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A finding of myocardial fibrosis on cardiac MRI did not necessarily warrant aggressive management in patients with normal left ventricular (LV) volumes, ejection fractions, and no apparent cardiac disease, the FINALIZE group reported.

No such patient, showing nonischemic patterns of late gadolinium enhancement (LGE), experienced sudden cardiac death (SCD) over a median 4.3 years. Only one had an aborted SCD more than 10 years after the finding of myocardial scarring on imaging, according to Dudley Pennell, MD, of Royal Brompton Hospital in London, and colleagues.

Thus, the 401 LGE+ patients with otherwise healthy hearts in the study were at similarly "reassuringly low risk" of SCD as 347 controls with no LGE, Pennell's group reported in a retrospective study in .

"This suggests that patients with incidental and otherwise unexplained, nonischemic patterns of LGE do not require ICD implantation if LV volumes, wall thickness, and ejection fraction are all within normal limits. Furthermore, this observation supports the notion that the genesis of ventricular arrhythmia is dependent on the presence of multiple factors, of which structural substrate is just one component," the authors said.

"Our data suggest that replacement myocardial fibrosis in a nonischemic pattern in the absence of other risk factors, such as LV dilatation, reduced LVEF [LV ejection fraction], or a family history of cardiomyopathy, is not a marker of high risk even over an extended period of follow-up," they continued.

As such, the investigators said their results do not support aggressive medical management or routine ICD implantation in this cohort.

Steffen Petersen, DPhil and Mohammed Khanji, PhD, both of Queen Mary University of London and St. Bartholomew's Hospital, agreed.

"Although future work to confirm the findings with larger patient groups would be useful to confirm the findings, what this initial study provides is reassurance that this patient group is at very low risk of SCD," they wrote in .

Incidental findings of subepicardial or midwall LGE in an otherwise healthy-looking heart is thought to be suggestive of previous myocarditis, Petersen and Khanji noted.

"Interpretation of the significance of such a finding may at times be challenging for the clinician and may potentially lead to patient anxiety and lifestyle implications," they said, noting that the conundrum can be expected to grow more common given the increasing adoption of contrast-enhanced cardiac MRI in research and clinical practice.

Worries about myocardial injury in COVID-19 in particular have contributed to recent interest in cardiac MRI. Professional societies continue to warn against routine MRI scanning in the absence of symptoms.

For the FINALIZE study, Pennell and colleagues collected records of more than 15,000 patients scanned at one center and selected people with normal LV volumes, wall thickness, and LVEF for comparison. Those with CAD or infarct-related LGE were excluded.

The study cohort had a median age of 50, and 38% were women. Median LVEF was 66%. Scan indications included chest pain (40%), palpitation (33%), and breathlessness (13%). Nearly 5% of the group had a family history of SCD.

There were no significant differences between LGE+ and LGE- groups in age, comorbidity, or scan indication. However, the LGE+ group constituted more men, people with histories of controlled hypertension, and individuals described as having New York Heart Association class II/III symptoms as opposed to class I.

People with myocardial scarring had a median LGE mass of 2.25% of overall LV mass.

All-cause mortality rates over follow-up were statistically no different between LGE+ and LGE- patients (3.7% vs 4.3%, P=0.71). Instead, the predictors of death were older age (HR 2.04 per 10 years, 95% CI 1.46-2.79) and high cholesterol (HR 4.13, 95% CI 2.01-8.47).

However, the LGE+ group did have more composite cardiovascular deaths and unplanned cardiovascular hospital admissions (5.2% vs 1.1%, adjusted HR 7.16, 95% CI 2.30-22.28). Suspected myocarditis and symptomatic ventricular tachycardia were the two most frequent indications for unplanned admission.

"[I]t is not known whether knowledge of LGE presence influenced the decision making of the patients (to present to the hospital) or the clinician (to refer or admit the patient)," Petersen and Khanji cautioned.

The retrospective design of the study left room for bias and confounding, Pennell's group acknowledged. In addition, their study population was a highly selected group of white individuals and study results therefore may not be broadly generalizable.

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