Factors affecting the exercise capacity of pediatric patients with aortic regurgitation

Although exercise testing is commonly employed to identify adult aortic regurgitation (AR) patients with early left ventricular (LV) dysfunction, the role and value of exercise testing in the management of pediatric AR patients have not been established. The purposes of this study were to evaluate the cardiorespiratory response to exercise of pediatric patients with chronic AR, examine the relation between exercise function and baseline echocardiographic measurements, and identify factors related to diminished exercise capacity (EC). The study group consisted of 26 patients aged 8 to 21 years (mean 14.4 +/- 3.7) with moderate or severe AR referred for exercise physiology testing. All patients underwent a baseline echocardiographic study and a symptom-limited, progressive cycle ergometer exercise test. LV diastolic dimension averaged 120 +/- 12% predicted, systolic dimension 112 +/- 20% predicted, shortening fraction 0.41 +/- 0.07, end-systolic wall stress 65 +/- 23 g/cm(2), and regurgitant fraction 38 +/- 16%. The average EC was 88 +/- 28% (56-143) predicted. No statistically significant correlation was found between EC and any of the echocardiographic parameters studied. Nine patients had EC < 75% predicted. These individuals did not differ from patients with higher EC with regard to any of the echocardiographic parameters or with regard to peak heart rate, blood pressure, respiratory exchange ratio, and incidence of ectopy or ST depression. However, the oxygen pulse at peak exercise (an index proportional to forward stroke volume at peak exercise) was significantly depressed among patients with EC < 75% predicted (77 +/- 6 vs. 106 +/- 16% predicted, p <. 0001). In conclusion, most pediatric patients with moderate or severe AR compensate well for their valve disease, maintain normal forward stroke volume during exercise, and have normal EC. However, a subset of AR patients have diminished EC secondary to an inability to augment forward stroke volume appropriately. These patients cannot be identified on the basis of resting echocardiographic studies. Timely identification of these patients, through formal exercise physiology testing, may have important clinical implications.