Continuous wave Doppler echocardiographic assessment of prosthetic valves in the mitral and aortic position

Noninvasive evaluation of the prosthetic valve function remains a clinical challenge. Earlier noninvasive technlques were of limited success because of their inability to provide hemodynamic inforrnation. However, recently developed continuous wave Doppler echocardiography has enabled us to determine transvalvular pressure gradients. We evaluated the prosthetic valve opening function in the mitral and aortic position using continuous wave Doppler echocardiography. I: Prosthetic mitral valve. To evaluate the opening function of prosthetic valves in the mitral position, the mitral flow velocity pattern was recorded with continuous wave Doppler echocardiography in 55 patients with prosthetic mitral valves (34 patients with St. Jude Medical and 21 with porcine xenograft valves). Twenty patients with mitral stenosis and 15 normal subjects were served as controls. An ultrasonic transducer was placed over the left ventricular apex and the direction of the ultrasonic beam was positioned to be parallel with the mitral flow using the Doppler audio-signals. A pressure gradient was calculated form the peak flow velocity with a simplified Bernoulli equation. The peak flow velocity, the pressure half time and the peak and mean pressure gradients were measured to evaluate the opening function of the prosthetic valves. The results were as follows; 1. The values of the peak flow velocity, the pressure half time, the peak and mean pressure gradients in patients with St. Jude Medical valves (1.4±0.3 m/sec, 90±20 mesc, 7.9±2.8 mmHg and 3.5±1.1 mmHg, respectively) and in patients with porcine xenograft valves (1.6±0.3 m/sec, 130±40 msec, 11.2±4.0 mmHg and 4.8±2.1 mmHg, respectively) were significantly larger than those in normal subjects (0.8±0.1 m/sec, 70±10 msec, 2.8±0.8 mmHg and 1.2±0.4 mmHg, respectively) (P<0.01 or P<0.001), but significantly smaller than those in patients with mitral stenosis (1.9±0.3 m/sec, 240±70 msec, 14.6±4.6 mmHg and 8.2±3.8 mmHg, respectively) (P<0.02, P< 0.01 or P<0.001). All measurements of the 4 indices in patients with the St. Jude Medical valves were significantly smaller than those in patients with the porcine xenograft valves (P<0.01). 2. The changes in the 4 indices related to the valvular size were small in patients with St. Jude Medical and porcune xenograft valves. 3. The correlation between the peak flow velocity (Y_1), the peak pressure gradient (Y_2) and the mean pressure gradient (Y_3) and the years after the valve replacement (X) in patients with porcine xenograft valves demonstrated a significant relationship (Y_1=0.1X+1.4, r=0.62, P<0.01; Y_2=0.7X+7.8, r=0.60, P<0.01 and Y_3=0.3X+3.3, r=0.50, P<0.01, respectively).II: Prosthetic aortic valve. To evaluate the opening function of prosthetic valves in the aortic position, the aortic flow velocity pattern was obtained with continuous wave Doppler echocardiography in 40 patients with prosthetic aortic valves (21 patients with Björk-Shiley valves, 12 patients with St. Jude Medical valves and 7 patients with Carpentier-Edwards valves) and in 25 normal subjects. The peak flow velocity across the aortic valve was recorded from the left ventricular apex, the suprasternal notch and the right parasternal border in the second intercostal space. The highest value was judged to be the peak flow velocity in each patient. The peak and mean pressure gradients were measured from the peak flow velocity with a simplified Bernoulli equation. The results were as follows; 1. The values of the peak flow velocity, the peak and mean pressure gradient in patients with Björk-Shiley valves (2.5±0.6 m/sec, 26±12 mmHg and 14±6 mmHg, respectively), in patients with St. Jude Medical valves (2.7±0.4 m/sec, 30±9 mmHg and 16±5 mmHg, respectively) and in patients with Carpentier-Edwards valves (2.7±0.7 m/sec, 31±15 mmHg and 18±9 mmHg, respectively) were significantly larger than those in normal subjects (1.1±0.2 m/sec, 5±2 mmHg and 3±1 mmHg, respectively) (P<0.001). But there were no significant differences of the values among the 3 groups of prosthetic valve. 2. The correlation between the peak flow velocity (Y_1), the peak (Y_2) and mean (Y_3) pressure gradients and the valvular size (X) in patients with Björk-Shiley valves demonstrated a significant inverse relationship (Y_1=-0.4X+3.5, r=-0.62, P<0.01; Y_2=-6.8X+45.9, r=-0.60, P<0.01 and Y_3=-4.1X+25.7, r=-0.65, P