Exertional oscillatory ventilation (EOV) has been noted during cardiopulmonary exercise testing (CPX) in patients with heart failure. EOV is a predictor of poor prognosis in adult patients with heart failure. The objective of this study was to clarify the incidence and influence of EOV in Fontan patients. Symptom-limited CPX was performed in 36 Fontan patients at 12.3 +/- 4.3 (6.5-24.4) years of age or 5.9 +/- 2.0 (3.0-11.2) years after total cavopulmonary connection (TCPC). Mean age at the time of TCPC was 6.3 +/- 3.3. All 36 TCPC patients were classified as New York Heart Association classification I or II. They also underwent cardiac catheterization subsequently. EOV was defined as cyclic fluctuations in minute ventilation at rest that persist during effort lasting >or=60% of the exercise duration, with an amplitude >or=15% of the average resting value. EOV was noted in 21 of 36 Fontan patients (58%) with good clinical status. Univariable analysis between Fontan patients with and those without EOV showed significant differences in age at TCPC (p < 0.05), age at CPX (p < 0.02), weight at CPX (p < 0.02), follow-up duration between TCPC and CPX (p < 0.04), ventricular morphology (p < 0.05), and metabolic equivalents (p < 0.05) and peak minute oxygen uptake (VO(2)) per body weight (p < 0.05). Multivariable analysis showed that EOV was significantly related to peak VO(2) per kilogram. In conclusion, EOV was frequently noted during exercise in Fontan patients with good clinical status. EOV during exercise seems to be related to higher peak VO(2) per kilogram and younger age at TCPC, which is a contrary result to those for adult patients with chronic heart failure. EOV is a remarkable phenomenon during exercise to compensate for impaired cardiopulmonary function in Fontan patients.