Sequential internal mammary-coronary artery bypass

J

THORAC CARDIOVASC SURG

86:697-702, 1983

Sequential internal mammary-coronary artery bypass Since April, 1977, a total of eight patients have undergone sequential bypass grafting of the internal mammary artery (IMA) to the coronary arteries at our institution. The indication for this newly described procedure was either insufficient supply of adequate veins (jour patients) or the presence of a diseased aortic wall (two patients). Operative procedures included left IMA bypass to the left anterior descending (LAD) artery and its major diagonal branch in six patients; to the obtuse marginal branch and distal circumflex artery in one patient; and to two consecutive sites on the LAD in one patient. All patients became angina-free after operation for a follow-up period lasting up to 6 years. Recatheterization studies were performed in four patients, in all of whom the IMA sequential grafts were found patent. We believe that IMA sequential grafting is an important option available to the cardiac surgeon in managing some patients with coronary artery disease.

Sami S. Kabbani, M.D., Elias S. Hanna, M.D., Tali T. Bashour, M.D., John R. Crew, M.D., and David G. Ellertson, M.D., San Francisco, Calif.

he

internal mammary artery (IMA) has been establishedas an excellent conduit for revascularization of the anterior myocardial wall.!" Its main virtue sterns from proven early and late high patency rates. Additional advantages include providing a suitable conduit in patients who lack adequate veins and obviating the need for a proximal aortic anastomosis. The application of IMA grafting, however, has been limited to one coronary vessel per one IMA. We describe here, for the first time, the use of sequential 1MA-coronary bypass as an alternative method in patients with an insufficient supply of adequate veins and in patients in whom a diseased aortic wall precludes the performance of a standard aorta-coronary bypass.

:Jv?f

- , - LIMA

1\'-''---

DB

Patient data

Sequential IMA-coronary bypass was performed on a total of eight patients since April, J977 (Table I). All patients were men. Average age was 61 years. Four patients had medically uncontrollable angina and four presented with unstable myocardial ischemia. Evidence of old myocardial infarction was present in five patients and one had had a recent infarction. Three patients had

From the Western Heart Institute at St. Mary's Hospital and Medical Center, San Francisco, Calif. Received for publication May 31, 1983. Accepted for publication June 29, 1983. Address for reprints: Dr. S. S. Kabbani, St. Mary's Hospital and Medical Center, 450 Stanyan St., San Francisco, Calif. 94117.

LAD

Fig. 1. Diagrammatic representation of sequential left internal mammary artery (LIMA)--eoronary bypass to the left anterior descending artery (LAD) and its major diagonal branch (DB).

a history of hypertension and two had diabetes mellitus. On physical examination, two patients were hypertensive and seven had a fourth heart sound. None of the patients had signs of congestive failure. Four patients 697

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6 9 8 Kabbani et al.

H - - - - LIMA

\;:~H---

1 + - - - - - LIMA

ex

\V--j-AJ--

LAD

'+t-iJ>'rl
LOM

-- LAD

Fig. 2. Diagrammatic representation of sequential LIMAcoronary bypass to the obtuse marginal branch (LOM) and distal circumflex artery (eX).

had varicosities of the lower extremities (three bilateral and one unilateral). One had peripheral arterial insufficiency and a history of phlebitis in both lower extremities. Cardiac catheterization revealed significant coronary artery occlusive disease, with left ventricular ejection fractions of 50% or above in all patients. At operation the saphenous veins were found to be unexpectedly fibrosed or diminutive in two patients. In one of these, however, it was possible to obtain a saphenous vein segment sufficient for two bypasses. Limitation of adequate saphenous veins due to varices precluded the full use of vein grafts for myocardial revascularization in four more patients. In two patients, the aortic root was so calcified that it was considered inappropriate for proximal vein anastomoses. Operative procedures included sequential left IMA bypass to the left anterior descending artery (LAD) and its major diagonal branch in six patients (Fig. 1); to the obtuse marginal branch and distal circumflex artery in one patient (Fig. 2); and to two sites on the LAD (in tandem) in one patient (Fig. 3). Saphenous bypass grafting was performed in addition to IMA bypass in four patients. Sequential IMA-coronary grafting was attempted in one other patient because of calcific aortic disease but had to be abandoned because the IMA was too fragile and small.

Fig. 3. Diagrammatic representation of sequential LIMAcoronary bypass to two sites on the LAD.

