#arrhythmogenic-cardiomyopathy #hypertrophic-cardiomyopathy #genetics #cardiomyopathy-genetics

Cascade Family Screening (ACM)

Definition

Cascade family screening refers to the systematic cardiovascular and genetic evaluation of first-degree relatives of a proband with a confirmed ACM diagnosis. It is ideally conducted within a multidisciplinary cardiovascular genetics program and aims to identify disease early, enable lifestyle modification, and inform ICD decisions before a sentinel arrhythmic event.

Key Concepts

Rationale

ACM is predominantly inherited as an autosomal dominant trait → first-degree relatives have a 50% a priori risk of harboring the familial variant.
Penetrance is incomplete and age-related; disease expression is less severe in relatives than probands and occurs at an older age.
Arrhythmic events in family members appear to occur only in the presence of manifest ECG and structural changes — making early detection actionable. (sources/acm-hrs-2019)

Screening Recommendations

COR I, LOE C-EO: A genetic counselor or appropriately experienced clinician should obtain a comprehensive 3-generation family history from the proband.
COR I, LOE B-NR: First-degree relatives should undergo clinical evaluation every 1–3 years starting at age 10–12 years.
COR I, LOE B-NR: Cardiovascular evaluation includes: 12-lead ECG, ambulatory ECG monitoring, and cardiac imaging (echo, CMR, or CT depending on availability).
COR IIb, LOE C-LD: Exercise stress testing may be considered as an adjunct to expose latent phenotype by initiating ventricular ectopy. (sources/acm-hrs-2019)

Genetic Cascade Testing

Offered to first-degree relatives only when a class 4 (likely pathogenic) or class 5 (pathogenic) variant has been identified in the proband.
Cascade testing requires comprehensive pretest genetic counseling (process, implications, psychosocial impact, insurance issues).
Family members negative for a class 5 variant may be released from regular cardiological follow-up (COR IIb, LOE C-EO) but should be educated to return if symptoms develop.
Family members negative for a class 4 variant remain in follow-up at longer intervals (individualized by clinical team).
Class 3 (VUS) variants should not drive cascade testing unless reclassified. (sources/acm-hrs-2019)

Pediatric Considerations

Disease expression under age 10 is almost exclusively seen in probands; relatives rarely develop disease this early.
Cascade testing in minors is controversial; testing is typically deferred until clinical features become likely, guided by the child's best interest, and conducted by a multidisciplinary team including cardiologists, geneticists, genetic counselors, and psychologists.

Expected Diagnostic Yield

In PKP2 families: approximately one-third of relatives have a diagnosis of ARVC, one-third have borderline disease, and one-third are unaffected.
Overall, relatives have less severe disease, are more commonly asymptomatic, and have later onset than probands.
Among at-risk relatives, electrocardiographic changes typically occur earlier and more commonly than structural changes; however, LGE on CMR (most frequently in LV) can be the first evidence of disease in a small subset. (sources/acm-hrs-2019)

ESC 2023 Updates to Family Screening

A 3–4-generation family pedigree is mandatory at initial evaluation for all patients with suspected cardiomyopathy (Class I, Level C), to identify inheritance pattern and at-risk relatives. (sources/esc-cmp-2023)
Contrast-enhanced CMR should be considered in genotype-positive/phenotype-negative family members to aid early diagnosis (Class IIa, Level B). (sources/esc-cmp-2023)
Relatives who do not carry the confirmed familial P/LP variant can generally be discharged from clinical follow-up. (sources/esc-cmp-2023)
Cascade testing is NOT indicated when a variant of uncertain significance (VUS) is identified in the proband — only for confirmed P/LP variants. (sources/esc-cmp-2023)
Transition of care from paediatric to adult cardiomyopathy services requires timely preparation and joint consultations (Class I, Level C). (sources/esc-cmp-2023)
Psychological support is recommended for all individuals who have experienced the premature SCD of a family member with cardiomyopathy (Class I, Level B). (sources/esc-cmp-2023)

