Educational draft · awaiting clinical reviewThe full textbook explains uncertainty but does not replace live national or local guidance, specialist advice, or current prescribing information.
Recognise arrhythmogenic cardiomyopathy, integrate electrical, imaging and genetic evidence, and reduce exercise-related and sudden-death risk.
Arrhythmogenic cardiomyopathy is an inherited myocardial disease in which ventricular arrhythmia may precede structural dysfunction. The traditional RV-predominant label remains clinically useful, but systematic LV assessment is essential.
A specialist diagnosis combines phenotype criteria, pedigree and carefully interpreted genomic evidence. Overdiagnosis from an athletic RV or incidental CMR fat is as harmful as missed disease.
Management focuses on exercise modification, arrhythmia surveillance and suppression, ICD selection, heart-failure care and cascade family management.
Many cases reflect pathogenic variants in proteins that maintain mechanical adhesion between cardiomyocytes. Inheritance is often autosomal dominant with incomplete penetrance, so a parent may carry the variant with little apparent disease; other inheritance patterns also occur.
Other inherited myocardial variants can produce biventricular or left-dominant phenotypes. A negative panel does not exclude a clinical diagnosis, and a variant of uncertain significance cannot establish one.
Repeated high-intensity endurance exercise increases mechanical stress on susceptible myocardium, promoting penetrance, scar progression and ventricular arrhythmia. It modifies inherited risk rather than acting as a sufficient cause alone.
In many desmosomal forms, impaired junctional integrity and signalling make cardiomyocytes vulnerable to injury during mechanical strain. Other arrhythmogenic-cardiomyopathy genes can reach a similar phenotype through different cellular mechanisms.
Myocyte injury may be accompanied by inflammatory episodes in some phenotypes, particularly desmoplakin-related disease. These hot phases can present with chest pain and troponin release, sometimes resembling acute myocarditis.
Injured myocardium is replaced by patchy fibrosis with variable fatty replacement, creating regional wall-motion abnormalities, ventricular dilatation and a heterogeneous electrical substrate in the RV, LV or both.
Slow and discontinuous conduction around patchy scar supports re-entry, producing ventricular ectopy and VT that may precede obvious structural dysfunction and can deteriorate into VF.
If myocardial loss and remodelling progress, RV and sometimes LV contractility decline, potentially causing biventricular heart failure and poorer tolerance of ventricular arrhythmias.
Palpitations, ventricular ectopy, VT or syncope in a young adult may occur before obvious structural disease.
T-wave inversion in right precordial leads, prolonged terminal activation and epsilon-like late potentials can support diagnosis but require age and conduction context.
VT arising from the RV commonly has left-bundle-branch-block morphology; axis and morphology help localise but are not diagnostic alone.
Regional RV akinesia/dyskinesia or aneurysm with RV dilatation/dysfunction is characteristic; LV fibrosis or dysfunction may coexist.
Chest pain and troponin rise with non-ischaemic scar, recurrent 'myocarditis' or a DSP family history should raise arrhythmogenic cardiomyopathy.
Exercise-related syncope, sustained VT or aborted sudden death needs urgent risk assessment and exercise cessation.
Physiological RV enlargement is usually proportionate, with preserved regional motion and no convincing scar or familial electrical phenotype. Deconditioning and expert quantitative imaging may resolve borderline findings.
This can produce left-bundle-pattern VT in an otherwise normal heart, but lacks progressive regional RV dysfunction, characteristic scar and the broader familial phenotype of arrhythmogenic cardiomyopathy.
A single inflammatory episode without evolving familial or structural features favours myocarditis, but recurrent hot phases may represent arrhythmogenic cardiomyopathy; CMR, pedigree and genetics require integrated interpretation.
High-grade AV block, extracardiac sarcoidosis, active patchy inflammatory uptake or granulomatous tissue may support sarcoidosis. Multimodality assessment is often needed because scar patterns and ventricular arrhythmias overlap.
Brugada usually has a structurally normal heart with a coved right-precordial ST pattern and fever-related events, rather than regional ventricular dilatation, wall-motion abnormality and replacement scar.
Scar-related re-entry causes sustained ventricular tachycardia, while unstable VT can degenerate into ventricular fibrillation. Life-threatening arrhythmia may be the first recognised manifestation.
Transient low output during rapid VT can cause abrupt loss of consciousness, often during exercise, with secondary trauma and a strong implication for sudden-death risk assessment.
Progressive myocardial replacement causes chamber dilatation, functional tricuspid regurgitation and systemic venous congestion; LV involvement adds pulmonary congestion and worsens prognosis.
Severe ventricular dilatation and regional akinesia promote stasis and mural thrombus. Resulting pulmonary or systemic embolism is less characteristic than arrhythmia but clinically important in advanced disease.
Ventricular ectopy or VT may be the first manifestation before RV dilatation is obvious.
DSP and other genotypes may cause prominent LV scar or biventricular disease.
CMR fat signal without regional/quantitative abnormalities can occur with age or obesity and should not anchor diagnosis.
Endurance and high-intensity exposure can increase penetrance and adverse events; exercise history is part of diagnosis and treatment.
Epicardial/endocardial substrate may recur as disease progresses; successful ablation does not remove ICD or surveillance needs.
Diagnosing ARVC from an epsilon wave, athletic RV enlargement or CMR fat alone.
Ignoring LV imaging because the historical name emphasises the RV.
Recommending unrestricted competitive exercise to an asymptomatic variant carrier.
Using a VUS to diagnose relatives.
Assuming ablation or antiarrhythmic medication replaces an indicated ICD.
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A highly trained endurance athlete has mild RV enlargement and visible epicardial fat on CMR but normal regional motion, function, ECG and rhythm monitoring. What is the best interpretation?
National guidance is shown before implementation-dependent detail. Apply principles in context and verify current guidance when a decision affects care. Source check completed 27 Aug 2026; clinical approval remains outstanding.
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