Surgical technique The IMA (usually the left) is harvested with the aid of a Crew-Hanna retractor.' Electrocautery is used to isolate the whole pedicle (IMA, vein and lymphatics), and severed IMA branches are secured with hemostatic clips. A sponge saturated with papaverine (30 mg/IOO ml saline solution) is applied against the IMA and left in place until cannulation is complete. Heparin is administered and the patient is cannulated while one of the surgeons obtains available saphenous veins. The IMA is then transected to allow for maximal length of the conduit (usually at the level of the fifth intercostal space), a 2 rom probe is passed once through the artery to relieve spasm, and the IMA blood flow is measured. The IMA graft is not used unless it is adequate in size and its blood flow equals or exceeds 100 ml/rnin. A Fogarty Hydragrip clamp" is temporarily applied to the base of the IMA pedicle, cardiopulmonary bypass is instituted, the ascending aorta is crossclamped, and about 500 ml of cardioplegic solution] is administered through the aortic root. We use a 2 L asanguineous prime, consisting of a balanced electrolyte solution, as our perfusate, normothermia (unless the patient's condition is unstable), and high flow rates in the range of 50 to 60 nil/kg/min. *American V. Mueller, Chicago, Ill. tPlegisol, Abbott Laboratories, North Chicago, Ill.

Volume 86 Number 5

Sequential IMA-eoronary bypass

November. 1983

Fig. 4. Postoperative angiogram of Patient 4 revealing patency of IMA sequential graft to the DB and LAD 4 years after operation.

The left side of the heart ordinarily is not vented. Distal saphenous vein-coronary artery anastomoses are first performed when veins are available. With the aid of 4.5 power magnification, a small (2 to 3 mm) coronary arteriotomy is made at the proper site on the first recipient coronary vessel (usually the diagonal branch). The IMA is then brought to lie comfortably over the arteriotomy, and a corresponding incision is made on its posterior wall at a 10 to 20 degree angle from its longitudinal axis. The site and angle of the proximal IMA incision are chosen after determining the final orientation of the conduit in relationship to both recipient coronary arteries. A continuous side-to-side anastomosis is then performed between the two arteriotomies starting at the superior angles and using 7-0 polypropylene suture. Air is vented from the anastomotic site before the last few "bites" by temporarily opening the Fogarty occluding clamp. The distal end of the IMA pedicle is then brought down on the second coronary vessel (usually the LAD). A longitudinal coronary arteriotomy is made at the appropriate site (slightly longer than the side-to-side arteriotomy to allow for proper tangential anchoring of the IMA graft on the terminal coronary artery). The anchoring site of the IMA graft on the terminal vessel is made as low as possible to permit a natural narrow angle between the IMA and coronary artery. The IMA is then shortened to appropriate length, its distal end trimmed in a "cobra-head" fashion, and the end-to-side anastomosis carried out with continuous 7-0 polypropylene suture, starting at the apex of the graft. Air is again vented from the graft by releasing the IMA Fogarty clamp before the final few "bites." During both IMA

699

Fig. 5. Postoperative angiogram of Patient 7 revealing patency of IMA sequential graft to proximal and mid-LAD 3 years after operation.

RIMA ------\\

ex

----t---,------,\H---

- - - - - - LIMA

DB LAD LOM

Fig. 6. Diagrammatic representation of possible application of internal mammary--coronary bypass to four coronary vessels. LIMA, Left internal mammary artery. DB, Major diagonal branch. RIMA, Right internal mammary artery. LOM, obtusemarginal branchof circumflex artery. LAD, Left anterior descending artery. ex,Distal circumflex artery.

anastomoses, care is taken not to touch or directly manipulate the IMA. The aortic cross-clamp is then removed, the heart defibrillated, and the necessary proximal aorta-saphenous vein anastomoses completed with the aid of a partial occlusion clamp applied to the ascending aorta.