HFSA 2018 — Cardiomyopathy Phenotypic Screening Intervals

Baseline phenotype screening recommended for all at-risk 1st-degree relatives regardless of genetic status (Level A); relatives confirmed genotype-negative for a known P/LP variant may be discharged from serial surveillance after baseline evaluation (sources/genetic-cmp-jcf-2018 — very high)
Serial screening recommended for relatives with unknown genetic status or confirmed P/LP carriers (sources/genetic-cmp-jcf-2018 — very high)
Suggested screening intervals by age and cardiomyopathy type:

Cardiomyopathy	0–5 yr	6–12 yr	13–19 yr	20–50 yr	>50 yr
DCM	Annually (+ FDR)	Every 1–2 yr	Every 1–3 yr	Every 2–3 yr	Every 5 yr
HCM	Annually (+ FDR)	Every 1–2 yr	Every 2–3 yr	Every 5 yr	Every 5 yr
ARVC	Once (consider, + FDR)	Every 5 yr	Every 1–3 yr	Every 2–3 yr	Every 3 yr
RCM	Annually (+ FDR)	Every 1–2 yr	Every 2–3 yr	Every 3 yr	Every 5 yr

Studies at each screening visit: ECG (all), 2D echo (all), Holter (HCM, ARVC), cardiac MRI when echo insufficient, CK-MM if neuromuscular disease suspected, metabolic screening for paediatric-onset (sources/genetic-cmp-jcf-2018 — very high)

HCM-Specific Family Screening (AHA 2024)

3-generation family history mandatory at initial HCM assessment (Class I). (sources/HCM-AHA-2024)
Screening intervals (ECG + echo) for first-degree relatives:
- Children in genotype-positive families or families with early-onset disease: start when HCM diagnosed in family member; repeat every 1–2 years.
- All other children/adolescents: start no later than puberty; repeat every 2–3 years.
- Adults: start at time of HCM diagnosis in family member; repeat every 3–5 years. (sources/HCM-AHA-2024)
Cascade genetic testing: Offered when a pathogenic or likely pathogenic (P/LP) variant identified in the proband; genotype-negative relatives can be released from ongoing clinical surveillance. (sources/HCM-AHA-2024)
Serial variant reclassification (Class I, Level B-NR): P/LP classification can change — 11% of HCM variants reclassified over 6 years in one study. Re-evaluate pathogenicity every 2–3 years; notify relatives if variant is downgraded and recommence clinical screening. (sources/HCM-AHA-2024)
Postmortem genetic testing (Class I): When sudden unexplained death with HCM at autopsy — facilitates cascade testing in living relatives. (sources/HCM-AHA-2024)
If proband has no identified P/LP variant: cascade genetic testing is NOT useful (Class III: No Benefit); ongoing clinical screening of relatives still required. (sources/HCM-AHA-2024)
VUS in proband: clinical genetic testing of phenotype-negative relatives for reclassification purposes has uncertain usefulness (Class IIb); should only be done with cardiovascular genetics expert guidance. (sources/HCM-AHA-2024)
Genotype-positive, phenotype-negative individuals: Serial ECG + cardiac imaging every 1–2 years (children) or 3–5 years (adults); screening generally continued until ~50 years of age. (sources/HCM-AHA-2024)

Real-World Cascade Testing Yield — Combined Cardiomyopathy + Arrhythmia Panel (JAMA Cardiology 2022)

In 954 index patients with a positive combined panel result (n=4,782 total cohort), 306 (32.1%) had family members referred for cascade testing (sources/genetic-yield-jama-card-2022 — high)
958 family members received cascade testing (mean 3.1 per index patient, range 1–17)
42.0% of family members received a positive result — confirming substantial familial genetic burden
46.5% received a negative result — freed from intensive longitudinal surveillance; this "clearance" benefit is one of the primary values of cascade genetic testing
Use of a combined panel (vs. disease-specific panel) for the index patient also benefited cascade testing: approximately 1 in 23 family members with positive results would have been missed if restricted panels had been used for the index patient
Cascade testing was utilised more frequently in postmortem-positive cases (61.1%) than in living-positive cases (32.1%) — highlighting the value of molecular autopsy for family protection
40.9% of family members of postmortem-positive decedents tested positive — demonstrating the yield of cascade testing even after a sudden death index case

