Dobutamine stress 99mTc-tetrofosmin quantitative gated SPECT predicts improvement of cardiac function after carvedilol treatment in patients with dilated cardiomyopathy

We evaluated whether dobutamine stress Tc-99m-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 mug/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 P-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 (DeltaLVEF) 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 DeltaLVEF 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: DeltaLVEF 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.