Quantification of Valve Regurgitation by Radionuclide Angiography Before and After Valve Replacement Surgery JOANN URQUHART, MD* RANDOLPH E. PATTERSON, MD, FACC’ MILTON PACKER, MD, FACC STANLEY J. GOLDSMITH, MD, FACC STEVEN F. HOROWITZ, MD, FACC ROBERT LITWAK, MD, FACC RICHARD GORLIN, MD, FACC New York, New York From the Divisions of Cardiology and Nuclear Medicine, Department of Medicine and the Divi- sion of Cardiovascular Surgery, Department of Surgery, Mount Sinai School of Medicine, New York, New York. This study was supported in part by Grants I-R23-HL2115 and I-R23-HL-25055-01 from the National Heart, Lung, and Blood Institute. Drs. Patterson and Packer are recipients of Young Investigator’s Research Awards from the National Institutesof Health, Bethesda, Maryland. This study was also supported by grants from the New York Heart Association, New York, New York, The Heart Research Foundation, New York, New York and the Heineman Foundation, New York, New York. Manuscript received April 1, 1980; revised manuscript received September 10, 1980; ac- cepted September 19, 1980. l Present address: Cardiology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland. Address for reprints: Joann Urquhart, MD, Cardiology Branch, Building 10, Room 78-15, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20014. Radionuclide gated cardiac blood pool imaging was used to quantify the severity of valve regurgitation in 20 patients, by calculating the ratio of left ventricular to right ventricular stcoke counts (end-diastolic minus end-systolic counts in right and left ventricular regions of interest). This ratio (the stroke index ratio) was substantially higher in patients wlth aortic and mitral regurgitation (3.91 f 1.45) than In a control group of 10 patients without regurgitation (1.32 f 0.15), p <O.OOl. The stroke index ratio correlated closely (r = 0.947) with measurements of regurgitant fraction derived from simultaneous determinations of total and forward stroke volumes during cardiac catheterization. After aortlc and mitral valve replacement in 18 patients, the stroke index ratio decreased from 4.03 f 1.48 to 1.38 f 0.23 (p <O.OOl), a value not significantly different from that observed in patients without regurgitation. All three patients with residual postoperative regurgitation had a stroke index ratio greater than 2 standard deviations above the mean values for the control group (>1.82), whereas the remaining 15 patients, who had no evidence of regurgitation, had values within the normal range. Therefore, radionuclide gated blood pool scanning provides a noninvasive method of quantifying valve regurgitation and assessing the results of medical or surgical interventions. Evaluation of the severity of aortic and mitral regurgitation is an im- portant clinical problem. Although auscultation remains the standard noninvasive method of diagnosing both the presence and the site of regurgitation, quantification of the magnitude of regurgitation requires the simultaneous invasive determination of the total and forward stroke volumes of the left ventric1e.l Because of the difficulties of this method, valve regurgitation is most frequently assessed qualitatively by a sub- jective evaluation of the magnitude of the regurgitant jet after contrast cineangiography. A less invasive and more accurate method of quanti- fying valve regurgitation is clearly needed. Rigo et a1.2 recently introduced a noninvasive method of quantifying left-sided regurgitant lesions with radionuclide angiocardiography. With this technique, the change in counts between diastole and systole over the left and right ventricles is calculated and expressed as a ratio (the stroke index ratio). Because in normal persons the right ventricular stroke volume is equal to the left ventricular stroke volume, the stroke index ratio should be unity in patients without regurgitant lesions and should be substantially greater than 1 in patients with significant aortic or mitral regurgitation. In the study of Rigo et al., the left ventricular/ right ventricular stroke index ratio in normal subjects (1.15 f 0.13) differed significantly from that in patients with mild (2.15 f 0.48) or severe regurgitation (4.00 f 1.15). A similar relation between the ra- dionuclide stroke index ratio and the angiographic estimation of the magnitude of valve regurgitation was recently confirmed by Lam et al.%? February 1981 The American Journal of CARDIOLOGY Volume 47 287