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Myocardial Fibrosis and Outcomes in Aortic Stenosis
Quick Takes
- In this cohort of 457 patients with moderate or asymptomatic severe aortic stenosis, diffuse interstitial myocardial fibrosis, as evidenced by increased extracellular volume fraction on CMR, correlated with the composite endpoint of mortality and HF hospitalization.
- Patients in the highest tertile of extracellular volume fraction had a 5-year event rate of 19.3%, as compared with 9.9% in the lowest tertile.
Study Questions:
How does diffuse interstitial myocardial fibrosis, as observed on cardiac magnetic resonance (CMR), correlate with clinical outcomes in moderate and asymptomatic severe aortic stenosis (AS)?
Methods:
This prospective, multicenter cohort study included patients with echocardiographically moderate AS (aortic valve area [AVA] 1.0-1.5 cm2) and asymptomatic severe AS (AVA ≤1.0 cm2 and New York Heart Association class I-II). All patients underwent contrast-enhanced CMR with analysis of extracellular volume fraction (ECV%), based on pre- and post-contrast myocardial T1 values, and late gadolinium enhancement (LGE). The clinical outcome of interest was a composite of mortality and unplanned hospital admission for heart failure (HF).
Results:
A total of 457 patients were included (176 with moderate AS and 281 with severe AS; mean age, 68.5 years; 67% male). LGE was present in 31.5% of patients but generally in minimal amounts (median <1% myocardial involvement). During a median follow-up period of 5.7 years, 311 patients (68.1%) underwent aortic valve replacement (AVR), and 83 patients (18.2%) had clinical events, including 67 deaths. In a multivariable analysis including patient demographics, imaging parameters, and major comorbidities, independent predictors of the composite endpoint included ECV% (adjusted hazard ratio [HR], 1.05; 95% confidence interval [CI], 1.00-1.10; p = 0.039), age, AVA, prior hospitalization for HF, and atrial fibrillation, but not LGE. Patients in the highest ECV% tertile (ECV% >28.6%) had significantly worse outcomes, with estimated 5-year event rates of 19.3%, 13.8%, and 9.9% for the high-, mid-, and low-ECV% tertiles, respectively (log-rank p = 0.009).
Conclusions:
Diffuse interstitial myocardial fibrosis appears to be an independent risk factor for adverse clinical outcomes in patients with moderate and asymptomatic severe AS.
Perspective:
The results of this study suggest that more advanced diffuse interstitial myocardial fibrosis, as denoted by ECV% >29%, is associated with a significantly increased risk of clinical decompensation, though this cutoff would need to be refined in prospective studies before use in decision-making for patients with AS. An ongoing randomized trial, EVoLVeD (Early Valve Replacement Guided by Biomarkers of LV Decompensation in Asymptomatic Patients With Severe AS; NCT03094143), is seeking to determine whether CMR assessment of LGE is helpful in risk stratification, though no randomized trials to date have employed T1 mapping in this manner.
Clinical Topics: Noninvasive Imaging, Valvular Heart Disease, Magnetic Resonance Imaging
Keywords: Aortic Valve Stenosis, Fibrosis, Magnetic Resonance Imaging
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