BACKGROUND: Both peak VO(2) and VE/VCO(2) 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 μg kg(-1)min(-1). LV dP/dt(max) at baseline and the percentage increase in LV dP/dt(max) (ΔLV dP/dt(max)) induced by DST served as indices of LV contractility and myocardial contractile reserve, respectively. RESULTS: Peak VO(2), and VE/VCO(2) slope were 18.6 mL kg(-1)min(-1) and 32.3, respectively. Peak VO(2) was not correlated with LV dP/dt(max) at baseline. However, peak VO(2) was significantly correlated with ΔLV dP/dt(max), and the correlation became more pronounced as the dose of dobutamine was increased. There was no correlation between VE/VCO(2) slope and ΔLV dP/dt(max). Multivariate regression analysis revealed that ΔLV dP/dt(max) was independently correlated with peak VO(2) (p=0.011). CONCLUSIONS: Peak VO(2), but not VE/VCO(2) slope, may reflect myocardial contractile reserve in ambulatory patients with IDCM. This study population is small, and therefore large confirmatory studies are needed.
BACKGROUND: Both peak VO(2) and VE/VCO(2) 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 μg kg(-1)min(-1). LV dP/dt(max) at baseline and the percentage increase in LV dP/dt(max) (ΔLV dP/dt(max)) induced by DST served as indices of LV contractility and myocardial contractile reserve, respectively. RESULTS: Peak VO(2), and VE/VCO(2) slope were 18.6 mL kg(-1)min(-1) and 32.3, respectively. Peak VO(2) was not correlated with LV dP/dt(max) at baseline. However, peak VO(2) was significantly correlated with ΔLV dP/dt(max), and the correlation became more pronounced as the dose of dobutamine was increased. There was no correlation between VE/VCO(2) slope and ΔLV dP/dt(max). Multivariate regression analysis revealed that ΔLV dP/dt(max) was independently correlated with peak VO(2) (p=0.011). CONCLUSIONS: Peak VO(2), but not VE/VCO(2) slope, may reflect myocardial contractile reserve in ambulatory patients with IDCM. This study population is small, and therefore large confirmatory studies are needed.