William S. Peters

Port-access coronary artery bypass grafting: A proposed surgical method

Minimally invasive surgical methods have been developed to provide patients the benefits of open operations with decreased pain and suffering. We have developed a system that allows the performance of cardiopulmonary bypass and myocardial protection with cardioplegic arrest without sternotomy or thoracotomy. In a canine model, we successfully used this system to anastomose the internal thoracic artery to the left anterior descending coronary artery in nine of 10 animals. The left internal thoracic artery was dissected from the chest wall, and the pericardium was opened with the use of thoracoscopic techniques and single lung ventilation. The heart was arrested with a cold blood cardioplegic solution delivered through the central lumen of a balloon occlusion catheter (Endoaortic Clamp; Heartport, Inc., Redwood City, Calif.) in the ascending aorta, and cardiopulmonary bypass was maintained with femorofemoral bypass. An operating microscope modified to allow introduction of the 3.5x magnification objective into the chest was positioned through a 10 mm port over the site of the anastomosis. The anastomosis was performed with modified surgical instruments introduced through additional 5 mm ports. In the cadaver model (n = 7) the internal thoracic artery was harvested and the pericardium opened by means of similar techniques. A precise arteriotomy was made with microvascular thoracoscopic instruments under the modified microscope on four cadavers. In three other cadavers we assessed the exposure provided by a small anterior incision (4 to 6 cm) over the fourth intercostal space. This anterior port can assist in dissection of the distal internal thoracic artery and provides direct access to the left anterior descending, circumflex, and posterior descending arteries. We have demonstrated the potential feasibility of grafting the internal thoracic artery to coronary arteries with the heart arrested and protected, without a major thoracotomy or sternotomy.

Minimally invasive cardiopulmonary bypass with cardioplegic arrest: A closed chest technique with equivalent myocardial protection☆☆☆★★★♢

Thoracoscopic cardiac surgery is presently under intense investigation. This study examined the feasibility and efficacy of closed chest cardiopulmonary bypass and cardioplegic arrest in comparison with standard open chest methods in a dog model. The minimally invasive closed chest group (n = 6) underwent percutaneous cardiopulmonary bypass and cardiac venting, as well as antegrade cardioplegic arrest through use of a specially designed percutaneous endovascular aortic occluder and cardioplegic solution delivery system. The control group (n = 6) underwent standard sternotomy and conventional open chest cardiopulmonary bypass, aortic crossclamping, and antegrade cardioplegia. Ischemic arrest time was 1 hour in each group. Ventricular pressures and sonomicrometer segment lengths were recorded before bypass and at 30 and 60 minutes after bypass. Left ventricular function did not differ significantly between the two groups, as demonstrated by measurements of elastance and end-diastolic stroke work. Also, the preload recruitable work area was 69% and 60% of baseline at 30 and 60 minutes after bypass in the minimally invasive group versus 65% and 62% in the conventional control group (p = not significant); the stroke work end-diastolic length relationship was 78% and 71% of baseline in the minimally invasive group at these intervals versus 77% and 74% in the conventional control group (p = not significant). Myocardial temperatures were similar throughout bypass in the two groups, and ultrastructural examination of prebypass and postbypass biopsy specimens showed no differences between groups. These results demonstrate that minimally invasive cardiopulmonary bypass with cardioplegic arrest is as feasible, safe, and effective as conventional open chest cardiopulmonary bypass. Thus current technology may allow wider clinical application of closed chest cardiac surgery.

Port-access mitral valve replacement in dogs

OBJECTIVE The objective was to assess mitral valve replacement in a minimally invasive fashion by means of port-access technology. METHODS Fifteen dogs, 28 +/- 3 kg (mean +/- standard deviation), were studied with the port-access mitral valve replacement system (Heartport, Inc., Redwood City, Calif.). Eleven dogs underwent acute studies and were sacrificed immediately after the procedure. Four dogs were allowed to recover and then were sacrificed 4 weeks after operation. Cardiopulmonary bypass was conducted by femoral cannulation with an endovascular balloon catheter for aortic occlusion, root venting, and antegrade delivery of cardioplegic solution. Catheters were inserted in the jugular vein for pulmonary artery venting and retrograde delivery of cardioplegic solution. Through the oval port, a prosthesis (St. Jude Medical, Inc., St. Paul, Minn., or CarboMedics, Inc., Austin, Texas) was inserted through the left atrial appendage and secured to the anulus with sutures. Deairing was performed. RESULTS Cardiopulmonary bypass duration was 114 +/- 24 minutes and aortic crossclamp time was 68 +/- 14 minutes. All animals were weaned from cardiopulmonary bypass in sinus rhythm. Cardiac output and pulmonary artery occlusion pressure were unchanged (2.8 +/- 0.7 L/min and 7 +/- 3 mm Hg before operation vs 2.6 +/- 0.6 L/min and 9 +/- 4 mm Hg after operation). There was no mitral regurgitation according to left ventriculography in 13 of 15 dogs. In two dogs there was interference with prosthetic valve closure by residual native anterior leaflet tissue. Pathologic examination otherwise showed normal healing without perivalvular discontinuity. Microscopic studies showed no damage to the valve surfaces. Transthoracic echocardiography of the four dogs in the long-term study showed normal ventricular and prosthetic valve function 4 weeks after the operation. CONCLUSION Mitral valve replacement with a minimally invasive method has been demonstrated in dogs. A clinical trial is in progress.

