Sports Cardiology

Regular exercise is one of the best things you can do for your heart. Yet in rare cases, an unrecognized heart condition can turn intense exercise into a life-threatening event. Sports cardiology sits between these two truths: it aims to keep athletes active while identifying the few who carry a hidden cardiac risk.

This page explains how training changes the heart, what we know about sudden cardiac death (SCD) in athletes, and how the Seattle criteria and their 2017 International update help clinicians tell a normal athlete’s ECG from one that needs further work-up

• Intense training causes normal, harmless ECG changes such as slow heart rate, high voltages, and early repolarisation.
• Sudden cardiac death in athletes is rare but devastating, and most causes are inherited or structural conditions.
• The Seattle criteria sort ECG findings into normal, borderline, and abnormal, which sharply reduces false positives without losing sensitivity.
• A normal ECG does not exclude all causes of SCD: symptoms, family history, and examination always matter.
• Most athletes with an abnormal ECG do not have serious disease, but they deserve a proper cardiology work-up.

1. The athlete’s heart

Regular intense training, typically 4 to 8 or more hours per week, produces structural and electrical adaptations: larger heart chambers, thicker walls, and higher vagal (parasympathetic) tone. These changes are called the athlete’s heart, and they show up on the ECG as:

• Slow resting heart rate (sinus bradycardia) and sinus arrhythmia
• Increased QRS voltage
• Incomplete right bundle branch block
• Early repolarisation
• First-degree and Mobitz type I (Wenckebach) AV block

The difficulty is that some of these changes can look similar to the early signs of cardiomyopathy or arrhythmia disorders. The challenge of sports cardiology is to separate physiology from pathology, without removing healthy athletes from sport for no reason.

2. Sudden cardiac death in athletes: the basics.

How common?

• Rare: roughly 1 per 50,000 to 1 per 100,000 athlete-years in most young athlete studies, with wide variation by population.
• Higher in males than females.
• Higher in some groups, such as black male athletes and certain sports like basketball and football in US data.

Who is affected?

• Mostly young competitive athletes under 35, but recreational athletes are affected too.
• Males account for the large majority of cases.
• In athletes aged 30 and over, coronary artery disease is the most common cause of SCD.

Why does it happen?

• Intense exercise acts as a trigger on an underlying condition.
• In many cases the heart looks normal at autopsy; 25 to 40% of sudden unexplained deaths under age 40 are autopsy-negative, with channelopathies implicated in up to 25 to 35% in selected cohorts.

Main causes in young athletes

Category	Examples	Can the ECG help?
Cardiomyopathies	Hypertrophic cardiomyopathy (HCM), arrhythmogenic right ventricular cardiomyopathy (ARVC), dilated cardiomyopathy	Yes: often shows T-wave inversion, ST depression, Q waves, or ventricular ectopy
Channelopathies	Long QT syndrome, Brugada syndrome, short QT, CPVT	Yes for long QT, Brugada, and short QT; limited for CPVT, which can have a normal resting ECG
Pre-excitation	Wolff-Parkinson-White (WPW)	Yes: short PR interval and delta wave
Myocarditis	Viral or inflammatory heart disease	Sometimes, depending on the stage
Coronary anomalies and premature atherosclerosis	Anomalous coronary artery origin, early coronary disease	Rarely. The paper notes the ECG does not readily detect these
Aortopathies	Marfan syndrome, aortic dissection	No

Brugada syndrome is estimated to cause up to 4% of sudden deaths in the general population and 5 to 20% of sudden unexplained deaths with structurally normal hearts at autopsy.

Red-flag symptoms in any athlete: fainting or near-fainting during exercise, chest pain with exertion, unexplained shortness of breath out of proportion to effort, palpitations, a family history of sudden death under 50, or a family history of inherited heart disease. These need cardiology evaluation even if the ECG looks normal.

3. The Seattle criteria for ECG interpretation in athletes

Early ECG screening criteria, such as the 2010 European Society of Cardiology (ESC) recommendations, flagged too many healthy athletes as abnormal. The Seattle criteria (2013) and their 2017 International Criteria update were developed to fix this. They were designed for asymptomatic athletes aged 12 to 35 and take into account age, sex, ethnicity, sport, and training load.

The logic is simple: every ECG finding falls into one of three groups.

