Dobutamine Echocardiography in Myocardial Hibernation

Abstract

Background Myocardial hibernation is a condition of chronic left ventricular dysfunction associated with severe coronary artery disease whereby significant recovery of function occurs after revascularization. Identification of hibernating myocardium has important prognostic and therapeutic implications. The presence of contractile reserve as assessed by dobutamine echocardiography may be promising in the detection of hibernation. We designed a prospective study to evaluate the accuracy and optimal dose of dobutamine echocardiography for predicting recovery of ventricular function after angioplasty in patients with stable coronary artery disease and ventricular dysfunction. Methods and Results Twenty patients with stable coronary artery disease and segmental ventricular dysfunction scheduled for coronary angioplasty underwent dobutamine echocardiography before revascularization using incremental doses of 2.5, 5, 7.5, 10, 20, 30, and 40 μg/kg per minute every 3 minutes. Digital images of all eight stages were displayed simultaneously (two quad screens side by side) and interpreted using a 16-segment ventricular model and a 6-grade scoring system. Serial resting echocardiograms before, early (<1 week), and late (≥6 weeks) after angioplasty were digitized and randomized in a quad-screen format for the assessment of recovery of function. Wall motion score index in the revascularized regions decreased from 2.86±0.76 before angioplasty to 2.12±1.03 late after angioplasty ( P <.05). Of 320 ventricular segments, 148 had abnormal wall motion at baseline and 114 were revascularized. Recovery of function (≥2 grades) occurred in 25% of revascularized segments early and in 33% late after angioplasty. Of the 34 abnormal segments not revascularized, recovery of function occurred in only 1. During dobutamine echocardiography, abnormal segments exhibited one of four responses: biphasic (improvement at low dose and worsening at high dose) in 28% of segments, sustained improvement (persistent improvement till peak dose) in 18%, worsening in 15%, and no change in 39%. A biphasic response had the highest predictive value (72%) for recovery of function followed by worsening only (35%), while the lowest was seen with a “no change” or sustained improvement response (13% and 15%). Combining biphasic and worsening responses resulted in a sensitivity of 74% and specificity of 73% for assessment of recovery of individual segments and 90% and 60%, respectively, for functional recovery of individual patients (n=10). In segments with a biphasic response, the low dose at which improvement in wall motion was most prevalent (84%) was 7.5 μg/kg per minute and increased to 94% when the 5 and 7.5 μg/kg per minute doses were displayed. The reworsening phase of the biphasic response was usually seen with doses ≥20 μg/kg per minute but was also observed as early as the 7.5 μg/kg per minute dose. Conclusions The wall motion response during dobutamine echocardiography is useful in the prediction of recovery of ventricular function after revascularization in patients with stable coronary artery disease and ventricular dysfunction. The administration of low as well as high doses of dobutamine is needed for optimal evaluation.