Doppler echocardiographic assessment of TTK Chitra prosthetic heart valve in the mitral position.

AIMS

TTK Chitra heart valve prosthesis (CHVP), a tilting disc mechanical heart valve of low cost and proven efficacy, has been in use for the last 15 years. Although various studies substantiating its long-term safety and efficacy are available, no study had assessed its echocardiographic characteristics. The purpose of this study was to determine the normal Doppler parameters of CHVP in the mitral position and to assess whether derivation of mitral valve area (MVA) using the continuity equation (CE) and more commonly used pressure half-time (PHT) method is comparable in the functional assessment of this tilting disc mitral prosthesis.

METHODS AND RESULTS

Doppler echocardiography was performed in 40 consecutive patients with CHVP in the mitral position. All patients were clinically stable, without evidence of prosthetic valve dysfunction such as significant obstruction or regurgitation, endocarditis, left ventricular dysfunction (ejection fraction <40%), or significant aortic regurgitation. Valve sizes studied included 25, 27, and 29 mm. Mitral valve area was derived both by the PHT method and by the CE, using the stroke volume measured in the ventricular outflow tract divided by the time-velocity integral of CHVP jet. The peak Doppler gradient ranged from 5 to 21 (mean 11.0) mmHg, and the mean gradient ranged from 1.7 to 9.2 (mean 4.1) mmHg. Mean gradient negatively correlated with an increase in the actual orifice area (AOA) derived from the valve orifice diameter given by the manufacturer (r = -0.45, P = 0.004). Mitral valve area calculated by both PHT and CE increased significantly with an increase in the AOA (r = 0.42, P = 0.007 and r = 0.32, P = 0.046, respectively). Mitral valve area by the CE averaged 1.55 +/- 0.36 cm(2) (range 0.85 cm(2) for a 25 mm valve to 2.41 cm(2) for a 29 mm valve) and was smaller than by PHT (mean 2.04 +/- 0.41 cm(2), range 1.40-3.14 cm(2); P = 0.0001; t-test), irrespective of whether PHT is less than or >110 ms.

CONCLUSION

The Doppler parameters obtained with CHVP in the mitral position are comparable with those obtained with the different prosthetic valves in common use. In the selected group of patients with CHVP, assessment of MVA by the PHT method is comparable with that by the CE. Areas by both methods were smaller than the AOA provided by the manufacturer, as seen in other similar design valves.