Gas exchange detection of right-to-left shunt in dyspneic patients: report of three cases.

We evaluated three patients with undiagnosed complaints of progressive dyspnea. Based on gas-exchange findings as the initial diagnostic tool, the high ventilatory equivalents for CO2, low sustained end-tidal PCO2, hypoxemia, and central cardiovascular dysfunction during cardiopulmonary exercise testing (CPET) suggested that each had significant pulmonary vasculopathy with right-to-left shunting. The diagnoses of Osler-Rendu-Weber syndrome, ventricular septal defect with Eisenmenger's complex, and hepatopulmonary syndrome were later confirmed by pulmonary angiography, cardiac catheterization, and contrast enhanced echocardiography respectively. We suggest that CPET is an appropriate noninvasive tool to begin and guide the evaluation of undiagnosed dyspnea.