Descending Thoracic Aortic Aneurysm Involving the Distal Arch
Descending thoracic aortic aneurysms often involve the distal aortic arch, or are associated with a distal arch that is calcified and severely atherosclerotic, making cross-clamping dangerous . In these situations we use the following technique.
(A) Distal arch descending thoracic aortic aneurysm with femoral artery perfusion.
(B) HCA and anastomosis to the distal arch.
(C) Selective cerebral perfusion.
(D) Reattachment of the left subclavian artery and completed repair.
Operation is carried out through a left thoracotomy in the 4th or 5th
intercostal space with the incision extended inferiorly across the
costochondral plate to improve exposure. The internal mammary artery
is usually preserved. The left femoral artery and vein are dissected
out in preparation for cannulation. The descending aorta is gradually
mobilized. Intercostal arteries are serially clamped and then
sacrificed when no changes in the SSEPs and MEPs develop. Care is
taken not to manipulate the distal arch adjacent to the left
subclavian artery. Cannulation for cardiopulmonary bypass is carried
out with a long perfusion catheter inserted via the femoral vein, and
positioned in the right atrium with the aid of a guide wire and
transesophageal echo monitoring. Occasionally the main pulmonary
artery is used for venous inflow. The left common femoral artery is
cannulated. Perfusion is begun gradually to avoid a rapid shift in
the perfusion patterns in the aorta that might dislodge atheromatous
debris. Once perfusion is established, care is exercised to avoid
manipulating the descending thoracic aorta, inasmuch as dislodged
debris would be carried retrograde toward the arch vessels and the
coronary arteries. During cooling and once ventricular fibrillation
has occurred, left ventricular distention is closely monitored
with transesophageal echo and pulmonary artery pressures. If there is
any sign of left ventricular dilatation, a vent is introduced into
the left ventricular apex or via the left atrium. After about 30 to
40 minutes of cooling, the esophageal temperature has usually
decreased to 11°C to 14°C, and the jugular venous saturation exceeds
95%. Femoral artery perfusion is discontinued.
The left ventricular vent is clamped, and the descending thoracic aorta is opened. A cuff of the underside of the aortic arch, extending inferiorly to the distal ascending aorta and superiorly to the margin of the left carotid artery, is fashioned. An attempt is made to preserve the recurrent laryngeal nerve. A graft is anastomosed to the native aorta with a running suture of 3-0 Prolene. Teflon felt is used, and the graft is invaginated within the aorta. The graft vessels are carefully aspirated. A perfusion cannula is then placed in the graft, and the arch vessels are de-aired, after which antegrade perfusion is begun through the brachiocephalic and coronary arteries. The subclavian artery is clamped.
Attention is now turned to the distal descending aorta. Perfusion via the femoral artery catheter is used briefly to wash any loose debris in the descending aorta out into the field. A distal cuff is fashioned, and the graft is anastomosed to it with a running 3-0 Prolene suture. Teflon felt is utilized. The clamp on the graft is removed, and the flow to the entire body is provided through the perfusion catheter placed in the graft. Rewarming, defibrillation, and weaning from cardiopulmonary bypass are carried out in standard fashion. During rewarming, a separate 8-mm graft is sewn to the left subclavian artery, trimmed to the appropriate length, and anastomosed to the descending graft with a side-biting clamp.
SSEP monitoring is continued throughout the first postoperative night, and arterial pressures are maintained in the high normal range. An intrathecal catheter is placed preoperatively and is used to drain CSF in order to keep CSF pressure below 10 mm Hg for the first 24 to 48 hours.