Arrhythmogenic cardiomyopathy

Article written and reviewed by Dr Luca Moretti

Arrhythmogenic cardiomyopathy, abbreviated ACM, is a myocardial disease characterized by nonischemic scar and vulnerability to ventricular arrhythmias, with predominant involvement of the right ventricle, the left ventricle or both. The term does not identify a single morphology or a single gene: it describes an arrhythmogenic continuum in which cell injury, fibrous repair and electrical instability occur in different proportions among individuals.

Historical arrhythmogenic right ventricular cardiomyopathy, ARVC, is the best-characterized form, but it does not encompass the entire spectrum. Tissue imaging and genetics have revealed left-sided and biventricular phenotypes in which scar may precede dilation and a decline in ejection fraction. This nosologic expansion corrects a diagnostic limitation without permitting every cardiomyopathy associated with arrhythmias to be labeled arrhythmogenic.

The disease is frequently inherited and often autosomal dominant, with incomplete penetrance and age-dependent expression. Carriers of the same variant may remain asymptomatic, show only premature ventricular contractions, or develop tachycardias, heart failure and sudden death; intense exercise and other modifiers contribute to this variability. The causal genotype establishes vulnerability, not an individual clinical destiny.

Electrical abnormalities may precede recognizable structural changes. A person with preserved global function may already have slow-conduction corridors within scar and present with sustained ventricular tachycardia, whereas another person with marked dilation may remain free of major arrhythmias for a long time. This electromechanical dissociation explains why ejection fraction alone is insufficient for diagnosis and prevention of sudden death.

There is no universal gold standard. Diagnosis, phenotypic distribution and risk emerge from the combination of history, pedigree, ECG, rhythm monitoring, echocardiography, cardiac magnetic resonance, genetics and sometimes biopsy. An integrated probability protects against two opposite errors: missing an early form because the heart is not dilated, or overdiagnosing an inherited disease on the basis of nonspecific findings.

Definition, nomenclature and epidemiology

The word dysplasia reflected the original hypothesis of abnormal right ventricular development, but pathologic and genetic studies have demonstrated a process acquired over the course of life on a predominantly inherited basis. Replacing dysplasia with cardiomyopathy recognizes a progressive myocardial dystrophy in which cell loss and scarring continue after cardiac development is complete.

The narrow meaning of ARVC requires a right-sided phenotype consistent with international criteria. The broader meaning of ACM includes left-dominant and biventricular forms related to a genetic and fibrotic substrate, but some US documents have also included systemic or inflammatory diseases capable of causing arrhythmias. Terminologic precision requires stating which definition is being used, especially in the literature and in family counseling.

The prevalence of the classic right-sided form is often estimated at approximately 1:2,000 to 1:5,000, but the figure varies with geography, access to expert centers and founder variants. Naxos disease and the TMEM43 p.Ser358Leu variant show much higher regional concentrations. The observed prevalence therefore reflects population biology and ascertainment intensity, not a uniform value transferable to every region.

Left-sided phenotypes are likely underestimated because the 2010 criteria were designed for the right ventricle and left ventricular fibrosis may coexist with normal chamber volumes. A previous diagnosis of recurrent myocarditis, arrhythmic DCM or idiopathic scar may conceal DSP, FLNC or PLN disease. Ascertainment bias makes precise epidemiologic estimates for the entire ACM spectrum premature.

Clinical presentation is uncommon before puberty in classic dominant forms, increases from adolescence onward and often becomes manifest in adulthood. This does not mean that a child carrying a variant is risk-free, nor that an older person with normal tests will necessarily develop disease. Age-dependent penetrance determines screening timing but must be modulated by the gene and the specific family history.

Sudden death in young people and athletes has made arrhythmogenic cardiomyopathy a paradigmatic disease, but reference cohorts overrepresent severe arrhythmic cases. Genetic and family screening identifies people with milder courses, whereas patients with advanced heart failure constitute another selected subgroup. Cohort prognosis must not be transferred without adjustment to an asymptomatic carrier.

Desmosomes, genetics and mechanisms of disease

The desmosome connects intermediate filaments of adjacent cells and allows cardiac tissue to withstand millions of mechanical cycles. Plakophilin-2, desmoplakin, desmoglein-2, desmocollin-2 and plakoglobin participate in this complex, which communicates with the fascia adherens, gap junctions and sodium channels. The integrated intercalated disc explains why a structural variant can produce conduction abnormalities before macroscopic myocardial loss occurs.

PKP2 is the most common gene in autosomal dominant ARVC and tends to produce a predominantly right-sided phenotype, although variability is wide. DSP is more frequently associated with left ventricular involvement, subepicardial scar and inflammatory episodes; DSG2 and DSC2 may cause right-sided or biventricular disease. Genotype-phenotype correlations are probabilistic and do not replace complete imaging of both ventricles.

