Cardiopulmonary exercise testing in adults with congenital heart disease: Prognostic role in cyanotic patients

There are few and conflicting data concerning cardiopulmonary exercise testing (CPET) in cyanotic congenital heart disease (CHD) in whom the ventilation patterns could be affected. Aim was to assess the functional capacity and stratifying power of CPET in cyanotic CHD. Retrospective evaluation of CHD adults submitted to CPET in a tertiary centre and followed for at least one year. Patients were divided according to presence of cyanosis (rest oxygen saturation<90%). CPET parameters were analysed as potential predictors of the primary endpoint of cardiac death and hospitalization. 286 patients, median age 34 years and 3.6 years of follow-up, sixty (21%) cyanotic. Primary endpoint was reached by 49.1% and 22.9% in cyanotic and non-cyanotic patients, respectively. There were significant differences in CPET parameters: cyanotic patients had lowest values for peak oxygen consumption, partial pressure end-tidal carbon dioxide stages, chronotropic index and higher minute ventilation/carbon dioxide production slope and optimal point of ventilation. In cyanotic population the predictors of primary endpoint were: chronotropic index (HR 0.985) in non-Eisenmenger patients; optimal point of ventilation (HR 1.269), rest oxygen saturation (HR 0.621), partial pressure end-tidal carbon dioxide at anaerobic threshold (HR 0.952) and chronotropic index (HR 0.973) after Fontan circulation; partial pressure end-tidal carbon dioxide at rest (HR 1.129) and rest oxygen saturation (HR 1.129) after biventricular repair. Cyanotic patients had worst exercise capacity and prognosis. Non-traditional CPET parameters as chronotropic index, optimal point of ventilation and partial pressure end-tidal carbon dioxide stages can predict major cardiac events in cyanotic subgroups.