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Doppler echocardiographic characteristics of normally functioning Allcarbon prostheses were studied in 149 consecutive patients with 157 valves in the mitral (n=73) and aortic (n=84) positions whose function was considered normal by clinical and echocardiographic evaluation. In the mitral position, the mean gradient and the effective mitral orifice area were not significantly different in either the 25-mm or the 31-mm size valves (from 5±1 to 4±1 mmHg and from 2.2±0.6 to 2.8±0.9 cm, respectively; =ns for both). Conversely, peak gradient was significantly and inversely correlated to actual orifice area (r=−0.70; <0.0006), decreasing from 15±3 mmHg in the 25-mm size valve to 9±1 mmHg in the 31-mm size. In the aortic position, the mean gradient was 29±8 mmHg in the 19-mm size valve; it decreased to 8±2 mmHg in the 29-mm size. Effective prosthetic aortic valve area, calculated using the continuity equation, ranged between 0.9±0.1 cm for the 19-mm size valve to 4.1±0.7 cm for the 29-mm size. By analysis of variance, effective prosthetic aortic valve area differentiated various valve sizes (F=25.3; <0.0001) better than peak (F=5.34; =0.012) or mean (F=4.34; =0.0052) gradients alone, and it correlated better with actual orifice area (r=0.89, r=−0.70 and r=−0.65, respectively). This study provides the normal range for Doppler haemodynamic characteristics of the various sizes of the Allcarbon valve in the mitral and aortic positions so that prosthetic malfunction can be identified. [ABSTRACT FROM PUBLISHER]