Detection of Subendocardial Ischemia in the Left Anterior Descending Coronary Artery Territory With Real-Time Myocardial Contrast Echocardiography During Dobutamine Stress Echocardiography

OBJECTIVES The purpose of this study was to test whether the transmural delineation of myocardial perfusion during dobutamine stress imaging with real-time myocardial contrast echocardiography (RTMCE) might permit visualization of dobutamine-induced subendocardial ischemia. BACKGROUND Significant coronary artery disease can be present despite normal transmural wall thickening (WT) responses during dobutamine stress echocardiography (DSE). One potential reason is dobutamine-induced recruitment of epicardial WT in the presence of subendocardial ischemia. METHODS Myocardial perfusion and WT were examined with RTMCE during DSE with a continuous infusion of ultrasound contrast in 94 patients with normal resting WT. Fifty-five of the patients had a >50% diameter stenosis in the left anterior descending coronary artery (LAD). The WT was visually assessed by a blinded reviewer at 2 time periods: initially after a high mechanical index impulse before myocardial contrast replenishment (MCR), and again during MCR. Subendocardial %WT was measured during MCR, if a subendocardial perfusion defect was visually evident, whereas transmural WT was quantified on the pre-MCR images. RESULTS Fifty patients (91%) with LAD stenoses exhibited a myocardial contrast defect at peak stress, with 45 defects being subendocardial. Transmural WT pre-MCR appeared normal in 35 of the 45 patients with subendocardial perfusion defects (78%). However, a subendocardial WT abnormality was apparent during MCR in 18 of these 35 patients, even though transmural WT was not different from the 17 patients with normal subendocardial WT (33 +/- 15% vs. 36 +/- 14%). Quantitative measurements of WT within the sub-endocardium were significantly less in the patients with visually evident subendocardial WT abnormalities, when compared with those who seemed to have normal WT during MCR (17 +/- 8% vs. 25 +/- 10%, p < 0.01). CONCLUSIONS In patients with significant LAD disease, RTMCE during DSE detects subendocardial ischemia even when transmural WT appears normal. Real-time myocardial contrast echocardiography should be the preferred ultrasound imaging method when using contrast to detect coronary artery disease during DSE. (J Am Coll Cardiol Img 2008; 1: 271-8) (C) 2008 by the American College of Cardiology Foundation