AIMS: To evaluate myocardial contractile reserve using low-dose dobutamine echocardiography in patients with chronic heart failure secondary to idiopathic dilated cardiomyopathy stratified by peak exercise oxygen consumption (VO(2)). METHODS AND RESULTS: Sixty clinically stable patients (56+/-11 years; 45 males) with idiopathic cardiomyopathy and NYHA class I to III symptoms of heart failure were studied and followed-up for 13+/-3 months. All patients underwent cardiopulmonary exercise testing and low-dose dobutamine. The dobutamine infusion protocol consisted of an initial dose of 2.5 micro. kg(-1)per 3 min, increasing by 2.5 micro. kg(-1)per min every 3 min; the maximal dose was 10 micro. kg(-1)per min. The end-systolic volume index, left ventricular ejection fraction and cardiac output were measured at baseline and peak dobutamine dose and their change calculated as ((peak dose value-baseline value)/baseline value]x100. Ten normal subjects with normal left ventricular function and no coronary artery lesions served as a control group to compare low-dose dobutamine results. All analysed echocardiographic variables either at baseline or following dobutamine infusion were significantly lower in patients with chronic heart failure as a whole compared to the control group. When the patients were grouped according to Weber's classification, a statistically significant decrease in percentange changes in end-systolic volume index (rho=-0.77;P<0.0001), left ventricular ejection fraction (rho=-0.72;P<0.0001) and cardiac output (rho=-0. 82;P<0.0001) from class A to class C was observed. The mean percentage decrease in end-systolic volume index following the dobutamine infusion was 28.7+/-9% in class A (peak VO(2)>20 ml. kg(-1). min(-1)), 18.6+/-8% in class B (peak VO(2)between 16 and 20 ml. kg. min(-1)), and only 6.4+/-6% in class C (peak VO(2)between 10 and 16 ml. kg(-1). min(-1)) patient groups. At multivariate analysis, only the percentage change in end-systolic volume index was significantly associated with a peak VO(2)<15 ml. kg(-1). min(-1)(P=0.006). During the follow-up, 17 patients had events (15 readmissions for worsening heart failure and two deaths). At multivariate analysis, only the percentage change in end-systolic volume index was significantly associated with the occurrence of events (P=0.003). The area under the receiver operating characteristic curve for percentage change in end-systolic volume index was not significantly different from that for peak VO(2)(0. 86+/-0.04 vs 0.80+/-0.06;P:ns). CONCLUSION: This study indicates that in patients with chronic heart failure secondary to idiopathic cardiomyopathy, the cardiac response to low-dose dobutamine, as assessed by echocardiography, is correlated with peak VO(2), an objective and accurate measure of the severity of the disease and clinical outcome. Copyright 2000 The European Society of Cardiology.
AIMS: To evaluate myocardial contractile reserve using low-dose dobutamine echocardiography in patients with chronic heart failure secondary to idiopathic dilated cardiomyopathy stratified by peak exercise oxygen consumption (VO(2)). METHODS AND RESULTS: Sixty clinically stable patients (56+/-11 years; 45 males) with idiopathic cardiomyopathy and NYHA class I to III symptoms of heart failure were studied and followed-up for 13+/-3 months. All patients underwent cardiopulmonary exercise testing and low-dose dobutamine. The dobutamine infusion protocol consisted of an initial dose of 2.5 micro. kg(-1)per 3 min, increasing by 2.5 micro. kg(-1)per min every 3 min; the maximal dose was 10 micro. kg(-1)per min. The end-systolic volume index, left ventricular ejection fraction and cardiac output were measured at baseline and peak dobutamine dose and their change calculated as ((peak dose value-baseline value)/baseline value]x100. Ten normal subjects with normal left ventricular function and no coronary artery lesions served as a control group to compare low-dose dobutamine results. All analysed echocardiographic variables either at baseline or following dobutamine infusion were significantly lower in patients with chronic heart failure as a whole compared to the control group. When the patients were grouped according to Weber's classification, a statistically significant decrease in percentange changes in end-systolic volume index (rho=-0.77;P<0.0001), left ventricular ejection fraction (rho=-0.72;P<0.0001) and cardiac output (rho=-0. 82;P<0.0001) from class A to class C was observed. The mean percentage decrease in end-systolic volume index following the dobutamine infusion was 28.7+/-9% in class A (peak VO(2)>20 ml. kg(-1). min(-1)), 18.6+/-8% in class B (peak VO(2)between 16 and 20 ml. kg. min(-1)), and only 6.4+/-6% in class C (peak VO(2)between 10 and 16 ml. kg(-1). min(-1)) patient groups. At multivariate analysis, only the percentage change in end-systolic volume index was significantly associated with a peak VO(2)<15 ml. kg(-1). min(-1)(P=0.006). During the follow-up, 17 patients had events (15 readmissions for worsening heart failure and two deaths). At multivariate analysis, only the percentage change in end-systolic volume index was significantly associated with the occurrence of events (P=0.003). The area under the receiver operating characteristic curve for percentage change in end-systolic volume index was not significantly different from that for peak VO(2)(0. 86+/-0.04 vs 0.80+/-0.06;P:ns). CONCLUSION: This study indicates that in patients with chronic heart failure secondary to idiopathic cardiomyopathy, the cardiac response to low-dose dobutamine, as assessed by echocardiography, is correlated with peak VO(2), an objective and accurate measure of the severity of the disease and clinical outcome. Copyright 2000 The European Society of Cardiology.