JACC. Case reports · 2026
Exercise-Induced Alternating Fascicular Block: Unmasking Lenègre-Lev Disease in a Patient With a Rosenbaum Pattern.
Клинический случайСтатьяНазвание и аннотация: Перевод в очереди
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Maximiliano-Nieva Hugo, Enríquez-Martínez Victor, Palacios-Espinoza Elba
Аннотация
BACKGROUND: Exercise-induced conduction failure may reveal advanced His-Purkinje system disease despite apparently stable resting electrocardiographic findings. This case underscores the value of functional stress testing in unmasking clinically high-risk infranodal conduction disorders.
CASE SUMMARY: A patient with recurrent syncope demonstrated complete right bundle branch block, left anterior fascicular block, and first-degree atrioventricular block on baseline electrocardiography. Exercise stress testing unmasked rate-dependent fascicular alternans with progression to advanced atrioventricular block and a 7-second episode of asystole. Findings were consistent with degenerative conduction system disease (Lenègre-Lev disease), prompting implantation of a permanent dual-chamber pacemaker.
DISCUSSION: Chronotropic stress exposed latent infranodal conduction failure due to diffuse His-Purkinje fibrosis. Exclusion of reversible etiologies supported permanent pacing, resulting in complete clinical resolution.
TAKE-HOME MESSAGE: Normal resting studies do not exclude life-threatening conduction disease; exercise stress testing is essential in the evaluation of unexplained syncope.
CASE SUMMARY: A patient with recurrent syncope demonstrated complete right bundle branch block, left anterior fascicular block, and first-degree atrioventricular block on baseline electrocardiography. Exercise stress testing unmasked rate-dependent fascicular alternans with progression to advanced atrioventricular block and a 7-second episode of asystole. Findings were consistent with degenerative conduction system disease (Lenègre-Lev disease), prompting implantation of a permanent dual-chamber pacemaker.
DISCUSSION: Chronotropic stress exposed latent infranodal conduction failure due to diffuse His-Purkinje fibrosis. Exclusion of reversible etiologies supported permanent pacing, resulting in complete clinical resolution.
TAKE-HOME MESSAGE: Normal resting studies do not exclude life-threatening conduction disease; exercise stress testing is essential in the evaluation of unexplained syncope.