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Diffuse Fibrosis in Hypertrophic Cardiomyopathy: Incremental Prognostic Value of Extracellular Volume.

Susan K. Keen Hesham Sheashaa Stuti Shah M. Abusafia S. Jadam Simrat Kaur A. Gaballa S. Ospina Katy Rutkowski Jay Ramchand Z. Popović M. Thamilarasan Nicholas G. Smedira P. Schoenhagen Michael Bolen Bo Xu M. Desai

Aug 2026 · JACC: Advances · pp. 103224 · 0 citations · 52 references

Medicine

Abstract

Background

Left ventricular (LV) myocardial extracellular volume (ECV), from cardiac magnetic resonance (CMR) T1 mapping, primarily reflects diffuse fibrosis and is a marker of adverse myocardial remodeling in hypertrophic cardiomyopathy (HCM).

Objectives

The authors sought to evaluate the prognostic value of ECV beyond established clinical and imaging variables in a large contemporary HCM cohort.

Methods

We evaluated 1,050 consecutive patients with HCM and preserved LV ejection fraction (≥50%) who underwent CMR, including quantification of ECV (%) and late gadolinium enhancement (LGE) burden (% LV mass, >6 SDs above remote myocardium), between 2012 and 2021. The primary endpoint was a composite of mortality, appropriate implantable cardioverter-defibrillator (ICD) therapy, or heart transplantation. Statistical methods included multivariable Cox proportional hazards regression, restricted cubic spline analysis, assessment of incremental discrimination using changes in the C-statistic, and net reclassification improvement analysis.

Results

Median age was 60 years (IQR: 49-68 years) with 44% women. Median follow-up was 5.6 years (IQR: 2.5-7.8 years). The primary endpoint occurred in 124 patients (11.8%), including 111 deaths (10.6%), 12 appropriate ICD discharges (1.1%), and 1 heart transplantation (0.1%). In multivariable Cox regression, older age (HR: 1.05, 95% CI: 1.03-1.06; P < 0.001), NYHA functional class ≥II (HR: 1.96, 95% CI: 1.23-3.11; P = 0.004), diabetes mellitus (HR: 1.89, 95% CI: 1.27-2.81; P = 0.002), and higher ECV (HR: 1.05 per 1% increase, 95% CI: 1.02-1.09; P = 0.001) were independently associated with the primary outcome. Patients with ECV ≥32% had lower event-free survival than those with ECV <32% (adjusted HR: 1.81, 95% CI: 1.24-2.64; P < 0.001).

Conclusions

Myocardial ECV was independently associated with long-term adverse outcomes. Multiparametric CMR assessment may improve risk stratification in HCM.

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