Criteria to detect mitral prosthetic valve dysfunction via continuous wave Doppler echocardiography

To detect the diagnostic criteria for mitral prosthetic valve dysfunction, Doppler echocardiography was used to assess valve function following mitral valve replacement in 100 patients [50 with St. Jude Medical (SJM) valves, 50 with Bjork-Shiley (B-S) valves]. Mitral valve area (MVA) was calculated by dividing a constant of 220 by pressure half time (PHT) measured via Doppler technique [220/PHT]. The relationship of MVA to left ventricular function, geometric valve area (GVA) of the prosthetic valve, body surface area (BSA), and maximum disc-opening angle (maxOA) were assessed. In the SJM valves, MVA significantly correlated with valve area index (GVA/BSA). The %area index [(MVA/valve area index) x 100] was 100.2 ± 12.8% on the average and no patients with the SJM valve showed the %area index of less than 73%. There was no incidence of valve dysfunction in the SJM valves. We concluded from these results that if the %area index is less than 73% (mean - 2SD), the SJM valve dysfunction should be diagnosed. When the B-S valves were examined, there were 19 patients in whom the maximum opening angle had decreased to under 58 degrees. These patients also had decreased MVA and %area index. Evaluation of the relationship between the maximum opening angle and the %area index revealed that the patients in whom the maximum opening angle had diminished to under 50 degrees had low %area index (of less than 70%). In the B-S valves, eight out of the nine patients who showed the %area index less than 70%, underwent reoperation because of valve dysfunction due to thrombus or pannus formation around the prosthetic valves. We determined that if the %area index is less than 70%, the B-S valve dysfunction should be diagnosed.