Characteristics of exercise-induced intrapulmonary arteriovenous fistula in patients with unexplained exertional dyspnea.

Dynamic appearance of intrapulmonary arteriovenous fistula (AVF) during exercise may be associated with unexplained exertional dyspnea (UED) and can be diagnosed with an agitated saline contrast study during exercise echocardiography. However, the occurrence of AVF during exercise in patients with UED has not been well described. Thus, the frequency of exercise-induced intrapulmonary AVF in the outpatients with UED was retrospectively analyzed. Thirty-nine outpatients (age: 53 ± 12, 33 female) with UED underwent symptom-limited supine bicycle exercise echocardiography. Ten patients (26%) developed exercise-induced intrapulmonary AVF. Patients with and without AVF showed the similar peak exercise heart rate, systolic blood pressure, and rate-pressure product. The patients with AVF demonstrated a small but significant decrease in arterial oxygen saturation with exercise as compare to baseline (95.6 ± 2.8% at peak, vs. 97.5 ± 2.5% at baseline, P < 0.05 with a paired Student t-test). Our study suggests that exercise-induced intrapulmonary AVF is relatively common in the outpatients with UED and associated with mild exercise desaturation; however, the mechanism of desaturation could not be determined by this study. Further investigation to characterize and determine the clinical significance of AVF is warranted.