RESUMEN

A 49-year-old woman presented with exercise-induced chest discomfort during long-distance running that was occasionally present during rest. Significant coronary artery disease was excluded and a diagnosis of "painful left bundle branch block (LBBB) syndrome" was made after correlation of LBBB aberrancy with symptoms during Holter monitoring. The patient underwent confirmatory testing consisting of rapid atrial pacing below and above 130 beats per minute, the rate cut-off for LBBB manifestation. His bundle pacing implantation was performed resulting in both non-selective and selective morphologies depending on output, both of which manifested with a painless narrow QRS regardless of rate. She was rendered completely pain free during long-distance running and remains so 6-months later. Her pain at rest, now thought to be due to severe anxiety secondary to her painful LBBB, has also subsided. Exercise-induced, painful LBBB is a rare phenomenon that manifests as chest discomfort when LBBB is present. This disease is frequently misdiagnosed as coronary angina, has limited medical treatment options, and can be disabling. HBP is an attractive treatment for this syndrome in an effort to avoid electromechanical dyssynchrony, the presumed mechanism of discomfort. This case report adds to the growing literature of painful LBBB syndrome and its effective treatment with HBP, with the added caveat that it can present with persistent symptoms at rest, in the setting of enhanced anxiety. HBP should be considered early on in the treatment of such patients.