JUP is implicated in Naxos disease, whereas biallelic DSP can cause Carvajal syndrome, both with cutaneous findings reflecting the role of desmosomes in tissues exposed to mechanical stress. Palmoplantar keratoderma and woolly hair are therefore diagnostic clues, not separate dermatologic details. Cardiocutaneous forms show how extracardiac examination can define the inheritance pattern and urgency of screening.

ClinGen reassessment assigns definitive evidence for ARVC to TMEM43, whereas PLN and DES reach moderate evidence; other causes of arrhythmic cardiomyopathy, such as FLNC or LMNA, may overlap nosologically without belonging to classic ARVC. The same validation process has refuted or downgraded historical associations, including RYR2 as an ARVC gene. A genetically valid panel reduces uncertain variants and false etiologic assignments.

Pathogenic variants reduce the amount or function of desmosomal proteins through haploinsufficiency, truncated proteins or specific functional alterations. The consequences include mechanical fragility, plakoglobin redistribution, altered Wnt and Hippo signaling, inflammation and abnormal electrical homeostasis. This multilevel pathogenesis is not a simple transformation of cardiomyocytes into adipocytes, but a network of cell loss and abnormal repair.

Fibrofatty replacement is more evident in classic right ventricular disease, often progressing from the epicardium toward the endocardium, whereas in the left ventricle subepicardial or mid-wall fibrosis may predominate with less apparent fat. Corridors of surviving myocardium within scar conduct slowly and sustain reentry. The three-dimensional substrate determines tachycardia morphology and the need for epicardial mapping.

Inflammation and myocardial injury interact particularly clearly in DSP cardiomyopathy. Chest pain, elevated troponin, edema and new areas of LGE may be interpreted as isolated myocarditis if family history and scar distribution are not considered. A myocarditis-like presentation does not prove persistent viral infection and may represent a phase of a genetic disease.

Endurance exercise increases right ventricular preload, wall stress and catecholaminergic stimulation. In desmosomal variant carriers, more intense and prolonged exposure has been associated with earlier onset, greater penetrance, arrhythmias and heart failure; reducing exposure after diagnosis appears beneficial but does not eliminate the substrate. The exercise modifier is one of the strongest demonstrated gene-environment interactions in cardiomyopathies.

Biological sex, hormones, multiple variants and still-unknown factors contribute to expressivity. Men have shown a more severe phenotype in some cohorts, but differences in activity and ascertainment may confound the association; DSP also has features that do not necessarily follow the PKP2-related ARVC pattern. Individual modifiers make it inappropriate to infer risk from sex or gene without clinical data.

Phenotypes and natural history

The earliest phase may be genetic only, with normal ECG, imaging and rhythm monitoring. In some individuals, an electrical phase follows in which premature ventricular contractions, nonsustained tachycardia or repolarization changes appear before major morphologic criteria. Prestructural disease cannot be diagnosed from the variant alone, but its possibility justifies surveillance and calibrated preventive recommendations.

In the right-sided phenotype, regional abnormalities often involve the outflow tract, inferior wall and apex, historically described as the triangle of dysplasia. However, disease does not respect fixed boundaries, and the concept of localized aneurysm requires caution in the era of high-resolution imaging. Right ventricular progression includes regional dysfunction, increasing chamber volumes and eventually global failure.

The left-sided phenotype shows inferolateral or circumferential subepicardial scar, ventricular arrhythmias originating from the left ventricle and sometimes mild functional depression without marked dilation. Fibrosis may appear disproportionate to geometry, distinguishing it from many advanced DCMs. This scar-predominant phenotype makes CMR essential and explains arrhythmic events despite an apparently reassuring ejection fraction.

Biventricular involvement may be simultaneous or emerge over time, with variable predominance. It should not be defined merely by a minimal abnormality in the other chamber because nonspecific findings are common; a convincing combination of criteria is required. The biventricular phenotype carries a greater heart failure burden and may alter risk, therapy and candidacy for mechanical support.

The phases do not necessarily proceed in a linear sequence. Cardiac arrest may occur before dilation, an inflammatory episode may leave new scar, or function may remain stable for years despite treated arrhythmias. The individual trajectory is reconstructed from serial data because the stage observed at the first visit does not summarize disease duration or rate of progression.

Right-sided heart failure causes jugular venous distention, edema, ascites, hepatic congestion and reduced output because of inadequate left ventricular filling. Left ventricular involvement adds pulmonary congestion and functional mitral regurgitation, while arrhythmias and pacing can worsen both chambers. Biventricular physiology is necessary to titrate diuretics and interpret symptoms that do not track left ventricular ejection fraction alone.

Progression may lead to transplantation for advanced heart failure, incessant arrhythmias or both. Other patients maintain a long life with minimal symptoms after exercise reduction and risk control. This prognostic variability requires communication that distinguishes real danger from inevitability, avoiding both absolute reassurance and a catastrophic portrayal of the diagnosis.

