Physical Address

304 North Cardinal St.
Dorchester Center, MA 02124

Aortic aneurysm


Aneurysm of the aorta in one of its segments or in its entirety may require replacement of the aorta. The need for operation is determined by the size of the aneurysm and the accompanying risk of rupture, occlusion of the aorta or its branches, thromboemboli originating from the aortic wall, or infection.

Morphology

Figure 38-1, A Operative photograph of aneurysm of the ascending aorta, atherosclerotic type. The aorta is dilated above the sinotubular junction. The aortic dilation extends into the proximal portion of the aortic arch. B Operative photograph of aneurysm of the ascending aorta, Marfan type. The aortic dilation includes the aortic sinuses. It is often described as onion-shaped. C Operative photograph of aneurysm of the aorta due to aortic dissection. The blue discoloration is blood within the aortic wall separating the intima and media from the aortic adventitia. The dissection includes the aortic sinuses and continues through the aortic arch. D Operative photograph of aortic dissection of the ascending aorta. The intima and media have separated from the aortic adventitia. E Anatomic specimen of aortic dissection of the ascending aorta. There is a tear through the intima and media of the ascending aorta just above the sinuses of Valsalva. Coronary arteries are not involved, and the aortic valve leaflets are normal. F Operative photograph of aneurysm of the ascending aorta and arch. The aortic dilation continues through the aortic arch. G Operative photograph of aneurysm of the ascending aorta and arch. This view, from the same patient as in Figure 38-1 , F , shows the upper portion of the descending aorta, which was previously replaced with a prosthetic graft for aneurysmal disease.

Cannulation strategies for aortic operations

Multiple cannulation techniques are available for cardiopulmonary bypass during aortic operations. Alternative techniques, such as partial cerebral perfusion, can make the operative field more accessible during complex reconstructions.

Figure 38-2, A Femoral-femoral bypass is instituted by placing an arterial cannula in the common femoral artery and a venous return cannula in the common femoral vein. For patients with small or diseased arteries, construction of a “side arm” with a prosthetic graft ensures distal perfusion of the leg. When using this strategy in acute aortic dissection, the surgeon should select the artery with the strongest pulse. High arterial pressure in the return cannula is strongly suggestive of impaired perfusion, and the cannula should be removed and placed in the opposite common femoral artery. B Antegrade perfusion via the right axillary artery is useful for operations on the aortic arch. It can be used as the sole method for arterial return during cardiopulmonary bypass, or it can be used to provide partial, selective antegrade cerebral perfusion during periods of hypothermic circulatory arrest. An oblique incision is made 1 cm below the right clavicle for exposure of the axillary artery. C The pectoralis major muscle is separated in the direction of its fibers to enter the subclavicular space. The artery is isolated with vascular loops, taking care to avoid injury to the brachial plexus. D A longitudinal incision is made in the artery. An 8 mm prosthetic graft is beveled and attached in an end-to-side fashion using continuous stiches of 5/0 polypropylene suture. E The graft is trimmed to about 20 cm in length, and a 22 F arterial return cannula is inserted into the graft. The cannula is secured with multiple ties around the graft and connected to the cardiopulmonary bypass circuit. Antegrade perfusion is delivered through the axillary graft to the right arm and the aortic arch. During periods of circulatory arrest, the innominate artery is clamped, and selective antegrade perfusion of the brain can be performed through the right common carotid artery. F When perfusion through a side graft is discontinued, the graft is clamped close to the artery, divided, oversewn with continuous stitches of 4/0 polypropylene, and sealed with BioGlue. G In cases of acute aortic dissection, central cannulation can be safely performed using the Seldinger guidewire technique. Under transesophageal echocardiographic guidance, a needle is placed directly into the distal ascending aorta, and the guidewire is advanced into the true lumen. H Successive dilation is performed over the guidewire, and the arterial cannula is placed through the aortic arch into the descending thoracic aorta. This ensures antegrade perfusion of the true lumen and avoids potential malperfusion and the differential flow patterns that can be associated with femoral artery cannulation.

