Left Ventricular Hypertrophy With Strain and Aortic Stenosis
What are the mechanisms (using cardiac magnetic resonance [CMR] imaging) and clinical implications of electrocardiogram (ECG) left ventricular hypertrophy (LVH) with strain among patients with aortic stenosis?
In a Mechanism Cohort, 102 patients (median age 70; interquartile range [IQR] 63, 75] years, 66% males, aortic valve area median 0.9 [IQR 0.7, 1.2] cm2) underwent ECG, echocardiography, and CMR imaging. Myocardial fibrosis was determined using late gadolinium enhancement (LGE, replacement fibrosis) and T1 mapping (diffuse fibrosis). The relationship between ECG-strain and CMR was then assessed in an external Validation Cohort (n = 64). An Outcome Cohort included 140 patients from the SALTIRE (Scottish Aortic Stenosis and Lipid Lowering Trial Impact on REgression) study, with follow-up for 10.6 years (1,254 patient-years).
Compared to those without LVH (n = 51) and LVH without ECG-strain (n = 30), patients with ECG-strain (n = 21) had more severe aortic stenosis, increased LV mass index, more myocardial injury (high-sensitivity plasma cardiac troponin I concentration [4.3 [IQR 2.5, 7.3] vs. 7.3 [IQR 3.2, 20.8] vs. 18.6 [IQR 9.0, 45.2] ng/L, respectively, p < 0.001), and increased diffuse fibrosis (extracellular volume fraction 27.4 ± 2.2 vs. 27.2 ± 2.9 vs. 30.9 ± 1.9%, respectively, p < 0.001). All patients with ECG-strain had mid-wall LGE (positive and negative predictive values 100% and 86%, respectively). LGE was independently associated with ECG-strain (odds ratio [OR], 1.73; 95% confidence interval [CI], 1.08-2.77; p = 0.02), a finding confirmed in the Validation Cohort. In the Outcome Cohort, ECG-strain was an independent predictor of aortic valve replacement or cardiovascular death (hazard ratio, 2.67; 95% CI, 1.35-5.27; p < 0.01).
The authors concluded that ECG-strain is a specific marker of mid-wall myocardial fibrosis and predicts adverse clinical outcomes in aortic stenosis.
This study found that a strain pattern on ECG is associated both with elevated plasma high-sensitivity cardiac troponin I and with increased diffuse myocardial fibrosis on CMR imaging, suggesting LV decompensation among patients with aortic stenosis and ECG strain. The association between ECG strain and cardiovascular death or aortic valve replacement suggests that this relatively simple tool could be useful in identifying patients with severe aortic stenosis who might benefit from earlier intervention.
Keywords: Hypertrophy, Left Ventricular, Troponin I, Gadolinium, Lipids, Confidence Intervals, Electrocardiography, Echocardiography
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