Cardiac MRI findings could flag sudden cardiac death risk in a tricky heart failure subgroup

Patients with heart failure with mildly reduced ejection fraction (HFmrEF) have long been a diagnostic gray zone — not as well-studied as those with severely reduced function, yet still at significant risk. Now, a large multicenter study suggests that cardiac MRI imaging markers could help clinicians identify which of these patients are most at risk for sudden cardiac death (SCD).

Researchers analyzed data from over 1,800 patients across five hospitals in China, tracking outcomes over roughly 3.5 years. They found that two MRI-derived measures — the extent of late gadolinium enhancement (LGE), which reflects scarring, and extracellular volume (ECV), which signals tissue damage — were each independently linked to a significantly elevated SCD risk. Combining both into a single risk model yielded the strongest predictive performance.

Key Takeaways:

• LGE extent ≥6.3% was associated with a 5.3x higher SCD risk
• ECV ≥28.4% carried a 3.4x higher SCD risk and helped reclassify patients with minimal scarring
• Native T1 z-score ≥2.7 predicted a 2.4x higher SCD risk — useful for patients who can't receive contrast dye
• The combined LGE + ECV model achieved a C-statistic of 0.79, indicating strong predictive accuracy

Why it matters: HFmrEF patients are often undertreated because their risk is harder to quantify. These imaging tools could enable more precise, personalized decisions about interventions like defibrillators — potentially improving outcomes in a population that has historically been difficult to risk-stratify.