Myocardial perfusion reserve and contractile pattern after beta-blocker therapy in patients with idiopathic dilated cardiomyopathy

BACKGROUND: In Idiopathic Dilated Cardiomyopathy (IDC) an imbalance between myocardial oxygen consumption and supply has been postulated. The ensuing subclinical myocardial ischemia may contribute to progressive deterioration of LV function. β-blocker is the therapy of choice in these patients. However, not all patients respond to the same extent. The aim of this study was to elucidate whether differences between responders and non-responders can be identified with respect to regional myocardial perfusion reserve (MPR) and contractile performance. METHODS: Patients with newly diagnosed IDC underwent Positron Emission Tomography (PET) scanning using both (13)N-ammonia as a perfusion tracer (baseline and dipyridamole stress), and (18)F-fluoro-deoxyglucose as a metabolism tracer, and a dobutamine stress MRI. MRI and PET were repeated 6 months after maximal β-blocker therapy. MPR (assessed by PET) as well as wall motion score (WMS, assessed by MRI) were evaluated in a 17 segment-model. Functional response to β-blocker therapy was assigned as a stable or improved LVEF or diminished LVEF. RESULTS: Sixteen patients were included (age 47.9 ± 11.5 years; 12 males, LVEF 28.6 ± 8.4%). Seven patients showed improved LVEF (9.7 ± 3.1%), and nine patients did not show improved LVEF (−3.4 ± 3.9%). MPR improved significantly in responders (1.56 ± .23 to 1.93 ± .49, P = .049), and MPR decreased in non-responders; however, not significantly (1.98 ± .70 to 1.61 ± .28, P = .064), but was significantly different between both groups (P = .017) after β-blocker therapy. A significant correlation was found between change in perfusion reserve and change in LVEF: a decrease in perfusion reserve was associated with a decrease in LVEF and vice versa. Summed rest score of wall motion in responders improved from 26 to 21 (P = .022) whereas in non-responders no change was observed from 26 to 25) (P = ns). Summed stress score of wall motion in responders improved from 23 to 21 (P = .027) whereas in non-responders no change was observed from 27 to 26) (P = ns). CONCLUSION: In IDC patients, global as well as regional improvement after initiation of β-blocker treatment is accompanied by an improvement in regional perfusion parameters. On the other hand in IDC patients with further left ventricular function deterioration after initiation of β-blocker therapy this is accompanied by a decrease in perfusion reserve.