Aortic Valve-Sparing Root Replacement
Tirone E. David
IndicationsTiming for surgery for aortic root aneurysm is largely determined by the diameter of the aortic root. Patients with Marfan syndrome and other genetically linked aortic root aneurysms should be considered for surgery when the transverse diameter of the aortic sinuses reaches 50 mm. In Loeys–Dietz syndrome the threshold is lower at 42 mm. If these patients have a family history of aortic dissection, surgery should be indicated even with smaller root diameters. In older patients without known aortic genetic link it may be appropriate to wait until the root reaches 55 mm.
Aortic valve-sparing operations were developed to preserve the aortic valve in patients with aortic root aneurysm. These patients may have aortic insufficiency, but the aortic cusps often remain normal or develop minor changes related to the increased mechanical stress caused by the dilatation of the aortic root at the sinotubular junction (STJ), aortoventricular junction (“aortic annulus”), or both. Cusps with minor abnormalities, namely an elongated free margin and prolapse or with stress fenestrations in the commissural areas, can be satisfactorily repaired during aortic valve-sparing operations.
There are basically two types of aortic valve-sparing operations: Remodeling of the aortic root and reimplantation of the aortic valve. In remodeling of the aortic root the aortic sinuses are replaced with a tubular Dacron graft that restores the diameter of the STJ and creates neoaortic sinuses, whereas in reimplantation of the aortic valve the aortic valve is placed inside a tubular Dacron graft changing the diameter and shape of the aortic annulus and STJ, and neoaortic sinuses may or may not be recreated. Each procedure provides excellent long-term results as long as they are correctly matched to the pathology of the aortic root aneurysm. The decision to perform one or the other procedure is largely based on the diameter of the aortic annulus at the time of surgery. However, it is important to consider that degenerative changes in the components of the aortic root are not synchronous and the aortic sinuses may dilate before the aortic annulus and STJ, particularly in aortic root aneurysms associated with genetic syndromes. These patients may develop large aortic sinuses with a relatively normal aortic annulus by the time they come to surgical attention. Dilatation of the aortic annulus may occur after remodeling of the aortic root if an annuloplasty is not performed at the time of surgery. On the other hand, in older patients with primarily an ascending aortic aneurysm in whom the aortic sinuses
become secondarily dilated and have a normal aortic annulus, there is no need for an annuloplasty at the time of replacement of the aortic sinuses.
become secondarily dilated and have a normal aortic annulus, there is no need for an annuloplasty at the time of replacement of the aortic sinuses.
Transesophageal echocardiogram is the best diagnostic tool to select patients for aortic valve-sparing operations. In addition to information regarding the size and shape of the aortic root, ascending aorta and aortic annulus, it can give important information on the quality of the aortic cusps. Thin, pliable, mobile aortic cusps are usually suitable for aortic valve sparing. The height of the cusps can also be estimated by echocardiography and it is a useful measurement because small cusps (e.g., with heights ≤12 mm) cannot adequately seal the aortic valve orifice. The relationship between the diameter of the aortic annulus at the base of the aortic cusps and the heights of the cusps is also valuable for the surgeon because after the operation the cusps should coapt within the reconstructed aortic root and for a length greater than 4 mm.
ContraindicationsAortic valve-sparing operations are an alternative to composite replacement of the aortic valve and ascending aorta (Bentall procedure). These two procedures are not competitive and both should be part of the armamentarium of aortic surgeons when treating patients with aortic root aneurysms. The indication for one or the other depends largely on the quality of the aortic cusps and the surgeon’s experience because aortic valve-sparing operations are technically more demanding than Bentall procedure, particularly the reimplantation of the aortic valve where every component of the aortic root is altered during the operation. Calcified aortic cusps, thickened and fibrotic cusps, or very small aortic cusps in relation to the diameter of the aortic annulus are contraindications for aortic valve-sparing operations. It is possible to replace parts of cusps or augment their heights with glutaraldehyde-fixed pericardium (autologous or bovine) to preserve the aortic valve, but there is no evidence that these procedures are more durable than a Bentall with a biologic or bioprosthetic valve. Overstretched and thinned out cusps are sometimes found in patients with large aortic root aneurysms and they are not suitable for repair either.