Clinical presentation and electrocardiography

Palpitations may correspond to premature ventricular contractions, nonsustained tachycardia, sustained tachycardia or atrial arrhythmia, but symptom perception does not quantify risk. A relatively slow ventricular tachycardia may be tolerated and persist for hours, whereas fibrillation or rapid tachycardia causes syncope or cardiac arrest. Rhythm documentation during symptoms is more informative than their subjective intensity.

Syncope requires reconstruction of posture, exertion, prodromes, duration and recovery. Sudden syncope without prodromes, especially during activity or in the presence of cardiomyopathy, raises concern for an arrhythmic cause; vasovagal forms nevertheless remain common in young people. Cardiac syncope is a prognostic factor only after rigorous clinical classification, not simply because the word appears in the history.

Chest pain with elevated troponin, ST-T changes and myocardial edema can mimic acute myocarditis or an acute coronary syndrome. In DSP-related forms, recurrent episodes increase suspicion of a genetic inflammatory phase, particularly with ring-like scar or a positive family history. Episodic myocardial injury still requires exclusion of treatable acute causes and is not retrospectively attributed to the gene without evaluation.

Dyspnea, fatigue, edema and early satiety indicate advanced dysfunction but may also result from arrhythmias, deconditioning or treatment. Examination assesses blood pressure, perfusion, jugular veins, liver, ascites, third heart sound and valvular signs. The hemodynamic profile distinguishes congestion from low output and guides therapy that may be harmful if based on weight alone.

In ARVC, T-wave inversion in V1-V3 or beyond, after puberty and in the absence of complete right bundle branch block, constitutes a repolarization criterion whose weight depends on its extent. Inferior abnormalities may accompany more diffuse disease. The topography of T waves is interpreted in relation to age, sex, ethnicity, athletic training and correct electrode placement.

Terminal activation delay and the epsilon wave reflect slowed conduction in the right ventricle, but the epsilon wave has limited sensitivity and suboptimal interobserver agreement. Filters, amplification and electrode misplacement can create or obscure it. The depolarization criterion should not become decisive when the remainder of the clinical picture is inconsistent.

With left ventricular involvement, low limb-lead voltages, inferolateral T-wave inversion and QRS fragmentation may occur, but none is pathognomonic. A mismatch between reduced voltages and preserved wall thickness can suggest diffuse myocardial loss. The left-sided ECG phenotype gains weight together with LGE, left ventricular arrhythmias and a causal genotype.

Premature ventricular contractions originating from the right ventricle typically show left bundle branch block morphology; a superior axis suggests an inferior origin and has greater specificity than the common outflow-tract pattern with an inferior axis. Arrhythmias with multiple morphologies indicate a more extensive substrate. Electrocardiographic localization distinguishes clues to scar from idiopathic ectopy without replacing imaging and diagnostic criteria.

A 24- or 48-hour Holter quantifies the burden of premature ventricular contractions and nonsustained tachycardia, but day-to-day variability limits rigid thresholds. Repeated or prolonged monitoring is appropriate when the question concerns rare symptoms or a change in risk. Serial arrhythmic burden is dynamic prognostic information and should be interpreted alongside activity, medications and recording quality.

Exercise testing may reveal latent ectopy, blood pressure response and functional capacity, but it is not used to provoke dangerous arrhythmias or to authorize intense sports. In asymptomatic carriers it may reveal an electrical substrate not apparent at rest. The functional test answers a specific clinical question and is performed in an environment appropriate to the risk profile.

Imaging, histology and diagnostic criteria

Echocardiography assesses right ventricular size and regional wall motion, the outflow tract, fractional area change, TAPSE, S′ wave and strain, as well as left ventricular structure and function. Linear measurements may be misleading in the complex geometry of the right ventricle and depend on the imaging plane. Multiview assessment distinguishes true akinesia or dyskinesia from a slicing artifact.

Athlete remodeling produces right ventricular dilation proportional to left ventricular enlargement, borderline global function and a larger outflow tract, but generally without regional aneurysms or pathologic scar. Atrial septal defect, anomalous pulmonary venous return and tricuspid regurgitation cause volume overload. Proportionality of remodeling is essential to avoid confusing adaptation or hemodynamic loading with ARVC.

Cardiac magnetic resonance quantifies biventricular volumes and ejection fractions without geometric assumptions and displays regional abnormalities on cine imaging. The right ventricle requires thin-slice acquisitions, dedicated planes and experience because moderator bands, insertion points and diaphragmatic motion can mimic trabeculation or dyskinesia. Technical quality precedes any application of diagnostic thresholds.

Late gadolinium enhancement detects focal extracellular expansion and makes left ventricular scar visible, often with an inferolateral or circumferential subepicardial distribution. In the right ventricle, the thin wall limits resolution and adjacent fat may confound interpretation, although modern sequences improve assessment. The distribution of LGE contributes to diagnosis and prognosis without identifying etiology by itself.

