INACCURATE AND MISLEADING VALVE SIZING - A PROPOSED STANDARD FOR VALVE SIZE NOMENCLATURE

Background. The sizes with which manufacturers label valves are nonuni form and haphazard. This has led to confusion and inappropriate compar isons of hemodynamics between valves with the same labeled size. Hemod ynamic performance of valves is primarily determined by the internal d iameter (ID) of their orifice. Methods. The purpose of this study was to determine the ID and external diameter of aortic valves used at our institution and compare the measurements to manufacturers' labeled si zes. We also evaluated valve size (ID, manufacturers' labeled size) in 527 patients undergoing isolated aortic valve replacement between 199 0 and 1996. Results. We demonstrated that no two manufacturers' tissue or mechanical valves have the same ID or external diameter for a give n labeled size. The labeled size of tissue valves was 1 to 4 mm larger than the measured ID. The labeled size of mechanical valves was 3 to 5 mm larger than the measured ID. The St. Jude HP mechanical valve has a greater ID than all other mechanical valves for each labeled size. Among 403 patients operated on for predominant aortic stenosis, those patients receiving the Toronto Stented Porcine Valve (n = 98) had a la rger mean ID (22.3 +/- 1.9 mm) than 204 patients receiving stented tis sue valves (ID = 20.9 +/- 1.9 mm) and the 101 patients receiving mecha nical valves (ID = 19.3 +/- 1.9 mm, p < 0.0001). However, when the man ufacturers' labeled size was used as a measure of the size, the result s were greatly exaggerated in favor of the Toronto Stented Porcine Val ve (ID = 26.3 +/- 1.9 mm) compared with stented tissue valves (ID = 23 .1 +/- 2.1) or mechanical valves (ID 23.6 +/- 1.9) (p < 0.0001). Concl usions. Manufacturers' labeling of valves is nonuniform and may lead t o erroneous comparisons and conclusions of hemodynamic differences bet ween valves. We therefore recommend a standardized nomenclature for th e size of all valves based on the ID measurement. (Ann Thorac Surg 199 8;66:1198-203) (C) 1998 by The Society of Thoracic Surgeons.