ Bypass Graft Operation (Open Technique)

A 68-year-old man with critical limb ischemia was scheduled for an in situ saphenous vein bypass from the common femoral artery to the posterior tibial artery. The long saphenous vein was exposed over its length to the mid-calf region, and the relevant arteries were exposed by conventional technique. The long saphenous vein was disconnected from the femoral vein, and the saphenofemoral valve was excised using arteriotomy scissors. A 2.3-mm multichannel angioscope was inserted via the proximal open end of the vein and advanced 6 cm to the point where the next venous valve was encountered. The flow of saline through the angioscope caused this valve to close. A Mills retrograde valvulotome was inserted through a large tributary vein in the distal thigh, and the hooked end of this valvulotome was gently advanced up the vein until it projected through the valve. The hook was then retracted forcefully through each of the two cusps of the valve under visual control. The division of the posterior valve appeared incomplete, and a further pass of the valvulotomy hook was made, with excellent result. The valve was now seen to be shredded and attenuated and offered little resistance to flow of the irrigation fluid. The valvulotome and angioscope were advanced simultaneously down to the next valve and a similar process undertaken. Flow of blood into the graft lumen at intervals down the vein revealed the site of small tributaries, which were then ligated. By repetition of this process down the length of the vein, all valves were divided under vision. A final check for patient tributaries was made as the angioscope was retracted out of the vein, and the anastomoses were then completed. Experience with blind retrograde valvulotomy in in situ bypass grafting has shown that the incidence of residual competent valves remains significant and valvulotome-induced injury to the vein wall is common. 27 Angioscopic monitoring can be valuable in reducing these problems and in detecting other complications. 11,51

Case 3: Angioscopic Monitoring of In Situ Bypass Operation (Closed Technique)

A 57-year-old diabetic man with a gangrenous toe and limb-threatening ischemia underwent an in situ saphenous vein bypass from the common femoral artery to the peroneal artery. Initially, only the distal and proximal 5 cm of the long saphenous vein were exposed, as were the common femoral artery and midpoint of the peroneal artery. A long flexible Miller valvulotome 28 (Olympus Corp, Lake Success, New York) was inserted from the distal aspect of the long saphenous vein and guided up the leg until it emerged from the proximal aspect of the vein where it had been divided at the saphenofemoral junction. The detachable blunt tip of this instrument was changed for a 2.5mm valvulotome blade, which was then drawn down the vein under angioscopic control. Incision of six venous valves was performed under direct vision of the angioscope (see Fig. 10), again in a retrograde fashion. The sites of major venous tributaries of the vein were identified angioscopically and marked on the skin by reference to the transilluminated angioscope light. Skin incisions approximately 3 cm long were made over the vein at these points to allow ligation of the tributaries. After division of all valves and ligation of seven tributaries by this technique, the angioscope was slowly withdrawn for a final

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check on the presence of patent large tributaries, especially those on the deep aspect of the vein that could have been communicating with the deep venous system. Six smaller tributaries were deemed not to require ligation. The anastomoses were then completed, and a check for large arteriovenous connections was made by palpation of the length of the graft for a thrill and by obtaining a completion angiogram. Angioscopic technique and use of this new long valvulotome device is reliable and safe. Miller and associates reported that the incidence of valvulotome-induced injury to the vein wall was reduced to 16% (5 of 32 veins) with angioscopically directed valvulotomy, compared with an observed rate of injury of 85% (45 of 53) in vein grafts prepared by blind retrograde valvulotomy.28 The principal drawback with this semiclosed technique is the number and length of mini-incisions made to ligate the medium-size and larger tributaries of the long saphenous vein to avoid subsequent arteriovenous fistula. Judgment as to which of these require ligation (and hence a skin incision) remains subjective, and it is possible to finish the procedure with a whole series of incisions down the leg in some patients.