T1 and T2 mapping and extracellular volume may detect diffuse abnormalities or edema, especially during inflammatory phases, but depend on the scanner, sequence and local reference values. They do not replace validated criteria or make a scar specific. Quantitative mapping is complementary information to be interpreted against clinical phase, troponin and previous imaging.

The revised 2010 Task Force Criteria organize major and minor findings into six domains: right ventricular morphofunctional abnormalities, histologic characterization, repolarization, depolarization or conduction, arrhythmias, and family history or genetics. Diagnosis is definite with two major criteria, one major plus two minor criteria, or four minor criteria belonging to different categories. It is borderline with one major plus one minor criterion or three minor criteria from different categories, and possible with one major criterion or two minor criteria from different categories. This cross-domain scoring does not allow redundant findings from the same category to be added as if they were independent evidence.

In the morphofunctional domain, echocardiography requires regional right ventricular akinesia, dyskinesia or aneurysm together with a quantitative threshold. Major criteria include a parasternal long-axis right ventricular outflow tract end-diastolic diameter of at least 32 mm, or at least 19 mm/m² when indexed, a short-axis diameter of at least 36 mm, or at least 21 mm/m², or a fractional area change no greater than 33%. Minor criteria, always together with a regional abnormality, include long-axis values from 29 to less than 32 mm or 16 to less than 19 mm/m², short-axis values from 32 to less than 36 mm or 18 to less than 21 mm/m², and a fractional area change greater than 33% but no greater than 40%. Echocardiographic quantification must be performed in the prescribed plane and cannot be replaced by a qualitative description.

On CMR, the major morphofunctional criterion combines regional akinesia, dyskinesia or dyssynchronous contraction with an indexed right ventricular end-diastolic volume of at least 110 mL/m² in men or 100 mL/m² in women, or a right ventricular ejection fraction no greater than 40%. Minor criteria are volumes from 100 to less than 110 mL/m² in men and from 90 to less than 100 mL/m² in women, or an ejection fraction greater than 40% but no greater than 45%, always with a regional abnormality. Angiography assigns major weight to regional akinesia, dyskinesia or aneurysm. The 2010 criteria do not include LGE among diagnostic criteria: CMR quantifies right ventricular shape and function in this framework, but gadolinium-detected scar does not enter the score.

Tissue characterization in the 2010 criteria is histologic. A major criterion requires, in at least one sample from the right ventricular free wall, residual myocytes below 60% by morphometric analysis, or below 50% by visual estimation, with fibrous replacement and with or without adipose tissue; the minor criterion includes residual myocytes from 60% to 75%, or from 50% to 65% when estimated, with fibrosis. These thresholds do not eliminate the problem of focal sampling and do not justify routine free-wall biopsy. Histologic evidence has high specificity when the specimen is adequate, but a negative biopsy does not exclude disease.

After age 14 years and in the absence of complete right bundle branch block, T-wave inversion from V1 through V3 or beyond is a major repolarization criterion; inversion limited to V1-V2 or present in V4-V6 is minor. In the presence of complete right bundle branch block, negative T waves from V1 through V4 have minor weight. An epsilon wave between the end of the QRS and onset of the T wave in V1-V3 is a major depolarization criterion, whereas late potentials on signal-averaged ECG or a terminal activation duration of at least 55 ms in V1-V3, in the absence of complete right bundle branch block, are minor criteria. The electrocardiographic context includes age, QRS duration and technical quality because none of these signs is immune to interpretive variability.

Sustained or nonsustained ventricular tachycardia with left bundle branch block morphology and a superior axis is a major criterion because it suggests an inferior or apical right ventricular origin; the same morphology with an inferior axis, typical of the outflow tract, or with an unknown axis is minor. More than 500 premature ventricular contractions in 24 hours also constitute a minor criterion, but they are common in benign conditions and must be characterized by morphology and complexity. The family-history domain assigns weight to confirmed disease in relatives and to a pathogenic variant associated with ARVC; a VUS does not satisfy the genetic criterion. Arrhythmic and familial specificity derives from the combination, not from the isolated count of premature beats.

The 2020 Padua criteria retain six major and minor categories but build separate sets for the right and left ventricles and incorporate LGE into structural characterization. To diagnose ACM, at least one morphofunctional or structural criterion, major or minor, from the involved chamber is required; the overall combination retains definite, borderline and possible levels. Right-sided structural or morphofunctional criteria alone point toward ARVC, demonstrated involvement of both chambers toward a biventricular form, whereas a left-sided structural lesion in the absence of right-sided criteria opens the pathway to ALVC. The Padua sequence first establishes the presence of disease and then its phenotypic distribution.

For the right ventricle, Padua assigns minor weight to isolated regional akinesia, dyskinesia or aneurysm and major weight when the regional abnormality is accompanied by global dilation or dysfunction, interpreted using nomograms for age, sex, body surface area and, when relevant, athletic status. Stria-pattern transmural LGE in at least one right ventricular region, confirmed in two planes, becomes a major structural criterion; for the left ventricle, nonischemic subepicardial or mid-wall LGE in at least one segment is major, again confirmed orthogonally and excluding junctional enhancement. This Padua tissue characterization thereby fills the main CMR gap in the 2010 criteria without turning every area of enhancement into ACM.

