Association between cardiopulmonary exercise and dobutamine stress testing in ambulatory patients with idiopathic dilated cardiomyopathy: A comparison with peak VO2 and VE/VCO2 slope

Background: Both peak VO2 and VE/VCO2 slope are considered to be useful predictors of cardiovascular events. The left ventricular (LV) response to dobutamine stress testing (DST) also provides useful prognostic information. However, the relationship between these variables has not been fully investigated. Therefore, the aim of this study is to investigate the association between myocardial contractile reserve measured by DST and cardiopulmonary exercise testing (CPX) variables in patients with idiopathic dilated cardiomyopathy (IDCM). Methods: Thirty-eight patients were subjected to CPX as well as cardiac catheterization for measurement of LV pressure. The maximum first derivative of LV pressure (LV dP/dt(max)) was measured at baseline and during dobutamine infusion at incremental doses of 5, 10, and 15 mu g kg(-1) min(-1). LV dP/dt(max) at baseline and the percentage increase in LV dP/dt(max) (Delta LV dP/dt(max)) induced by DST served as indices of LV contractility and myocardial contractile reserve, respectively. Results: Peak VO2, and VE/VCO2 slope were 18.6 mL kg(-1) min(-1) and 32.3, respectively. Peak VO2 was not correlated with LV dP/dt(max) at baseline. However, peak VO2 was significantly correlated with Delta LV dP/dt(max), and the correlation became more pronounced as the dose of dobutamine was increased. There was no correlation between VE/VCO2 slope and Delta LV dP/dt(max). Multivariate regression analysis revealed that Delta LV dP/dt(max) was independently correlated with peak VO2 (p = 0.011). Conclusions: Peak VO2, but not VE/VCO2 slope, may reflect myocardial contractile reserve in ambulatory patients with IDCM. This study population is small, and therefore large confirmatory studies are needed. (c) 2011 Elsevier Ireland Ltd. All rights reserved.