Cascade Screening for Inherited Arrhythmias (EHRA/HRS/APHRS/LAHRS)

Genetic testing of first-degree relatives is indicated once a class 4/5 variant is identified in the proband — applicable to LQTS, BrS, CPVT, SQTS, and other arrhythmia syndromes with positive family history. (sources/arrhythmia-genetics-mgenetik-2025)
Variant reclassification rates >36% in channelopathies mean that results communicated to family members can change over time — requiring periodic re-evaluation and active notification protocols. (sources/arrhythmia-genetics-mgenetik-2025)
Best executed in interdisciplinary cardiogenetic centres combining electrophysiology, imaging, genetics, and genetic counselling. Access is currently limited to academic centres. (sources/arrhythmia-genetics-mgenetik-2025)
Diagnostic scores for inherited arrhythmias (Schwartz score for LQTS, Shanghai score for BrS) already incorporate the presence of a pathogenic variant — making a confirmed genetic result clinically equivalent to full diagnosis in some syndromes. (sources/arrhythmia-genetics-mgenetik-2025)

Cascade Testing in an Early-Onset AF Clinic

Targeted cascade genotyping is a small but real yield. In an early-onset AF genetics clinic, 48 probands tested positive and four further carriers were found through targeted familial-variant testing, taking the genotype-positive group to 52 and the evaluated cohort to 246. Relatives had single-variant testing only, not full panels. (sources/genetic-eoaf-ehj-2026, rating: high)
Relatives are counted in the management analysis, not just the pedigree. The penetrance and management figures in that cohort pooled 48 probands with the 4 cascade-identified relatives (N=52), on the principle that the syndrome — not the route by which the variant was found — determines surveillance.
Gene-elusive disease limits cascade testing. Where the proband is genotype-negative but phenotypically affected — 9% of that cohort — there is no variant to cascade, and relatives must be screened clinically instead. This is the single largest structural limitation of variant-directed family screening.

Reproductive Cascade — What a Positive Result Enables Before Conception

Cascade testing is usually framed as finding relatives who need surveillance. For a woman of childbearing potential it does something else as well: it converts an unknown variant into a reproductive decision that can still be acted on (sources/cmp-pregnancy-jaccadv-2026, rating: medium).

A known P/LP variant before conception is the only route to preimplantation genetic testing (PGT-M). PGT-M with IVF screens embryos and avoids transferring those carrying the familial variant — but it requires a diagnostic linkage analysis protocol, which in turn requires multiple genotype-positive family members to establish phase. A de novo variant in a single proband may therefore be ineligible for PGT-M even though the variant is fully pathogenic.
PGT-M is not offered for a VUS, and cannot detect some variant classes (small deletions, duplications, complex chromosomal rearrangements) with current analytical strategies.
Prenatal diagnosis remains available when conception is already underway — chorionic villus sampling (procedural loss ~1/200, plus confined placental mosaicism risk), or amniocentesis (~1/1,000).
Cascade testing in pregnancy is not too late to change management, only too late to change reproductive options. Finding a FLNC variant in the third trimester still prompted postpartum CMR, which found a 47% LVEF with 7% LGE, and an EP referral — but the PGT-M conversation had already closed.
High-risk family history that should trigger a preconception genetics referral: a known familial cardiomyopathy, family members with advanced cardiac therapies (ablation, cardiac surgery, transplant, ICD), sudden death before age 40, and relatives with positive cardiomyopathy genetic testing.
A negative cascade result releases relatives from surveillance but not from pregnancy risk planning — in a genotype-negative relative, the risk reverts to the general population and the obstetric management should reflect that.