Port-access coronary artery bypass with cardioplegic arrest: acute and chronic canine studies

BACKGROUND Our goal is to perform minimally invasive coronary artery bypass grafting without sacrificing the benefits of myocardial protection with cardioplegia. METHODS Twenty-three dogs underwent acute studies and 4 dogs underwent survival studies. The left internal mammary artery was taken down using a thoracoscope. Cardiopulmonary bypass was conducted via femoral cannulas and using an endovascular balloon catheter for ascending aortic occlusion, root venting, and delivery of antegrade blood cardioplegia. Pulmonary artery venting was achieved with a jugular vein catheter. An internal mammary artery-to-coronary artery anastomosis was performed using a microscope through a 10 mm port. RESULTS All animals were weaned from cardiopulmonary bypass in sinus rhythm without inotropes. Cardiopulmonary bypass duration was 104 +/- 28 minutes and aortic clamp duration was 61 +/- 22 minutes. Cardiac output and pulmonary artery occlusion pressure were unchanged. The internal mammary artery was anastomosed to the left anterior descending artery (25) or the first diagonal (2) with patency shown in 25 of 27. One dog in the survival study had a very short internal mammary artery pedicle under tension and was euthanized for excessive postoperative hemorrhage. Three weeks postoperatively the remaining dogs had angiographically patent anastomoses, normal transthoracic echocardiograms, and histologically normal healing and patent grafts. CONCLUSIONS Endovascular cardiopulmonary bypass using a balloon catheter is effective in arresting and protecting the heart to allow thoracoscopic internal mammary artery-to-coronary artery anastomosis.

Extracorporeal circulation for port-access cardiac surgery.

Minimally invasive techniques for cardiac surgery are a new approach in performing some cardiac operations. Minimally invasive surgery may minimize patient discomfort, length of stay in the hospital and postoperative rehabilitation. These procedures utilize a small thoracotomy for direct visualization of the heart. However, without the use of cardiopulmonary bypass, this approach is limited to some epicardial procedures such as coronary bypass grafting, where the heart rate is pharmacologically reduced. Port-access cardiac surgery is a new approach which provides all the benefits of minimally invasive surgery without sacrificing the advantages of cardiopulmonary bypass and myocardial preservation. Port-access cardiac surgery uses an anterior mediastinotomy and thoracic ports in conjunction with a specially designed set of endovascular catheters. These catheters provide a mode to arrest, preserve and vent the heart through an endoaortic occlusion balloon positioned in the ascending aorta, A pulmonary artery vent and coronary sinus cardioplegia catheter can also be used. These endovascular catheters, integrated with a modified heart-lung machine, provide complete cardiopulmonary support through extrathoracic cannulae inserted in a femoral artery and vein. Maintenance and monitoring of this endovascular cardiopulmonary bypass system requires the use of a kinetic pump in the venous drainage line to augment return to the heart-lung machine. Special guidelines and management parameters exist to optimize bypass with this catheter system. Using this system, port-access, minimally invasive surgery can be applied to a wider range of both epicardial and intracardiac procedures.

Extra-Aortic Balloon Counterpulsation An Intraoperative Feasibility Study

Background—Current methods of counterpulsation or ventricular assistance have significant vascular and limb complications. The aim of this study was to determine the safety and performance of a new method of non-blood–contacting counterpulsation using an inflatable cuff around the ascending aorta (extra-aortic balloon [EAB]). Methods and Results—In 6 patients undergoing first time off-pump coronary bypass surgery via sternotomy, the EAB was secured around the ascending aorta and attached to a standard counterpulsation console. At baseline and with 1:2 and 1:1 augmentation, hemodynamic and echocardiographic parameters of ventricular function and coronary flow were measured. High-intensity transient signals were measured using transcutaneous Doppler over the right common carotid artery. No complications occurred. With EAB there was no significant change in heart rate or blood pressure and no increase in high-intensity transient signals. There was a 67% increase in diastolic coronary blood flow (mean left-main diastolic velocity time integral 15.3 cm unassisted versus 25.1 cm assisted, P<0.05). Measurements with transesophageal echocardiography at baseline and with 1:1 counterpulsation demonstrated a 6% reduction in end-diastolic area (P=NS), a 16% reduction in end-systolic area (P<0.01), a 31% reduction in left ventricular wall stress (P<0.05), and a 13% improvement in fractional area change (P<0.005). Conclusions—EAB counterpulsation augments coronary flow and reduces left ventricular afterload. Further testing is warranted to assess the use of the EAB for chronic non-blood–contacting support of the failing heart.

