Electrocardiographic (ECG) aberrations and arrhythmias occur frequently among athletes due to normal variants, subclinical cardiac disease or structural and electrical remodeling in response to training. It is unclear whether these changes are associated with adverse clinical outcomes over time among otherwise asymptomatic, healthy athletes. Consensus guidelines have been developed to guide the clinician regarding further management of these arrhythmias. The purpose of this review is to summarize prospective data regarding cardiovascular outcomes related to ECG changes among athletes and compare these findings with current guidelines. A review of the literature was conducted using the PubMed database (1966--present). Outcomes of interest included documented cardiac symptoms or events, such as episodes of cardiac or cerebral hypoperfusion, sudden death or prophylactic procedural interventions. Studies were included for analysis if they involved (1) athletes with documented, baseline arrhythmias and/or abnormal ECG variations; (2) a study design with longitudinal follow-up (designated as >1 month, to exclude short-term Holter studies); and (3) outcomes that include documented cardiac symptoms or events. A total of 33 studies met the above criteria, encompassing over 4,200 athletes, with follow-up ranging from 2 months to 14.6 years. There were few adverse outcomes among cases of sinus bradycardia >30 bpm, sinus pauses <3 s, first-degree atrioventricular (AV) block, second-degree type I AV block and incomplete right bundle branch block. Results among these studies are concordant with guidelines that recommend work-up in the setting of cardiac symptoms, history or physical examination indicative of cardiac disease, severe sinus bradycardia or AV block that does not resolve with exercise or hyperventilation. Outcomes among prospective studies also support guidelines that recommend further evaluation for repolarization abnormalities and supraventricular tachycardias, including atrial fibrillation, atrial flutter and Wolff-Parkinson-White syndrome. Ventricular arrhythmias in the setting of structural cardiac disease are associated with an increased risk of adverse events, including sudden cardiac death, and warrant special consideration with regards to sports eligibility. Findings in this review are limited by a lack of control groups, limited assessment of confounding factors (such as performance-enhancing drugs), and under-representation of women and certain ethnicities. Further prospective studies are needed to better characterize the long-term outcome of ECG abnormalities among athletes and provide evidence for ECG interpretation guidelines.
