CARDIAC magnetic resonance (CMR) findings suggest that patients with acute myocarditis and advanced atrioventricular block (AVB) may be identified through elevated extracellular volume (ECV) in the basal superior ventricular septum, according to a retrospective single-centre study.
The imaging marker was also observed in the small number of patients who experienced adverse clinical outcomes, potentially warranting further investigation as a risk stratification tool.
Acute myocarditis is an inflammatory condition of the heart muscle that can disrupt electrical conduction pathways and lead to arrhythmias, including AVB. While AVB in this setting is often transient, identifying patients at risk of more severe conduction abnormalities remains a clinical challenge.
CMR Findings Highlight Differences in Acute Myocarditis
The study evaluated 105 patients admitted with acute myocarditis between June 2018 and April 2024. The cohort included 53 patients without AVB, 34 with non-advanced AVB, and 18 with advanced AVB. Overall, 49.5% were male and the median age was 34 years.
Researchers analysed CMR functional and tissue parameters and compared findings across the different patient groups. Most patients showed no evidence of ongoing AVB at the time of CMR examination, reinforcing the often temporary nature of conduction disturbances in acute myocarditis.
Compared with patients without AVB, those with AVB had significantly (both p<0.05) higher heart rates and lower left ventricular ejection fraction (LVEF).
Septal ECV as a Potential Risk Marker
Among patients with AVB, those with advanced disease demonstrated higher ECV values across multiple myocardial segments (p<0.05). Other tissue parameters did not show significant differences between advanced and non-advanced AVB subgroups.
The strongest signal came from the basal superior ventricular septum, with higher ECV values helping distinguish advanced from non-advanced AVB. The researchers identified 36.95% as the threshold within their cohort.
Link to Clinical Outcomes
Adverse clinical outcomes were defined as death, heart failure decompensation requiring hospital readmission, or implantation of an implantable cardioverter-defibrillator or cardiac resynchronisation therapy device.
Adverse clinical outcomes were observed exclusively among three patients with advanced AVB and elevated ECV in the basal superior ventricular septum, a finding that reached statistical significance (p=0.016).
Implications for Imaging Assessment
The findings suggest that CMR-derived ECV assessment of the basal superior ventricular septum could provide clinically useful information when evaluating conduction abnormalities in acute myocarditis. However, the retrospective, single-centre design means further validation is needed before the marker can be incorporated into routine risk assessment pathways.
Reference
Liao R et al. Feasibility of cardiac magnetic resonance for assessing atrioventricular block in acute myocarditis. Clin Radiol. 2026;DOI:10.1016/j.crad.2026.107418.
Featured image Christian cantarelli on Adobe Stock
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