A practical course on distinguishing physiological athletic cardiac adaptation from cardiomyopathy and primary arrhythmia syndromes.
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What learners will be able to do
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Recognize overlap
Explain why training adaptations can resemble cardiomyopathy or channelopathy.
Read warning signs
Identify ECG, imaging, exercise, rhythm, and family-history clues that shift concern toward disease.
Plan surveillance
Use longitudinal monitoring when findings are equivocal rather than forcing a false black-and-white answer.
Source basis: Adapted for education from Sivalokanathan et al., Heart 2026, “Grey zone between physiological adaptation and cardiac disease in athletes.â€
This course is educational and does not replace specialist sports cardiology judgment.
1DefineGrey zone and athlete's heart
2CompareHCM, DCM, ACM patterns
3InvestigateECG, echo, CMR, CPET, Holter
4DifferentiateLQTS, Brugada, CPVT
5FollowGenetics, surveillance, decisions
Module 1
Understanding the grey zone
The grey zone is the uncertain area where athletic adaptation, incomplete phenotypic expression, and early cardiac disease may overlap.
It is a dynamic clinical spectrum, not a final diagnosis.
Training can produce electrical, structural, and functional cardiac changes.
Age, sex, ethnicity, sport type, and training load influence normal adaptation.
Equivocal findings may need surveillance because disease expression can evolve over time.
A dichotomous “normal versus abnormal†approach may be misleading in borderline cases.
Interpretation moves along the continuum as symptoms, ECG, imaging, exercise performance, rhythm monitoring, and family history are integrated.
Quick check
What is the safest interpretation of an isolated grey-zone finding?
Module 2
Differentiating cardiomyopathies from athlete's heart
The article emphasizes three common structural patterns: increased LV wall thickness, dilated LV, and dilated RV. Each can be physiological, borderline, or disease-associated.
HCM overlap
Mild asymmetric LVH of 13-15 mm can be difficult. Red flags include lateral/inferolateral T-wave inversion, ST depression, pathological Q waves, high relative wall thickness, small cavity size, diastolic impairment, and LGE.
DCM overlap
Endurance athletes may have LV dilation and low-normal EF. Concern rises with LBBB, low voltages, abnormal repolarisation, impaired augmentation during exercise, arrhythmias, or replacement fibrosis.
ACM overlap
Right ventricular enlargement may reflect training, but regional wall-motion abnormalities, reduced RV function, frequent or complex PVCs, and concerning T-wave patterns push toward disease.
Clinical context
Symptoms, family history, ethnicity, sport type, training history, and serial change matter as much as a single measurement.
Pattern
More physiological
More concerning
LV hypertrophy
Balanced chamber enlargement and normal function
Lateral TWI, RWT > 0.5, LGE, small cavity
Dilated LV
High exercise capacity and normal rhythm monitoring
Low reserve, LBBB, fibrosis, complex arrhythmias
Dilated RV
Proportionate athletic remodelling
Regional dysfunction, aneurysm, ACM-type ECG/PVCs
Module 3
Diagnostic tools in the grey zone
No single test resolves every case. The article favors an integrated diagnostic armamentarium, especially when an ECG or echocardiogram is not fully reassuring.
ECGVoltage alone may be athletic; lateral TWI, ST depression, Q waves, LBBB, or low voltages raise concern.
EchoAssess cavity size, wall thickness, RWT, systolic and diastolic function, RV size and function.
CMRClarifies morphology, volumes, function, tissue characterisation, fibrosis, and LGE.
CPET/HolterHigh pVO2 and absent arrhythmias support physiology; impaired reserve or complex arrhythmia raises concern.
GeneticsMost useful when clinical suspicion is high or uncertainty persists after phenotype testing.
Clinical pearl: A normal echocardiogram is not always enough when lateral T-wave inversion is present; CMR and annual monitoring may be needed.
Module 4
Primary arrhythmia syndromes
Channelopathies can be especially challenging because the heart may look structurally normal. The history, ECG phenotype, provocation testing, exercise response, and family history become central.
Long QT syndrome
Borderline QT intervals require careful measurement, repeat assessment, medication review, family history, and phenotype-specific interpretation.
Brugada syndrome
Diagnosis may require recognising spontaneous or provoked type 1 patterns. Fever, drugs, and provocative testing can reveal risk in selected cases.
CPVT
Exercise or catecholamine-triggered ventricular ectopy in a structurally normal heart is a key clue and should not be dismissed as benign athletic ectopy.
Shared decision-making
Sport participation decisions should be individualised, risk-stratified, and made with experts in inherited disease and sports cardiology.
Module 5
Longitudinal management and final judgment
The article's major message is humility: some cases cannot be resolved immediately. The right answer may be careful follow-up, repeat testing, and revisiting the diagnosis as the athlete ages or training changes.
1. Frame uncertaintyExplain what is known, unknown, and potentially evolving.
2. Integrate testsCombine ECG, echo, CMR, CPET, Holter, genetics, and family history.
3. Risk stratifyIdentify disease features and manage according to inherited disease guidance.
4. Follow over timeUse annual or shorter surveillance when the phenotype is equivocal or symptoms occur.
5. Decide togetherUse shared decisions for sport, testing burden, and ongoing monitoring.
Bottom line: Grey-zone athletes need a learned, contextual, longitudinal approach rather than premature reassurance or premature labeling.
Final Exam
Course exam
Answer all questions, then submit for a score and answer review. A score of 80% or higher is marked as passing.