Normal findings (training-related)

Finding	Definition
Increased QRS voltage	Isolated LVH voltage: SV1 + RV5 or RV6 >3.5 mV. Isolated RVH voltage: RV1 + SV5 or SV6 >1.1 mV
Incomplete RBBB	rSR′ in V1, qRS in V6, QRS <120 ms
Early repolarisation	J-point elevation, ST elevation, J waves, or terminal QRS slurring in inferior and/or lateral leads
Black-athlete repolarisation variant	J-point elevation and convex (“domed”) ST elevation followed by T-wave inversion in V1-V4, in black athletes
Juvenile T-wave pattern	T-wave inversion V1-V3 in athletes under age 16
Sinus bradycardia	30 bpm or more
Sinus arrhythmia	Heart rate varies with breathing
Ectopic atrial rhythm	P waves differ from sinus P waves
Junctional escape rhythm	Narrow QRS, typically under 100 bpm, faster than the sinus rate
First-degree AV block	PR 200 to 400 ms
Mobitz type I (Wenckebach)	Progressively lengthening PR until a dropped beat

Borderline findings

Finding	Definition
Left axis deviation	-30° to -90°
Left atrial enlargement	P wave >120 ms in I or II, with negative portion in V1 of at least 1 mm depth and 40 ms duration
Right axis deviation	>120°
Right atrial enlargement	P wave 2.5 mm or more in II, III, or aVF
Complete RBBB	rSR′ in V1, S wave wider than R in V6, QRS 120 ms or more

Important: a single borderline finding is not a disease. Two or more borderline findings together are classified as abnormal.

Abnormal findings

Finding	Definition
T-wave inversion	1 mm or deeper in 2 or more contiguous leads, excluding aVR, III, and V1. Territories: anterior (V2-V4), lateral (I, aVL, V5, V6), inferolateral, inferior (II, aVF). Exceptions: black-athlete variant, athletes under 16 with TWI V1-V3, and biphasic T waves confined to V3
ST depression	0.5 mm or more in 2 or more contiguous leads
Pathological Q waves	Q/R ratio 0.25 or more, or duration 40 ms or more, in 2 or more leads (excluding III and aVR)
Complete LBBB	QRS 120 ms or more, negative QRS in V1, upright notched or slurred R in I and V6
Profound non-specific conduction delay	Any QRS 140 ms or more
Epsilon wave	Low-amplitude signal between end of QRS and start of T wave in V1-V3
Ventricular pre-excitation	PR under 120 ms with a delta wave and QRS 120 ms or more
Prolonged QTc	470 ms or more (male), 480 ms or more (female). 500 ms or more is marked prolongation
Brugada type 1	Coved ST elevation of 2 mm or more (“high take-off”), downsloping, then negative symmetric T wave in at least one of V1-V3
Profound sinus bradycardia	Under 30 bpm, or sinus pauses of 3 seconds or more
Profound first-degree AV block	PR 400 ms or more
Mobitz type II or third-degree AV block	Intermittently dropped P waves with fixed PR, or complete heart block
Atrial tachyarrhythmias	SVT, atrial fibrillation, atrial flutter
Premature ventricular contractions	2 or more PVCs per 10-second tracing
Ventricular arrhythmias	Couplets, triplets, non-sustained ventricular tachycardia

Measuring the QT interval correctly

• Use the Bazett correction, ideally at a heart rate of 60 to 90 bpm.
• Measure manually in lead II or V5 with the “teach-the-tangent” method, so the U wave is excluded.
• If the heart rate is under 50 bpm, repeat after mild aerobic activity. Bazett underestimates the QTc at slow rates and overestimates it above 90 bpm.
• A single QTc above threshold calls for evaluation, not an automatic diagnosis of long QT syndrome.

Special populations

• Black athletes: J-point elevation with convex ST elevation followed by T-wave inversion in V1-V4 is a normal variant. The paper reports TWI in up to 25% and ST elevation in more than two-thirds of black athletes. TWI that does not follow this pattern, or that extends to lateral leads, is not normal.
• Adolescents under 16: anterior T-wave inversion in V1-V3 is a normal juvenile pattern if there are no symptoms or family history. It was reported in 10 to 15% of white 12-year-olds and 2.5% of white 14 to 15-year-olds.
• Female athletes: QTc thresholds are higher (480 ms), and anterior TWI is slightly more common than in males.
• Endurance athletes: more bradycardia, LVH voltage, and early repolarisation. TWI extending to V3 was more frequent in endurance than non-endurance athletes (4.0% vs 1.1%).
• Athletes aged 30 and over: coronary artery disease becomes the main concern, and work-up focuses on ischemia and risk factors.

4. How well does ECG screening work?

The 2017 paper summarizes several cohorts comparing the Seattle criteria with earlier rules. The main message is that the newer criteria cut false positives sharply while keeping sensitivity high:

Study population	Result reported
1,078 elite Australian athletes	False positives fell from 17% (2010 ESC) to 4.2% (Seattle), with no change in sensitivity
2,017 US high-school athletes	Seattle false-positive rate 2.8%, with 100% sensitivity for the SCD-associated conditions identified
1,417 high-school, college, and professional athletes	Abnormal ECGs: 26% (ESC), 8.1% (Stanford), 5.7% (Seattle)
5,505 elite athletes	Abnormal ECGs: 21.5% (ESC), 9.6% (Seattle), 6.6% (refined criteria). All identified 98.1% of athletes with established HCM. 14 of 15 (93%) serious conditions were detected by ECG
2,533 athletes aged 14-35 vs 9,997 controls	Excluding axis deviation and atrial enlargement lowered false positives from 13% to 7.5% and raised specificity from 90% to 94%, with a small drop in sensitivity (91% to 89.5%)

These are individual study results, not universal test characteristics. In the paper’s words, “no single ECG abnormality has perfect accuracy.”

