Port-access cardiac operations with cardioplegic arrest

Port-Access Cardiac Operations With Cardioplegic Arrest James I. Fann, MD, Mario F. Pompili, MD, John H. Stevens, MD, Lawrence C. Siegel, MD, Frederick G. St. Goar, MD, Thomas A. Burdon, MD, and Bruce A. Reitz, MD Departments of Cardiothoracic Surgery, and Anesthesia, Stanford University School of Medicine, Stanford, and Section of Cardiothoracic Surgery, Department of Surgery, Veterans Affairs HCS, Palo Alto, California

Background. A less invasive approach to cardiac surgery has been propelled by recent advances in videoassisted surgery. Previous obstacles to minimally invasive cardiac operations with cardioplegic arrest included limitations in operative exposure, inadequate perfusion technology, and inability to provide myocardial protection. Methods. Port-access technology allows endovascular aortic occlusion, cardioplegia delivery, and left ventricular decompression. The endoaortic clamp is a triplelumen catheter with an inflatable balloon at its distal end. Antegrade cardioplegia is delivered through a central lumen, which also acts as an aortic root vent, a second lumen is used as an aortic root pressure monitor, and a third lumen is used for balloon inflation to provide aortic occlusion. Results. Experimental and clinical studies have dem-

onstrated the feasibility of port-access coronary artery bypass grafting and port-access mitral valve procedures. Endovascular cardiopulmonary bypass using the endoaortic clamp was effective in achieving cardiac arrest and myocardial protection to allow internal mammary artery to coronary artery anastomosis in a still and bloodless field. Intracardiac procedures, such as mitral valve replacement or repair, have been successfully performed clinically. Conclusion. The port-access system effectively achieves cardiopulmonary bypass and cardioplegic arrest, thereby enabling the surgeon to perform cardiac procedures in a minimally invasive fashion. This system provides for endovascular aortic occlusion, cardioplegia delivery, and left ventricular decompression. (Ann Thorac Surg 1997;63:$35-9) © 1997 by The Society of Thoracic Surgeons

dvances in laparoscopic and thoracoscopic technology have irreversibly altered the approach to many general and thoracic surgical disorders [1-3]. Minimizing the invasiveness of surgical procedures benefits patients in terms of less morbidity, shorter hospitalization, and, consequently, decreased overall cost. Facilitated by the rapid progress in video-assisted surgery, a minimally invasive approach to cardiac surgery is now a reality [4-11]. Previous obstacles to less invasive cardiac procedures with cardioplegic arrest included limitations in operative exposure and instrumentation, inadequate perfusion technology, and most importantly, inability to provide myocardial protection and ventricular decompression. The recent development of an endovascular system that achieves cardiopulmonary bypass and cardioplegic arrest has enabled the surgeon to perform various cardiac procedures using a minimally invasive approach [4-6, 12, 13].

an alternative to the conventional approach [7-9, 14-17]. Many investigators have reported the relative safety of coronary revascularization without cardiopulmonary bypass if performed properly by an experienced surgeon [9, 17-19]. Potential advantages of this technique include decreased transfusion requirements, reduced incidence of low cardiac output syndrome, shorter hospitalization, and decreased cost [9, 17-19]. Certain patients in particular, including those with compromised left ventricular function, women, the elderly, and those requiring a reoperation, may benefit from this approach [18]. Reported perioperative morbidity and mortality rates are low and graft patency rates satisfactory [9, 17-19]. Along with these advantages of coronary artery bypass grafting without cardiopulmonary bypass, there are benefits of a limited left anterior thoracotomy exposure [9, 16]. With the limited incision, the patient is more comfortable postoperatively, and pericardial and mediastinal adhesions are less likely to develop, thereby simplifying reoperations. Furthermore, the left internal mammary artery to left anterior descending artery anastomosis is facilitated by the proximity of the left anterior descending artery to the anterior thoracotomy [9, 16].

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Coronary Revascularization Without C a r d i o p u l m o n a r y Bypass Coronary artery bypass grafting without cardiopulmonary bypass, along with smaller incisions, has been proposed as Presented at The Second Utrecht MICABGWorkshop, Utrecht, the Netherlands, Oct 4-5, 1996. Address reprint requests to Dr Fann, Department of Cardiothoracic Surgery, Stanford University Medical Center, 300 Pasteur Dr, Stanford, CA 94305. © 1997 by The Society of Thoracic Surgeons Published by Elsevier Science Inc

Doctors Fann, Pompili, St. Goar, Burdon, and Reitz are consultants of Heartport, Inc. Doctor Stevens is a member of the Board of Directors of Heartport, Inc. Doctor Siegel is an employee of Heartport, Inc.

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MICABG F A N N ET AL PORT-ACCESS CARDIAC OPERATIONS

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exposure [17]. Hemodynamic instability from cardiac manipulation required to expose as a graft target the posterior descending branch of the right coronary artery necessitates the use of cardiopulmonary bypass.

