Prognostic value of cardiopulmonary exercise testing in Idiopathic Dilated Cardiomyopathy

Background Although cardiopulmonary exercise testing (CPET) is considered as an important tool in risk stratification of patients with heart failure (HF), prognostic data in the specific setting of Idiopathic Dilated Cardiomyopathy (iDCM) are still undetermined. The aim of the study was to test the prognostic value of CPET in a large cohort of iDCM patients. Methods and results We analyzed 381 iDCM patients who consecutively performed CPET. The study end-point was a composite of cardiovascular death/urgent heart transplantation (CVD/HTx). In the overall population the average values of peak oxygen consumption (peak VO₂/kg) and percent-predicted peak VO₂ (peak VO₂%) were 17.1 ± 5.1 ml/kg/min and 59 ± 15%, respectively. Mean VE/VCO₂ slope was 29.8 ± 6.1. During a median follow-up of 47 months (interquartile range 23–84), 83 patients experienced CVD/HTx. Peak VO₂% (Area Under the Curve [AUC] 0.74; 95% CI 0.71–0.85, p < 0.001) and VE/VCO₂ slope (AUC 0.78; 95% CI 0.74–0.84, p < 0.001) were more accurate in predicting CVD/HTx compared to peak VO₂/kg (AUC 0.60; 95% CI 0.54–0.68, p = 0.003) (p < 0.001 for both comparisons). The most accurate threshold values for outcome prediction in our iDCM cohort were < 60% for peak VO₂% and > 29 for VE/VCO₂ slope. At multivariable analysis peak VO₂% and VE/VCO₂ slope were the strongest predictors of CVD/HTx, either as continuous and categorical variables, whereas peak VO₂/kg was not independently related with prognosis. Conclusion In a large population of iDCM patients peak VO₂% and VE/VCO₂ slope emerged as the strongest prognostic CPET variables. Prospective studies will be necessary to confirm these data.