Intermittent High-Grade Atrioventricular Block as a Presenting Sign of Left Ventricular Noncompaction

Q: What is the clinical evidence from this study?

Study design: Case Report. Population: Left ventricular noncompaction presenting with intermittent high-grade atrioventricular block (n=1). Intervention: Implantable loop recorder surveillance and cardiac magnetic resonance evaluation. Primary outcome: Diagnosis of left ventricular noncompaction via diastolic noncompacted:compacted (NC/C) ratio on cardiac magnetic resonance.

Q: What does this research mean for the field?

Left ventricular noncompaction can present as intermittent high-grade atrioventricular block in young adults even in the presence of preserved ejection fraction and absent late gadolinium enhancement. Novelty: ClaimNovelty.CONFIRMATORY. Consensus alignment: ConsensusAlignment.NEUTRAL.

Mashkurul Haque; Aubriannah Larson; Ola Abdelkarim; Vikram Sharma

doi:10.1016/j.jaccas.2026.107647

March 1, 2026JACC Case ReportsOpen Access

Intermittent High-Grade Atrioventricular Block as a Presenting Sign of Left Ventricular Noncompaction

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Key result

CMR identifies left ventricular noncompaction in high-grade AV block, guiding surveillance over immediate pacing.

n=1

Figures

Graphical abstract published by JACC Case Reports — Graphical abstract · Published by JACC Case Reports · CC BY

Key Points

To describe a case of unexplained intermittent high-grade atrioventricular block presenting as the initial manifestation of left ventricular noncompaction in a young adult.
Evaluated a 37-year-old man presenting after a 30-day ambulatory event monitor recorded intermittent high-grade (Mobitz II) atrioventricular block with a pause of 3.7 seconds.
Diagnostic workup included 12-lead electrocardiography, transthoracic echocardiography, and cardiac magnetic resonance imaging.
Management involved multidisciplinary electrophysiology assessment leading to implantable loop recorder placement and counseling for genetic testing.
Cardiac magnetic resonance demonstrated hypertrabeculation with an apicolateral diastolic noncompacted-to-compacted ratio of 3.5, meeting diagnostic criteria for left ventricular noncompaction.
Left ventricular ejection fraction was preserved at 56% with no late gadolinium enhancement, demonstrating that clinically relevant conduction disease can occur without overt myocardial fibrosis or systolic dysfunction.
Longitudinal rhythm surveillance using an implantable loop recorder was selected to monitor conduction disease while deferring immediate permanent pacemaker implantation.

Study Design

Type

Case Report (n=1)

Multicenter

No

Structured PICO

P

Population

A 37-year-old man with intermittent high-grade atrioventricular block (longest pause 3.7 seconds) and preserved left ventricular ejection fraction (56%) diagnosed with left ventricular noncompaction via cardiac magnetic resonance.

I

Intervention

Cardiac magnetic resonance imaging for structural evaluation and longitudinal rhythm surveillance with an implantable loop recorder (Boston Scientific LUX-Dx II+), deferring permanent pacemaker implantation.

Unexplained high-grade atrioventricular block in a young adult should prompt cardiac magnetic resonance evaluation to exclude left ventricular noncompaction, as clinically relevant conduction disease can coexist with preserved ejection fraction and absent late gadolinium enhancement.

Limitations

Single-patient case report
Genetic testing was not performed because authorization was denied by insurance
Long-term follow-up outcomes after implantable loop recorder placement are not reported

Implication

Case of LVNC with high-grade AV block and preserved LVEF; hypothesis-generating for CMR evaluation in young adults with unexplained conduction disease.

Abstract

Unexplained high-grade atrioventricular block in a young adult should prompt advanced structural evaluation-including cardiac magnetic resonance-to exclude left ventricular noncompaction and other cardiomyopathies. Preserved ejection fraction and absent late gadolinium enhancement can coexist with clinically relevant conduction disease in left ventricular noncompaction. Implantable loop recorder-guided surveillance enables individualized timing of device therapy and complements genetic evaluation and cascade family screening.

Discussion

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Cite This Study

Haque et al. (2026) conducted a case report in Left ventricular noncompaction presenting with intermittent high-grade atrioventricular block (n=1). Implantable loop recorder surveillance and cardiac magnetic resonance evaluation was evaluated on Diagnosis of left ventricular noncompaction via diastolic noncompacted:compacted (NC/C) ratio on cardiac magnetic resonance. Cardiac magnetic resonance identified left ventricular noncompaction (NC/C ratio 3.5, LVEF 56%, no LGE) in a 37-year-old man with intermittent high-grade AV block (3.7-second pause).

synapsesocial.com/papers/69c76fff8bbfbc51511e05b6 https://doi.org/10.1016/j.jaccas.2026.107647

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Intermittent High-Grade Atrioventricular Block as a Presenting Sign of Left Ventricular Noncompaction

Figures

Key Points

Study Design

Structured PICO

Limitations

Implication

Abstract

Discussion

Cite This Study

Intermittent High-Grade Atrioventricular Block as a Presenting Sign of Left Ventricular Noncompaction

Figures

Key Points

Study Design

Structured PICO

Limitations

Implication

Abstract

Discussion

Cite This Study

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