Among left-sided electrical markers, Padua introduces as minor criteria T-wave inversion from V4 through V6 in the absence of complete left bundle branch block, low limb-lead voltages below 0.5 mV, and frequent premature ventricular contractions or tachycardias with right bundle branch block morphology, excluding fascicular patterns. On the right side, the epsilon wave is downgraded from major to minor because of limited reproducibility, while late potentials on signal-averaged ECG are not retained. This revision of electrical signs favors findings consistent with the chamber of origin and reduces the weight of historical indicators with limited specificity.

For isolated ALVC, Padua specifically requires the combination of a major left ventricular structural criterion, namely nonischemic LGE with a subepicardial or mid-wall distribution, and a pathogenic or likely pathogenic variant in a gene causally associated with ACM, in the absence of right ventricular morphofunctional or structural criteria. This genetic gate was intended to protect against the limited specificity of left ventricular scar, but it belongs to the 2020 system and should not be transformed into a universal rule. The Padua genetic requirement is satisfied neither by a negative panel nor by a variant of uncertain significance.

The European Task Force criteria are referred to in the literature as ETF 2023 because they were published online on October 14, 2023, although they appeared in volume 395 in January 2024. They refine Padua, retain the six domains and certainty combinations, and require at least one morphofunctional or structural criterion from the chamber defining the phenotype. For ALVC, in the absence of right ventricular morphofunctional or structural criteria, diagnosis may therefore be definite, borderline or possible through an appropriate clinical combination that includes nonischemic left ventricular LGE. The combinations remain two major criteria, or one major plus two minor criteria, or four minor criteria for definite disease; one major plus one minor criterion or three minor criteria for borderline disease; and one major criterion or two minor criteria for possible disease, using different categories. An isolated major LGE criterion therefore defines possible ALVC, not automatically definite disease. The 2023-2024 ETF consensus is a proposed framework and not a gold standard already validated in every population.

For the left ventricle, the ETF consensus assigns major value to stria-pattern subepicardial or mid-wall LGE involving at least three segments of the bull’s-eye model and confirmed in two orthogonal planes; the segments may be contiguous and form the typical ring pattern or may be discontinuous. Involvement of one or two segments has minor weight, whereas patchy, focal or septal-junction LGE does not satisfy the criterion. In the right ventricle, unequivocal LGE in at least one region, confirmed in two planes and excluding the tricuspid valve area, is downgraded from major to minor; histologic fibrosis retains major weight. Isolated regional left ventricular hypokinesia or akinesia is removed because it is too nonspecific. The ring-like pattern remains a diagnostic hallmark, not a pathognomonic finding capable by itself of excluding myocarditis, sarcoidosis, muscular dystrophy or another cardiomyopathy.

Electrically, ETF retains as minor criteria negative T waves from V4 through V6 in the absence of left bundle branch block and upgrades voltages below 0.5 mV in all limb leads to a major criterion after excluding obesity, emphysema, pericardial effusion, amyloidosis and technical causes. Frequent premature ventricular contractions, spontaneous or exercise-induced, and tachycardias with right bundle branch block morphology remain minor left-sided criteria, excluding fascicular patterns; multiple morphologies and cardiac arrest due to fibrillation or tachycardia of undocumented origin are also considered. In the genetic domain, a variant classified as pathogenic counts as major, a likely pathogenic variant as minor, and a VUS contributes no criterion. ETF specificity depends on more restrictive definitions and convergence across domains.

The most important difference from Padua concerns the relationship between phenotype and etiology. In the ETF framework, ALVC can be recognized using clinical criteria regardless of whether the cause proves genetic, familial without an identified causal variant, idiopathic or acquired; genetics and family history can still contribute to the level of certainty within the sixth domain and are then interpreted when attributing cause. A negative test does not erase a clinically coherent phenotype, and a VUS does not certify its hereditary origin. This phenotype-cause separation avoids both missing gene-negative forms and mistaking a phenocopy for a monogenic cardiomyopathy.

The 2023 ESC guidelines also use the category NDLVC for a nondilated left ventricle with nonischemic scar or fatty replacement, or with isolated global hypokinesia without scar. NDLVC and ALVC can overlap but are not synonymous: the former is an etiologically neutral morphofunctional description, whereas the latter requires the arrhythmogenic profile defined by the relevant criteria. Diagnosis of a left-sided form therefore remains vulnerable to overinterpretation and requires multiparametric coherence among LGE, ECG, arrhythmias, history, genetics and the differential diagnosis.

