117 Tissue velocity imaging and myocardial contrast echocardiography with power Doppler harmonic imaging during adenosine stress

Abstract

Background: LV function improves after early revascularisation in patients with extensive myocardial ischaemia, if there are many viable segments, and surgery also improves survival.Identifying patients who will benefit is difficult.In a prospective study, we investigated if pre-operative myocardial responses to dobutamine, assessed by tissue Doppler echocardiography (TDE), could predict improved regional function after coronary artery bypass surgery (CABG).Methods: We studied 23 patients (21 men, aged 61±10 years) with multivessel coronary disease and poor LV function (ejection fraction EF<35% on Technetium 99 blood pool imaging).All had graded dobutamine stress echocardiography, with storage of digital loops (GE Vingmed) for off-line TDE analysis, and nitrateenhanced rest-redistribution Thallium 201 perfusion imaging.Perfusion scans were analysed and scored from polar plots scaled to 100% using a 16-segment model and a colour cut-off of 50%.Both investigations were repeated 6-8 months after elective CABG.Graft patency was confirmed by CT angiography.Results: After CABG, mean segmental perfusion scores improved (from 6.7±2.7 pre-op to 9.8±2.7;p<0.02) and anginal symptoms abated (Canadian Cardiac Society class, from 2.08±0.85 to 0.74±0.75,p<0.005).There was a smaller reduction in NYHA class (from 2.48±0.5 to 1.65±0.88;p<0.005), global EF was unchanged (32±17% pre-op v 34±13% post-op).Systolic strain rate in basal myocardial segments imaged from apical windows (thus assessing subendocardial, longitudinal function) increased with dobutamine both before and after CABG, but there were no significant differences between pre-op and post-op studies.Peak myocardial systolic velocities increased similarly during both studies, and were also not greater after CABG.Maximal systolic strain fell during dobutamine pre-op (from -8.4±0.9 to -6.1±0.7%,p<0.05) suggesting ischaemia, while after CABG it remained low at rest but did not deteriorate during dobutamine (-8.2±0.9 to -7.1±0.7%,ns).Post-systolic strain was observed during dobutamine before CABG (-9.6±0.8 to -7.6±0.6%,p<0.05) but not afterwards (-0.1±0.01 to -0.1±0.01%)(p<0.05between pre-and post-op studies). Conclusion:The elimination of post-systolic strain observed following successful revascularisation may be a sensitive non-invasive marker of improved myocardial perfusion and resolution of ischaemia.This study supports further investigation of post-systolic strain as a potential clinical marker of hibernating myocardium.