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Coronary revascularization without cardiopulmonary bypass is not without pitfalls. The procedure is technically more challenging than with a still and bloodless field; however, the surgeon does have the option of using cardiopulmonary bypass should the need arise [7, 9, 16, 17]. Coronary revascularization without cardiopulmonary bypass may not be possible in some patients, and the results may not be as reproducible as the conventional approach [16]. In their series, Buffolo and colleagues [16] excluded patients with left main disease and those with combined valvular and coronary diseases. Also, a small left anterior descending artery and a small left internal m a m m a r y artery contribute to the difficulty of this technique [17]. Although some surgeons have found occlusion of left anterior descending artery during the anastomosis not to be problematic [9], it is of concern should the patient develop hemodynamic instability or arrhythmias during the procedure. Using this technique, Calafiore and associates [9] reported 1 patient who had kinking of the left internal m a m m a r y artery graft detected postoperatively, presumably as a result of lengthening of the skeletonized left internal m a m m a r y artery. Therefore, a technically satisfactory result depends not only on the size of the coronary artery, but also on satisfactory hemodynamics during cardiac retraction for

Peters [20] originally proposed a method of minimally invasive cardiac operation with peripheral cardiopulmonary bypass using a novel aortic balloon catheter that could provide aortic occlusion, delivery of cardioplegia, and aortic root venting. This design was modified providing the basis for an effective peripheral endovascular system for cardiopulmonary bypass with cardioplegic arrest and myocardial protection (Endoaortic Clamp; Heartport, Inc, Redwood City, CA) [4-6, 11]. The portaccess system enables the surgeon to perform various open cardiac procedures using a less invasive approach and avoiding a standard median sternotomy. The endoaortic clamp is a triple-lumen catheter with an inflatable balloon at its distal end (Figs 1 and 2) [4-6, 11]. Cardioplegic solution is delivered in an antegrade fashion through a central lumen that extends to the tip; this lumen also acts as an aortic root vent after cardioplegia delivery. A second lumen is used as an aortic root pressure monitor. The third lumen allows for inflation of the aortic occlusion balloon. Proper positioning of the balloon is important as misplacement can result in aortic valve incompetence and left ventricular distention, unequal distribution of cardioplegic solution, occlusion of the arch vessels, or an inability to achieve cardiac arrest. Fluoroscopy and transesophageal echocardiography are used to guide and confirm placement of the endoaortic clamp. Percutaneously placed through the jugular vein and passed into the pulmonary artery, the pulmonary artery venting catheter (Endopulmonary Vent; Heartport, Inc) further assists in ventricular decompression. In a series of acute and chronic canine studies, Stevens and associates [4, 5] demonstrated the feasibility of portaccess coronary artery bypass grafting. Experimentally, the internal m a m m a r y artery was easily accessed using video-assisted thoracoscopic dissection (Fig 3). Endovascular cardiopulmonary bypass using a balloon catheter was effective in arresting and protecting the heart, allowing internal m a m m a r y artery to coronary artery anastomosis in a still and bloodless field. After deflation of the endoaortic occlusion catheter, all animals were successfully weaned from cardiopulmonary bypass. The mean aortic clamp time was 61 minutes, and the mean cardiopulmonary bypass time was 104 minutes. The early patency rate was 93% (25/27). This approach thus duplicated the advantages of traditional open-chest coronary revascularization, while using a less invasive approach than conventional median sternotomy. Although earlier efforts were directed at a closed chest technique using multiple ports and a stereomicroscope (true port-access), an alternative mini-anterior mediastinotomy was later used to achieve better visualization and access (Fig 3) [4]. Clinically, 10 patients (8 men and 2 women) underwent

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a feasibility trial of port-access coronary revascularization with cardioplegic arrest, grafting the left internal mammary artery to the left anterior descending artery, at Stanford University between April 1995 and February 1996 [6]. Similar to the laboratory experience, because of early technical difficulties with a true port-access technique and prolonged operative times, a mini-anterior thoracotomy approach through the bed of the fourth costal cartilage was adopted. The left internal mammary artery was harvested using video-assisted thoracoscopy. A soft tissue retractor (Heartport, Inc), varying in size from 6 cm to 9 cm in diameter, was seated, thereby providing a working port. In all cases, the endoaortic clamp functioned well achieving cardioplegic arrest and adequate myocardial protection. There was no operative mortality; however, 3 patients did require conversion to open procedure because of early thrombosis (n ~- 1), kinking of the internal mammary pedicle at the pericardial edge (n = 1), and trauma to the distal internal mammary artery during dissection (n = 1). In the 7 patients who did not require conversion to an open procedure, the mean hospital stay ranged from 2 to 6 days. At follow-up, all patients are alive, and 9 of 10 patients have functioning grafts. Because the arrested heart allows for better exposure of the lateral and posterior aspects of the heart, it was theorized that the port-access approach would permit multivessel revascularization. Recently, multivessel coronary artery bypass grafting was successfully performed experimentally [21] and clinically. Fann and coworkers [21] performed two-vessel coronary revascularization in 5 dogs using an arterial conduit as a T graft from the internal mammary artery, grafting the obtuse marginal and left anterior descending arteries. Clinically, twovessel coronary artery bypass grafting has been performed, grafting the left internal mammary artery to the left anterior descending artery and a radial artery T graft to the obtuse marginal artery. The port-access system