Replacement of ascending aorta with prosthetic graft

Ascending aortic aneurysm or dissection is repaired by replacing the ascending aorta with a prosthetic graft. Placement of the arterial cannula in the proximal aortic arch facilitates placement of the cross-clamp and construction of the distal aortic anastomosis. If the aneurysm approaches the innominate artery, use of the hemiarch technique may be necessary to extend the repair and effectively resect all aneurysmal tissue. The hemiarch technique is also useful for the repair of acute aortic dissection.

Figure 38-3, A The arterial perfusion cannula is placed in the proximal aortic arch. Cardiopulmonary bypass is established, the aorta occluded, and cardiac arrest achieved with cold cardioplegia given retrograde through the coronary sinus. The aorta is transected 1 cm above the sinotubular junction and 1 cm from the aortic cross-clamp. The entire aneurysmal portion is removed, taking care to avoid injury to the right pulmonary artery, which lies directly behind the ascending aorta. B A prosthetic graft is attached to the distal aorta in an end-to-end fashion using continuous stitches of 4/0 polypropylene suture. The suture line is first constructed across the back wall of the aorta and then carried up to the front of the anastomosis. C The prosthetic graft is trimmed appropriately to avoid excess length, which can result in kinking. The graft is attached to the sinotubular junction of the native aortic root using continuous stitches of 4/0 polypropylene suture. D BioGlue is used to reinforce the suture lines before removing the aortic cross-clamp. This effectively seals the needle holes. More significant areas of bleeding should be reinforced with interrupted pledgetted sutures. E If the aneurysm involves the distal ascending aorta or proximal aortic arch, the hemiarch technique should be used to resect all aneurysmal tissue. The arterial perfusion cannula is placed in the distal aortic arch. The cross-clamp is placed at a convenient point on the dilated ascending aorta. The aorta is transected 1 cm above the sinotubular junction and below the cross-clamp. F A short period of circulatory arrest under deep hypothermia is required to construct the distal aortic anastomosis. The cross-clamp is removed, and the aorta is trimmed to the level of the innominate artery and beveled underneath the aortic arch. G A prosthetic graft is selected and beveled to match the hemiarch configuration. It is attached in an end-to-end fashion using continuous stitches of 4/0 polypropylene suture. The suture line is first constructed across the back wall of the aorta and then carried up to the front of the anastomosis. H Cardiopulmonary bypass is reinstituted, and de-airing maneuvers are employed to evacuate air and debris from the arch vessels and the descending thoracic aorta. After appropriate de-airing, the cross-clamp is placed on the distal portion of the prosthetic graft, and full cardiopulmonary bypass flow is reestablished. I The prosthetic graft is trimmed appropriately and attached to the sinotubular junction of the native aortic root using continuous 4/0 polypropylene suture. J BioGlue is used to reinforce the suture lines before removing the aortic cross-clamp. This effectively seals the needle holes. More significant areas of bleeding should be reinforced with interrupted pledgetted sutures. K In the setting of acute aortic dissection, the arterial cannula is placed in the distal ascending aorta using the Seldinger guidewire technique. Transesophageal echocardiography is used to place the guidewire into the true lumen, and the arterial cannula is advanced over the guidewire out into the descending thoracic aorta. L The cross-clamp is placed at a convenient point on the ascending aorta. The aorta is transected 1 cm above the sinotubular junction and 1 cm from the cross-clamp. M The aortic root is inspected, looking for extension of the dissection. If the dissection is limited to the noncoronary sinus or there is minimal extension below the sinotubular junction, BioGlue is used to reapproximate the aortic layers and reinforce the sinotubular junction. N A short period of circulatory arrest under deep hypothermia is required to construct the distal aortic anastomosis. The cross-clamp and the arterial cannula are removed, and the aorta is trimmed to the level of the innominate artery and beveled underneath the aortic arch. The arch is inspected for evidence of an intimal tear. O BioGlue is used to reapproximate the aortic layers. A balloon catheter is inflated in the aortic arch while the glue is applied sequentially around the circumference of the aorta. This prevents the glue from flowing down the false lumen into the descending thoracic aorta. P A prosthetic graft is selected and beveled to match the hemiarch configuration. It is attached in an end-to-end fashion using continuous 4/0 polypropylene suture. The suture line is first constructed across the back wall of the aorta and then carried up to the front of the anastomosis. Q The arterial cannula is placed back through the prosthetic graft (as shown in Figure 38-3 , R ) and the tip of the cannula positioned in the distal aortic arch under direct vision. Cardiopulmonary bypass is reinstituted, and de-airing maneuvers are employed to evacuate air and debris from the arch vessels and the descending thoracic aorta. After appropriate de-airing, the cross-clamp is placed on the distal portion of the prosthetic graft, and full bypass flow is reestablished. R The prosthetic graft is trimmed appropriately and attached to the reinforced sinotubular junction of the native aortic root using continuous stitches of 4/0 polypropylene suture. S BioGlue is used to reinforce the suture lines before removing the aortic cross-clamp. This effectively seals the needle holes. More significant areas of bleeding should be reinforced with interrupted pledgetted sutures. The completed repair is shown with BioGlue sealing the suture lines and arrows demonstrating proper blood flow to the true aortic lumen.

