We evaluated whether dobutamine stress (99m)Tc-tetrofosmin quantitative gated SPECT (D-QGS) could predict improvement of cardiac function by carvedilol therapy in patients with dilated cardiomyopathy (DCM).
Methods: The study included 30 patients with idiopathic DCM and a left ventricular ejection fraction (LVEF) of <45%. D-QGS was performed in all patients to measure LVEF at rest and during dobutamine infusion (10 microg/kg/min). LVEF and left ventricular end-diastolic volume (LVEDV) were determined by echocardiography, plasma brain natriuretic peptide (BNP) was measured, and the New York Heart Association (NYHA) functional class was estimated at baseline and after 1 y of combined treatment with an angiotensin-converting enzyme (ACE) inhibitor, diuretic, and the beta-blocker carvedilol. After treatment, the echocardiographic LVEF improved by >5% in 15 patients (group A) but did not improve in the remaining 15 patients (group B).
Results: The baseline LVEF, LVEDV, plasma BNP, and NYHA functional class were similar in both groups. However, there was a greater increase of LVEF (Delta LVEF) with dobutamine infusion during D-QGS in group A than that in group B (12.0% +/- 5.8% vs. 2.7% +/- 4.2%, P < 0.0001). When a cutoff value of 6.6% for Delta LVEF was used to predict the improvement of LVEF by carvedilol therapy, the sensitivity was 86.7%, the specificity was 86.7%, and the accuracy was 86.7%. LVEDV, plasma BNP, and NYHA functional class all showed superior improvement in group A compared with group B.
Conclusion: Delta LVEF measured by D-QGS was significantly larger in patients who responded to carvedilol than that in nonresponders. These findings indicate that D-QGS can be used to predict improvement of cardiac function and heart failure symptoms by carvedilol therapy in patients with idiopathic DCM.