Minimally invasive mitral valve surgery without aortic cross-clamping.

Minimally invasive mitral valve surgery (MIMVS)—developed to decrease surgical trauma, postoperative pain, recovery time, and complications—has been applied to several different approaches to the mitral valve. The partial lower sternotomy or right parasternal approach does preserve all or part of the sternum, but it is essentially the same operation as the transsternal procedure. The Heart Port system was developed by Stanford University and New York University Hospital in 1994.1,2 When using this system, the surgeon approaches the heart through a right thoracotomy in the 3rd or 4th intercostal space. Cardiopulmonary bypass is initiated by means of special cannulae in the femoral artery and vein. Aortic occlusion is accomplished either with a balloon catheter inserted through the arterial cannula or with a long vascular (Chitwood) clamp3 in the 2nd intercostal space. Cardioplegic solution is administered through the end of the balloon catheter, through a coronary sinus catheter, or directly into the ascending aorta. The Heart Port procedure was initially done under direct vision, but it has evolved into a video-assisted or robotic technique. Although excellent results have been attained,2,4 setup and operative times can be long and the learning curve difficult. The initial outlay for equipment is significant, which increases the cost per case. At the Vanderbilt Heart & Vascular Institute, we have used a simplified MIMVS technique that entails hypothermic fibrillatory arrest and direct vision through a 5- to 6-cm anterior right thoracotomy in the 4th intercostal space. During the induction of anesthesia, we place a single-lumen endotracheal tube, arterial pressure-monitoring catheter, pacing Swan-Ganz pulmonary artery catheter, transesophageal echocardiographic probe, and external defibrillator (Zoll) pads. After systemic heparinization, we cannulate the femoral artery with an 18F or 16F straight cannula over a guidewire (Edwards Lifesciences, LLC; Irvine, Calif). If the femoral artery is not usable due to atherosclerotic disease, the same cannula is used in the right axillary artery. Venous drainage is performed through a branch of the saphenous bulb by using a long CardioVations 25F cannula (Edwards Lifesciences) positioned through the right atrium and approximately 2 cm up the superior vena cava. The patient is placed on cardiopulmonary bypass with vacuum-assisted drainage and is systemically cooled to 28 °C. If fibrillatory arrest has not occurred spontaneously, it is induced by means of rapid ventricular pacing through the pacing pulmonary artery catheter. The left atrium is immediately opened through the intra-atrial groove, and a suction catheter is placed through the mitral valve to decompress the left ventricle. A sump sucker is placed in the left pulmonary veins to keep the operative field clear, and carbon dioxide is insufflated into the chest cavity to displace air. Rewarming is started while the surgeon ties the commissural ring or valve sutures and oversews the left atrial appendage. If cardioversion occurs spontaneously, the mitral valve is kept incompetent to prevent air emboli; otherwise, cardioversion is accomplished with the Zoll pads just before left atrial closure. A catheter is kept across the mitral valve, and blood is allowed to fill the left ventricle and atrium. The catheter is removed and the left atrial suture tied.5 Myocardial protection is accomplished by cooling to 28 °C in order to decrease myocardial oxygen consumption, while maintaining perfusion pressure at 50 to 70 mmHg. Endomyocardial coronary perfusion is maintained by keeping the ventricles empty and decompressed. The increase in stroke rate that has been associated with beating or fibrillating MIMVS6 is probably due to air emboli, because there is very little manipulation of the ascending aorta or arch. Insufflation of saline into the left ventricle to test the mitral valve should not be done: this can cause air emboli by pushing air into the unclamped aorta. The surgeon should, rather, test the valve by retracting the aortic root, thereby inducing enough aortic insufficiency to fill the ventricle. While the heart is open, carbon dioxide is continuously flushed into the chest cavity to displace air. Aortic pressure is kept above 50 mmHg to keep the aortic valve closed. Aortic insufficiency greater than mild is a contraindication to this procedure, due to the likely exposure of blood in the operative field. In addition to mitral valve replacement or repair, this technique is excellent for atrial septal defect or patent foramen ovale closure, tricuspid valve repair or replacement, the maze procedure, and removal of atrial tumors. This technique facilitates MIMVS in patients with previous coronary artery bypass surgery who have a patent left internal mammary artery graft, because the mammary artery cannot be occluded to perform cardioplegic arrest. The advantage of the procedure is its simplicity, which eliminates costly equipment, enables quick setup and short operative times, and decreases the learning curve.7 The operative mortality rate has remained less than 3% even in high-risk groups.7 Major complications are also low: there have been no wound infections, and neurologic events have occurred at a rate of less than 3%.7 The initial outlay for equipment is under $50,000; when decreased operative and postoperative times are considered, the cost per procedure is equal to or lower than the cost of standard transsternal surgery. At Vanderbilt Hospital, over 90% of isolated mitral valve surgery is performed using this technique, and many of our mitral valve patients requiring concomitant coronary artery bypass undergo this procedure in the hybrid room with coronary stenting followed by MIMVS.