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Table I. Clinical data in eight male patients

Patient

Age

Angina

Previous MI

Hypertension

Diabetes

Significant coronary lesions

55

Severe

Yes

No

No

LAD, DB, RCA, OMB

2

68

Severe

Yes

Yes

No

LAD, DB, OMB, CX, RCA

3

72

Severe

Yes

Yes

Yes

LAD, DB, CX, RCA

4

69

Unstable

Yes

No

No

LAD,OMB

5

54

Unstable

No

No

No

LAD, DB

6

63

Unstable

Yes

No

No

LAD, DB, RCA

7

58

Unstable

Yes (recent)

No

Yes

LAD (proximal), LAD (middle), RCA (AMB), RCA (PO), OMS

8

54

Severe

No

Yes

No

LAD, DB

Legend: M I. Myocardial infarction. EF. Ejection fraction. IMA, Internal mammary artery. LAD, Left anterior descending. DB, Diagonal branch. RCA, Right coronary artery. OMB, Obtuse marginal branch. CX, Circumflex artery. AMB, Acute marginal branch. PD. Posterior descending. PVD, Peripheral vascular (arterial) disease. LIMA, Left internal mammary artery. SVG, Saphenous vein graft. RIMA, Right internal mammary artery.

Results The hospital postoperative course was uneventful in six patients. One patient had pneumothorax necessitating tube thoracotomy, and another had bronchopneumonia which cleared with treatment in 4 days. All patients became angina-free after operation and have remained so until the present time-a follow-up period lasting 3 to 6 years. Thallium stress tests were negative in five patients, 1 to 5 years following operation. Recatheterization studies were performed in four patients 2 to 5 years after operation and, in all, the IMA sequential grafts were patent (Figs. 4 and 5). Discussion Cardiac surgeons are sometimes faced with situations in which application of the standard saphenous veincoronary artery bypass operation is limited by the absence of adequate vein conduits or the presence of a diseased ascending aorta. Saphenous vein stripping, varicosities, and phlebitis are the major causes of inadequate supply of vein grafts. Although other veins such as the cephalic and umbilical veins, saphenous vein allografts, and synthetic grafts have been utilized as substitute conduits', all these have proven to be inferior to autologous saphenous veins. Calcification, other degenerative changes of the ascending aorta, and occasionally reoperation may also

pose technical difficulties for the surgeon in performing the standard aorta-coronary bypass operation. The IMA, a superior revascularization conduit for the anterior myocardial wall,':' can be used as a substitute in all these situations, provided it is of good size and has adequate blood flow. Traditionally one IMA (usually the left) is grafted to one coronary artery (usually the LAD or major diagonal branch). With sequential IMA-eoronary bypass, the proven benefits of the IMA graft can be extended to a greater number of recipient vessels, a shorter segment of vein graft is required for other necessary venous bypasses, and a sometimes difficult aortic anastomosis is avoided. Sequential (bridge or jump) grafts, performed with the saphenous vein, have been utilized for many years.r" In addition to allowing for shorter operative time, advantages of sequential vein grafting include the ability to bypass small branches that cannot by themselves support individual grafts.v? tt Optimal patency rates are claimed for sequential grafts by their proponents. Patency is attributed to higher velocity of flow in the proximal segment and lower coronary vascular resistance. t2 Principles in sequential grafting, such as reserving the side-to-side anastomosis for the smaller coronary vessel, have now been established. Technical pitfalls due to such problems as kinking and twisting at the side-to-side anastomosis, which were responsible for failures in the

Volume 86 Number 5 November, 1983

EF (%)

Sequential IMA-eoronary bypass

Indications for sequential IMA grafting

Postoperative results

Procedure

76

Fibrosed veins + PVD

50

Bilateral varices

65

Bilateral varices

60

Diseased aorta

LIMA to DB + LAD, SVG to RCA, SVG to OMB LIMA to OMB + CX, RIMA to RCA, SVG to DB LIMA to DB + LAD, SVG to RCA, SVG to OMB LIMA to DB + LAD

65

Bilateral vances

LIMA to DB

78

Diseased aorta

LIMA to DB + LAD

60

Varices in one extremity

LIMA to proximal + mid-LAD, SVG to AMB + PDA, SVG to OMB

73

Small and fibrosed veins

LIMA to DB

+ LAD

+ LAD

earlier series, to a large extent have been recognized and avoided in later reports." 10. II Sequential IMA-eoronary bypass theoretically combines the attributes of both IMA and sequential grafting. The conduit used is an artery similar in nature and size to the coronary, and it requires no proximal anastomosis. Velocity of flow, already higher in IMA than vein grafts because of smaller conduit size, could be further enhanced by the sequential technique and probably allows for superior patency rates, although IMA flows after grafting were not measured in our series. Perhaps the only criticism of the procedure is that it is technically more demanding. However, with the availability of high-power magnification and ultrafine suture material, this should not pose a problem to the cardiac surgeon. Our experience with eight patients demonstrates the feasibility of sequential IMA-coronary bypass. All patients became free of angina 'after. operation. Furthermore, the patency of sequential grafts was documented in four patients who underwent repeat angiography 2 to 5 years postoperatively. .The procedure is probably best suited for the left IMA in situations in which the LAD and diagonal branch are diseased (as was the case in six of our patients). Since the diagonal branch is usually the smaller of the two vessels, it should be anastomosed first to the IMA (side-to-side) and then end to side to the LAD, which usually has the better runoff (Figs. 1 and 4).