Replacement of ascending aorta and aortic root

Concomitant replacement of the ascending aorta and the aortic root is necessary when there is combined disease. Aortic dissection that extends deep into the aortic root, rendering the aortic valve unrepairable, is an indication for replacement of both the ascending aorta and the aortic root. Another common indication is aortic valve incompetence due to root dilation from aneurysmal disease, such as that associated with Marfan syndrome. An additional indication is a bicuspid aortic valve with associated dilation of the ascending aorta. Durable repair is achieved with the use of either a composite mechanical valved conduit or a tissue aortic root bioprosthesis and a prosthetic graft.

Figure 38-4, A The arterial perfusion cannula is placed in the distal ascending aorta or proximal aortic arch, depending on the extent of the ascending aortic aneurysm. The cross-clamp is placed in the ascending aorta distal to the aneurysm, and retrograde cardioplegia is used to arrest the heart. The aorta is transected 1 cm above the sinotubular junction and 1 cm from the aortic cross-clamp. The aneurysmal aorta is resected. B The aortic valve is excised, and the aortic root exposure is enhanced by placing traction sutures at the top of each commissure. The aortic tissue is removed from each sinus, leaving a 5 to 6 mm rim of aortic tissue along the aortic annulus. The left and right coronary arteries are mobilized on generous buttons of aortic sinus tissue. C The diameter of the aortic annulus is measured, and a mechanical valved composite graft is selected for the repair. A porcine aortic root prosthesis can also be used. Interrupted mattress stitches of 2/0 braided suture are placed down through the aortic annulus and brought up through the sewing ring of the prosthesis. Suture placement is started in the right coronary sinus and proceeds in a clockwise fashion, similar to standard aortic valve replacement. Repair of the left coronary sinus follows in a counterclockwise fashion, and the repair is completed in a clockwise fashion through the noncoronary sinus. D The valved composite prosthesis is lowered down on the aortic annulus, ensuring that the valve is seated properly without impinging on the leaflets or valve occlusion mechanism. The sutures are tied down first in the noncoronary sinus in a counterclockwise fashion. The second group of sutures in the left coronary sinus is tied in a counterclockwise fashion, and the repair is completed in the right coronary sinus in a clockwise fashion. A running suture technique is also acceptable, provided the annulus is strong enough to support this type of repair. E Openings are made into the sides of the Dacron graft exactly opposite the coronary artery ostia using a battery-operated ophthalmic cautery unit. Large openings make the technical aspects of the repair easier and avoid narrowing the anastomosis. An adequate amount of graft should be left between the bottom of these openings and the sewing ring of the prosthesis. The left coronary ostium is attached first using continuous stitches of 5/0 polypropylene. All the suture loops are placed around the inferior rim of the coronary ostium before they are tightened in order to accurately approximate the ostium to the graft opening. F Both coronary ostia are approximated to the graft in a similar fashion. The right coronary artery anastomosis can be completed either before or after the distal aortic anastomosis if there is concern about the proper orientation of the right coronary artery. G Secure, accurate stitches must be placed in the coronary artery button wall for secure approximation to the side of the graft. The stitches are placed in a “wagon wheel” fashion, taking wide bites of the surrounding Dacron graft or bioprosthetic aortic sinus tissues. This is particularly important in the case of aortic dissection, because the aortic tissue can be fragile. Use of BioGlue or Teflon felt “washers” is advised to support these critical coronary reimplantations. H When there has been extensive dissection into the coronary arteries, the main coronary arteries must be trimmed to some degree. Small, short interposition PTFE grafts can then be used to compensate for the loss of coronary artery length. The interposition grafts are attached in an end-to-end fashion to each main coronary artery using continuous stitches of 6/0 polypropylene sutures; then the grafts are attached to the openings in the composite graft using continuous stitches of 5/0 polypropylene suture. Careful attention must be paid to the length of each interposition graft to avoid kinking and improper orientation. BioGlue is applied to reinforce these suture lines. An alternative method is to use a single interposition graft for the reimplantation. The left main coronary artery (LCA) is trimmed back to healthy tissue, and a small prosthetic graft is attached in an end-to-end fashion using continuous stitches of 6/0 polypropylene. This prosthetic graft is then routed behind the main composite graft and attached to the front of it using continuous stitches of 4/0 polypropylene. The right coronary artery (RCA) is also trimmed back