Atrial Standstill — Inheritance Patterns and Surveillance

Atrial standstill is the clearest example in this wiki of a single phenotype generated by four inheritance patterns, each requiring a different family strategy: (sources/atrial-standstill-hrs-2026, rating: medium)

Gene	Inheritance	First-degree recurrence risk	Surveillance
LMNA	Autosomal dominant	50%	Cascade testing from 10–12 y; if positive, annual ECG, Holter, echo
EMD	X-linked recessive	Brothers 50% if mother is a carrier; sisters 50% carrier risk; all daughters of an affected male are obligate carriers	Annual ECG, Holter, echo from diagnosis. Carrier females: annual ECG and Holter, echo every 1–2 y — they may develop conduction disease and atrial arrhythmias, later and milder than affected males
NPPA	Autosomal recessive	25% (siblings)	Carrier screening in the founder population; ECG, Holter, echo every 1–2 y from age 20
SCN5A	Autosomal dominant, variable penetrance; biallelic forms recessive with 25% sibling risk	50% heterozygous (modifier dependent); 25% biallelic	Cascade testing with GJA5 genotype context; annual ECG and Holter, echo every 1–2 y; screen for the full SCN5A spectrum (BrS, LQT3, conduction disease)

A negative atrial standstill phenotype is not a negative result in SCN5A families — the same variant can produce Brugada syndrome or LQT3 in a relative, so cascade evaluation must include BrS ECG, QTc and PR/QRS. (sources/atrial-standstill-hrs-2026)
Predictive testing in minors is contested for NPPA, where penetrance begins after age 20 and childhood surveillance would not alter management.
EDMD cardiac involvement can be life threatening even when skeletal muscle disease is mild, so cardiac surveillance must be independent of neurological severity (2017 AHA scientific statement).
Reproductive options — prenatal diagnosis and preimplantation genetic diagnosis — should be discussed for autosomal recessive NPPA.

Incidental Variant Cascade Testing (AHA 2023)

LP/P incidental variants — once confirmed as disease-associated by the Bayesian framework — should trigger cascade genetic testing in first-degree relatives, regardless of whether the proband is phenotypically affected (sources/incident-gene-aha-2023 — high)
Cascade testing must NOT be performed on VUS variants from incidental contexts, identical to the rule for diagnostic probands (sources/incident-gene-aha-2023 — high)
Genotype-positive family members found via incidental variant cascade testing should undergo the same three-step Bayesian evaluation framework (pretest probability → variant pathogenicity re-evaluation → posttest probability)
Genotype-positive relatives without phenotypic evidence of disease still require longitudinal follow-up at guideline-directed intervals
The Bayesian framework should be conducted at or in close consultation with a specialised multidisciplinary cardiovascular genetics centre (sources/incident-gene-aha-2023 — high)
See concepts/Incidental-Cardiovascular-Variants for the complete Bayesian evaluation framework

DTC-GT Cascade Testing — Challenges and Gaps

Traditional cascade testing adoption in clinical genetics workflows is <50%; the specific frequency for DTC-GT-triggered cascade testing is unknown (sources/consumer-genetictest-aha-2025 — high)
DTC companies do NOT actively facilitate cascade testing — unlike clinical genetics services that provide family letters and contact protocols; patients must self-initiate family communication (sources/consumer-genetictest-aha-2025 — high)
No current professional guidelines address cascade screening specifically after DTC-GT results — this is a major regulatory and clinical gap given that >33 million DTC-GTs were performed in 2022 (sources/consumer-genetictest-aha-2025 — high)
DTC-GT cascade testing risks: misclassified variants (especially from SNP-chip based tests) may generate false-positive results that, if shared with family members, lead to unnecessary stress, procedures, and financial burdens (sources/consumer-genetictest-aha-2025 — high)
PRS cascade testing is not strongly indicated given the non-mendelian nature of polygenic risk; however, high concordance between first-degree relatives with high CAD PRS (Reid et al., Circ Genom Precis Med 2021) may justify consideration (sources/consumer-genetictest-aha-2025 — high)
Confirmatory CLIA-certified testing should precede any DTC-GT-triggered cascade testing — to avoid propagating potentially erroneous results through families (sources/consumer-genetictest-aha-2025 — high)
See concepts/DTC-Genetic-Testing for full clinical approach framework

