Usefulness of the indexed effective orifice area at rest in predicting an increase in gradient during maximum exercise in patients with a bioprosthesis in the aortic valve position

This study examines the hemodynamic behavior of aortic bioprosthetic valves during maximum exercise. Nineteen patients with a normally functioning ste nted bioprosthetic valve and preserved left ventricular function were submi tted to maximum ramp bicycle exercise. In 14 of the 19 patients, valve effe ctive orifice area and mean gradient were measured at rest and during exerc ise using Doppler echocardiography. At peak exercise (mean maximal workload 118 +/- 53 W), the cardiac index increased by 122 +/- 34% (+3.18 +/- 0.71 L/min/m(2), p <0.001), whereas mean gradient increased by 94 +/- 49% (+12 /- 8 mm Hg, p <0.001), and effective orifice area by 9 +/- 13% (+0.15 +/- 0 .22 cm(2), p = 0.02). A strong correlation was found between the increase i n mean gradient during maximum exercise and the valve area at rest indexed for body surface area (r = 0.84, p <0.0001). Due to the increase in valve a rea, the increase in gradient was less (-9 +/- 7 mm Hg, -41 +/- 33%, p = 0. 0006) than theoretically predicted assuming a fixed valve area. These resul ts suggest that the effective orifice area of the bioprostheses has the cap acity to increase during exercise; therefore, limiting the increase in grad ient. The relation found between the indexed effective orifice area at rest and the increase in gradient during exercise should be useful in predictin g the hemodynamic behavior of a stented bioprosthesis during exercise. (C) 1999 by Excerpta Medica, Inc.