Thomas A. Burdon

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.

First report of the port access international registry

BACKGROUND For minimally invasive cardiac operations to be widely applicable, the risks must be equivalent to those of standard open-chest operations. This study analyzed the outcomes of patients recorded in the multicenter Port Access (PA) International Registry to establish operative risks. METHODS Data were analyzed for intent to treat in 583 patients who underwent PA coronary artery bypass grafting (CABG), 184 who underwent PA mitral valve replacement, and 137 who underwent PA mitral valve repair at 121 centers. RESULTS Port Access was attempted in 1,063 patients and completed in 1,004 (94%). The operative mortality rate was 1% for PA CABG, 3.3% for PA mitral valve replacement, and 1.5% for PA mitral valve repair. Perioperative morbidity was low in all categories: stroke = 1.1% to 3.6%, myocardial infarction = 0 to 1%, primary procedure reoperation = 0 to 0.7%, renal failure = 0.2% to 0.7%, multiorgan failure = 0 to 0.5%, and atrial fibrillation = 5% to 7.3%. CONCLUSIONS Data on 1,063 patients from 121 centers demonstrate that PA CABG and PA mitral valve operations can be performed safely, with morbidity and mortality rates similar to those associated with open-chest operations. Further studies are indicated to establish the long-term efficacy of this method and to analyze its effect on recovery time.

Beating Heart Catheter-Based Edge-to-Edge Mitral Valve Procedure in a Porcine Model Efficacy and Healing Response

Background—Surgical edge-to-edge repair has been used in the treatment of mitral regurgitation. We evaluated the ability of a catheter-delivered clip (Evalve, Inc) to achieve edge-to-edge mitral valve approximation without cardiopulmonary bypass and the healing response of this technique. Methods and Results—Twenty-one pigs underwent general anesthesia and left thoracotomy. A 10F flexible delivery catheter with a clip was placed into the left atrium. With echocardiographic and fluoroscopic guidance, the clip grasped and approximated the mid portion of the anterior and posterior leaflets. After a double orifice had been confirmed, the clip was detached and the catheter withdrawn. All animals survived and had successful clip placement. Three animals were euthanized at 4 weeks, 9 at 12 weeks, 1 at 17 weeks, 7 at 24 weeks, and 1 at 52 weeks. The clip was well positioned, with leaflet approximation in all animals except 1, in which the clip separated from the posterior leaflet at 4 weeks without affecting valve function. The clip was modified and implanted in 4 pigs; all were intact at 12 to 24 weeks. Scanning electron microscopy showed clip encapsulation with complete endothelialization. Mitral stenosis and thromboembolism did not develop. Two animals developed endocarditis (1 at 12 weeks and 1 at 17 weeks). Progressive healing occurred in all other animals. Conclusions—Edge-to-edge mitral valve approximation can be successfully and reliably achieved with a catheter-delivered clip without cardiopulmonary bypass, resulting in durable healing. The success of this device supports the development of a percutaneous catheter-based system for mitral valve repair.

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.

Influence of three-dimensional vision on surgical telemanipulator performance

Background: Different viewing conditions (two- and three-dimensional National Television Standard Committee [2D-NTSC and 3D-NTSC] and two-dimensional high-definition television [2D-HDTV]) on telemanipulator performance were evaluated. Methods: Six taskes were performed by 15 endoscopic surgeons using the daVinci telemanipulation system. Performance time and errors were measured. Encoder data from the system were used for kinematic analysis of motion. A self-evaluation questionnaire regarding performance under various viewing conditions was obtained. Results: Resolution was better with 2D-HDTV. The estimate of relative distance was not influenced by the different visualization systems. Motor skill tasks were performed faster with binocular vision (3D-NTSC) than with monocular vision (2D-NTSC, 2D-HDTV). For both 2D settings, the deceleration phase of motion was prolonged (p < 0.05 vs 3D). Peak velocity was reduced with 2D-HDTV as compared with 3D-NTSC (p = 0.01). The surgeons tended to favor the 3D system despite their use of 2D systems in their own practice. Conclusions: Three-dimensional vision enhances telemanipulator performance as compared with a 2D system at the same or higher level of resolution. Because it allows faster and more precise movement, future surgical systems should focus on 3D visualization.

Port-access cardiac operations with cardioplegic arrest

BACKGROUND A less invasive approach to cardiac surgery has been propelled by recent advances in video-assisted 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 triple-lumen 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 demonstrated 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.