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Fig 2. Circuit diagram of the endovascular cardiopulmonary bypass system. Femoral venous drainage is assisted by an in-line centrifugal pump. Aortic root and pulmonary artery vent lines are controlled by roller pumps. A line is split off the arterial catheter to provide blood cardioplegia, which is delivered antegrade through the central lumen of the endoaortic clamp. (KAVD = kinetic-assisted venous drainage.) (Reproduced with permission from The Society of Thoracic Surgeons [Ann Thorac Surg 1996;62:43544113

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permits rotation of the heart to fully expose the lateral and posterior vessels. The clinical results of multivessel coronary revascularization are being reviewed.

Port-Access Mitral V a l v e Procedures Video-assisted thoracoscopy has been employed as an adjunct in a minimally invasive approach to mitral valve surgical procedures [22]. Lin and associates [22] reported two patients who underwent video-assisted mitral valve procedure for mitral regurgitation using a limited right anterior thoracotomy and peripheral cardiopulmonary

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Fig 3. Anastomosis performed under direct vision through an anterior port. The fourth intercostal space port is extended medially and the soft tissues are retracted to create a port.

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bypass with hypothermic fibrillatory arrest. Both patients recovered and had an uneventful postoperative course. Port-access technology has been extended to procedures on the mitral valve. Using this approach, Pompili and colleagues [11] performed mitral valve replacements in 11 dogs acutely and 4 dogs chronically. An oval port (measuring 35 × 17 ram) was placed in the fifth intercostal space for access, and a smaller port was placed in the fourth intercostal space for the thoracoscope. After pericardiotomy and left atriotomy, mitral valve replacement was performed with a mechanical prosthesis. Myocardial protection was achieved using a combination of antegrade and retrograde cardioplegia delivery; cardioplegia was delivered retrogradely through a percutaneously placed catheter directed into the coronary sinus (Endosinus catheter; Heartport, Inc) [11]. All animals were weaned from cardiopulmonary bypass after removal of air with the assistance of the aortic root vent. The aortic cross-clamp time averaged 68 minutes and the cardiopulmonary bypass time averaged 114 minutes. Mitral valve replacement and rnitral valve reconstruction are thus possible using the port-access system. The results of clinical trials of mitral valve procedures (repair or replacement) are forthcoming.

Preservation of Ventricular Function With PortAccess Cardiac Surgical Procedures Schwartz and associates [12, 13] recently analyzed the effectiveness of the port-access system in providing myocardial protection during aortic clamping. Based on indices of left ventricular contractility, including maximal elastance, end-diastolic stroke work, preload recruitable stroke work, and stroke work end-diastolic length relationship, no difference was detected between animals that underwent cardiopulmonary bypass using the portaccess system and those undergoing conventional cardiopulmonary bypass [12]. In a similar analysis, the safety of port-access mitral valve replacement was documented experimentally [13]. After port-access mitral valve replacement and weaning from cardiopulmonary bypass, there was good recovery of left ventricular function at 30 and 60 minutes after cardiopulmonary bypass. Preload recruitable stroke work returned to 96% and 85 % of baseline at 30 and 60 minutes after conclusion of cardiopulmonary bypass. Transesophageal echocardiography demonstrated normal prosthetic valve function and normal regional and global ventricular wall motion. By providing adequate delivery of cardioplegic solution with prompt cardiac arrest and myocardial cooling, the port-access system achieved effective myocardial protection [12, 13]. Summary Coronary revascularization without cardiopulmonary bypass through median sternotomy and limited thoracotomy has been proposed as an alternative to the conventional approach. In an attempt to minimize the invasiveness of cardiac operations, many surgeons have reported the

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relative safety of coronary revascularization without cardiopulmonary bypass using a small anterior thoracotomy or mediastinotomy in selected patients. In spite of the potential advantages, including decreased transfusion requirements, reduced incidence of low cardiac output syndrome, shorter hospitalization, and lower cost, coronary artery bypass grafting without cardiopulmonary bypass is technically more challenging, may have limited applications, and may be associated with less reproducible results. An endovascular system for cardiopulmonary bypass and cardioplegic arrest has been developed using peripheral cardiopulmonary bypass and a transfemoral placement of an endoaortic balloon catheter. This system facilitates endovascular aortic occlusion, delivery of cardioplegic solution, and left ventricular decompression, thereby enabling the surgeon to effectively perform various cardiovascular procedures using a less invasive approach. Port-access coronary artery bypass grafting and mitral valve procedures have been performed successfully in both experimental and clinical settings.

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