BETA-ADRENERGIC CONTRACTILE RESERVE AS A PREDICTOR OF CLINICAL OUTCOME IN PATIENTS WITH IDIOPATHIC DILATED CARDIOMYOPATHY

To examine the ability of beta-adrenergic contractile reserve assessment to predict the outcome of patients with heart failure, a prospective study was undertaken in 35 patients with idiopathic dilated cardiomyopathy and radionuclide ejection fraction below 40%. During right- and left-sided catheterization, right atrial and left ventricular (LV) pressures, peak positive LV dp/dt, cardiac index, and plasma norepinephrine and epinephrine concentrations were measured at baseline. After a left main intracoronary infusion of dobutamine (25 to 200-mu-g . min-1), beta-adrenergic contractile responsiveness was assessed as the net increase in peak positive LV dp/dt (DELTA-LV dp/dt). After the initial examination, patients were treated with diuretics, digitalis, and angiotensin converting enzyme inhibitors and then followed-up. After a mean follow-up period of 13 +/- 7 months, two groups of patients were distinguished: those who responded to medical therapy (group A, n = 26) and those with clinical deterioration (group B, n = 9) leading to death (n = 4) or heart transplantation (n = 5). Initial peak positive LV dp/dt, LV end-diastolic pressure, cardiac index, and LV ejection fraction were better in group A than in group B (p < 0.001). Initial plasma norepinephrine and epinephrine concentrations were significantly higher and DELTA LV dp/dt was lower in group 8 than in group A (p < 0.001). Multivariate stepwise logistic regression analysis showed that DELTA-LV dp/dt (p < 0.0001) and LV ejection fraction (p = 0.0001) were independently related to prognosis. At threshold values of either 250 mm Hg . sec-1 for DELTA-LV dp/dt or 20% for LV ejection fraction, their prognostic predictive values were 69% and 53%, respectively. When the same threshold values were used, a combination of these two parameters led to a positive predictive value of 100%. In conclusion, patients who do not respond to medical therapy were those with the lowest beta-adrenergic contractile reserve. Regarding clinical outcome, low- and high-risk populations may be discriminated by combining LV ejection fraction and beta-adrenergic contractile reserve assessment.