SurgeryThoracic Incision, Cardiopulmonary Bypass, and Myocardial Preservation
Although it is possible to do these operations through a 6- to 8-cm skin incision and mini-sternotomy down to the fourth intercostal space, a full median-sternotomy through a limited skin incision (8 to 10 cm) is preferred because it gives access to all parts of the aortic root and transverse arch. Cardiopulmonary bypass is established by placing an arterial cannula in the aortic arch immediately after the origin of the innominate artery and a double-stage venous cannula into the right atrium, unless mitral valve repair is also necessary in which case the superior and inferior vena cava are cannulated through the right atrium. We clamp the ascending aorta immediately below the innominate artery, place a ventricular vent through the right superior pulmonary vein, and transect the aorta above the STJ. We deliver blood cardioplegia directly into the coronary artery orifices by using soft, self-inflating coronary artery cannulas, much smaller than the arteries to avoid intimal damage. We give 1 L of cardioplegia over 5 to 6 minutes and 500 mL every 20 minutes. The body temperature is maintained at around 34°C unless the transverse arch needs replacement in which case we lower the temperature to 25°C and use antegrade cerebral perfusion during circulatory arrest.
Remodeling of the Aortic Root
The aortic root is dissected circumferentially down to the level of the aortic annulus. The right and left coronary arteries are detached from their aortic sinuses leaving 3 to
5 mm of arterial wall attached to the aortic annulus as illustrated in Figure 9.1. Stay sutures of 4-0 polypropylene are placed immediately above each commissure and pulled upward and toward each other to allow the cusps to coapt. If the cusps don’t come together, the tip of a wall suction cannula can be placed in between them and the negative pressure will force the cusps to coapt. The diameter of the imaginary circle made up by the three commissures when the cusps coapt is the diameter of the Dacron graft used to reconstruct the aortic root. If one is in doubt between two sizes, it is safer to select the larger of the two. Next, the tubular Dacron is tailored to recreate three neoaortic sinuses by incising the tube into three parts for a length equal to its diameter and then rounding each of the three ends as illustrated in Figure 9.2. The division of the graft into three parts should imitate the native aortic root, that is, if the three cusps are identical in size, the three neoaortic sinuses should also be identical, but if one cusp is smaller than the other two (a common finding), the width of that neoaortic sinus should be proportionally smaller. The arterial wall immediately above the commissures is sutured on the outside of the Dacron graft and the neoaortic sinuses of Dacron are secured to the remnants of aortic sinuses and aortic annulus with continuous 4-0 polypropylene sutures. We prefer to start at the commissure and move downward toward the aortic annulus on both sides of an aortic sinus and tie the ends of the sutures at the nadir of the sinus. Once the three neoaortic sinuses are sutured to the aortic root, the cusps are inspected to make sure they coapt at the same level and well above the nadir of the aortic annulus. In our experience approximately one-half of all patients require shortening of the free margin of one or more cusps because of prolapse as illustrated in Figure 9.3
5 mm of arterial wall attached to the aortic annulus as illustrated in Figure 9.1. Stay sutures of 4-0 polypropylene are placed immediately above each commissure and pulled upward and toward each other to allow the cusps to coapt. If the cusps don’t come together, the tip of a wall suction cannula can be placed in between them and the negative pressure will force the cusps to coapt. The diameter of the imaginary circle made up by the three commissures when the cusps coapt is the diameter of the Dacron graft used to reconstruct the aortic root. If one is in doubt between two sizes, it is safer to select the larger of the two. Next, the tubular Dacron is tailored to recreate three neoaortic sinuses by incising the tube into three parts for a length equal to its diameter and then rounding each of the three ends as illustrated in Figure 9.2. The division of the graft into three parts should imitate the native aortic root, that is, if the three cusps are identical in size, the three neoaortic sinuses should also be identical, but if one cusp is smaller than the other two (a common finding), the width of that neoaortic sinus should be proportionally smaller. The arterial wall immediately above the commissures is sutured on the outside of the Dacron graft and the neoaortic sinuses of Dacron are secured to the remnants of aortic sinuses and aortic annulus with continuous 4-0 polypropylene sutures. We prefer to start at the commissure and move downward toward the aortic annulus on both sides of an aortic sinus and tie the ends of the sutures at the nadir of the sinus. Once the three neoaortic sinuses are sutured to the aortic root, the cusps are inspected to make sure they coapt at the same level and well above the nadir of the aortic annulus. In our experience approximately one-half of all patients require shortening of the free margin of one or more cusps because of prolapse as illustrated in Figure 9.3
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