Endomyocardial biopsy may show myocyte loss, fibrosis and fatty replacement, but a negative septal specimen does not exclude a disease that begins subepicardially in the free wall. Electroanatomic mapping or imaging may guide sampling toward abnormal areas while maintaining attention to procedural risk. Biopsy yield is greater when sarcoidosis, a specific myocarditis or another treatable diagnosis is also being sought.

Autopsy after sudden death requires systematic examination of both ventricles, histology, and coronary, toxicologic and molecular evaluation. Isolated fat in the right ventricle can be physiologic and does not establish ACM without myocyte loss and fibrosis. Expert cardiovascular pathology prevents an incorrect postmortem diagnosis from improperly directing evaluation of the entire family.

The main alternatives include myocarditis, sarcoidosis, DCM, laminopathy, congenital heart disease, pulmonary hypertension, athlete’s heart and idiopathic tachycardias. PET may be useful when sarcoidosis is suspected, CT for vascular anomalies and coronary angiography when ischemic injury is plausible. The differential diagnostic pathway selects tests according to probability, avoiding indiscriminate screening that cannot resolve borderline findings.

Genetic testing and family evaluation

Genetic testing is offered to the proband with a convincing phenotype to clarify etiology, refine the profile and enable cascade screening. Yield is higher in typical ARVC and in families with aggregation, but a negative result does not exclude disease because genes, genomic regions or mechanisms may not be detected. Testing the proband should precede indiscriminate testing of relatives when no familial variant is known.

Pretest counseling discusses possible results, technical limitations, family implications and the possibility of unexpected findings. A panel focused on genes with strong disease associations offers a better signal-to-noise ratio than a very broad list; broader analyses are appropriate when the phenotype suggests syndromes or overlapping conditions. The genetic strategy arises from the clinical picture, not from commercial availability of the largest panel.

A pathogenic or likely pathogenic variant contributes to diagnosis only if the gene and mechanism are coherent with the phenotype. Classification follows international criteria and integrates population frequency, prediction, functional data, published cases and segregation; it may change as new evidence emerges. Periodic reclassification is particularly important in cardiomyopathies, in which historical assignments have subsequently been downgraded.

A variant of uncertain significance does not confirm causation, does not justify an ICD and should not be sought as a predictive test in healthy relatives. Family segregation may generate useful evidence, but a VUS present in an affected relative does not automatically become pathogenic. Interpretive discipline prevents cascades of diagnoses, anxiety and restrictions based on an inconclusive finding.

First-degree relatives of the proband undergo history, examination, ECG, rhythm monitoring and imaging even when the case appears isolated. If a causal variant exists, cascade testing distinguishes carriers from noncarriers; the latter can generally be discharged from disease-specific surveillance unless they have their own phenotype or another familial cause. Cascade screening concentrates resources and reduces uncertainty compared with perpetual follow-up of the entire family.

In phenotype-negative carriers, follow-up intervals depend on age, gene, activity and severity within the family. Adolescence and early adulthood are periods of particular attention, but some variants manifest later; symptoms or an increase in exercise exposure prompt earlier reassessment. Preventive surveillance does not turn the person into a symptomatic patient and should preserve proportionality in daily life.

When the proband is gene-elusive, relatives cannot be reassured by an uninformative negative test and continue clinical screening. An apparently negative pedigree may result from small families, young relatives, incomplete penetrance or incorrect diagnoses. Residual familial risk is explained explicitly and distinguished from true negativity for an already demonstrated causal familial variant.

Reproductive counseling addresses transmission probability, uncertain penetrance, prenatal diagnosis and preimplantation testing without prescribing a choice. In dominant forms, the probability of inheriting the variant is often 50%, but the probability of developing a specific outcome is much less predictable. Reproductive autonomy requires information about the specific gene rather than a simplistic translation of the Mendelian percentage into prognosis.

Arrhythmic risk stratification

Secondary prevention is the clearest setting: resuscitated cardiac arrest, ventricular fibrillation or hemodynamically intolerated sustained tachycardia identify a risk of recurrence that generally justifies an ICD when there is no completely reversible cause. Even tolerated sustained tachycardias have a high probability of recurrence. A previous major event retains greater weight than individual primary-prevention markers.

In the absence of sustained arrhythmias, risk derives from cardiac syncope, nonsustained tachycardia, number and complexity of premature ventricular contractions, extent of T-wave inversion, ventricular function, scar and genotype. Age and sex modify some associations without acting uniformly. This multidimensional assessment avoids isolated thresholds that miss interactions between electrical and structural disease.

The corrected ARVC model republished in 2022 estimates the probability of a first sustained arrhythmia in patients with ARVC defined by the 2010 criteria and no previous sustained events. It uses age, sex, recent syncope, nonsustained tachycardia, premature ventricular contraction burden, T-wave inversions and right ventricular ejection fraction. The validated calculator does not include left ventricular ejection fraction in the final model and does not replace shared decision-making.