to healthy tissue, and a small opening is made in the side of the small prosthetic graft. The right coronary artery is attached to the side of the graft using continuous stitches of 6/0 polypropylene. In cases of Marfan type aortic aneurysm, the coronary ostia may be widely separated by the size of the aneurysm of the aortic root. An interposition graft may be anastomosed directly to the aorta around the coronary ostia without resection of part of the root aneurysm. The interposition graft may be anastomosed to the posterior aspect of the aortic graft, or interiorly as seems best. I The distal end of the graft is trimmed to an appropriate length and attached in an end-to-end fashion using continuous stitches of 4/0 polypropylene sutures. The suture line is first constructed across the back wall of the aorta and then carried up to the front of the anastomosis. J A short “collar” of graft material is used to support the distal anastomosis. The collar must be cut and placed around the graft prior to construction of the anastomosis. The collar is pulled up to cover the anastomosis and BioGlue is inserted beneath the collar to reinforce the suture line. K In patients in whom it is desirable to avoid anticoagulation, concomitant replacement of the aortic root with a Freestyle tissue bioprosthesis provides an excellent alternative to a composite mechanical valved conduit. The initial part of the operation is identical to that for aneurysmal disease of the ascending aorta and aortic root. The arterial return cannula is inserted into the distal aortic arch, and the ascending aorta is resected. L The aortic root is prepared after placing traction sutures at the top of each commissure. All diseased aortic sinus tissue is removed, and the coronary arteries are mobilized on generous buttons of aortic tissue. The aortic annulus diameter is measured, and an appropriate Freestyle porcine aortic root bioprosthesis is selected. The diameter top of the Freestyle graft is measured, and a prosthetic graft of similar diameter is selected for the ascending aortic repair. M A short period of circulatory arrest under deep hypothermia is required to construct the distal aortic anastomosis. After trimming the distal aorta in a hemiarch manner, a prosthetic graft is beveled and attached in an end-to-end fashion using continuous stitches of 4/0 polypropylene. The Freestyle sizer is inserted inside the graft to distend the suture line, and BioGlue is applied to reinforce the anastomosis. Cardiopulmonary bypass is reinstituted at low flow. After air and debris are removed from the aortic arch, the graft is clamped, and full cardiopulmonary bypass is reinstituted. N The Freestyle porcine aortic root bioprosthesis is attached to the left ventricular outflow tract using continuous 3/0 polypropylene sutures. The bioprosthesis is aligned in an anatomic fashion, with the stumps of the porcine left and right coronary arteries facing the native coronary buttons. The suture line is begun at the commissure between the left and right sinuses. The suture is brought in a clockwise fashion along the right coronary sinus to the halfway point of the noncoronary sinus, taking generous bites of the aortic annulus and bringing the needle up through the collar of the Freestyle tissue bioprosthesis just below the dashed marker line. The other end of the suture is brought in a counterclockwise fashion along the left coronary sinus to the halfway point of the noncoronary sinus, meeting the previous suture. Silk sutures are looped around every third stitch, acting as “pulleys” that are gently tightened as the bioprosthesis is lowered into position. This ensures even, symmetric tightening of the anastomosis without breaking the suture. BioGlue is used to reinforce the suture line. O The left coronary stump of the Freestyle porcine aortic root bioprosthesis is removed to create an opening in the porcine root. The left coronary ostium is attached using continuous 5/0 polypropylene sutures. Several suture loops are placed along the inferior rim of the left coronary ostium before tightening the suture line; this ensures precise placement of the stitches. The right coronary stump of the Freestyle bioprosthesis usually does not align exactly opposite the patient’s right coronary artery. A second opening is made in the right coronary sinus of the bioprosthesis at the approximate location, and the right coronary ostium is attached in a similar fashion. Both coronary artery anastomoses are reinforced with BioGlue. P The bioprosthetic graft is trimmed to appropriate length and beveled to match the bevel of the aorta. Beveling re-creates the natural contour of the ascending aorta, forming a small curvature on the central or leftward part of the graft. Q The Freestyle tissue bioprosthesis is attached to a prosthetic graft using continuous stitches of 4/0 polypropylene. A short “collar” of graft is used to support the anastomosis. The collar is cut from the unused portion of the graft and must be placed over the graft prior to performing the anastomosis. The collar is pulled over the completed anastomosis and BioGlue is inserted beneath the collar to reinforce the suture line.