Case 4: Angioscopy for Diagnosis of Cause of Graft Failure During Revision Operation A 48-year-old man had a femoropopliteal bypass with a 6-mm diameter polytetrafluoroethylene (PTFE) graft. The graft failed within the first 24 hours. He was returned to the operating room, and during the redo operation, a thrill was palpated in the femoral artery. A 5-Fr Fogarty catheter was introduced up the external iliac artery via an incision in the hood of the graft at the proximal anastomosis, and the catheter balloon was inflated to block inflow of blood. Angioscopy of the iliac artery then demonstrated a 75% stenotic lesion, which was treated by dilatation with an 8-mm angioplasty balloon. After dilatation, the lumen of the iliac artery was shown angioscopically to be considerably improved. The PTFE graft was cleared of thrombus with a 4-Fr Fogarty catheter. Angioscopic inspection of the graft then showed good clearance of thrombus from the graft, but there was significant residual thrombus just distal to the popliteal anastomosis. This was eventually retrieved after further passages of the embolectomy catheter. A twist of the PTFE graft was also identified approximately 15 cm from the proximal anastomosis. This was revised by dividing the graft transversely and suturing the two ends after removal of the rotation. The original preoperative angiograms were reviewed, and the stenotic lesion of the iliac artery was thought to be concealed by overlay of the external and internal iliac arteries on the uniplanar films. The graft remains patent in follow-up of 14 months. The availability of intraoperative angioscopy for acute and emergency operations is a great advantage, particularly for the management of acute arterial thromboembolus or for revision operations after graft failure and other complications of vascular surgery. These operations are often performed urgently without arteriography (for acute embolus) or in a situation in which arteriograms are unlikely to be particularly helpful (for acute graft failure in the early postoperative period) in delineating the cause of thrombosis. Angioscopy can be performed immediately after the artery has been opened and gives detailed information regarding the status of the lumen of inflow artery, run-off (excluding distal tibial and foot vessels), and the wall of a graft. Technical errors may be detected and the results of revision monitored immediately. On

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other occasions, poor angiograms or the imprecision of angiographic images may conceal significant lesions that are nicely demonstrated by endoscopy of the arterial lumen. Case 5: Angioscopic Monitoring of Retrieval of an Intraarterial Foreign Body

A metal laserprobe tip became detached from its fiberoptic cable during laser recanalization of an occluded superficial femoral artery in a 58-year-old man. Attempts to snare the detached tip with a Dormia basket and with flexible biopsy forceps under fluoroscopic monitoring were unsuccessful, partly because the proximal end of the detached probe tended to dig into the arterial wall. An angioscope was then introduced and the probe tip identified visually. The Dormia basket was now able to be placed appropriately and retrieval of the foreign body achieved easily. The advantages of the three-dimensional view provided by angioscopy for intravascular instrumentation and manipulation were dramatically demonstrated in this case, whereas it had been frustratingly difficult to grab the foreign body with the guidance of the radiologic image alone. Case 6: Angioscopic Control of Endovascular Recanalization and Stent Placement

A 49-year-old man underwent percutaneous laser-assisted balloon angioplasty of a 7-cm occlusion of the superficial femoral artery at the adductor canal level. Under local anesthetic, an 8-Fr access sheath was inserted antegrade down the common femoral artery over a O.035-inch guidewire. The guidewire was then removed from the sheath, and a 2.3-mm multichannel angioscope was introduced. Inspection of the arterial lumen showed a relatively undiseased section of artery leading to the region of occlusion, which had the appearance of an atherosclerotic encroachment into the lumen, without evidence of fresh thrombus. Laser recanalization of the arterial lumen was then performed successfully with a 2.5-mm laserprobe. Injection of angiographic contrast now demonstrated a narrow, irregular lumen in this region, and repeat endoscopic inspection confirmed a very narrow channel with evidence of thermal damage to the wall and irregular sections of old intraluminal and mural thrombus. The channel was next dilated with a 6-mm angioplasty balloon over a guidewire. The angiographic appearance now appeared quite satisfactory, with a larger, patent lumen and a small quantity of intramural contrast medium, suggestive of a minor longitudinal dissection. In contrast to this radiologic appearance, angioscopy demonstrated persistence of a very irregular lumen with a significant intimal flap and a dissection plane extending along most of the length of the recanalization channel. Portions of debris within the lumen constituted a hindrance to blood flow. It seemed most unlikely that patency of the vessel would be maintained. On the basis of this angioscopic appearance, a decision was made to insert a 6-mm flexible Strecker stent, 8 cm in length. After successful positioning and expansion of the stent, the angioscopic appearance of the lumen was vastly improved with a wider channel and all debris and flaps compressed and held back against the wall by the stent. The complete length of the stent was confirmed to be fully expanded, with a smooth transition from the intimal surface to the interior of

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the stent at each end. This recanalized artery has remained patient in followup of 9 months to date. Angioscopy gives a precise evaluation of the result of various endovascular procedures and, in our preliminary experience, is a valuable guide to whether a vascular stent is indicated in a recanalized femoral artery. When arterial occlusions have been reopened by intraluminal instrumentation, angioscopy frequently reveals features similar to those described in this case, even though angiograms obtained at the same stage of the procedure may show an apparent restoration of a good arterial lumen. The true diameter of the new channel tends to be overestimated by the radiographic image, and the wall changes are not well reproduced. We currently find that the angioscopic picture is therefore more valuable in the decision about whether a stent should be placed after endovascular recanalization of the superficial femoral artery. COMPLICATIONS AND LIMITATIONS OF ANGIOSCOPY