The version originally published in 2019 was withdrawn and republished because of an error in the equation, so only the corrected 2022 version should be used and cited. Even this estimate can change as predictors evolve and should be recalculated during follow-up. Correct use of the model includes the version, population and time of application, not merely entering the numbers.

The calculator endpoint includes sustained tachycardia and appropriate ICD therapy, clinically important events that are not equivalent to sudden death. A threshold chosen to prevent a relatively slow tachycardia may lead to more implants than a threshold focused only on rapid arrhythmias. The nature of the outcome should be discussed with the patient before a probability is translated into a procedure.

Transferability to left-sided phenotypes, DSP cardiomyopathy and individuals who do not meet the 2010 criteria is limited. In DSP disease, left ventricular scar and injury episodes may confer risk with relatively preserved function and variables different from those used in the ARVC model. External validity requires not applying a familiar calculator outside the population in which it was studied.

CMR adds information on left ventricular involvement, LGE extent and the biventricular phenotype. Observational studies associate specific presentations with different outcomes, but quantitative thresholds are not uniformly validated for every genotype. Scar-related risk complements ventricular function and appears particularly relevant when ejection fraction is not severely reduced.

Programmed electrophysiologic testing may induce tachycardia and contribute in selected settings, but its prognostic value is not sufficiently uniform to serve as a universal arbiter. Results depend on protocol, medications and disease stage, and a negative study does not prove absence of risk. Programmed stimulation is used when it adds information to a concrete decision or accompanies an ablation strategy.

Risk is not static. New syncope, an increase in premature ventricular contractions, progression of dysfunction, new scar or reduced activity exposure change the estimate and may alter the indication for a device. Serial restratification is more faithful to a progressive disease than a decision made only once at diagnosis.

Exercise, defibrillator and treatment of arrhythmias

Patients with manifest ACM are generally advised against competitive sports and high-intensity endurance exercise, especially in desmosomal forms. The recommendation addresses both acute risk during exertion and acceleration of progression over time; evidence for a dose-response effect derives mainly from observational cohorts of ARVC and desmosomal variant carriers and is not equally strong for every left-sided genotype. Reducing exposure is considered an intervention capable of modifying risk, without removing scar that has already formed.

Exercise prescription distinguishes intensity, duration, frequency and type of activity. Low- to moderate-intensity recreational exercise may be compatible in selected individuals after evaluation, whereas activities involving adrenergic surges, contact or inability to obtain prompt assistance require greater caution. Shared exercise prescription avoids both hazardous competitive activity and sedentary behavior that worsens metabolic health and well-being.

In genotype-positive, phenotype-negative carriers, recommendations are more individualized, but competitive endurance exercise remains unfavorable for ARVC-associated forms. Risk varies by gene and has not been demonstrated with the same strength for every left-sided variant. Prevention in carriers considers family data, preferences and uncertainty, explaining that a normal examination does not make prolonged intense exposure neutral.

The ICD is the implantable strategy capable of automatically recognizing and terminating a potentially lethal tachyarrhythmia and is a cornerstone after cardiac arrest or a major arrhythmia when no reversible cause exists. In primary prevention, the expected benefit is weighed against infection, hematoma, perforation, malfunction, inappropriate shocks, replacements and psychological impact. Device selection is particularly complex in a young adult who may live with the system for many decades.

A transvenous system provides antitachycardia pacing, which can terminate monomorphic tachycardia without a shock, and bradycardia pacing if needed. A subcutaneous ICD avoids intravascular leads but does not provide ATP or chronic pacing; an extravascular system may broaden options in appropriate centers. ICD configuration depends on the type of arrhythmia, age, anatomy and pacing requirements.

Programming uses detection zones and durations that treat clinical tachycardias while reducing unnecessary interventions. Arrhythmias in ARVC may be slower than ischemic tachycardias, so thresholds that are too high can leave prolonged symptoms, whereas low thresholds increase therapy for non-dangerous tachycardias. Individualized programming is updated after every documented event.

Beta-blockers blunt adrenergic activation and may reduce symptoms or arrhythmic burden in selected patients, although disease-specific randomized evidence is limited. Sotalol and amiodarone may reduce recurrences or shocks, but QT prolongation, bradycardia and organ toxicity limit their use. Antiarrhythmic pharmacotherapy complements ICD therapy and ablation and is not a guarantee against sudden death.

Stable sustained tachycardia is treated acutely according to hemodynamic status, with immediate cardioversion when there is compromise. Correction of electrolyte abnormalities, ischemia, fever and proarrhythmic drugs reduces triggers, while 12-lead tracings should be preserved to localize the circuit. Event management combines immediate safety with collection of data useful for the definitive strategy.

Ablation is indicated or considered for recurrent tachycardias despite medications, electrical storm or repeated ICD shocks. In ARVC, the substrate is often more extensive epicardially, making an endocardial-only approach insufficient; pericardial access, however, carries its own risks. The endo-epicardial strategy is planned in centers experienced in the disease and its procedural complications.

