Key result
Larger MRI myocardial gray zone predicts ~3% greater ICD shock or mortality risk per gram.
Why the study?
To compare the predictive value of different myocardial scar quantification thresholds on cardiac MRI for appropriate ICD shock and mortality.
Does myocardial scar quantification and gray zone extent on cardiac MRI predict appropriate ICD shock and mortality in patients with cardiomyopathy receiving an ICD?
Cohort (n=374)
Blinded readers
Yes
Does myocardial scar quantification and gray zone extent on cardiac MRI predict appropriate ICD shock and mortality in patients with cardiomyopathy receiving an ICD?
Effect estimate: adjusted HR 1.025 (95% CI 1.008-1.043)
Absolute Event Rate: 37.5% vs 26.6%
p-value: p=0.005
The extent of the intermediate signal 'gray zone' on cardiac MRI LGE independently predicts appropriate ICD shock or death in patients with cardiomyopathy, offering a potential tool for refined risk stratification.
Gray zone extent may aid ICD risk stratification in cardiomyopathy; leaves open prospective validation.
Purpose To compare the predictive value of different myocardial scar quantification thresholds using cardiac MRI for appropriate implantable cardioverter defibrillator (ICD) shock and mortality. Materials and Methods In this retrospective, two-center observational cohort study, patients with ischemic or nonischemic cardiomyopathy underwent cardiac MRI prior to ICD implantation. Late gadolinium enhancement (LGE) was first determined visually and then quantified by blinded cardiac MRI readers using different SDs above the mean signal of normal myocardium, full-width half-maximum, and manual thresholding. The intermediate signal “gray zone” was calculated as the differences between different SDs. Results Among 374 consecutive eligible patients (mean age, 61 years ± 13 [SD]; mean left ventricular ejection fraction, 32% ± 14; secondary prevention, 62.7%), those with LGE had a higher rate of appropriate ICD shock or death than those without (37.5% vs 26.6%, log-rank P = .04) over a median follow-up of 61 months. In multivariable analysis, none of the thresholds for quantifying scar was a significant predictor of mortality or appropriate ICD shock, while the extent of gray zone was an independent predictor (adjusted hazard ratio per 1 g = 1.025; 95% CI: 1.008, 1.043; P = .005) regardless of the presence or absence of ischemic heart disease (P interaction = .57). Model discrimination was highest for the model incorporating the gray zone (between 2 SD and 4 SD). Conclusion Presence of LGE was associated with a higher rate of appropriate ICD shock or death. Although none of the scar quantification techniques predicted outcomes, the gray zone both in infarct and nonischemic scar was an independent predictor and may refine risk stratification. Keywords: MRI, Scar Quantification, Implantable Cardioverter Defibrillator, Sudden Cardiac Death Supplemental material is available for this article.
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Shalmon et al. (2023) conducted a cohort in Ischemic or nonischemic cardiomyopathy (n=374). Myocardial scar quantification (gray zone extent) vs. Presence vs absence of LGE was evaluated on Appropriate ICD shock or mortality (adjusted HR 1.025, 95% CI 1.008-1.043, p=0.005). The extent of the myocardial intermediate signal gray zone on cardiac MRI was an independent predictor of appropriate ICD shock or mortality (adjusted HR per 1 g 1.025; 95% CI 1.008-1.043; P=0.005).
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