A Patient With Athlete's Heart Syndrome: When the Abnormal Is Normal.

Long-term athletic training can result in structural and conduction changes within the heart, leading to Athlete's heart syndrome (AHS). This syndrome is characterized by increased left ventricle (LV) dimensions, thickness, and mass. Dynamic exercise significantly contributes to these alterations, with sinus bradycardia being a common conduction abnormality, often accompanied by first-degree atrioventricular (AV) block. However, higher degrees of AV conduction abnormalities, such as second- and third-degree blocks, though rare, might occur due to parasympathetic hypertonia. Prompt evaluation is necessary to rule out underlying structural or infiltrative heart diseases. We present the case of a 66-year-old lifelong long-distance runner with marked sinus bradycardia, AV dissociation, and junctional escape rhythm, alongside left ventricular hypertrophy (LVH) and T-wave repolarization abnormalities. Subsequent studies ruled out possible pathologies, and the patient was diagnosed with AHS, characterized by cardiac remodeling and bradycardia due to prolonged cardiac loading. This case underscores the importance of clinical assessment, cardiac imaging, and exclusion of pathologic causes to distinguish normal physiological adaptations from potentially concerning conditions.