Abstract
Simultaneous ischemia in two myocardial regions is a potentially lethal clinical condition often unrecognized whose corresponding electrocardiographic (ECG) patterns have not yet been characterized. Thus, this study aimed to determine the QRS complex and ST-segment changes induced by concurrent ischemia in different myocardial regions elicited by combined double occlusion of the three main coronary arteries. For this purpose, 12 swine were randomized to combination of 5-min single and double coronary artery occlusion: Group 1: left Circumflex (LCX) and right (RCA) coronary arteries (n = 4); Group 2: left anterior descending artery (LAD) and LCX (n = 4) and; Group 3: LAD and RCA (n = 4). QRS duration and ST-segment displacement were measured in 15-lead ECG. As compared with single occlusion, double LCX+RCA blockade induced significant QRS widening of about 40 ms in nearly all ECG leads and magnification of the ST-segment depression in leads V1–V3 (maximal 228% in lead V3, p < 0.05). In contrast, LAD+LCX or LAD+RCA did not induce significant QRS widening and markedly attenuated the ST-segment elevation in precordial leads (maximal attenuation of 60% in lead V3 in LAD+LCX and 86% in lead V5 in LAD+RCA, p < 0.05). ST-segment elevation in leads V7–V9 was a specific sign of single LCX occlusion. In conclusion, concurrent infero-lateral ischemia was associated with a marked summation effect of the ECG changes previously elicited by each single ischemic region. By contrast, a cancellation effect on ST-segment changes with no QRS widening was observed when the left anterior descending artery was involved.
Highlights
Simultaneous interruption of blood flow in two coronary arteries is a potentially lethal clinical condition (Mahmoud et al, 2015) that may occur in about 2.5% of patients with ST-segment elevation myocardial infarction (STEMI) (Pollak et al, 2009)
In a previous experimental study in pigs, we found that simultaneous occlusion of the left anterior descending (LAD) and right coronary arteries attenuated the ST-segment elevation and blunted the reciprocal ST-segment depression in the 12-lead ECG (Cinca et al, 2014), but combination of double occlusions involving the three main coronary systems were not explored
Single left Circumflex (LCX) occlusion induced a QRS widening of about 20 ms affecting all ECG leads but this lengthening was negligible after right coronary artery (RCA) occlusion
Summary
Simultaneous interruption of blood flow in two coronary arteries is a potentially lethal clinical condition (Mahmoud et al, 2015) that may occur in about 2.5% of patients with ST-segment elevation myocardial infarction (STEMI) (Pollak et al, 2009). ECG Changes During Double Coronary Occlusion prevalence This assumption is based on the finding of multiple complex coronary plaques in 39.5% of patients with STEMI (Goldstein et al, 2000) and on the observation of ruptured plaques in non-culprit vessels in 10.5 to 37.5% of patients with acute coronary syndromes (Rioufol et al, 2002; Kotani et al, 2003; Tanaka et al, 2005). The trigger event of the double coronary occlusion may have different etiologies, being the coronary plaque rupture and the coronary vasospasm the most frequently alluded. These clinical reports do not allow to ascertain whether the magnitude of the ECG changes induced by a double coronary occlusion results from a summation or a cancellation of those changes elicited separately by each single vessel occlusion. The location of the two concurrent ischemic regions could influence the changes in the QRS complex duration
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