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

Abstract

INTRODUCTION 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. OBJECTIVE To make head-to-head comparison of high-dose dobutamine stress-echocardiography and exercise testing in prognostic stratification of patients with idiopathic dilated cardiomyopathy. METHODS 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 echo-cardiographic window have been studied. Dobutamine stress echocardiography was performed using 5, 10, 20, 30 and 40 meg/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 ventric-ulectomy and hospitalization for congestive heart failure. RESULTS Out of 61, 19 (31%) patients met combined end-point during follow-up [cardiac death in 6/61 (10%), partial left ventricu-lectomy 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. DISCUSSION 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. CONCLUSION 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.Cilj rada je bio da se utvrditi uporedni prognosticki znacaj dobutaminske stres-ehokardiografije i testa fizickim opterecenjem kod bolesnika s idiopatskom dilatacionom kardiomiopatijom. U studiju su ukljucena 63 ?uzastopna" bolesnika. Dobutaminska stres-ehokardiografija je radjena u progresivnim nivoima koji su trajali po pet minuta, s pocetnom dozom od 5 ?g/kg u minuti, koja je povecavana na 10,20,30 i 40 ?g/kg u minuti. Kao indeksi kontraktilne rezerve korisceni su indeks pokreta zidova leve komore srca i ejekciona frakcija. Test fizickim opterecenjem je radjen pomocu tzv. lezeceg bicikla u progresivnim nivoima opterecenja od po 25 W, u trajanju od po120 sekundi. Bolesnici su nadgledani tokom godinu dana zbog pojave kombinovanog ciljnog dogadjaja koji je obuhvatao kardijalnu smrt, parcijalnu levu ventrikulektomiju i hospitalizaciju zbog insuficijencije rada srca. Ciljni dogadjaj je zabelezen kod 19 bolesnika (31%) od 61 bolesnika, i to kardijalna smrt kod sest bolesnika (10%), parcijalna leva ventrikulektomija kod cetiri (7%) i hospitalizacija zbog slabosti srca kod devet bolesnika (15%). Kaplan-Majerova (Kaplan-Meier) kriva prezivljavanja je pokazala da bolesnike, u odnosu na ciljni dogadjaj, najbolje razdvaja promena indeksa pokreta zidova leve komore uzrokovana dobutaminom (Log Rank 25,34, p<0,001), zatim promena ejekcione frakcije (Log Rank 16,83, p<0,001) i duzina tolerancije fizickog opterecenja (Log Rank 13,85, p=0,002). Pomocu Koksovog (Soh) hazardnog modela identifikovana je promena indeksa pokreta zidova leve komore kao jedinog nezavisnog prediktora kombinovanog ciljnog dogadjaja (p<0,001). Dobutaminska stres-ehokardiografija i test fizickim opterecenjem imaju mesto u stratifikaciji rizika kod bolesnika s idiopatskom dilatacionom kardiomiopatijom. Izgleda da dobutaminska stres-ehokardiografija ima nesto veci prognosticki potencijal u odnosu na test fizickim opterecenjem.