Two methods for increasing sensitivity of dobutamine stress echocardiography: strain imaging and heart-type fatty acid-binding protein levels

Dobutamine stress echocardiography (DSE) is a valuable tool for evaluating patients with established or suspected coronary artery disease (CAD). However, conventional DSE assesses visually ; the visual assessment of regional wall motions is subjective and strongly dependent on experience (1, 2). Tissue Doppler-based longitudinal strain and strain rate (SR) permit the more quantitative and sensitive assessment of wall motions (3). Heart-type fatty acidbinding protein (hFABP) levels rapidly and sensitively increase in serum after myocardial damage (4). hFABP levels could increase after DSE in response to ischemia, and ischemia can be detected by measuring hFABP levels before and after DSE. Combination strain and SR imaging with hFABP levels on DSE could give additional information for predicting the severity of coronary lesions. In this study, we evaluated the diagnostic accuracy of strain, SR, and hFABP levels and compared it to frasionatal flow reserve (FFR) val ues in intermediate coronary lesions on DSE. A total of 31 patients undergoing coronary angiography with a diagnosis of stable angina pectoris (SAP) were enrolled in this prospective observational study. Each patient had only one intermediate coronary lesion in a major epicardial coronary artery. The stenosis diameters of all coronary lesions, which were measured by quantitative coronary analysis, were between 40% and 70%. FFR was planned for all lesions. Coronary angiography and FFR were performed in two different sessions. DSE was performed after coronary angiography and before FFR. DSE images were recorded for the analyses of strain and SR imaging. Blood samples were collected to measure hFABP levels before and 4 h after DSE. The analysis of tissue Doppler derived-strain and SR measurements was performed offline by two independent cardiologists without knowledge of the FFR results. Measurements were performed in each of the following culprit segments in line with the AHA recommendations: the anterior wall was analyzed from apical two-chamber images for the left anterior descending artery, the lateral wall was analyzed from apical four-chamber images for the left circumflex artery, and the inferior wall was analyzed from api cal two-chamber images for the right coronary artery (5). Longitudinal strain, SR, and post-systolic strain indices (PSIs) of each wall were determined. PSIs were calculated as the ratio of post-systolic shortening to peak systolic strain. The diagnostic accuracies of the mean SR values and PSIs of three segments (basal, mid-, and apical) of the wall parameters of the culprit vessel were determined as areas under the curve (AUC)receiver operating characteristics (ROC). In all tests, a p-value of <0.05 was accepted to be statistically significant. Sixteen patients whose FFR value was 0.80 and under 0.80 were added to the ischemic group. Fifteen patients whose FFR value was over 0.80 were added to the non-ischemic group. The mean FFR values were significantly lower in the ischemic group than in the non-ischemic group (0.74±0.03 and 0.87±0.04, respectively; p=0.001). Low-dose stage strain values were reduced in the ischemic group; however, an increase was seen in the non-ischemic group. Lowdose stage strain values were significantly lower in the basal and apical segments in the ischemic group than in the non-ischemic group (p=0.020 and p=0.004, respectively). High-dose stage strain values were higher in the basal and apical segments in the nonischemic group than in the non-ischemic group (p=0.006 and p=0.047, respectively). There was no difference between the two groups in baseline SR values. SR values increased with dobutamine infusion in the two groups. Low-dose stage SR values were signifi cantly low in the mid- and apical segments in the ischemic group. High-dose stage SR values were significantly low in all segments in the ischemic group. The mean SR values of all three segments were significantly lower in the ischemic group than in the non-ischemic group (–1.34±0.42 s–1 vs. –2.02±0.38 s–1, respectively; p=0.001). The baseline PSIs were similar in all three segments. PSIs developed in 34 segments in the ischemic group in the high-dose dobutamine stage and in only 10 segments in the non-ischemic group. PSIs were significantly higher in the ischemic group in all segments in the low- and high-dose dobutamine stages. hFABP levels increased in the ischemic group 4 h after DSE (from 4422±2328 pg/mL to 4783±3708 pg/mL, p=0.479), whereas they decreased in the non-ischemic group 4 h after DSE (from 3777±2540 pg/mL to 3183±1721 pg/mL, p=0.097). hFABP levels did not signifi cantly change in the two groups after DSE.