Mitral Valve Surgery

In 1997, two independent groups reported the first robotically assisted mitral valve repair.^{[45] [46]} In November 2002, the FDA approved the use of robot-assisted surgery in performing mitral valve repairs. Mitral valves repair, initially done through mini-thoracotomy incisions, could be done completely with a closed chest. However, mitral valve replacements may still require a small thoracotomy to introduce the new prosthetic valve.

Anesthetic Implications for Mitral Valve Surgery

Mitral valve surgery employing robotic devices is being done at a few cardiac centers in the United States and Europe. The anesthetic techniques and other relevant considerations have been described previously.^[47] Patients are initially evaluated by cardiac catheterization to estimate the degree of coronary artery stenosis and to assess valve function. Severe mitral regurgitation is a mechanical problem that requires surgery for cure. Most patients are medically treated with afterload reducers, such as angiotensin-converting enzyme (ACE) inhibitors if they are hypertensive. An enlarged left atrium is often susceptible to atrial fibrillation. Patients with persistent atrial fibrillation may be taking anticoagulants concomitantly with therapy for rate control. Chronic elevation in left atrial pressure may manifest with pulmonary hypertension, which may be further exacerbated by obstructive lung disease. Severe pulmonary hypertension renders a patient unsuitable for robotic surgery.^[48]

Patients are provided with a large peripheral intravenous line. Light sedation with midazolam and local anesthesia is offered before the placement of bilateral radial arterial lines. The patient is routinely monitored with ECG leads II and V₅ , pulse oximetry and a right radial artery pressure line to exclude endovascular aortic balloon misplacement. Modern ECG monitors can provide automatic ST segment analysis for the detection of ischemia. After ample oxygenation, the patient is anesthetized with a combination of midazolam, fentanyl, and isoflurane. On muscle relaxation, the trachea is intubated with a double-lumen endotracheal tube ( Table 66-1 ). Proper tube position is confirmed by bronchoscopy. A TEE

TABLE 66-1 -- One-lung ventilation strategy

Use FIO2 = 1.0.

Begin one-lung ventilation with pressure control ventilation, maintaining a plateau pressure of <30 cm H2 O.

Adjust the respiratory rate so that PaCO2 approaches 40 mm Hg.

Check arterial blood gas pressure.

Apply continuous positive airway pressure to nonventilated lung.

Apply positive end-expiratory pressure to ventilated lung.

probe is inserted to assess heart and valve function and to guide central line placement. A mid-esophageal, bicaval view at 90 degrees is used for guidance in positioning the superior vena cava (SVC) and inferior vena cava (IVC) cannulas ( Fig. 66-7 ). Initially, a left, 9-Fr introducer catheter is inserted by means of the Seldinger technique, and an 8-Fr pulmonary artery catheter is floated into the pulmonary artery. Next, the right neck is prepared

Figure 66-7 A, Ultrasound image of the superior vena cava cannula. B, Ultrasound image of a bicaval view depicting the inferior vena cava containing a J guidewire. Both views are helpful in correctly placing cardiopulmonary bypass venous cannulas.

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After the patient's pelvis is positioned supine and the right shoulder is tilted 30 degrees to the left, transcutaneous defibrillation and pacing pads are applied. The surgeon can then determine proper location for port access, which may vary according to a patient's body habitus.

After the right femoral vessels are exposed and left-sided, single-lung ventilation is established, a right-sided mini-thoracotomy incision is made. The heart is exposed after a pericardial opening is made. The pericardium is anchored open to the chest wall by two percutaneous stay sutures. After the patient is heparinized based on an activated clot time (ACT)-guided protocol, the femoral vein and artery are cannulated in anticipation of femoral-femoral cardiopulmonary bypass. First, the femoral vein is cannulated, and a 21-Fr cannula is placed over a guidewire and passed into the IVC-RA junction with the aid of TEE. One end hole and 12 side holes resist collapse under the high negative pressure that is created by augmented venous return pumps. Likewise, the femoral artery is cannulated with a 24-Fr cannula, and cardiopulmonary bypass is initiated with venous drainage from the femoral and jugular veins. Anterograde and retrograde cardioplegia cannulas are placed. Some surgical teams prefer to cannulate the ascending aorta using a Heartport Straight-shot.^[48] A transthoracic aortic cross-clamp is passed percutaneously through the right axilla and applied to the ascending aorta. The robotic arms are engaged through their respective trocars lateral to the mini-thoracotomy incision while the camera arm passes directly through the thoracotomy incision. The left atrium can be entered for mitral valve repair or replacement.

Before terminating cardiopulmonary bypass, TEE is used to evaluate the function of the mitral valve, residual valvular regurgitation and to confirm the disappearance of intracardiac air. The anterior leaflet of the mitral valve is further inspected for systolic anterior motion.

Patient selection is important for optimal results. Table 66-2 lists the risk factors that make patients unsuitable candidates for robotic mitral valve surgery.