ACM Diagnostic Criteria
Definition
The diagnostic criteria for arrhythmogenic cardiomyopathy are a multi-parametric scoring system built because no single test is sensitive and specific enough: structural and morpho-functional ventricular abnormalities, tissue characterisation, ECG repolarisation and depolarisation, ventricular arrhythmias, and family history/genetics are each graded major or minor, and a diagnosis is reached by combining categories. Four generations exist — the 1994 Task Force criteria for ARVC, the 2010 revised International Task Force criteria, the 2020 International ("Padua") criteria for the whole ACM spectrum, and the 2023 European Task Force criteria — with the last two incorporating cardiac magnetic resonance tissue characterisation and left-ventricular phenotypes. (sources/acm-padua-criteria-ijc-2020, rating: high; sources/acm-european-tf-criteria-rcm-2024, rating: high)
Key Concepts
The Four Generations
| Version | Scope | Key advance | Principal limitation |
|---|---|---|---|
| 1994 Task Force | RV-dominant ARVC | Six categories; major/minor grading; multi-parametric diagnosis | Qualitative imaging; no LV criteria; insensitive to early/familial disease |
| 2010 Revised ITF | RV-dominant ARVC | Quantitative sex/BSA-indexed imaging; borderline and possible tiers; EMB morphometry; genetics in family-history category | Still RV-only; CMR tissue characterisation excluded |
| 2020 Padua | ARVC, biventricular, ALVC | CMR LGE as a structural criterion in both ventricles; LV ECG and arrhythmia criteria | ALVC required a pathogenic variant; CMR-dependent; unvalidated |
| 2023 European TF | ARVC, biventricular, ALVC | Three-step process; split RV/LV blocks; low voltages major; genetic requirement for ALVC removed; "scarring/arrhythmogenic" framing | Still unvalidated; conflicts with ESC 2023 nomenclature |
(sources/acm-padua-criteria-ijc-2020; sources/acm-evolving-criteria-jaha-2021, rating: high; sources/acm-european-tf-criteria-rcm-2024)
The Six Categories
| Category | RV involvement | LV involvement |
|---|---|---|
| 1. Morpho-functional | Major: regional akinesia/dyskinesia/aneurysm + global RV dilatation or dysfunction. Minor: regional wall-motion abnormality alone | Minor: global LV systolic dysfunction ± dilatation. (2020 also allowed regional LV hypokinesia/akinesia; removed in 2023) |
| 2. Structural | 2023: major = fibrous replacement on EMB; minor = RV LGE. (2020: transmural RV LGE was major) | 2023: major = "ring-like" LGE ≥3 segments; minor = LGE 1–2 segments; septal junctional LGE excluded |
| 3. Repolarisation | Major: negative T V1–V3 or beyond, ≥14 years, no complete RBBB, not preceded by J-point/ST elevation. Minor: V1–V2; beyond V3 with complete RBBB; beyond V3 at <14 years | Minor: negative T V4–V6 without complete LBBB |
| 4. Depolarisation/conduction | Minor: epsilon wave; terminal activation duration ≥55 ms | Major (2023): low QRS voltages <0.5 mV in all limb leads, after excluding other causes. (Minor in 2020) |
| 5. Arrhythmias | Major: >500 PVCs/24 h or NSVT/SVT, LBBB morphology, non-inferior axis. Minor: LBBB inferior axis (RVOT pattern); cardiac arrest from VF/VT of unknown morphology | Minor: frequent or exercise-induced RBBB PVCs (excluding fascicular); RBBB NSVT/SVT; cardiac arrest of unknown morphology |
| 6. Family history/genetics | Major: pathogenic variant in the patient; affected first-degree relative meeting criteria; pathological confirmation in a first-degree relative. Minor: likely pathogenic variant; unconfirmed affected first-degree relative; premature SCD <35; affected second-degree relative | Same — applied to both ventricular blocks |
(sources/acm-european-tf-criteria-rcm-2024; sources/acm-padua-criteria-ijc-2020)
Diagnostic Thresholds
- Definite: 2 major, or 1 major + 2 minor, or 4 minor criteria from different categories.
- Borderline: 1 major + 1 minor, or 3 minor.
- Possible: 1 major, or 2 minor.
- A criterion from category 1 or 2 is mandatory at every level. Genetics, ECG abnormalities or arrhythmia alone cannot diagnose ACM, because ACM is a structural heart muscle disease — the same logic that requires hypertrophy for HCM. (sources/acm-padua-criteria-ijc-2020)
Phenotypic Variants and Their Rules
| Variant | Requirements | Specificity safeguard |
|---|---|---|
| ARVC (dominant-right) | RV criteria only, no LV involvement | Standard threshold count |
| Biventricular ACM | ≥1 morpho-functional and/or structural criterion in both RV and LV; total criteria across both ventricles | Concurrent RV criteria supply specificity to the non-specific LV findings |
| ALVC (dominant-left) | LV structural ± morpho-functional abnormality, no RV involvement. 2020: plus a pathogenic ACM variant. 2023: clinical criteria alone, regardless of genotype or aetiology | 2020 relied on genetics; 2023 relies on the specificity of the LGE pattern and accepts phenocopies |
(sources/acm-padua-criteria-ijc-2020; sources/acm-european-tf-criteria-rcm-2024)
Why CMR Became Central
- LGE is the most sensitive structural marker. All patients with LV involvement have LGE, but a sizeable proportion have no global LV dysfunction or overt wall-motion abnormality, because the scar is segmental and subepicardial/mid-myocardial. LV involvement therefore cannot be excluded by a normal echo or cine-CMR. (sources/acm-evolving-criteria-jaha-2021, rating: high)
- The pattern matters. Subepicardial or mid-myocardial stria in the inferolateral free wall, often with septal involvement and a circumferential "ring-like" distribution, is characteristic; patchy/focal LGE and septal junctional LGE at the RV insertion are non-diagnostic.