Aortic arch

Reconstruction of the aortic arch may be necessary for atherosclerotic aneurysm or dissection of the aorta that extends into the arch, making repair impossible or inadvisable proximal to the innominate artery. This region was once accessible only with great difficulty and risk using continuous-flow cardiopulmonary bypass techniques. The application of circulatory arrest with the patient under deep body hypothermia has made the aortic arch much more accessible.

Ascending aorta and hemiarch replacement with arch thromboendarterectomy

Atherosclerotic disease with aneurysm of the ascending aorta may extend into the aortic arch. There may be ulcerated atherosclerotic plaques in the aorta, placing the patient at risk for intraoperative stroke due to atheroemboli. Addressing this risk factor during ascending aorta and partial arch (hemiarch) replacement should improve survival and reduce neurologic comorbidity.

Figure 38-5, A An aortic perfusion cannula is placed in the distal part of the aortic arch, with the tip in the upper portion of the descending thoracic aorta beyond the origin of the left subclavian artery. A two-stage venous uptake cannula is placed in the right atrium. The patient is perfused with blood cooled to 12 o C until the body temperature (nasopharyngeal) reaches 16 to 18 o C. An induction dose of thiopental sodium (Pentathol), corticosteroids, and mannitol are useful pharmacologic adjuncts. Circulatory arrest under these conditions should be well tolerated for 60 minutes. This period can be extended by interval hypothermic perfusion of the brain. Some surgeons favor retrograde cerebral perfusion via the superior vena cava as a means of cerebral protection, but data on the efficacy of this method are not conclusive. An occlusion clamp is placed on the ascending aorta when ventricular fibrillation occurs. The occlusion clamp must be placed on a disease-free area; this can be determined by gentle palpation of the aorta. The best spot is often just above the sinotubular junction. A vent catheter is placed in the left superior pulmonary vein and passed into the left ventricle. Retrograde perfusion of the coronary sinus is begun, and the heart is cooled to 4 o C. When the target body temperature is reached, cardiopulmonary bypass is discontinued. The occlusion clamp is removed from the aorta. The aorta is divided above the sinotubular junction. It is divided distally just proximal to the origin of the brachiocephalic artery in an oblique manner across to the inferior aspect of the aortic arch, including part of the arch. B A dissection plane is opened between the aortic intima-media and the adventitia, working through the open end of the aorta. C Endarterectomy of the portions of the arch affected by atherosclerotic disease is performed. Removal of all the arch intima and media may be required, extending the dissection into the arch branches. A smooth transition to the arterial intima, with firm attachment, must be present at the end points of the endarterectomy. Extending the endarterectomy into the branch vessels beyond visualization (blind endarterectomy) may be required, but this adds risk to the procedure. D A tubular Dacron vascular graft is tailored obliquely when part of the arch has been removed. The short angle of the graft is placed medially on the aortic arch to avoid kinking as the graft is brought down to the aortic root. An end-to-end anastomosis of the graft to the aortic arch is constructed using continuous stitches of 4/0 polypropylene. E The anastomosis is sealed with BioGlue. Cardiopulmonary bypass is resumed, with the patient in a head-down position. Air and debris are removed from the arch and its branches by gentle agitation and floated out the open proximal end of the graft. An occlusion clamp is placed on the graft. The proximal anastomosis of the graft to the proximal aorta is completed during the rewarming process.

