Safety and Diagnostic Accuracy of Dobutamine Stress Echocardiography

Exercise and pharmacologic stress echocardiography has been used routinely in clinical practice for the past twenty to thirty years. Dobutamine stress echocardiography (DSE) is well established as a safe, feasible, and accurate modality for detection of myocardial ischemia and prognostication in patients with known or suspected coronary artery disease, particularly when they have limited exercise capacity. Serious side effects during or shortly after DSE are uncommon, with ventricular fibrillation or myocardial infarction occurring in approximately 1 of 2,000 studies. No deaths have been reported. On the basis of a total number of 2,246 patients, reported in 28 studies, the sensitivity, specificity and accuracy of the test for the detection of coronary artery disease (CAD) were 80%, 84% and 81%, respectively. Mean sensitivities for one, two and three-vessel disease were 74%, 86% and 92%, respectively. The sensitivity of detection of disease in the let circumflex coronary artery (55%) was lower, both compared with that for left anterior descending (72%) and right coronary artery disease (76%). The sensitivity of predicting multivessel disease by multiregional echocardiographic abnormalities varied widely, from 8% to 71%. In direct comparisons, DSE was superior to exercise electrocardiography and dipyridamole echocardiography and comparable to exercise echocardiography and radionuclide imaging. DSE is useful, feasible and safe exercise independent stress modality for assessing the presence, localization and extent of CAD.

Effects of GIK (glucose–insulin–potassium) on stress-induced myocardial ischaemia

Despite the evidence in experimental animal models that insulin, or GIK (glucose–insulin–potassium), improves left ventricular function and perfusion during both acute and chronic ischaemia, clinical studies have generated conflicting results. We tested the hypothesis that pretreatment with GIK attenuates the vascular and functional effects of stress-induced myocardial ischaemia in humans. Twenty-two patients with evidence of inducible myocardial ischaemia were enrolled; 11 patients with normal ventricular function underwent two dipyridamole echocardiography tests, and 11 with regional contractility defects from previous myocardial infarction were submitted to two ECG exercise tests combined with 201Tl myocardial perfusion scintigraphy; the tests were preceded by 60 min of either normal saline or an isoglycaemic GIK infusion. On a stress echocardiogram, a 30% reduction in the severity of ischaemia was observed. On ECG ergometry, GIK infusion slightly increased the time to ischaemia (+0.6 min, P=0.07); however, the higher workload (+8%, P=0.07) was achieved at a similar rate–pressure plateau. On scintigraphy, an increase in ischaemic segments (+48%, P<0.001) was imaged mainly at the expense of viable (but non-ischaemic) and non-viable segments, which were reduced by 60%. GIK affected stress-induced left ventricular underperfusion only marginally (GIK: 39.7±2.5 compared with saline: 35.4±2.2 units, P<0.05), but significantly improved its acute reversibility (−42±4 compared with −25±4%, P<0.001). We conclude that GIK pretreatment attenuates the effect of ischaemia on myocardial contractility, slightly improves exercise tolerance and causes a more rapid and diffuse recovery of post-ischaemic reperfusion.