Can gated pool radionuclide imaging detect abnormal left ventricular function during exercise in asymptomatic patients with severe aortic regurgitation?
Abnormalities of left ventricular function can be demonstrated on exercise in a significant proportion of asymptomatic patients with severe aortic regurgitation, which cannot be predicted by resting clinical parameters.
Abstract The optimal time for valve replacement in asymptomatic patients with severe aortic regurgitation is uncertain and is usually based on changing patterns in the ECG, radiographic heart size, or decreasing effort tolerance. The relationship between these parameters and changes in left ventricular function however has not been defined. In this study 28 patients, ages 20 to 66 years (mean 35 years) underwent gated pool radionuclide imaging at rest and at submaximal exercise (to greater than 85% maximum heart rate predicted for age) to quantitate ejection fraction (EF) and severity of aortic regurgitation. All patients had a 12‐lead ECG and chest x‐ray and 18 patients underwent echocardiography and maximal treadmill exercise testing. Severity of left ventricular hypertrophy on ECG was assessed by the Estes scoring system, heart size was expressed as cardiothoracic ratio (CTR). Echocardiograms were analyzed with respect to left ventricular end‐systolic diameter (LVESD) and fractional shortening. EF was below the normal range at rest (<0.45%) in only 6 patients (21%), but was abnormal during exercise in 18 patients (64%). Reduction in EF on exercise by 20% was judged to represent significant deterioration and occurred in 12 patients (43%), all of whom had an EF of less than 0.45% on exercise. Comparison of ECG, heart size, echocardiogram, exercise performance, and resting EF in this group of 12 patients with the remaining 16 patients showed no significant differences. In the group as a whole, stress EF was abnormal in 14 of 19 patients (73%) with an Estes score of 5 or greater, and was significantly lower (p < 0.05, mean 0.42) than in patients with an Estes score less than 5 (mean 0.52). There was no significant correlation between EF at rest or during exercise and any of the other parameters. Severity of aortic regurgitation (regurgitant fraction) showed poor correlation with heart size and LVESD (r = 0.24 and 0.32, respectively). It is concluded that abnormalities of left ventricular function can be demonstrated on exercise in a significant proportion of patients with aortic regurgitation despite the absence of symptoms, and that these changes cannot be predicted by readily available clinical parameters or by assessment of resting left ventricular function. Gated pool imaging may be a sensitive method for detection of early changes in LV function in these patients, but its value in assessing the timing of valve replacement requires serial investigation.
Thompson et al. (Fri,) studied this question.