Increased heart wall thickness in athletes: differentiating physiology from pathology
Updated: Sep 21
In this article, we explore whether athletes have increased heart wall thickness, what the research tells us about normal ranges across different sexes and ethnicities, and how sports cardiologists approach the critical distinction between a healthy training adaptation and an underlying cardiac condition such as hypertrophic cardiomyopathy.
In this article:
One of the most common reasons athletes are referred to a sports cardiologist is an incidental finding of increased heart wall thickness on echocardiography. For many, the result arrives with little explanation, and understandably causes concern. In most cases, that concern is unwarranted. But the distinction between a normal training adaptation and an underlying cardiac condition requires careful assessment, and it is not one that should be made without specialist input.
As lead author for a paper giving an overview of studies looking at heart wall thickness in athletes, I want to set out what the evidence tells us, how we interpret these findings in practice, and when further investigation is appropriate.
How regular training changes the heart
Regular endurance and strength training places sustained haemodynamic demands on the heart. Over time, the myocardium adapts to meet those demands. One well-documented consequence of this is an increase in left ventricular wall thickness (LVWT), the wall of the heart's main pumping chamber.
Large cohort studies consistently show that athletes exhibit a 15 to 20% increase in LVWT compared to healthy sedentary controls. In the vast majority of cases this remains well within normal limits, and represents a benign physiological adaptation rather than a pathological process.
The clinically significant threshold is 12mm. Above this, the picture becomes more complex, because a LVWT in the range of 12 to 16mm can be seen both in highly trained athletes and in patients with hypertrophic cardiomyopathy (HCM), a structural abnormality of the heart muscle that carries a very different prognosis.
How common is increased heart wall thickness in athletes?
What the data tells us about athletes above the 12mm threshold
In two large European studies, only 1.5 to 1.7% of athletes had a LVWT exceeding 12mm, with a maximum recorded measurement of 16mm across both cohorts. Several patterns are important:
Athletes with LVWT above 12mm are almost exclusively male
It is very rare for white female athletes to exceed 11mm as a consequence of physiological adaptation alone
Physiological hypertrophy causing LVWT above 16mm is rare regardless of sex or ethnicity, and should always prompt further investigation
The role of ethnicity in heart wall thickness
Ethnicity is a significant and often underappreciated variable in interpreting LVWT findings in athletes. Research demonstrates that black male athletes have a greater mean maximal wall thickness than their white counterparts (11.3mm versus 10mm), with a substantially higher proportion exceeding the 12mm threshold:
LVWT above 12mm: 18% of black male athletes versus 4% of white male athletes
LVWT above 15mm: 3% of black male athletes versus 0% of white male athletes
A comparable pattern is seen in female athletes, with LVWT above 11mm recorded in 3% of black female athletes versus none of their white counterparts. No female athlete in the studies reviewed exceeded 13mm.
These findings have direct clinical relevance. An echocardiographic result that might prompt concern in a white athlete may fall comfortably within the expected physiological range for a black athlete of similar training load, and vice versa. Ethnicity must be factored into any clinical interpretation of LVWT.
Heart wall thickness in young and adolescent athletes
Young athletes demonstrate analogous adaptive responses, though at lower absolute thresholds. In a study of predominantly white athletes aged 14 to 18, mean LVWT was significantly greater than in sedentary controls (9.5mm versus 8.4mm). However, all female athletes remained at or below 11mm, and only 0.4% of male athletes exceeded 12mm, with a maximum of 14mm.
In ethnically mixed adolescent cohorts, 5.5% of black athletes aged 14 to 16 had LVWT above 12mm, compared to none of the white athletes, with measurements reaching up to 15mm. The same ethnic patterns observed in adult athletes are therefore present in the adolescent population, and the same clinical considerations apply.
How do we tell the difference between normal adaptation and a heart condition?
The central clinical challenge is differentiating a training-related adaptation from hypertrophic cardiomyopathy in the 12 to 16mm overlap zone. This cannot be done reliably on the basis of a single echocardiographic measurement. Assessment should incorporate clinical history, family history, symptoms, additional imaging, and in some cases a period of detraining to observe whether wall thickness regresses, which it typically does in physiological hypertrophy but not in HCM.
The flowchart below, developed as part of my published research, outlines a structured approach to making this distinction in clinical practice.
When you should seek a specialist opinion
An increased LVWT finding warrants specialist assessment if any of the following apply:
LVWT above 12mm on echocardiography
Symptoms during exercise including chest pain, exertional breathlessness, palpitations or pre-syncope
A family history of hypertrophic cardiomyopathy or unexplained sudden cardiac death
An ECG with features atypical of normal athlete adaptation
If you have received a result suggesting increased heart wall thickness and would like a formal assessment, Sports Cardiology UK offers consultant-led evaluation at clinics in Bristol, Bath and London.
Reference: Augustine DX, Howard L. Left Ventricular Hypertrophy in Athletes: Differentiating Physiology From Pathology. Curr Treat Options Cardiovasc Med. 2018 Oct 26;20(12):96. doi: 10.1007/s11936-018-0691-2. PMID: 30367318.
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