Endoscopic computer-enhanced beating heart coronary artery bypass grafting

BACKGROUND Telemanipulation systems have enabled coronary revascularization on the arrested heart. The purpose of this study was to develop a technique for computer-enhanced endoscopic coronary artery bypass grafting on the beating heart. METHODS The operation was performed using the daVinci telemanipulation system. Through three ports, the left internal thoracic artery was harvested in 10 mongrel dogs (30 to 35 kg) using single right-lung ventilation and CO2 insufflation. Through a fourth port an articulating stabilizer, manipulated from a second surgical console, was inserted to stabilize the heart. The left anterior descending artery was snared using silicone elastomer slings anchored in the stabilizer cleats and the graft to coronary artery anastomosis was performed. RESULTS In 7 of 10 dogs, total endoscopic beating heart bypass grafting, cardiac stabilization, arteriotomy, and arterial anastomosis were performed using computer-enhanced technology. Endoscopic stabilization and temporary left anterior descending artery occlusion were well tolerated. All grafts were patent although minor strictures were found in 2. In 3 dogs, the procedure could not be completed (1 ventricular arrhythmia, 1 left atrial laceration, and 1 right ventricular outflow tract compression). CONCLUSIONS Endoscopic beating heart coronary artery bypass grafting is possible in a canine model using a computer-enhanced instrumentation system and articulating stabilization.

Health status after transcatheter aortic valve replacement in patients at extreme surgical risk: Results from the CoreValve U.S. Trial

OBJECTIVES The purpose of this study was to characterize health status outcomes after transcatheter aortic valve replacement (TAVR) with a self-expanding bioprosthesis among patients at extreme surgical risk and to identify pre-procedural patient characteristics associated with a poor outcome. BACKGROUND For many patients considering TAVR, improvement in quality of life may be of even greater importance than prolonged survival. METHODS Patients with severe, symptomatic aortic stenosis who were considered to be at prohibitive risk for surgical aortic valve replacement were enrolled in the single-arm CoreValve U.S. Extreme Risk Study. Health status was assessed at baseline and at 1, 6, and 12 months after TAVR using the Kansas City Cardiomyopathy Questionnaire (KCCQ), the Short Form-12, and the EuroQol-5D. The overall summary scale of the KCCQ (range 0 to 100; higher scores = better health) was the primary health status outcome. A poor outcome after TAVR was defined as death, a KCCQ overall summary score (OS) <45, or a decline in KCCQ-OS of 10 points at 6-month follow-up. RESULTS A total of 471 patients underwent TAVR via the transfemoral approach, of whom 436 (93%) completed the baseline health status survey. All health status measures demonstrated considerable impairment at baseline. After TAVR, there was substantial improvement in both disease-specific and generic health status measures, with an increase in the KCCQ-OS of 23.9 points (95% confidence interval [CI]: 20.3 to 27.5 points) at 1 month, 27.4 points (95% CI: 24.2 to 30.6 points) at 6 months, 27.4 points (95% CI: 24.1 to 30.8 points) at 12 months, along with substantial increases in Short Form-12 scores and EuroQol-5D utilities (all p < 0.003 compared with baseline). Nonetheless, 39% of patients had a poor outcome after TAVR. Baseline factors independently associated with poor outcome included wheelchair dependency, lower mean aortic valve gradient, prior coronary artery bypass grafting, oxygen dependency, very high predicted mortality with surgical aortic valve replacement, and low serum albumin. CONCLUSIONS Among patients with severe aortic stenosis, TAVR with a self-expanding bioprosthesis resulted in substantial improvements in both disease-specific and generic health-related quality of life, but there remained a large minority of patients who died or had very poor quality of life despite TAVR. Predictive models based on a combination of clinical factors as well as disability and frailty may provide insight into the optimal patient population for whom TAVR is beneficial. (Safety and Efficacy Study of the Medtronic CoreValve® System in the Treatment of Symptomatic Severe Aortic Stenosis in High Risk and Very High Risk Subjects Who Need Aortic Valve Replacement; NCT01240902).

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.

Establishment of a transcatheter aortic valve program and heart valve team at a Veterans Affairs facility.

BACKGROUND The US Food and Drug Administration recently approved a transcatheter aortic valve for patients for whom open heart surgery is prohibitively risky. METHODS A multidisciplinary heart valve team partnered with administration to launch a transcatheter aortic valve replacement (TAVR) program. Clinical registries were used to show robust valve caseloads and outcomes at our Veterans Affairs (VA) facility and to project future volumes. A TAVR business plan was approved by the VA leadership as part of a multiphase project to upgrade and expand our surgical facilities. RESULTS The heart valve team completed a training program that included simulations and visits to established TAVR centers. Patients were evaluated and screened through a streamlined process, and the program was initiated successfully. CONCLUSIONS Establishing a TAVR program at a VA facility requires a multidisciplinary team with experience in heart valve and endovascular therapies and a supportive administration willing to invest in a sophisticated infrastructure.