AHA 2020 — Legal and Institutional Context for Cascade Testing

HIPAA (US) restricts providers from directly contacting at-risk relatives without patient authorization; providers should supply patients with a standardized family letter accurately summarizing the genetic finding and directing relatives toward cascade evaluation (sources/genetic-test-aha-2020 — high)
Genetic Information Nondiscrimination Act (GINA 2008): prohibits genetic discrimination in health insurance and employment; does NOT cover life insurance, disability insurance, or long-term care insurance; does not apply to employers with <15 employees — patients must be counselled about these limitations before undergoing testing (sources/genetic-test-aha-2020 — high)
When cascade extends beyond the immediate family: for any family member found to have the disease phenotype or a positive genetic result, their own first-degree relatives should in turn be offered testing — the cascade continues outward until all at-risk relatives have been offered clinical screening and genetic testing (sources/genetic-test-aha-2020 — high)
Family members who test negative for the familial P/LP variant: exonerated from further structured surveillance (risk reverts to general population level); exception if clinical phenotype is atypical for the identified variant, oligogenic contribution is suspected, or penetrance uncertainty remains (sources/genetic-test-aha-2020 — high)
Family members who decline genetic testing: uncertain genetic status — clinical surveillance recommended at the same intervals as genotype-positive individuals (sources/genetic-test-aha-2020 — high)
Prenatal genetic testing and preimplantation genetic diagnosis (PGD): a confirmed familial P/LP variant enables prospective parents to consider these reproductive management options (sources/genetic-test-aha-2020 — high)

Contradictions / Open Questions

VUS variant handling — testing vs. not testing relatives: Both HRS 2019 and ESC/AHA guidelines agree that VUS variants should not drive cascade genetic testing of relatives. However, in practice, a significant proportion of HCM and ACM probands carry VUS rather than confirmed P/LP variants — meaning the majority of families with a likely inherited disease still cannot access gene-informed cascade testing. The gap between the recommendation (don't test for VUS) and clinical reality (most probands have VUS) is substantial. (sources/acm-hrs-2019, sources/HCM-AHA-2024)
Serial reclassification responsibility: AHA 2024 recommends re-evaluating variant pathogenicity every 2–3 years (Class I, Level B-NR). In practice, there is no standardized system for notifying relatives when a variant is downgraded from P/LP to VUS (or upgraded). If a relative was told they are "gene-negative" based on a proband variant later upgraded to P/LP, they may have been incorrectly discharged from follow-up. The clinical infrastructure for systematic reclassification notification does not yet exist in most centers. (sources/HCM-AHA-2024)
The reproductive benefit of cascade testing accrues only to relatives found before conception. PGT-M requires a pathogenic variant known in advance plus multiple genotype-positive relatives for linkage; de novo cases and VUS carriers are excluded by construction. The families with the newest and least-characterised diagnoses are therefore the ones for whom cascade testing offers the least reproductive value — an inversion of where the need is greatest. (sources/cmp-pregnancy-jaccadv-2026, rating: medium)
Screening interval heterogeneity across guidelines: ACM screening (HRS 2019): every 1–3 years from age 10–12. HCM screening (AHA 2024): every 1–2 years for children, every 3–5 years for adults. The difference reflects disease-specific penetrance rates but can create confusion for individuals with mixed or uncertain phenotypes. (sources/acm-hrs-2019, sources/HCM-AHA-2024)

Connections

Related to concepts/Arrhythmogenic-Cardiomyopathy
Related to entities/ARVC
Related to entities/ALVC
Related to entities/PKP2
Related to entities/HCM
Related to concepts/Cardiogenetic-Centers
Related to concepts/Variant-Reclassification
Related to entities/Long-QT-Syndrome
Related to entities/Brugada-Syndrome
Related to entities/CPVT
Related to concepts/Genetic-Testing-in-Cardiomyopathy
Related to concepts/Genetic-Testing-in-Arrhythmias
Related to sources/genetic-cmp-jcf-2018
Related to concepts/DTC-Genetic-Testing
Related to concepts/Incidental-Cardiovascular-Variants
Related to sources/incident-gene-aha-2023
Related to sources/genetic-test-aha-2020
Related to concepts/Atrial-Standstill — four inheritance patterns for one phenotype
Related to entities/EMD — obligate carrier daughters, X-linked
Related to entities/NPPA — autosomal recessive, 25% sibling risk
Related to concepts/Pregnancy-in-Genetic-Cardiomyopathy — the reproductive endpoint of cascade testing