HETEROGENEITY OF LEFT-VENTRICULAR REGIONAL WALL THICKENING FOLLOWING DOBUTAMINE INFUSION IN NORMAL HUMAN-SUBJECTS - A QUANTITATIVE 2-DIMENSIONAL ECHOCARDIOGRAPHIC STUDY

Background: Pathophysiological data and pragmatic clinical experience with stress echocardiography suggest that inotropic stimulation with s imultaneous changes in heart rate and loading conditions can affect th e function of various myocardial regions asymmetrically, inducing hete rogeneity in wall motion and thickening possibly mimicking 'ischaemic' regional hypokinesis or lack of hyperkinesis during stress. Objective s: To describe, in a quantitative fashion, the physiological contracti le response of different left ventricular regions following dobutamine infusion. Methods: Two hundred and twenty-three in-hospital patients undergoing dobutamine stress echocardiography and coronary angiography were initially considered. Of these 223 patients, 18 had angiographic ally normal coronary ar tel ies, normal resting function, negative erg onovine and exercise stress tests, and negative dobutamine stress echo cardiograms; of the 18, only in II patients (six females, age=56 +/- 1 0 years) was it possible to obtain quantitative measurements of the mi ddle segments of the inferior, anterior, lateral, and septal walls. Tw o-dimensional echocardiographic measurements of wall thickness were ob tained at the end-diastolic (onset of Q wave) and end-systolic phases, both at baseline (rest) and at the peak of the dobutamine infusion (4 0 mu g . min(-1). kg(-1) plus atropine). Results: Dobutamine increased heart rate (rest=69 +/- 9 vs dobutamine = 138 +/- 13 beats . min(-1); P<0.01), whereas systolic blood pressure did not change significantly (rest=136 +/- 15 vs dobutamine=150 +/- 25 mmHg, P=ns). During stress, % systolic thickening decreased in the inferior wall (rest=73 +/- 24 vs dobutamine +/- 50 +/- 9%, P<0.01), whereas if tended to increase to a variable extent in the other regions, i.e. septal (rest=46 +/- 17 v s dobutamine=68 +/- 13%, P<0.01), anterior (rest 62 +/- 19 vs dobutami ne=69 +/- 11%, P=ns), and lateral wall (rest=48 +/- 16 vs dobutamine=6 1 +/- 18%, P=ns). The decrease in % systolic thickening of the inferio r wall was inversely correlated with the increase in end-diastolic wal l thickness (r= -0.75; P<0.01), but neither with heart rate (r=0.15; P =ns) nor with systolic blood pressure changes (r=0.05, P=ns). Conclusi ons: Heterogeneity of left ventricular wall thickening can be induced or magnified by dobutamine infusion even in subjects without coronary artery disease, with the inferior wall showing a lack of hyperkinesis, lip to relative hypokinesis, in comparison with other myocardial regi ons. Caution in aggressive dobutamine stress echocardiography reading, especially in the inferior wall, might be warranted.