Transmural repolarisation in the left ventricle in humans during normoxia and ischaemia

Background: Studies in isolated tissues and myocytes show different repolar isation properties in subepicardium, midmyocardium and subendocardium. Whet her these differences are present in vivo and are relevant to humans has be en the subject of controversy, Our objectives were (1) to ascertain whether transmural repolarisation gradients are present in humans, (2) to determin e whether the greater sensitivity of subepicardial cells to ischaemia in vi tro is manifest during early ischaemia in humans in vivo, Methods and resul ts: We studied 21 patients during routine coronary artery surgery. Unipolar activation recovery intervals (ARI) were recorded from five transmural loc ations between subepicardium and subendocardium in the left ventricular wal l. A pacing protocol spanned a range of cycle lengths from a cycle length o f 300 ms to the maximum permitted by the intrinsic atrial activity. Followi ng the onset of cardiopulmonary bypass recordings were obtained before (con trol) and during a 3-min period of global ischaemia. During control transmu ral ARIs were homogeneous between 300 and 1500 ms (ventricular pacing) and 750 and 1500 ms (atrial spontaneous brats), During ischaemia, ARIs shortene d similarly at all transmural electrode sites and transmural homogeneity wa s maintained, Conclusions: Transmural repolarisation differences within the ventricular wall of the human heart were absent at cycle lengths within th e physiological range but also during prolonged cycles. During early (globa l) ischaemia repolarisation changed equally in subepicardial and subendocar dial regions and transmural homogeneity of repolarisation was preserved. (C ) 2001 Elsevier Science B.V. All rights reserved.