Application of the flow convergence region method to the determination of stroke volume and cardiac output in patients with mitral stenosis.

OBJECTIVE

This study was undertaken to investigate the feasibility and accuracy of determination of stroke volume and cardiac output by calculating transmitral flow volume using the flow convergence region method in patients with mitral stenosis.

PATIENTS AND INTERVENTIONS

Fifty-six patients with rheumatic mitral stenosis were studied using imaging and Doppler echocardiography. Aliasing velocities of 20 to 23 cm/s were used to record the flow vonvergence region proximal to the stenotic mitral orifice. The stroke volume (mL) was calculated by multiplying peak transmitral flow rate which was obtained using an angle-corrected hemispheric flow convergence equation, by transmitral velocity time integral (cm) divided by peak transmitral velocity (cm/s) recorded using continuous wave Doppler method.

MAIN RESULTS

Stroke volume calculated using the flow convergence region method was not significantly different from that calculated using aortic Doppler two-dimensional echocardiographic method in 39 patients with pure mitral stenosis (75+/-19 [mean+/-1SD] versus 73+/-19 mL, P=0.12), and from that calculated using pulmonic Doppler two-dimensional echocardiographic method in nine patients with mitral stenosis with associated>2+ aortic regurgitation (77+/-12 versus 75+/-14 mL, P=0.49). No significant difference existed between the cardiac output obtained using the flow convergence region method and that obtained using Fick method in 12 patients with pure mitral stenosis. The stroke volume was overestimated by the flow convergence region method when compared with those obtained using aortic Doppler two-dimensional echocardiographic method in patients with mitral stenosis with associated >2+ mitral regurgitation (123+/-40 versus 67+/-15 mL, P=0.001).

CONCLUSIONS

The present study provided an alternative way to calculate the stroke volume and cardiac output in patients with mitral stenosis.