Mapping during sinus rhythm identifies low voltage, late potentials and channels, whereas tachycardia mapping is possible when the rhythm is tolerated. Substrate ablation can markedly reduce arrhythmic burden, but new abnormal areas emerge as the disease progresses. Procedural success means prolonged clinical control, not elimination of the cardiomyopathy or removal of the indication for an ICD.

Electrical storm requires sedation, correction of triggers, beta-blockade, antiarrhythmic drugs and urgent assessment for ablation; mechanical support may be necessary if arrhythmia and shock compromise perfusion. Repeated shocks should not be accepted as an inevitable feature of device function. An urgent electrophysiology network reduces trauma and hemodynamic injury when therapy is coordinated promptly.

Heart failure, special situations and follow-up

Therapy for left-sided heart failure follows guidelines for reduced ejection fraction, including renin-angiotensin system inhibition or ARNI, a beta-blocker, a mineralocorticoid receptor antagonist and an SGLT2 inhibitor when appropriate and tolerated. Diuretics control congestion without directly modifying the substrate. Prognosis-modifying therapy is started early when dysfunction appears, without waiting for terminal dilation.

In predominantly right-sided heart failure, excessive diuresis may reduce left ventricular filling and cardiac output, whereas persistent congestion damages the kidneys and liver. Venous pressure, perfusion, weight and renal function are reassessed together. Preload balance requires small, frequent adjustments rather than a fixed dose derived from left-ventricle-only protocols.

Tricuspid regurgitation may result from dilation and intracardiac leads, worsening congestion; any valve intervention must consider right ventricular function and myocardial progression. Cardiac resynchronization has a role when standard criteria for dyssynchrony and left ventricular dysfunction are present, not for the diagnosis of ACM alone. Structural therapy addresses selected consequences without correcting the original cellular defect.

Anticoagulant therapy is not routine for every patient with ACM. It is indicated according to atrial fibrillation, documented thrombus, previous embolism or analogous risk conditions, recognizing that aneurysms and severe dysfunction may promote stasis. Thromboembolic prevention follows actual risk rather than a generic concern associated with a dilated chamber.

Transplantation is considered for refractory biventricular failure or uncontrollable arrhythmias before irreversible end-organ damage develops. Isolated left ventricular assist support may be unsuitable when the right ventricle is severely compromised, and previous epicardial access can complicate surgery. Advanced-therapy selection integrates hemodynamics, arrhythmias, end-organ status and procedural history.

Pregnancy is often tolerated in stable women, but increases in blood volume, heart rate and adrenergic load may promote arrhythmias or heart failure. Preconception counseling evaluates function, events, medications, ICD status and genetic risk; some heart failure therapies are contraindicated and must be changed in advance. Cardio-obstetric management continues postpartum, when hemodynamic changes and reduced sleep may destabilize rhythm.

In children, clinical expression before puberty is unusual but possible in recessive or severe forms. Adult-derived criteria have limitations because of juvenile T-wave patterns and body size, making pediatric expertise essential. Transition to adult care ensures continuity precisely during the period when sports participation and penetrance increase.

Driving regulations depend on the country, syncope, arrhythmias, ICD status and recent interventions. Occupations involving risk to third parties, work at height or isolation require a separate occupational assessment. Occupational safety is discussed using transparent criteria, avoiding indefinite restrictions that are not updated after stabilization.

Anxiety about shocks, hypervigilance, fear of exercise and implications for children are part of the disease experience. Psychological support and adapted rehabilitation improve quality of life and adherence, especially after cardiac arrest or electrical storm. Psychological health is not a secondary outcome because it affects behavior, perceived symptoms and the ability to live with uncertainty.

Follow-up includes clinical review, ECG, ICD interrogation, rhythm monitoring, echocardiography and CMR when it can change management. The frequency and combination of tests vary with stability, gene and previous risk; a standard annual visit is neither sufficient for everyone nor necessary in the same way for every person. Proportionate surveillance intensifies after new symptoms, arrhythmias or changes in activity.

Each visit updates a timeline of arrhythmic burden, ventricular function, scar, exercise, medications and device interventions. Small isolated changes may reflect measurement variability, whereas concordant trends indicate true progression. Longitudinal interpretation prevents overreaction to noise and failure to recognize slow deterioration distributed over several years.

Prognosis has improved with earlier recognition, reduction of harmful exercise, selective ICD use and ablation, but morbidity from recurrences and devices remains important. Heart failure and transplantation are less common than arrhythmias in ARVC cohorts, whereas some left-sided genotypes follow a different trajectory. The prognostic profile must be specific to phenotype and gene rather than derived from an average across the entire spectrum.

Optimal management requires a center capable of integrating biventricular imaging, electrophysiology, genetics, heart failure care and exercise counseling. The patient and family should understand which elements are certain, which are probable and which remain evolving. This precision medicine does not consist of a single sophisticated test, but of linking cause, scar, rhythm and trajectory to decisions that can be reassessed over time.