Regional ventricular dynamics during acute coronary occlusion: A comparison of invasive with non-invasive echocardiographic markers to detect and quantify myocardial ischaemia—observations made during off-pump coronary surgery

Abstract

Objectives To investigate the performance of non-invasive markers used in stress echocardiography to detect the presence and depth of myocardial ischaemia. We therefore sought to compare these non-invasive markers during acute coronary occlusion in humans. Methods 27 patients with stable angina and normal LV cavity size were studied during off-pump coronary artery bypass grafting to the left anterior descending coronary artery using transoesophageal echocardiography and simultaneous high fidelity LV pressure. Regional power development of the anterior wall was plotted throughout the cardiac cycle, allowing the measurement of its time course, peak value and time integral (intrinsic work). Regional effective myocardial work was calculated and its reduction during acute occlusion was used as the invasive standard for ischaemic dysfunction. Results In all patients acute coronary occlusion led to a delay in the onset of regional wall thickening which persisted after aortic valve closure. These time intervals of myocardial thickening had the highest qualitative concordance with the gold standard of a fall in effective work. Regression models identified three significant predictors of the depth of myocardial ischaemia; the interval from Q wave to the onset of regional thickening, duration of post-ejection thickening and peak thickening rate. Objective wall thickening and thinning rates were not significant predictors. Conclusions The regional timing of myocardial thickening and peak thickening rate accurately predicted the presence and indicated the depth of local ischaemia during acute coronary occlusion. These markers may complement subjective wall motion scores aimed at predicting the presence of epicardial coronary artery disease. Condensed abstract We compared non-invasive markers commonly used in stress echocardiography using measurements of the fall in regional myocardial work with coronary occlusion as a standard. 27 patients were studied using transoesophageal echocardiography and simultaneous high fidelity left ventricular pressure during off-pump coronary surgery. Delayed myocardial thickening had the highest qualitative concordance with the gold standard of a fall in effective work, while regression models identified three significant predictors; the interval Q wave to the onset of regional thickening, duration of post-ejection thickening and peak thickening rate. These markers may complement current non-invasive indices of ischaemia during clinical stress testing.