Some of the possible disadvantages of angioscopy are listed in Table 5. In particular, these fine fiberscopes are delicate instruments that require meticulous care in handling, usage, and cleaning. Proper techniques will greatly reduce the need for costly repair and will prolong the life of the instruments. Small and tortuous or branched vessels present special difficulties for cannulation and inspection. It often is not possible to monitor endovascular procedures directly, because the angioscope will not fit comfortably into the lumen at the same time as the therapeutic device in use. In these cases, the inspection is limited to examination of the effects at the conclusion of treatment. Microinstruments that may be passed through the angioscope working channel have been developed but are not generally of great use. The limitations of the use of angioscopy are primarily related to the time, cost, and design constraints of the present technology, and the potential for vessel trauma caused by the angioscope itself exists if great care is not exercised. There may be a tendency to overestimate the severity of the observed abnormalities, with resultant overtreatment of minor faults. Table 5. COMPLICATIONS AND LIMITATIONS OF ANGIOSCOPY

Instrumentation and techniques Instrument fragility Costs of equipment and accessories Space requirements and set-up time Limited lifespan of the fiberoptic catheters Necessity for gas sterilization Vessel size and tortuosity (limits of guidable penetration) Image interpretation Subjective measurement, affected by distance from lens No quantification of flow Requires experience for technical proficiency Potential complications Intimal and vessel wall trauma Contamination of sterile field; infection Fluid overload Thrombosis, embolization Late vessel narrowing, myointimal hyperplasia

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Angioscopy cannot be regarded as a total replacement for intraoperative arteriography, because the angioscopes generally do not pass safely into the small vessels, and, thus, no information is conveyed regarding the status of the run-off vessels beyond the examined area. The diameter of current angioscopes precludes visualization of most arteries distal to the popliteal, but extremely flexible small-diameter endoscopes, as thin as 0.2 mm, are under evolution. Intimal trauma caused by the angioscope has been reported. 21 However, evidence from several series featuring regular use of angioscopy in bypass operations shows that there is no higher incidence of bypass graft failure after use of angioscopy.15, 26, 34 There also is no quantification of the flow through the anastomosis or vessels with angioscopy. In cases in which these may be important considerations, intraoperative angiograms still playa valuable role and may be obtained by infusions of contrast via the fluid channel. Training and experience are necessary to achieve sufficient technical skill and interpretive ability and to aid in the selection of appropriate instrumentation. As use becomes more general, there may be a temptation to overreach the capabilities of the angioscope in therapy. Even under very optimistic circumstances, endoscopic intravascular intervention, as described in this article, will be limited to a few carefully selected patients. As experience grows and the technology becomes more refined, angioscopy will come to occupy a more important place in the management of vascular disease.

SUMMARY Endoscopy of the vascular system has evolved over recent years from an experimental procedure to a sophisticated diagnostic and therapeutic technique for surgical or percutaneous interventions of the peripheral vascular system. Particularly in procedures involving remote instrumentation of arteries, the angioscope provides a method of controlled guidance and a monitor of the effects of the various instruments on the vessel wall and allows immediate assessment of results. Angioscopic examination reveals the extent of intimal injury after angioplasty, in situ vein preparation, trauma, and thrombectomy and gives insights into the mechanisms and effects of endovascular devices.

References 1. Abela G, Seeger JM, Barberi E, et al: Laser angioplasty with angioscopic guidance in humans. J Am Coli Cardiol 8:184-192, 1986 2. Ahn SS, Auth DD, Marcus DR, et al: Removal of focal atheromatous lesions by angioscopically guided high-speed rotary atherectomy. J Vasc Surg 7:292-300, 1988 3. Allen DS, Graham EA: Intracardiac surgery-A new method. JAMA 79:1028-1030, 1922 4. Bauriedel G, Dartsch pc, Voisard R, et al: Selective percutaneous "biopsy" of atheromatous plaque tissue for cell culture. Basic Res Cardiol 84:326-331, 1989 5. Brock RC: Surgical treatment of aortic stenosis. Br Med J 1:1019-1028, 1957 6. Crew J: Angioscopy for in-situ bypass grafting. In White GH, White RA (eds): Angioscopy: Vascular and Coronary Applications. Chicago, Year Book Medical Publishers, 1988, pp 65-71 7. Crispin HA: Experience with the vascular brush. J Cardiovasc Surg (Torino) 28:4549, 1987 8. Crispin HA, Van Baarle AF: Intravascular observation and surgery using the flexible fiberscope. Lancet 1:750-751, 1973

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Address reprint requests to Geoffrey H. White, MB BS, FRACS Department of Surgery University of Sydney NSW 2006 Australia