Grading of mitral regurgitation by quantitative Doppler echocardiography: Calibration by left ventricular angiography in routine clinical practice

Background: Quantitative Doppler echocardiography and proximal flow convergence methods are validated techniques for quantifying mitral regurgitation. However, the clinical interpretation of the values calculated is hindered by the absence of calibration of ranges of severity in large numbers of patients. Methods and Results: In 180 consecutive patients (men, 62%; mean age ± SD, 66 ± 11 years), the results of Doppler quantification of isolated mitral regurgitation were calibrated by use of left ventricular angiographic grading performed within 3 months in routine practice and without intervening events. The thresholds of the quantitative variables corresponding to the angiographic grades were identified by maximizing the sum of sensitivity and specificity and minimizing their difference. The mitral regurgitation grade by angiography was 2.7 ± 1.3. The mean value and correlation with angiographic grades for effective regurgitant orifice were 43 ± 37 mm and r=.79 (P<.0001); for regurgitant volume, 62 ± 45 mL and r=.80 (P<.0001); and for regurgitant fraction, 45 ± 17% and r=.78 (P<.0001). Despite some overlap, differences between mitral regurgitation grades were all significant (all P<.05). The thresholds for severe mitral regurgitation (grade 4) were 60 mL, 50%, and 40 mm² for regurgitant volume, regurgitant fraction, and orifice, respectively. Conclusions: In routine practice in large numbers of patients in a clinical laboratory, Doppler echocardiographic quantification of mitral regurgitation shows highly significant correlation with qualitative angiographic grades. Despite an expected overlap between classes, the calibration by angiography of grading ranges for the quantitative variables provides a framework for their interpretation and allows the definition in clinical practice of thresholds for severe mitral regurgitation.