Athlete Cardiac Screening

Sustained training, particularly endurance training, produces real structural and electrical changes in a normal heart, known collectively as the athlete's heart. The chambers enlarge, the walls may thicken modestly, the resting heart rate falls as vagal tone rises, and the electrical trace changes to match. This adaptation is entirely benign, but it overlaps with the early appearance of disease, which is what makes interpretation hard.

On the ECG, the expected consequences of adaptation include a slow resting rate, or sinus bradycardia, sinus arrhythmia, first-degree block at the atrioventricular node, and Mobitz type I second-degree block, particularly when they resolve with exertion, along with voltage changes suggesting larger chamber size. Early repolarisation and an incomplete right bundle branch block (RBBB) are also common and normal in this context. By contrast, a profoundly slow rate, a very long PR interval, Mobitz type II block or complete heart block are not training changes and need evaluation. The guiding principle is that the benign training-related findings, in an athlete with no symptoms and no concerning family history, do not require further investigation. Difficulty arises when a finding sits outside this pattern, when several borderline findings appear together, or when the history raises a flag.

The history is the most valuable part of screening and the most often underused. It asks about the athlete's own symptoms, chest pain, breathlessness out of proportion to effort, palpitations, dizziness and above all syncope or near-syncope on exertion, since exertional syncope is the symptom that must never be dismissed. It also asks about the family: any sudden, unexplained or premature death, drownings, unexplained road accidents, or a known inherited cardiac condition in a close relative. The examination looks for a murmur that behaves like dynamic outflow obstruction, the features of Marfan syndrome, reduced or delayed femoral pulses, and the blood pressure. On their own, history and examination miss a substantial share of what matters, which is the argument for adding the ECG.

Modern interpretation follows international consensus criteria, which sort ECG findings into three groups. Normal, training-related findings, such as isolated increases in voltage, a slow rate, early repolarisation and incomplete right bundle branch block, are the result of adaptation and, in an athlete with no symptoms or family history, need no further evaluation. Borderline findings, which include left or right axis deviation, left or right atrial enlargement, and complete right bundle branch block, are innocent in isolation but warrant investigation when two or more occur together. Abnormal findings fall outside athletic adaptation and always require assessment, whatever the athlete feels. These include ST-segment depression, pathological Q waves, profound conduction disease, a type 1 Brugada pattern, a markedly prolonged or short corrected QT interval (QTc), the short PR interval and delta wave of ventricular pre-excitation, and T-wave inversion beyond the patterns accepted in athletes.

T-wave inversion is the commonest trap. Anterior T-wave inversion confined to leads V1 to V3 is accepted in athletes under 16, and in athletes of African or Afro-Caribbean descent a pattern of J-point and ST-segment elevation followed by anterior T-wave inversion is a recognised normal variant. Lateral or inferolateral T-wave inversion, though, carries a real risk of underlying cardiomyopathy and always needs assessment. Each abnormal pattern maps onto a condition covered elsewhere in this section, and the value of the criteria is that they raise the threshold for calling an ECG abnormal, which cuts false positives while still catching disease. The trace is never read alone: a finding dismissed in an asymptomatic athlete takes on weight when the history or examination is also concerning.

A completely normal screen, with no symptoms, no family history and an ECG showing only training changes, allows the athlete to be cleared. Before escalating an unexpected finding, confirm the trace is technically sound and the leads, especially the precordial leads, are correctly placed, and repeat it if there is doubt, since misplacement can create false anterior patterns. When a screen is genuinely positive, the next step is targeted secondary investigation rather than automatic permanent disqualification, since most positive screens turn out not to be disease. Depending on the finding, this means echocardiography, cardiac magnetic resonance imaging where the echo is inconclusive or a specific condition is suspected, an exercise test, ambulatory rhythm monitoring, and referral to a sports cardiologist or an inherited cardiac conditions service. An athlete with concerning symptoms, examination findings or an abnormal ECG should not be cleared for high-intensity or competitive sport until that assessment is complete.

Two cautions matter. A normal resting ECG does not overrule exertional syncope, exertional chest pain, concerning palpitations or a significant family history, all of which still require specialist assessment, since some conditions develop over time or evade a resting test. And no screening programme removes the need for on-site emergency preparedness, because a proportion of sudden cardiac arrests happen in people who screened normal or were never screened, and immediate cardiopulmonary resuscitation and defibrillation remain the decisive response.

• •International consensus criteria for electrocardiogram interpretation in athletes, developed through a lineage of European and Seattle expert groups, standardise the separation of normal training changes from abnormal patterns.
• •European Society of Cardiology (ESC) guidance on sports cardiology and pre-participation evaluation informs screening practice.
• •The UK National Screening Committee does not currently recommend systematic population screening for cardiac conditions causing sudden cardiac death in people under 40, an area that remains under active review and debate.
• •Cardiac Risk in the Young (CRY) provides cardiac screening for young people in the United Kingdom and supports affected families, and Resuscitation Council UK field-of-play and community sport guidance underpins the emergency response that screening does not replace.

• •Athlete cardiac screening combines a personal and family history, an examination and a 12-lead electrocardiogram, and in masters athletes acquired coronary artery disease is the main concern.
• •Training adapts the heart, so increased voltages, sinus bradycardia, first-degree and Mobitz type I block, early repolarisation and incomplete right bundle branch block are normal.
• •Borderline findings matter mainly in twos; abnormal findings include ST-segment depression, pathological Q waves, a type 1 Brugada pattern, an abnormal corrected QT interval and pre-excitation.
• •Anterior T-wave inversion has age and ethnicity-specific normal variants, but lateral T-wave inversion always needs assessment.
• •Exertional syncope and a family history of premature sudden death mandate assessment even when the electrocardiogram is normal.
• •A positive screen leads to targeted investigation and specialist referral, not automatic disqualification, and never replaces on-site defibrillation.