Angina-free smce April, 1977 Angina free since May, 1977 Angina free since October, 1977 Angina free since September, 1978 Angina free since January, 1979 Angina free since May, 1979 Angina free since February. 1980

Angina free since June, 1980

701

Recatheterization Not performed Not performed 5 yr later: patent SVG and LIMA graft 4 yr later: patent LI MA graft 2 yr later: patent LIMA graft Not performed 3 yr later: patent LIMA, patent SVG to AMB, stenosed DB distal to SVG anastomosis Not performed

Another potentially useful application of this procedure is in bypassing two consecutive lesions in the same coronary vessel (Figs. 3 and 5). In one patient, we were able to anastomose the left IMA sequentially to the obtuse marginal and distal circumflex arteries (Fig. 2). Although the right IMA was not used by us for sequential coronary bypass, it possibly can also be used to bypass the LAD and diagonal branch if it is long enough. A theoretical possibility of simultaneously bypassing four coronary vessels with this technique is depicted in Fig. 6. We believe that sequential IMA-coronary bypass grafting is a feasible option in myocardial revascularization, helpful in situations in which vein conduits are absent or insufficient and in which the ascending aorta is diseased. Wider experience with this technique will further define its efficacy and applicability. We wish to thank Ms. Janet Placke for typing the manuscript. REFERENCES Geha AS, Krone, RJ, McCormick JR, Baue AE: Selection of coronary bypass. Anatomic, physiological, and angiographic considerations of vein and mammary artery grafts. J THORAC CARDlOYASC SURG 70:414-431, 1975 2 Jones JW, Ochsner JL, Mills NL, Hughes L: The internal mammary bypass graft. A superior second coronary artery. J THORAC CARDlOYASC SURG 75:625-631, 1978 3 Tyras DH, Barner HB, Kaiser GC, Codd JE, Pennington DG, Willman VL: Bypass grafts to the left anterior

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descending coronary artery. Saphenous vein versus internal mammary artery. J THORAC CARDIOVASC SURG 80:327-333, 1980 4 McKeown PP, Crew JR, Hanna ES, Jones RA: Modified sternal retractor for exposure of internal mammary artery. Ann Thorac Surg 32:619, 1981 5 Ullyot DJ: Current controversies in the conduct of the coronary bypass operation. Ann Thorac Surg 30:192-203, 1980 6 Flemma RJ, Johnson WD, Lepley D Jr: Triple aortocoronary vein bypass as treatment for coronary insufficiency. Arch Surg 103:82-83, 1971 7 Grow JB Sr, Brantigan CO: The diamond anastomosis. A technique for creating a right-angie side-to-side vascular anastomosis. J THORAC CARDIOVASC SURG 69:188-189, 1975 8 Cheanvechai C, Groves LK, Surakiatchanukul S, Tana-

9

10

11

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ka N, Effler DB, Shirey EK, Sones FM Jr: Bridge saphenous vein graft. J THORAC CARDIOVASC SURG 70:6368, 1975 Bigelow JC, Bartley TD, Page SU, Krause AH: Longterm follow-up of sequential aorto-coronary venous grafts. Ann Thorac Surg 22:507-513, 1976 Hutchins GM, Bulkley BH: Mechanisms of occlusion of saphenous vein--eoronary artery "jump" grafts. J THORAC CARDIOVASC SURG 73:660-667, 1977 Grondin CM, Vouhe P, Bourassa MG, Lesperance J, Bouvier M, Campeau L: Optimal patency rates obtained in coronary artery grafting with circular vein grafts. J THORAC CARDIOVASC SURG 75:161-167, 1978 O'Neill MJ, Wolf PD, O'Neill TK, Montesano RM, Waldhausen JA:· A rationale for the use of sequential coronary artery bypass grafts. J THORAC CAROIOVASC SURG 81:686-690, 1981