What the ECG cannot do: it does not readily detect anomalous coronary arteries, premature coronary atherosclerosis, or aortopathies. A normal ECG never replaces a good history and physical examination. Symptoms, a concerning family history, or an abnormal exam need broader evaluation even when the ECG is normal.

5. What happens after an abnormal ECG?

An abnormal ECG is a reason to investigate, not a diagnosis. Evaluation should be led by a doctor, and the tests depend on the finding:

ECG finding	Typical next steps
Lateral or inferolateral T-wave inversion	Echocardiogram, cardiac MRI, exercise ECG, at least 24-hour monitor; consider family evaluation and genetics. MRI is a routine part of the work-up for this pattern, since it is better for apical HCM
Anterior T-wave inversion (non-variant)	Echocardiogram, cardiac MRI, exercise ECG, 24-hour monitor, signal-averaged ECG (ARVC concern)
Inferior-only T-wave inversion	At least an echocardiogram; consider MRI and annual reassessment
ST depression or pathological Q waves	Echocardiogram, consider MRI, assess coronary risk. If QS is isolated to V1-V2, repeat the ECG with correct lead placement first
Complete LBBB	Echocardiogram and cardiac MRI with stress perfusion
Epsilon wave	Echocardiogram, MRI, exercise ECG, 24-hour monitor, signal-averaged ECG
2 or more PVCs on a 10-second ECG	Echocardiogram, 24-hour monitor, exercise ECG. If more than 2,000 PVCs in 24 hours or non-sustained VT, comprehensive testing including MRI. Detraining is not recommended as a diagnostic or therapeutic measure
WPW or pre-excitation	Exercise ECG and echocardiogram. Abrupt loss of the delta wave on exercise suggests a low-risk pathway. Consider an electrophysiology study if low risk cannot be confirmed, especially for moderate-to-high intensity sport
Prolonged QTc	Repeat ECG on a separate day, check QT-prolonging drugs and electrolytes, consider relatives’ ECGs, exercise testing, genetics. Refer promptly for QTc above 500 ms without a reversible cause
Brugada type 1	Cardiologist or electrophysiologist referral. Check lead placement; consider high precordial leads if unclear
Profound bradycardia or very long PR	Repeat after mild activity. If the rate rises appropriately and the athlete is asymptomatic, no further testing is needed
Mobitz II or complete AV block	Echocardiogram, ambulatory monitor, exercise ECG; refer to a rhythm specialist
Atrial tachyarrhythmias	Echocardiogram, 24-hour monitor, exercise ECG; consider MRI or electrophysiology study
Couplets, triplets, non-sustained VT	Echocardiogram, MRI, 24-hour monitor, exercise ECG

The paper suggests considering temporary restriction from sport for an abnormal ECG of uncertain significance until the secondary evaluation is complete. Athletes with an abnormal ECG suggestive of cardiomyopathy may need annual follow-up even if the first tests are normal: in cohorts cited in the paper, about 6% later developed a cardiomyopathy or an arrhythmic event.

6. Practical points for the sports physician

1. History first. Ask about exertional syncope, chest pain, palpitations, and family history of sudden death or cardiomyopathy. Perform a focused examination.
2. Use a structured ECG approach. Classify each finding as normal, borderline, or abnormal. Count the borderline findings.
3. Check technique. Poor lead placement can create false QS patterns in V1-V2 or false Brugada patterns. Repeat before escalating.
4. Consider age, sex, ethnicity, and sport. This is where most false positives are avoided.
5. Have a pathway. If ECG screening is used, the paper stresses access to cardiology expertise and secondary testing, and screening early enough to allow follow-up before the season.
6. For athletes aged 30 and over, assess coronary risk factors and consider stress testing, as coronary artery disease is the main cause of SCD.
7. Be ready to respond. Emergency action plans, access to an AED, and trained staff at events save lives, regardless of screening strategy.

7. Key points

• Training causes normal ECG adaptations, such as bradycardia, high voltage, early repolarisation, and incomplete RBBB, that need no work-up in asymptomatic athletes.
• SCD in athletes is rare, mainly due to cardiomyopathies, channelopathies, pre-excitation, and (in older athletes) coronary artery disease.
• The Seattle criteria classify findings as normal, borderline, or abnormal. Two or more borderline findings count as abnormal.
• Compared with older criteria, they cut false positives (for example from 17% to 4.2% in an elite athlete cohort) while keeping sensitivity high.
• The ECG has limits: it misses coronary anomalies, early atherosclerosis, and aortopathies.
• An abnormal ECG means investigate, not disqualify, and the work-up depends on the specific finding.

Disclaimer: This page is for educational purposes only and does not replace individualized medical advice. Athletes with symptoms such as fainting, chest pain, or unexplained breathlessness during exercise, or with a family history of sudden cardiac death, should be evaluated by a physician or cardiologist.