Maximizing prosthetic valve size with the Top Hat supra-annular aortic valve.

BACKGROUND AND AIM OF THE STUDY: The CarboMedics Top Hat supra-annular aortic valve allows a one-size (and often two-size) increase over the standard intra-annular valve. This advantage should minimize the risk of patient-prosthesis mismatch, where the effective prosthetic valve orifice area is less than that of a normal valve. It is suggested that the ability to implant Top Hat valves having greater size, relative to standard intra-annular valves, may currently be under-utilized. Further, there has been some concern that Top Hat implantation can cause obstruction of the coronary ostia. This study evaluates the authors' clinical experience with Top Hat supra-annular aortic valve size selection, and the technical aspects of implantation.

METHODS: Between January 1999 and October 2005, a total of 251 consecutive patients underwent 252 aortic valve replacements with Top Hat supra-annular mechanical prostheses (CarboMedics, Inc., Arvada, CO, USA) at two institutions. Size frequency distribution was compared to published series, and to the manufacturer's US registry. The ventriculoaortic junction (VAJ) size was available in 234 patients, and compared to the size of the Top Hat valve implanted.

RESULTS: Valves implanted were 2 mm larger than the VAJ in 56% of patients (130/234), 3 mm larger in 1.7% (4/234), and 4 mm larger in 42% (98/234). Numbers of 19-mm and 21-mm valves were less (p <0.001) in the present series (22%) than in published series (52%) and the US registry (46%). No patient required unplanned coronary bypass, and 30-day mortality was 2.0% (5/251), indicating a good safety profile for the valves implanted in this series.

CONCLUSION: The general distribution of implant sizes in the US indicates that cardiac surgeons may be under-sizing the Top Hat supra-annular aortic valve during aortic valve replacement, thereby missing the full advantage of its unique design for lowering the transvalvular gradient and, consequently, left ventricular workload, leading to a reversal of left ventricular hypertrophy.