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Type A Aortic Dissection With Hemi Arch Replacement
A 53-year-old man with a history of hypertension and coronary artery disease, status postcoronary artery bypass grafting x3 with left internal mammary artery (LIMA) to left anterior descending artery, saphenous vein graft (SVG) to the first obtuse marginal branch, and SVG to the right coronary artery, presented to the emergency room with severe substernal and back pain. Computed tomography (CT) scan revealed an acute type A aortic dissection with mild dilatation of the ascending aorta. Transesophageal echocardiogram (TEE) demonstrated central aortic valve regurgitation. There was no evidence of malperfusion. Pulses were equal in all four extremities.
General anesthesia was induced, and the patient received invasive hemodynamic monitoring with a right heart catheter and bilateral arterial lines. This is important particularly if the axillary artery is cannulated for arterial inflow since the right radial pressure is falsely elevated when the patient is on cardiopulmonary bypass (CBP). An activated clotting time > 480 seconds indicates adequate anticoagulation before initiating CBP. Aminocaproic acid was used. Near infrared spectroscopy (Somanetics Corp., Troy, MI) was also used to confirm symmetric cerebral perfusion during the operation. The patient’s head was packed in ice once cooling began.
An infraclavicular incision was performed to expose the right axillary artery. The right axillary artery was cannulated using a side graft. Next, cannulation of the right atrium and the coronary sinus were performed. The patient was placed on cardiopulmonary bypass and was cooled to 24°C (minimum cooling time is 30 minutes). During cooling, the innominate vein as well as the two SVGs were mobilized. The LIMA was identified and clamped with a bulldog clamp. The aorta was then cross-clamped 2 cm proximal to the innominate artery, and electromechanical arrest was achieved with cardioplegia given in a retrograde fashion. A left ventricular vent was inserted. A transverse aortotomy was performed 2 cm above the sinotubular junction. An aortic island with the 2 vein grafts attached was prepared. There was an intimal tear 1 cm above the sinotubular junction. The dissection extended proximally in the right and noncoronary sinuses. The aortic root was mobilized by dividing its attachments to the pulmonary artery and dome of the left atrium. Three 4-0 pledgeted polypropylene sutures were placed at the tip of the three commissures and secured, effectively resuspending the aortic valve. The integrity of the aortic valve was easily assessed by pulling the commissural sutures tight, securing them in the operative field, and applying suction on the aortic valve.
Clot in the false lumen of the dissected aortic root was gently removed. Teflon felt was fashioned corresponding to the size and shape of the dissected sinuses and was placed between the intima and adventitia of the noncoronary and right coronary sinuses respectively. BioGlue (CryoLife, Inc, Atlanta, Ga) was used to approximate the intima and adventitia to the felt forming a neomedia. This technique eliminates the dissected space, increases the strength of the dissected tissue, and helps to prevent bleeding from the anastomosis of the aortic graft to the root. Additional 4-0 polypropylene pledgeted sutures were used to secure the resuspended aortic valve. Next, the aorta was trimmed leaving 1 cm of residual aorta above the sinotubular junction.
Hypothermic circulatory arrest was initiated at 24°C. The aortic arch was inspected. There was no secondary tear in the arch. The innominate artery was mobilized, and antegrade cerebral perfusion (ACP) was initiated via the right axillary artery by gently clamping the innominate artery. A second balloon tipped cannula was placed in the left carotid artery for further delivery of ACP. The ACP flow was established at 8-10 cc/kg per minute with a perfusion pressure between 50-70 mm Hg, a temperature of 24°C, and a hematocrit of 25%. Alpha stat was used for pH monitoring. Cerebral perfusion was monitored with oximetry.
The aortic arch was transected in a beveled fashion. Neomedia was created in the dissected arch using the previously described technique. A 26 mm graft was anastomosed to the arch with 4-0 polypropylene suture in a continuous fashion. Teflon felt was used to reinforce the anastomosis. In addition, 4-0 polypropylene pledgeted sutures were used liberally to prevent bleeding. The cannula to the left carotid was removed prior to completing this anastomosis. Then, the clamp on the innominate artery was removed. The graft was de-aired and clamped and systemic rewarming began, keeping a gradient of 10°C between the blood and the patient’s core temperature.
Subsequently, the graft was trimmed to the appropriate length, and the proximal anastomosis between the graft and aortic root was fashioned with 4-0 polypropylene suture. This anastomosis was reinforced with Teflon felt and liberal use of 4-0 polypropylene pledgeted sutures. The clamp was removed, and the heart was de-aired under TEE guidance. The left ventricular vent was removed. CPB was discontinued at 35°C. The chest was closed in standard fashion after hemostasis was achieved. The TEE showed that the aortic valve was competent and the right and left ventricular functions were normal. The patient had an uneventful hospital course and was discharged home on postoperative day seven.
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