Assessing options for the small aortic root

Abstract

Valve selection for the small aortic root is a multifactorial process. Considerations include the effective orifice (EOA) of the implanted valve, annular size, body surface area (BSA), and valvular outflow tract of each patient. To decide if a valve is adequate for a patient, the valve EOA and patient BSA are used to calculate the indexed EOA (EOA/BSA). An indexed EOA <0.85 is associated with significant increases in mean systolic gradient with increase in cardiac output. The gradient remains low when indexed EOA is >0.85, leading to improved left ventricular mass reduction and decreased long-term risk of arrhythmias, congestive heart failure, and death. Biologic valves are usually used in patients aged over 65 years. Stented biologic valves tend to have a low EOA for their size. A 21-mm pericardial valve has an indexed EOA of 0.81 when implanted in a 1.6-m, 58-kg woman, and 0.69 in a 1.7-m, 72-kg man. Stentless valves (xenograft and homograft) have excellent EOAs and consequently very low gradients with good ventricular mass reduction. This allows for insertion of a larger valve, and results in more normal opening and flow dynamics. Hence, the best approach in over 65-year-old aortic valve patients when using a biologic valve is a stentless subcoronary implant. If this is not possible for anatomic reasons, a stented valve with an indexed EOA >0.85 is the best alternative. An option is root replacement with a xenograft or homograft, but the operative risk is significantly increased. The decision in younger patients (aged <65 years) is more complex. In-vivo EOAs for mechanical valves vary greatly; the St. Jude HP and Regent valves have consistently excellent EOAs. Recent results with the St. Jude Regent valve show gradients and left ventricular mass reduction close to those for stentless biologic valves. In a small aortic annulus, the decision must be made to use a more efficient valve (e.g. the Regent) or a biologic stentless valve, to perform annular enlargement (increasing surgical risk), or to tilt the stented valve to be supra-annular in the non-coronary cusp. The subvalvular outflow tract should not be ignored. Septal hypertrophy is not uncommon, and may increase the gradient across the outflow tract just below the valve. Finally, suture techniques (e.g. pledgetted versus interrupted simple sutures) can affect the long-term gradient. Pledgetted sutures can draw tissue underneath the valve and reduce the EOA. In conclusion, multiple factors must be evaluated when deciding which valve to use as a replacement in the small aortic root. These include patient age, lifestyle, pregnancy status, and drug compliance, as well as the indexed EOA of available prosthetic valves and the surgical procedure required for implant.