Value of the ECG in Asymptomatic AS

Abstract & Commentary

By Michael H. Crawford, MD, Editor

Source: Greve AM, et al. Clinical implications of electrocardiographic left ventricular strain and hypertrophy in asymptomatic patients with aortic stenosis: The simvastatin and ezetimibe in aortic stenosis study. Circulation 2012;125:346-353.

Although electrocardiogram (ECG) left ventricular hypertrophy (LVH), especially with ST-T changes (strain pattern), is known to be of prognostic value in patients with aortic stenosis, its valve in patients who are being followed is unclear. Thus, these investigators from the Simvastatin and Ezetimibe in Aortic Stenosis Study (SEAS) studied the 1533 patients in this trial with baseline ECGs suitable for assessing the presence of LVH. This was a study of patients with moderate aortic stenosis — defined as an aortic peak velocity between 2.5 and 4 m/s and normal systolic function — who were randomized to cholesterol-lowering drug therapy or placebo and followed for a mean of 4 years. The primary endpoint was major cardiovascular events, including aortic valve replacement and death, which occurred in 627 patients. On the baseline ECG, LVH with strain was present in 24%, LVH alone by Sokolow-Lyons criteria in 17%, and by Cornell criteria in 15%. By multivariable analysis, ECG LVH plus strain increased the risk of myocardial infarction (hazard ratio [HR] 3.1; 95% confidence interval [CI], 1.4-6.8; P = 0.004). LVH by both criteria increased the risk of heart failure (HR 5.8; CI, 2.0-16.8; P = 0.001); aortic valve replacement (HR 2.0, CI 1.3-3.1, P = 0.001); and the combined endpoint of myocardial infarction, heart failure, or cardiovascular death (2.5; 1.3-4.9; P = 0.008). LVH and strain remained strong predictors of a poor prognosis when adjusted for clinical parameters, aortic valve area, and gradient. LVH and strain were not altered by drug therapy. The authors concluded that ECG LVH and LVH with strain were independently predictive of cardiovascular events, including aortic valve replacement in asymptomatic patients with moderate aortic stenosis.

Commentary

Many clinicians believe that LVH voltage, especially with a strain pattern, is associated with a poor prognosis in aortic stenosis patients. This substudy of the SEAS trial solidifies this belief. ECG LVH by voltage criteria clearly increased the risk of heart failure, myocardial infarction, cardiovascular death, and aortic valve replacement, even when adjusted for other clinical prognostic factors and echo severity of aortic stenosis. The presence of LVH with the strain pattern was independently predictive of myocardial infarction. This finding is of interest because it has long been believed that the strain pattern indicates subendocardial ischemia, either due to myocardial oxygen supply-demand imbalance or silent coronary artery disease. Unfortunately, there was not enough cardiac catheterization data collected to fully analyze this issue, but the ischemia mechanism seems to be supported by these data. Thus, in the asymptomatic patient with moderate aortic stenosis and normal left ventricular function, ECG LVH and the strain pattern should be considered in determining the patient's management.