[Continuous wave Doppler assessment of prosthetic valves in the mitral position: comparison of the St. Jude medical mechanical valve and the porcine xenograft valve].

To assess the opening function of prosthetic valves in the mitral position with special reference to the type and size of the valve and the years since replacement, we recorded maximum flow velocity through the mitral orifice using continuous wave Doppler echocardiography for 50 patients with mitral valve replacement and 15 normal subjects. There were 33 patients with St. Jude Medical valves and 17 with porcine xenograft valves. An ultrasonic transducer was placed over the left ventricular apex and the direction of the ultrasonic beam was positioned to be parallel with mitral flow using the Doppler audio signals. A pressure gradient was calculated from continuous wave Doppler flow velocity with a simplified Bernoulli's equation proposed by Hatle et al. The peak and mean maximum flow velocity, mean pressure gradient across the valve and the pressure half time were measured to evaluate the opening function of the prosthetic valve. The results were as follows: All four measurements were significantly larger in patients with valve replacements than in normal subjects, and were significantly increased in patients with porcine xenograft valves compared to those with St. Jude Medical valves. The opening function was well maintained in patients having larger valves than in those having smaller ones in the group of St. Jude Medical valve replacement. In patients who had porcine xenograft valve for four years or more, the opening function was decreased the more years they had been implanted. We conclude that continuous wave Doppler echocardiography is a useful noninvasive method for the quantitative assessment of the diastolic opening function of the prosthetic mitral valve.(ABSTRACT TRUNCATED AT 250 WORDS)