Head-to-head comparison of high-dose dobutamine stress-echocardiography and exercise testing in prognostic stratification of patients with idiopathic dilated cardiomyopathy

Abstract

It is of the utmost importance to make an accurate assessment of prognosis in patients with idiopathic dilated cardiomyopathy. Both high-dose dobutamine stress-echocardiography and exercise testing have been used for prognostic stratification of these patients. To make head-to-head comparison of high-dose dobutamine stress-echocardiography and exercise testing in prognostic stratification of patients with idiopathic dilated cardiomyopathy. A total of 63 consecutive patients (55 men, mean age 50.1 +/- 9.6 years, mean ejection fraction 19.2 +/- 8.4%) with idiopathic dilated cardiomyopathy, left ventricular end-diastolic diameter >60mm, ejection fraction <35%, and adequate echocardiographic window have been studied. Dobutamine stress echocardiography was performed using 5, 10, 20, 30 and 40 mcg/kg/min infusions, in progressive stages lasting 5 minutes each. Wall motion score index and ejection fraction were considered the indices of the left ventricular contractility. Contractile reserve was defined as the difference between the values of these indices obtained at peak dobutamine dose during the test and the baseline values. Exercise testing was performed as supine bicycle ergometry in progressive stages of 25 W lasting 120 seconds each. Patients were followed one year for combined end-point consisting of cardiac death, partial left ventriculectomy and hospitalization for congestive heart failure. Out of 61, 19 (31%) patients met combined end-point during follow-up [cardiac death in 6/61 (10%), partial left ventriculectomy in 4/61 (7%) and hospitalization for heart failure in 9/61 (15%) patients]. Kaplan-Meier survival analysis demonstrated that dobutamine-induced change of wall motion score index was the best parameter for separation of patients in terms of prognosis during the follow-up (log rank=25.34, p<0.001), followed by change of ejection fraction (log rank=16.83, p<0.001) and duration of exercise testing (log rank 13.85, p=0.002). Cox model identified dobutamine-induced change of wall motion score index as the only independent predictor (p<0.001) of combined end-point during one-year follow-up. There is a number of studies dealing with the left ventricular contractile indices. These studies are different with respect to studied population, method used to elicit the left ventricular contractile response and the indices of contractile reserve. A number of studies has suggested that the amount of pharmacologically or physically induced change of wall motion score index and ejection fraction can identify patients with dismal prognosis. Peak oxygen consumption is traditionally considered the most accurate prognostic index, but its usefulness has been recently questioned. Our data suggest that high-dose dobutamine stress-echocardiography may be superior to exercise testing for prognostic stratification of patients with idiopathic dilated cardiomyopathy. The reasons for such observation are not clear, but it can be hypothesized that this may be due to multifactorial nature of the exercise tolerance. The most serious potential drawback of methodology is that, because of technical limitations, we did not test peak oxygen consumption in our patients, but since it has been shown that oxygen consumption correlates well with the duration of exercise, we believe that our methodology is valid. Both high-dose dobutamine stress-echocardiography and exercise testing can identify patients with dismal prognosis during one-year follow-up, but it appears that dobutamine stress-echocardiography may yield better prognostic significance.