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Predicting Left Main and Triple-vessel Disease in ACS
Abstract & Commentary
By Andrew J. Boyle, MBBS, PhD, Assistant Professor of Medicine, Interventional Cardiology, University of California, San Francisco. Dr. Boyle reports no financial relationship relevant to this field of study.
Source: Kosuge M, et al. An early and simple predictor of severe left main and/or three-vessel disease in patients with non–ST-segment elevation acute coronary syndrome. Am J Cardiol. 2011;107:495-500.
Patients presenting with acute coronary syndromes (ACS) should be administered dual anti-platelet therapy with aspirin and a thienopyridine, such as clopidogrel. However, some patients are subsequently found to have left main (LM) or multivessel disease (MVD) and require coronary artery bypass graft (CABG) surgery. For patients who have been loaded with clopidogrel, early CABG can result in excess bleeding; the alternative is costly prolonged hospitalization until the clopidogrel has worn off before performing CABG. Neither of these options is optimal. Thus, it would be advantageous to have a simple rapid screening tool on admission to identify those patients who are likely to have LM/MVD, so one could avoid clopidogrel in these patients and, thereby, facilitate early CABG without excess bleeding. Kosuge and colleagues studied patients presenting with ACS who subsequently underwent cardiac catheterization to determine if such predictors exist.
The authors identified 572 patients presenting to their hospital with non-ST elevation ACS who subsequently underwent coronary angiography. They excluded patients with uninterpretable ECGs (left or right bundle branch block, ventricular pacing, and left ventricular hypertrophy). Based on the coronary angiogram, they divided their cohort into 3 groups: severe LM/MVD (n = 55), non-severe LM/MVD (n = 57), and no LM/MVD (n = 460). They defined severe LM/MVD as either one or both of the following: ≥ 75% stenosis of the left main or triple-vessel disease, with ≥ 90% stenosis of the proximal left anterior descending artery plus ≥ 90% stenosis of the right and/or circumflex coronary arteries. Not surprisingly, patients with severe LM/MVD were more likely to undergo CABG than those with non-severe LM/MVD or no LM/MVD (46% vs. 2% vs. 2% respectively; p < 0.001). Univariate analysis showed that patients with severe LM/MVD had higher rates of diabetes, lower blood pressure, faster heart rate, were more likely to present with Kilip class 3 or 4, higher troponin levels, and worse renal function. There were several ECG findings associated with severe LM/MVD, including more leads with ST depression, greater degree of ST depression, and greater ST elevation in aVR. After multivariable analysis, there were only two predictors of the presence of severe LM/MVD: elevated troponin (odds ratio 1.27; p = 0.044) and the degree of ST elevation in aVR (odds ratio 29.1; p < 0.001). The finding of ≥ 1mm ST elevation in aVR predicted severe LM/MVD with 80% sensitivity, 93% specificity, 56% positive predictive value, and 98% negative predictive value. Greater degrees of ST elevation in aVR were associated with higher specificity for severe LM/MVD. The authors conclude that ST elevation ≥ 1mm in lead aVR on admission ECG is highly suggestive of severe LM/MVD in patients with non-ST elevation ACS, and that selected patients with this finding might benefit from prompt angiography and withholding clopidogrel to allow early CABG.
The optimal management of patients presenting with non-ST elevation ACS remains controversial in particular, it remains unclear who should undergo early invasive vs. early conservative therapy, who should receive dual or even triple antiplatelet therapy, and the optimal timing of the antiplatelet therapy. This study may help clinicians identify a subset of patients that is likely to have LM/MVD and, thus, may benefit from early coronary angiography with a view to early CABG. Because these patients should all have an ECG on admission, this test is basically free of charge and widely available. It may help reduce prolonged hospital stays, either from post-CABG bleeding or for waiting for clopidogrel to wear off, and may, thus, reduce health care costs.
ST elevation in aVR has been associated with left main or multivessel disease before, and has been shown to correlate with prognosis. This study takes this a step further, and demonstrates the independent predictive power of this simple ECG finding as superior to other clinical and ECG parameters in the ACS population. It is important to note this is an observational study. Whether changing antiplatelet therapy or timing of coronary angiography based on ST elevation in aVR results in better clinical outcomes remains speculative and must be tested prospectively in randomized trials.