REGURGITANT VOLUME IN AORTIC REGURGITATION FROM A PARAMETER-ESTIMATION PROCEDURE

The regurgitant volume and regurgitant orifice area as well as total p eripheral resistance and arterial compliance were estimated in a cardi ovascular hydromechanical simulator and in 10 patients with aortic reg urgitation. A parameter estimation procedure based on a simple model o f the cardiovascular system, Doppler measurements of the regurgitant j et, aortic systolic flow, and systolic and diastolic blood pressures w as used. In the cardiovascular simulator the estimated regurgitant ori fice area was compared with the size of a hole in the disk of a mechan ical aortic valve. In the patients the regurgitant fraction was compar ed with semiquantitative grading from echocardiography routinely perfo rmed in our laboratory. In the hydromechanical simulator, the estimate d regurgitant orifice area of 26.5 +/- 3.5 (SD) mm(2) (n = 9) was not different from the true value of 24 mm. In the patients there was a fa ir relationship between the estimated regurgitant fraction and the sem iquantitative grading. The estimated regurgitant orifice areas varied between 1.6 and 31.2 mm(2). The estimated mean values of total periphe ral resistance and arterial compliance were 1.67 +/- 0.55 mmHg.s.ml(-1 ) and 1.30 +/- 0.42 ml/mmHg, respectively.