Abstract 1715: The Association Between Myocardial Contractile Reserve by Dobutamine Stress Testing and Cardiopulmonary Exercise Testing Variables in Patients With Idiopathic Dilated Cardiomyopathy
Introduction. Cardiopulmonary exercise testing (CPX) is important in assessment of patients with chronic heart failure, with peak oxygen consumption (VO2) being a strong predictor of overall mortality and a determinant of risk stratification for such individuals. The left ventricular (LV) response to dobutamine stress testing (DST) also provides useful prognostic information.
Hypothesis. We have investigated the hypothesis that CPX variables might be related to myocardial contractile reserve revealed by DST in patients with idiopathic dilated cardiomyopathy (IDCM).
Methods. Twenty-four ambulatory patients with IDCM were subjected to CPX as well as to cardiac catheterization for measurement of LV pressure. The maximal first derivative of LV pressure (LV dP/dtmax) was measured at baseline and during dobutamine infusion at incremental doses of 5, 10, and 15 μg kg−1 min−1. LV dP/dtmax at baseline and the percentage increase in LV dP/dtmax (ΔLV dP/dtmax) induced by DST served as indexes of LV contractility and myocardial contractile reserve, respectively.
Results. Mean values of LV ejection fraction, peak VO2, and minute ventilation/carbon dioxide production (VE/VCO2) slope were 33.2%, 20.2 mL kg−1 min−1, and 32.5, respectively, for the study subjects. Peak VO2 was not correlated with LV dP/dtmax at baseline. However, ΔLV dP/dtmax was significantly correlated with peak VO2, and the correlation became more pronounced as the dose of dobutamine increased. A significant inverse correlation between ΔLV dP/dtmax and VE/VCO2 slope was apparent only at the highest dose of dobutamine. Multivariate linear regression analysis revealed that ΔLV dP/dtmax was independently correlated with peak VO2 (p = 0.025).
Conclusions. These finding suggest that the LV response to DST reflects peak VO2 rather than VE/VCO2 slope in ambulatory patients with IDCM.