Closed-Chest Cardiopulmonary Bypass and Cardioplegia: Basis for Less Invasive Cardiac Surgery

BACKGROUND We developed a method of closed-chest cardiopulmonary bypass to arrest and protect the heart with cardioplegic solution. This method was used in 54 dogs and the results were retrospectively analyzed. METHODS Bypass cannulas were placed in the right femoral vessels. A balloon occlusion catheter was passed via the left femoral artery and positioned in the ascending aorta. A pulmonary artery vent was placed via the jugular vein. In 17 of the dogs retrograde cardioplegia was provided with a percutaneous coronary sinus catheter. RESULTS Cardiopulmonary bypass time was 111 +/- 27 minutes (mean +/- standard deviation) and cardiac arrest time was 66 +/- 21 minutes. Preoperative cardiac outputs were 2.9 +/- 0.70 L/min and postoperative outputs were 2.9 +/- 0.65 L/min (p = not significant). Twenty-one-French and 23F femoral arterial cannulas that allowed coaxial placement of the ascending aortic balloon catheter were tested in 3 male calves. Line pressures were higher, but not clinically limiting, with the balloon catheter placed coaxially. CONCLUSIONS Adequate cardiopulmonary bypass and cardioplegia can be achieved in the dog without opening the chest, facilitating less invasive cardiac operations. A human clinical trial is in progress.

Port-access bilateral internal mammary artery grafting for left main coronary artery disease: canine feasibility study.

Abstract Background: To extend the applications of minimal access cardiac surgery, an endovascular cardiopulmonary bypass (CPB) system that allows cardioplegia delivery and cardiac venting was used to perform bilateral internal mammary artery (IMA) bypass grafting in six dogs. Methods: The left IMA (LIMA) was taken down thoracoscopically from three left lateral chest ports, followed by the right IMA (RIMA) from the right side. One left‐sided port was extended medially 5 cm with or without rib resection, to expose the pericardium. Both IMAs were divided and exteriorized through the left anterior mediastinotomy. Flow and pedicle length were satisfactory in all cases. Femoral‐femoral bypass was used and the heart arrested with antegrade delivery of cardioplegic solution via the central lumen of a balloon catheter inflated to occlude the ascending aorta. All anastomoses were made through the mediastinotomy under direct vision. In five studies the RIMA was attached to the left anterior descending artery (LAD) and the LIMA to the circumflex, and in one study the RIMA was tunneled through the transverse sinus to the circumflex and the LIMA was anastomosed to the LAD. All animals were weaned from CPB in sinus rhythm without inotropes. CPB duration was 108 ± 27 minutes (mean ± SD) and the clamp duration was 54 ± 10 minutes. Results: Preoperative and postoperative cardiac outputs were 2.9 ± 0.71/min and 2.4 ± 0.31/min, respectively (p = NS), and corresponding pulmonary artery occlusion pressures were 6 ± 3 mmHg and 7 ± 2 mmHg, respectively (p = NS). All 12 grafts were demonstrated to be fully patent. Postmortem examination revealed well aligned pedicles and correctly grafted target vessels. Conclusion: This canine model demonstrates the potential for a less invasive approach to the surgical management of left main coronary artery disease in humans.

Minimally Invasive Right Heart Operations: Techniques for Bicaval Occlusion and Cardioplegia ☆

Peripheral cardiopulmonary bypass with cardioplegia has facilitated minimally invasive coronary artery bypass grafting and mitral valve replacement. The cardiopulmonary bypass system was modified to allow bicaval occlusion for right heart operations. In 4 canine studies, three variants of bicaval cannulation techniques were successfully used for atrial septal defect repair via a right minithoracotomy.

Port-access cardiac surgery: a system analysis.

Cardiopulmonary bypass (CPB) has been established as safe and effective, and is essential to the performance of a variety of cardiac surgical procedures. A method of closed chest CPB with cardioplegia to facilitate thoracoscopic or video-assisted cardiac surgical procedures was first proposed in 1993. The essential components included femoral vein–femoral artery CPB, and a transfemoral ascending aortic balloon catheter which could occlude the ascending aorta and arrest the heart.1 A similar system was successfully tested in dogs.2 Pulmonary artery venting and retrograde coronary sinus cardioplegia, with respective catheters placed via the jugular veins, were also used in this system.3 The clinical aims of this system were to reduce patient discomfort, morbidity, and hospital costs, and to permit faster rehabilitation and better cosmetic results. Following the first procedure using the endovascular CPB system to allow minimally invasive, or port-access, coronary artery bypass grafting (CABG) at Stanford University Medical Center in April 1995,4 over 2200 cases world-wide have been performed. This includes multivessel CABG, mitral valve replacement and repair (MVR), right heart surgical procedures, and combined procedures.5 This paper presents the technique and functional data of the bypass system as used in the first 115 patients. In particular, the pressure and flow characteristics of the peripheral catheters in providing adequate systemic perfusion, cardioplegia and cardiac decompression are analysed. The safety and efficacy of the aortic balloon occlusion catheter is also examined. The surgical results have been reported elsewhere.4,5