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Myocardial scarring, indicated as a pattern of late gadolinium enhancement on cardiac magnetic resonance (CMR) imaging, might help with implantable cardioverter defibrillator (ICD) decisions in cardiomyopathy, two meta-analyses suggested.

A meta-analysis of data from hypertrophic cardiomyopathy (HCM) patients found that over 3 years, positive results of late gadolinium enhancement imaging were tied to:

• Sudden cardiac death (odds ratio [OR] 3.41, 95% CI 1.97 to 5.94)
• All-cause mortality (OR 1.80, 95% CI 1.21 to 2.69)
• Cardiovascular mortality (OR 2.93, 95% CI 1.53 to 5.61).

There was a trend, without reaching statistical significance, for more heart failure deaths as well (OR 2.21, 95% CI 0.84 to 5.80), reported Yang He, MD, of China's First Affiliated Hospital of Soochow University, and colleagues.

In the study, published online in JACC: Cardiovascular Imaging, the investigators showed that every 10% increase in late gadolinium enhancement was associated with mounting odds of sudden cardiac death after multivariable adjustment (hazard ratio 1.36, 95% CI 1.10 to 1.69).

"Quantitative late gadolinium enhancement by CMR exhibited a substantial prognostic value in sudden cardiac death events prediction, independent of baseline characteristics," they concluded. "Extensive late gadolinium enhancement may thus be potentially considered a novel risk marker to help identify high risk patients who are be candidates for life saving therapy with ICD."

An accompanying editorial by , of Minneapolis Heart Institute Foundation, and , of Tufts Medical Center in Boston, highlighted the importance of He's finding.

It is "apparent that not all patients at unacceptably high risk can be identified with the available conventional markers and that sudden death can occur occasionally in vulnerable patients without risk factors," the duo wrote. "Furthermore, in some HCM patients, sudden death risk may remain ambiguous even when using the conventional risk marker algorithm, such as in those patients with one risk factor, who do not fall precisely into high or low risk categories."

He's group acknowledged, however, that "although the presence of late gadolinium enhancement clearly portends a higher risk of adverse events, it is clinically impractical to use that as a binary tool for making clinical decisions (particularly for primary ICD implantation), as up to 70% of all HCM patients have some degree on late gadolinium enhancement on CMR."

"The data thus infers that most of such patients can be considered potential candidates for ICDs, which would include a substantial proportion of low-risk patients that would not benefit from such therapy."

The meta-analysis included five studies (n=2,993) but with heterogeneous study populations. Additionally, "without access to the original data to both studies, it is difficult to ascertain whether late gadolinium enhancement has truly independent prognostic value after adjusting for traditional risk factors, including left ventricular ejection fraction," He and colleagues suggested.

Scarring visible from the late gadolinium enhancement technique of CMR was also tied to sudden death and arrhythmic events in patients with ischemic (ICM) and nonischemic cardiomyopathy (NICM), a separate meta-analysis in the same journal found.

The composite of sudden death, aborted sudden death, ventricular tachycardia/ventricular fibrillation, and appropriate ICD therapy was more common in those with late gadolinium enhancement (23.9% versus 4.9%, OR 5.62, 95% CI 4.20 to 7.51), according to , of Santa Chiara Hospital in Italy, and colleagues. This association was strong in ICM and NICM patients alike.

Patients with mean ejection fractions of 30% or worse had an even stronger association between late gadolinium enhancement and arrhythmic events (OR 9.56, 95% CI 5.63 to 16.23).

"Late gadolinium enhancement is a powerful predictor of ventricular arrhythmic risk in patients with ventricular dysfunction, irrespective of ICM and NICM etiology. The prognostic power of late gadolinium enhancement is particularly strong in patients with severely depressed ejection fraction, which suggests its potential to improve patient selection for ICD implantation," Disertori's group concluded.

"Considering the burden of heart failure, the large volume of ICDs implanted every year, and the cost associated with these ICDs, the use of late gadolinium enhancement to identify optimal ICD candidates could have a large public health impact," agreed , of University of Virginia Health System in Charlottesville.

"Late gadolinium enhancement data could be used to identify current patients with left ventricular [LV] dysfunction meeting guideline-based primary prevention criteria for ICD implantation who may not need an ICD, or expand the pool of ICD candidates by identifying patients with lesser degrees of LV dysfunction but higher ventricular arrhythmia risk. Late gadolinium enhancement findings could also aid in patient selection for prophylactic ventricular tachycardia ablation or antiarrhythmic drug therapy early after ICD implantation," Bilchick suggested in an accompanying editorial.

"However, to be put into practice late gadolinium enhancement-CMR protocols need to be standardized with respect to execution modalities and the setting of diagnostic thresholds," Disertori and colleagues wrote.

Their meta-analysis took data from 19 studies (n=2,850) with a median follow-up of 2.8 years. It was limited by the different definitions of arrhythmic endpoints and late gadolinium enhancement cutoffs encountered among the studies included.