Left ventricular ejection fraction and myocardial fibrosis in sudden cardiac death

Left ventricular ejection fraction (LVEF) remains the key determinant in the evaluation for the risk of sudden cardiac death (SCD). Myocardial fibrosis has gained increasingly more interest in the context of various myocardial diseases. We determined the spectrum of LVEF and evaluated the association between myocardial fibrosis and pre-SCD LVEF in a population-based SCD cohort.

The Fingesture study and clinical data have been collected from consecutive autopsy-verified SCD victims from Northern Finland between 1998 and 2017 (n = 5869). The cause of death was verified in medicolegal autopsy in all subjects. Electronic health records were used to identify those with pre-mortem echocardiography data. The extent of myocardial fibrosis at autopsy was characterized macroscopically and from histology samples. The LVEF recorded median 2 years (interquartile range 1-5) prior to SCD was evaluated in 716 SCD subjects. Proportional LVEF values were as follows: 62.7% (n = 449) normal LVEF (≥50%), 21.9% (n = 157) mildly reduced LVEF (36-49%), and 15.4% (n = 110) severely reduced LVEF (≤35%). At autopsy 19.6% (n = 140) had substantial, 53.8% (n = 386) moderate, and 22.1% (n = 158) mild fibrosis, and 4.5% (n = 32) had no myocardial fibrosis. The extent of myocardial fibrosis and LVEF had poor correlation (Spearman's ρ 0.21, CI 0.141-0.285, P < 0.001). Only 21.4% of those with substantial fibrosis at autopsy had LVEF ≤35%.

The proportion of SCD subjects with LVEF ≤35% is low, and the prevalence of myocardial fibrosis is high. The LVEF has a weak correlation with the extent of myocardial fibrosis. Our study suggests that LVEF is a poor surrogate of myocardial fibrosis in SCD victims.