Abstract 6097: Coronary Flow Reserve Exceeds Resting Myocardial Perfusion Abnormalities in Hibernating Myocardium: Implications for Using Resting Myocardial Contrast Echocardiography Versus Dobutamine Echocardiography for the Detection of Hibernating Myocardium
Background: Relationship between resting myocardial perfusion, coronary flow reserve (CFR) and contractile reserve (CR) in hibernating myocardium (HM) remains unclear. This has not only pathophysiological implications but may impact on the optimum diagnostic technique for the identification of HM.
Methods: Accordingly 27 patients with severe symptomatic ischemic cardiomyopathy (LVEF:30±10%) who were scheduled to undergo revascularisation underwent, resting and vasodilator myocardial contrast echocardiography (MCE) and dobutamine echocardiography (DE). Resting myocardial perfusion parameters assessed were myocardial blood volume (A)(db), myocardial blood flow (β)(db/sec), coronary flow reserve (CFR)(β stress/β rest) and contractile reserve (improvement in function during dobutamine). HM was defined as improvement in resting function of a dysfunctional segment or improvement of contractile function in a persistently dysfunctional segment during DE 3 to 6 months after revascularisation.
Result: Of the 310 dysfunctional segments (17 segment LV model) in 23 patients available for follow up 224 (74%) demonstrated HM. A and β were significantly reduced in HM (A:7.2±2.3 and β: 0.67±0.56) compared to normal myocardium (A:8.1±2.1 and β: 0.85±0.47, p<0.05, p<0.01 respectively) but was significantly higher compared to necrotic myocardium (A:4.4 ± 2.3 and β 0.43 ± 0.32, p<0.01, p<0.01 respectively). CFR, however, was similarly reduced (p = NS) in HM (1.3±3.3) and necrotic myocardium (0.82±3.2) compared to normal myocardium (1.68±1.02 p<0.01). Contractile Reserve (CR) was directly related to CFR (p = 0.03) but not to resting myocardial perfusion. Sensitivity of MCE was 87% compared to 67% (p < 0.001) with DE with similar specificity (67% vs 63% respectively) for the detection of HM.
Conclusion: Resting myocardial perfusion parameters but not CFR identifies HM. Thus, DE which assesses CR (which is influenced by CFR), underestimates HM compared to MCE.