- RV LGE is specific but insensitive because of the thin RV wall, poor spectral resolution and contrast-to-noise ratio; the 2023 criteria therefore demoted it to minor while promoting EMB histology to major. (sources/acm-european-tf-criteria-rcm-2024)
- In ALVC, LVEF and LGE are linearly related; in DCM they are not — a mechanistic discriminator that supports LGE as a disease-specific finding rather than an epiphenomenon. (sources/acm-evolving-criteria-jaha-2021)
ECG and Arrhythmia Specificity
- T-wave inversion V1–V3 is major only if it is not preceded by J-point/ST elevation — otherwise it is benign early repolarisation, a common athlete pattern. (sources/acm-european-tf-criteria-rcm-2024)
- Epsilon waves were downgraded to minor because identification depends on filtering and sampling rate and interobserver agreement is poor; signal-averaged ECG was removed entirely.
- Low limb-lead QRS voltages reflect LV myocardial loss and were upgraded to major in 2023; sensitivity is <30%, so a normal voltage does not exclude LV involvement.
- RBBB-morphology VT is a weak localising sign. In a mapping series, two-thirds arose from the apical/inferior septum of a dilated RV with early transition by V3, and only 17% from the LV. This is why the LV arrhythmia criterion is minor. (sources/acm-evolving-criteria-jaha-2021)
- LBBB VT with non-inferior axis is major for RV disease; the RVOT pattern (inferior axis) is minor, because idiopathic RVOT VT is common and benign.
Clinical Impact of the 2020 Criteria
- In 112 Padua patients classified by the 2010 criteria, 51 of 87 definite ARVC became biventricular, 5 of 15 borderline became definite and 6 biventricular, and 7 of 9 possible cases became ALVC on the LV LGE criterion. (sources/acm-evolving-criteria-jaha-2021)
- The reclassification is the strongest argument that the 2010 criteria under-recognised left-sided disease — but it comes from the cohort that generated the criteria.
Contradictions / Open Questions
- The 2023 European TF criteria and ESC 2023 use incompatible frameworks. The European TF diagnoses ACM by tissue characterisation and admits ALVC regardless of aetiology; ESC 2023 diagnoses ACM using the 2010 criteria and classifies LV-dominant disease as DCM or NDLVC by end-diastolic volume. The same patient can be ALVC in one system and NDLVC in another. (sources/acm-european-tf-criteria-rcm-2024; sources/esc-cmp-2023, rating: very high)
- Removing the genetic requirement for ALVC trades specificity for sensitivity. Padua required a variant precisely because LV LGE overlaps with DCM, myocarditis and sarcoidosis; the 2023 criteria accept that overlap in exchange for diagnosing genotype-negative and post-myocarditis cases. No study has measured how many phenocopies are now labelled ALVC. (sources/acm-padua-criteria-ijc-2020; sources/acm-european-tf-criteria-rcm-2024)
- The LV morpho-functional tightening is unvalidated. The 2023 criteria removed the regional LV hypokinesia/akinesia minor criterion but promoted low voltages to major — one change reduces sensitivity, the other increases it, and neither is supported by prospective accuracy data. (sources/acm-european-tf-criteria-rcm-2024)
- RV LGE was major in 2020 and is minor in 2023. The same finding, in the same patients, changed diagnostic weight within three years on the basis of technical limitations rather than new outcome evidence. (sources/acm-padua-criteria-ijc-2020; sources/acm-european-tf-criteria-rcm-2024)
- "Likely pathogenic" was major in 2020 and minor in 2023. A variant class that contributes to a definite diagnosis in one version cannot in the next, which changes the diagnosis of genotype-positive relatives without any change in the variant. (sources/acm-padua-criteria-ijc-2020; sources/acm-european-tf-criteria-rcm-2024)
- All four criteria sets lack external prospective validation. The 1994 and 2010 criteria were consensus-derived; Padua was derived from one institution's 30-year practice and validated post hoc in its own cohort; the 2023 revision has no accuracy data at all. (sources/acm-evolving-criteria-jaha-2021; sources/acm-european-tf-criteria-rcm-2024)
- The "scarring/arrhythmogenic cardiomyopathy" rename is a proposal, not a classification. It has not been adopted by ESC, and it would make aetiology irrelevant to the diagnosis — a fundamental change from every prior version, which assumed a genetic cardiomyopathy. (sources/acm-european-tf-criteria-rcm-2024)
- The biventricular rule borrows specificity from the RV. LV findings are only interpretable when RV criteria are also met; in isolated LV disease the same findings are non-specific. This means the criteria are internally asymmetric and cannot be applied ventricle-by-ventricle. (sources/acm-padua-criteria-ijc-2020)
Connections
- Disease pages: entities/ARVC · entities/ALVC · entities/NDLVC · concepts/Arrhythmogenic-Cardiomyopathy
- Predecessor criteria: concepts/ARVC-Task-Force-Criteria — the 2010 criteria in detail
- Imaging: concepts/Late-Gadolinium-Enhancement
- Mechanism and genetics: concepts/Desmosome · concepts/Final-Common-Pathway · concepts/ClinGen-Gene-Disease-Validity · concepts/Genetic-Testing-in-Cardiomyopathy
- Family and outcomes: concepts/Cascade-Family-Screening · concepts/Sudden-Cardiac-Death · concepts/Exercise-Restriction-in-ARVC
- Classification conflict: concepts/Phenotypic-Approach-to-Cardiomyopathy