Valve-sparing aortic root replacement-reimplantation technique (Yacoub/David II operation)

Occasionally, aneurysmal disease of the ascending aorta is associated with normal aortic valve cusps and no dilation of the aortic valve annulus. It may be possible to preserve aortic valve function in this situation. The principles of repair are based on techniques described by Yacoub and David and on aortic root dimensions detailed by Kunzelman.

Figure 38-6, A Cardiopulmonary bypass is established as usual. The aorta is occluded and retrograde cold cardioplegia given through the coronary sinus. The aneurysm of the ascending aorta is incised longitudinally. The aorta is divided distally above the aneurysm. B The aortic valve is inspected to determine the feasibility of repair. If the aneurysmal disease is restricted to the aorta, with dilation of the sinuses of Valsalva, it may be possible to preserve the aortic valve. The aortic valve cusps should be normal. There should be no dilation of the aortic annulus, although there are techniques to narrow the annulus. In the situation depicted here, the aortic valve is determined to be incompetent due to separation of the commissures by aneurysmal dilation of the aorta. C The sinus aorta is excised, retaining only a 3 to 5 mm rim above the fibrous connecting point of the aortic valve (annulus). A button of sinus aorta is retained around ostia of the left and right coronary arteries. D Average dimensions of the aortic leaflets are obtained. The length of the free margin of the leaflets is determined, and the height of the leaflets is measured. The sinotubular diameter is calculated using dimensions determined by Kunzelman: if the diameter of the aortic root at the ventriculoaortic junction (“the “annulus”) is taken as 1.0, the diameter of the sinotubular junction (which will also be the diameter of the prosthetic graft chosen for the repair) is 0.91 of the annulus diameter. For example, if the diameter of the aortic valve annulus measures 25 mm, a 22 mm diameter tubular prosthesis is chosen (25 × 0.9 = 22.5). A practical method for selecting an appropriately sized prosthetic graft is to simply measure “the annulus,” as would be done for an aortic valve replacement, and choose a tubular graft diameter that is about 90% of the diameter of the annulus. E A graft of the appropriate size is selected. Double-velour knitted Dacron that has been collagen coated for hemostasis is usually chosen. The graft is cut at three symmetric points to accommodate the commissures of the aortic valve. The cuts usually extend six or seven crimp ridges into the graft, depending on the height of the leaflets. The graft material between these cuts will become the reconstructed sinuses of Valsalva. F The edges of the graft are attached to the sinus aortae remnant at the hinge point of the aortic leaflets. Continuous stitches of 3/0 or 4/0 polypropylene are used for the repair. The commissures of the aortic valve are brought into the apices of the cuts in the graft. G Openings are cut into the graft, opposite the location of the coronary arteries, using a hot cautery. The coronary arteries are anastomosed to the openings in the graft with continuous stitches of 5/0 polypropylene. H An end-to-end anastomosis of the graft to the aorta completes the repair. All vascular anastomoses are sealed with BioGlue.

You're Reading a Preview

Become a Clinical Tree membership for Full access and enjoy Unlimited articles

Become membership

If you are a member. Log in here

Related Posts