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The ECG of Athletes: Normal variations you must know.

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The ECG of the athletes can pose a challenge in distinguishing pathological changes from those physiological changes, that are associated with physical training and cardiac remodelling. We don’t want to erroneously attribute heart disease to those with normal variants and more importantly, we don’t want potentially life threatening cardiac conditions being erroneously dismissed as normal variants.

The changes we see are related to:

  1. Increased vagal tone
  2. Enlarged cardiac chamber size

Those athletes that participate in endurance sports experience a volume load on all heart chambers, whereas those that participate in strength training experience a pressure overload on the heart, secondary to increased systemic vascular resistance(1).

In 2010, The European Society of Cardiology produced recommendations for ECG interpretation in athletes. In 2015, a meeting of sports physicians and sports cardiologists produced the most up to date set of criteria for determining normal and abnormal ECGs in athletes. These were the Seattle Criteria(2).

A CASE of an incidental finding in an ECG of an athlete

A 23 year old male who is training for a triathlon presents with a history of a mechanical fall. He trains over 8 hours per week and today whilst running tripped and fell. He has had a head strike, but no loss of consciousness. He complains of a small amount of midline neck pain. He is in bed with a cervical collar in-situ. There are no other injuries. He has full memory of the event and feels well. The nurse does as ECG and hands it to you. This is the ECG. What do you make of it?

Drezner JA, et al. Br J Sports Med 2013;47:125–136

The Answer: Mobitz Block; Wenkebach

Wenkebach is present as a normal variant in about 10% of athletes (Am Heart J. 1990:119;1378-91). The mechanism by which it occurs is the same as that with bradycardia:

  • Increased parasympathetic tone and/or
  • Decreased sympathetic resting tone

How do we exclude pathological cause on this patient? There should be resolution of symptoms with exercise, or even hyperventilation. This excludes a pathological cause.

As we can see, what might be considered abnormal in the everyday person, may be an expected finding in athletes. It’s important to have a set of criteria to assist us in determining what is benign and what is not.

The Seattle Criteria for the ECG of Athletes

In 2015, the Seattle Criteria were defined(2). ECG findings were divided into two groups:

  1. Benign training-induced cardiac changes that needed no further workup and
  2. Those indicating underlying pathology, warranting further evaluation

A. Normal Findings in Athletes

  • Sinus Bradycardia, but >30bpm
  • Sinus Arrhythmia
  • Ectopic Atrial Rhythm
  • Junctional Escape Rhythm(see below)
  • First Degree Block
  • Mobitz I Second Degree Block i.e. Wenkebach
  • Incomplete RBBB
  • Isolated Voltage Criteria for Left Ventricular Hypertrophy(see below)
  • Early Repolarisation V1-V4(see below)

B. Abnormal Findings in Athletes

It’s probably important to treat this list as you would for any other patient presenting. If the normal findings aren’t present, then abnormal findings related to any other patient apply. Here is the list:

  • T wave inversion in two or more leads
  • ST Depression in two or more leads
  • Sinus Tachycardia
  • Q waves (>3mm deep, > 4ms duration in>2 leads except III and aVR)
  • LBBB
  • Left Axis
  • Left Atria Enlargement
  • Right Ventricular Hypertrophy(RV1 + SV5>10.5mm + Right Axis)
  • Ventricular Pre-excitation(WPW)
  • Brugada Pattern
  • Sinus Bradycardia < 30bpm
  • PVCs(>2 PVCs per 10 second tracing or non-sustained VT

Normal ECG Findings in Athletes

Lets look at some examples of what is considered normal in athletes.

Ectopic Atrial Rhythm

Drezner et al BJ Sports Med, Vol 51, Issue 9, 2016

Ectopic P waves are present in about 8% of athletes. They have a different morphology to the normal P wave. In the ECG above we see negative p waves in the inferior leads.

Junctional Escape Rhythm

Drezner et al BJ Sports Med, Vol 51, Issue 9, 2016

The normal sinus rate, or rate of P waves is slow in athletes. In an escape or nodal rhythm, the escape rate is faster than the sinus rate. The QRS complexes will be narrow as the source is the AV node. The R-R interval should be constant.

The patient will return to sinus rhythm as soon as activity commences.

Incomplete Right Bundle Branch Block

Drezner et al BJ Sports Med, Vol 51, Issue 9, 2016

In athletes with right ventricular remodelling, there is increased conduction time in the right ventricle. The QRS is <120ms and there is a terminal R wave in lead I and terminal S waves in leads I and VI.

Voltage Criteria for LVH

The athlete’s heart usually has increased ventricular dimensions and an increased ventricular mass. This left ventricular hypertrophy manifests as an isolated increase in QRS amplitude. A high percentage of athletes’ ECGs fulfil electrocardiographic LV hypertrophy using Sokolow and Lyon criteria(S wave in V1 + R wave in V5.35 mm).

Abnormalities that infer a pathological cause for the left ventricular hypertrophy ie., hypertrophic cardiomyopathy (HCM), aortic valve disease or hypertensive heart disease also include other ECG changes such as(3):

  • atrial enlargement,
  • left axis deviation,
  • ST-segment and T-wave abnormalities, and
  • pathological Q waves

Corrado et al. European Heart Journal doi:10.1093/eurheartj/ehp473

The above ECG shows increased voltages and T wave inversion in the lateral leads. Hypertrophic Cardiomyopathy was diagnosed on ECHO.

Early Repolarisation

Early Repolarisation is present in up to 80% of athletes’ ECGs.(4) These changes are usually confined to the precordial leads but can extend to the lateral leads. There are two morphological patterns:

  1. In Caucasians, there is an ST segment elevation with upward concavity and a peaked T wave. Pattern A below.
  2. In African- Caribbean athletes, there is an elevated ST-segment with an upward convexity, followed by a negative T-wave in V2 – V4. This needs to be distinguished from the Brugada pattern. Pattern B below.

Corrado et al. European Heart Journal doi:10.1093/eurheartj/ehp473


Remember that there are benign changes in the ECGs of athletes. Know these and question all others.

Here they are again:

Drezner et al BJ Sports Med, Vol 51, Issue 9, 2016


  1. Pelliccia A, Maron BJ, Spataro A, Proschan MA, Spirito P. The upper limit of physiologic cardiac hypertrophy in highly trained elite athletes. N Engl J Med. 1991 Jan 31;324(5):295–301
  2. Drezner JA, Ackerman MJ, Anderson J et al. Electrocardiographic interpretation in athletes: the Seattle Criteria. Br J Sports Medicine. 2013 Feb;47(3):122–4
  3. Melacini P, Cianfrocca C, Calore C, et al. Marginal overlap between electrocardiographic abnormalities in patients with hypertrophic cardiomyopathy and trained athletes: implications for preparticipation screening. Circulation 2007;116:765
  4. Bianco M, Bria S, Gianfelici A, Sanna N, Palmieri V, Zeppilli P. Does early repo- larization in the athlete have analogies with the Brugada syndrome? Eur Heart J 2001;22:504 – 510


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