Abnormal ventilatory response to exercise in adults with congenital heart disease relates to cyanosis and predicts survival

Background - Limited data exist with which to stratify risk in adult congenital heart disease (ACHD). An increased ventilatory response to exercise, expressed as ventilation per unit of carbon dioxide production (V-E/VCO2 slope), is an established predictor of impaired survival in acquired heart disease. We sought to establish the distribution, relation to cyanosis, and prognostic value of the V-E/ VCO2 slope across a wide spectrum of ACHD patients. Methods and Results - Five hundred sixty ACHD patients of varying diagnoses and 50 healthy controls underwent cardiopulmonary exercise testing at a single laboratory between 2001 and 2004. Patient age was 33.2 +/- 12.9 years (mean +/- SD). Peak oxygen consumption was 23.5 +/- 9.0 mL(.)kg(-1.)min(-1). V-E/VCO2 slope for all patients was 36.3 +/- 15.3. The slope was raised in all ACHD groups compared with controls and was 73% higher in cyanotic patients. Cyanosis, with or without pulmonary arterial hypertension, was the strongest predictor of abnormal V-E/VCO2 slope. The V-E/VCO2 slope was the most powerful univariate predictor of mortality in the noncyanotic group and the only independent predictor of mortality among exercise parameters on multivariate analysis. In cyanotic patients, no parameter was predictive of death. Conclusions - Ventilatory response to exercise is abnormal across the spectrum of ACHD. Cyanosis is a powerful stimulus for such exaggerated ventilatory patterns irrespective of the presence of pulmonary arterial hypertension. Increased V-E/VCO2 slope is the strongest exercise predictor of death in noncyanotic ACHD patients.