Endovascular Treatment of Acute Descending Thoracic Aortic Dissections

The hybrid operating room: successful endovascular repair of complex aortic pathologic treatment begins with a team of cardiac and vascular surgeons, cardiovascular anesthesiologists, neurology, and nursing in an appropriately equipped hybrid operating room. The ideal hybrid operating room is designed with a fixed high-quality ceiling- or floor-mounted image intensifier, adequate space to accommodate transesophageal echocardiography (TEE) equipment, intravascular ultrasound (IVUS), neuromonitoring equipment, and a cardiopulmonary bypass pump if necessary, and multiple movable viewing screens that can display angiography, hemodynamics, TEE, and IVUS simultaneously.

Acute type B dissection with limb malperfusion: a patient presented with acute Stanford type B aortic dissection starting distal to the origin of the left subclavian artery and extending to below the iliac bifurcation. The entry tear is seen in the typical position in the greater curve of the distal arch/proximal descending thoracic aorta. (A) The visceral segment arises from the true lumen, which is significantly compressed in the lower thoracic aorta. (B) The right iliac artery is fully occluded by the dissection flap, causing malperfusion of right lower extremity. (C) The goal of therapy is to cover the entry tear site, re-expand the true lumen, and relieve the malperfusion. a. = artery.

Acute type B dissection with limb malperfusion: a patient presented with acute Stanford type B aortic dissection starting distal to the origin of the left subclavian artery and extending to below the iliac bifurcation. The entry tear is seen in the typical position in the greater curve of the distal arch/proximal descending thoracic aorta. (A) The visceral segment arises from the true lumen, which is significantly compressed in the lower thoracic aorta. (B) The right iliac artery is fully occluded by the dissection flap, causing malperfusion of right lower extremity. (C) The goal of therapy is to cover the entry tear site, re-expand the true lumen, and relieve the malperfusion. a. = artery.

Arterial access: access to the pulseless right common femoral artery is performed via surgical cut-down (A). Depending on size, the artery may be controlled with vessel loops or double purse-string sutures (B). The left common femoral artery is accessed percutaneously using a Seldinger technique. Fluoroscopy is employed to ensure puncture over the femoral head and passage of all wires. a. = artery; v. = vein.

The artery is accessed with purse-string suture through which a 9-Fr. sheath is inserted over a multipurpose J-wire. (A) A flexible tip Bentson guidewire is passed into the thoracic aorta under fluoroscopic guidance using a guide catheter and an IVUS catheter is passed over the wire to verify that the true lumen has been accessed. (B) In the left femoral artery, a 5-Fr. sheath is placed, through which a marker pigtail catheter is passed over a Bentson wire into the ascending aorta. On the right side, the Bentson wire is exchanged using an exchange catheter for a stiff Lunderquist wire, which will be used for device placement. (C) The 9-Fr. sheath is exchanged for the device sheath through which the stent-graft will be delivered. a. = artery; IVUS = intravascular ultrasound.

Initially, a 10- to 15-cm-length thoracic aortic stent-graft is deployed with a 10 to 20% diameter oversize compared with the total diameter of the native aorta. Ideally, the stent-graft is deployed such that there is at least 2 cm of nondissected aorta in the proximal landing zone in a segment without significant caliber change, atheroma, or thrombus. Because the entry tear in most type B dissections occurs along the greater curve of the distal aortic arch just beyond the left subclavian artery takeoff, partial or total subclavian artery coverage is frequently required. In all elective cases, we prophylactically perform left-carotid-left-subclavian artery bypass. In emergency cases, this bypass is performed when there is left arm malperfusion post stent-graft insertion. Excessive oversizing is avoided to prevent infolding or stent collapse. Frequently, the distal aspect of the stent may be partially collapsed and will slowly dilate to its nominal diameter over time. Ballooning is avoided to prevent the dreaded complication of retrograde propagation of the dissection into the ascending aorta, unintended fenestration at the distal end of the stent-graft, or even aortic rupture from excessive radial forces.

After insertion of the first stent-graft, visceral malperfusion worsened as the dynamic dissection flap compressed the origins of the visceral vessels. A second stent-graft was placed with generous overlap to further re-expand the true lumen. (A) This relieved the visceral malperfusion but residual right lower extremity malperfusion remained. This was managed with deployment of a bare metal stent in the infrarenal aorta and bilateral common iliac artery stents. (B) Similar approaches may be employed in other areas of static obstruction (ie, renal arteries) with bare metal stents as needed. a. = artery.