Low-dose dobutamine responsiveness in idiopathic dilated cardiomyopathy: relation to exercise capacity and clinical outcome

Aims To evaluate myocardial contractile reserve using low-dose dobutamine e chocardiography in patients with chronic heart failure secondary to idiopat hic dilated cardiomyopathy stratified by peak exercise oxygen consumption ( VO2). Methods and Results Sixty clinically stable patients (56 +/- 11 years; 45 m ales) with idiopathic cardiomyopathy and NYHA class I to III symptoms of he art failure were studied and followed-up for 13+/-3 months. All patients un derwent cardiopulmonary exercise testing and low-dose dobutamine. The dobut amine infusion protocol consisted of an initial dose of 2.5 mu . kg(-1) per 3 min, increasing by 2.5 mu . kg(-1) per min every 3 min; the maximal dose was 10 mu . kg(-1) per min. The end-systolic volume index, left ventricula r ejection fraction and cardiac output were measured at baseline and peak d obutamine dose and their change calculated as ((peak dose value-baseline va lue)/ baseline value] x 100. Ten normal subjects with normal left ventricul ar function and no coronary artery lesions served as a control group to com pare low-dose dobutamine results. All analysed echocardiographic variables either at baseline or following dobutamine infusion were significantly lowe r 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-systoli c volume index (rho=-0.77; P<0.0001), left ventricular ejection fraction (r ho= -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 volum e index following the dobutamine infusion was 28.7 +/- 9% in class A (peak VO2 >20 ml . kg(-1) . min(-1)), 18.6 +/- 8% in class B (peak VO2 between 16 and 20 ml . kg . min(-1)), and only 6.4 +/- 6% in class C (peak VO2 betwee n 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 VO2 <15 ml . kg(-1) . min(-1) (P=0.006). During the follow-up, 17 patients had events (15 readmissions for worsening heart fai lure and two deaths). At multivariate analysis, only the percentage change in end-systolic volume index was significantly associated with the occurren ce of events (P=0.003). The area under the receiver operating characteristi c curve for percentage change in end-systolic volume index was not signific antly different from that for peak VO2 (0.86 +/- 0.04 vs 0.80 +/- 0.06; P:n s). Conclusion This study indicates that in patients with chronic heart failure secondary to idiopathic cardiomyopathy, the cardiac response to low-dose d obutamine, as assessed by echocardiography, is correlated with peak VO2, an objective and accurate measure of the severity of the disease and clinical outcome. (Eur Heart J 2000; 21: 927-934) (C) 2000 The European Society of Cardiology.