Electrocardiographic changes in athletes usually reflect benign structural and electrical remodelling of the heart as an adaptation to regular physical training (athlete's heart) 1 2.
In rare cases, abnormalities of an athlete’s EKG may be an expression of an underlying heart disease putting the athlete at risk of sudden cardiac death during sport 2.
EKG interpretation is an essential skill for all physicians involved in the cardiovascular care of athletes.
Cardiovascular-related sudden death is the leading cause of mortality in athletes during sport and exercise 1 3 4.
The majority of disorders associated with an increased risk of sudden cardiac death are suggested or identified by abnormalities on a resting 12-lead EKG 3.
Regular and long-term participation in intensive exercise, minimum of 4 hours per week, is associated with electrical manifestations that reflect enlarged cardiac chamber size and increased vagal tone 1 3.
These EKG findings in athletes are considered normal, physiological adaptations to regular exercise and do not require further evaluation 1 3.
Related article: Left ventricular hypertrophy on the EKG.
The presence of isolated QRS voltage criterion for left ventricular hypertrophy does not correlate with pathology in athletes and is present in isolation (without other associated EKG abnormalities) in less than 2% of patients with hypertrophic cardiomyopathy 3.
In contrast, pathological left ventricular hypertrophy is commonly associated with additional EKG features such as T wave inversion in the inferior and lateral leads, ST-segment depression, and pathological Q waves 3.
Therefore, the isolated presence of high QRS voltages fulfilling voltage criterion for left ventricular hypertrophy in the absence of other EKG or clinical markers suggestive of pathology are considered part of normal and training-related EKG changes in athletes and does not require further evaluation 3.
More information: Left ventricular hypertrophy on the EKG.
Related article: Right ventricular hypertrophy on the EKG.
Voltage criterion for right ventricular hypertrophy is also common in athletes with up to 13% of athletes 3.
QRS voltages for right ventricular hypertrophy, when present in isolation, is part of the normal spectrum of EKG findings in athletes and do not correlate with underlying pathology in athletes. These findings do not require further evaluation 3.
More information: Right ventricular hypertrophy on the EKG.
Related article: Incomplete right bundle branch block.
Incomplete right bundle branch block is defined by QRS complex duration between 110 and 120 ms in adults and a rsr', rsR', or rSR' pattern in leads V1 or V2 5. It is seen in less than 10% of the general population but is observed in up to 40% of highly trained athletes 1.
The presence of incomplete right bundle branch block in an asymptomatic athlete with a negative family history and physical examination does not require further evaluation 1.
Particular care should be devoted to the auscultation of a fixed splitting of the second heart sound because incomplete RBBB can be an associated EKG finding in patients with an atrial septal defect.
Incomplete right bundle branch block may be seen in patients with arrhythmogenic right ventricular cardiomyopathy (ARVC). However, ARVC should be suspected when the pattern of incomplete RBBB is associated with T-wave inversion extending beyond V2 to include leads V3 and V4, or in the presence of premature ventricular beats with a left bundle branch block morphology 1.
More information: Incomplete right bundle branch block.
Related article: Early repolarization.
Early repolarization is defined as elevation of the QRS-ST junction (J point) by ≥ 0.1 mV with a terminal QRS slurring or notching (J wave) often associated with concave upward ST-segment elevation and prominent T waves 6 7.
Early repolarization is common in healthy populations and is more prevalent in athletes, young individuals and males.
Some studies on survivors of cardiac arrest and patients with primary ventricular fibrillation have suggested an association between early repolarization and the risk of ventricular fibrillation.
However, to date there are no data to support an association between inferior early repolarization and sudden cardiac death in athletes 3.
Based on current evidence, all patterns of early repolarization, when present in isolation and without clinical markers of pathology, should be considered benign variants in athletes 3.
More information: Early repolarization.
Black athletes commonly demonstrate a repolarization variant consisting of J-point elevation and convex ST-segment elevation in the anterior leads (V1–V4) followed by T wave inversion which is regarded as a normal variant
In the absence of other clinical or EKG features of cardiomyopathy, should not result in further investigation 3 8.
T wave inversion on the anterior precordial leads may be considered a normal age-related pattern in adolescent athletes up to the age of 16 years old 3.
The term ‘juvenile’ EKG pattern is used to denote T wave inversion or a biphasic T wave beyond lead V2 in adolescents who have not reached physical maturity 3.
Based on current evidence, T wave inversion in the anterior leads (V1–V3) in adolescent athletes <16 years of age should not prompt further evaluation in the absence of symptoms, signs, or a family history of cardiac disease 3.
Common consequences of increased vagal tone include sinus bradycardia and sinus arrhythmia 3 8.
Other, less common markers of increased vagal tone are junctional or ectopic atrial rhythms, first degree AV block, and Mobitz Type I second degree AV block (Wenckebach phenomenon) 3 8.
In the absence of symptoms, heart rates ≥30 bpm are considered normal in highly trained athletes. Sinus rhythm should resume and bradycardia should resolve with the onset of physical activity.
Recent data suggest that some EKG findings previously categorized as abnormal may represent normal variants or the result of physiological cardiac remodelling in athletes and do not usually represent pathological cardiac disease 3.
These EKG findings have been categorized as ‘borderline’ findings in athletes 3.
Based on the recent considerations, left axis deviation, left atrial enlargement, right axis deviation and right atrial enlargement and complete right bundle branch block are considered borderline variants in athletes.
The presence of any one of these findings in isolation or with other recognized physiological electrical patterns of athletic training does not warrant further assessment in asymptomatic athletes without a family history of premature cardiac disease or sudden cardiac death 3.
Conversely, the presence of more than one of these borderline findings places the athlete in the abnormal category warranting additional investigation 3.
These common training-related ECG alterations are physiological adaptations to regular exercise, considered normal variants in athletes, and do not require further evaluation in asymptomatic athletes 1.
