2024 AHA/ACC HCM Guideline

Authors, Journal, Affiliations, Type, DOI

• Lead authors: Steve R. Ommen MD (Chair), Carolyn Y. Ho MD (Vice Chair), and 20 additional writing committee members
• Organizations: American Heart Association / American College of Cardiology, in collaboration with AMSSM, HRS, PACES, SCMR
• Journal: Circulation, Published online May 8, 2024; 149:e1239–e1311
• Type: Clinical practice guideline (reaffirmed current as of May 2025)
• DOI: 10.1161/CIR.0000000000001250

Overview

The 2024 AHA/ACC HCM Guideline is the most comprehensive US practice guideline for hypertrophic cardiomyopathy, updating the 2020 version based on a systematic literature review through May 2023. Key paradigm shifts include the formal recommendation against universal exercise restriction (Class III: No Benefit), the elevation of cardiac myosin inhibitors (mavacamten) to Class I second-line therapy for symptomatic obstructive HCM, and the absolute contraindication of mavacamten in pregnancy (Class III: Harm). The guideline provides a major risk-factor-based framework for SCD prevention, distinct from the ESC 2023 threshold-driven calculator approach.

Keywords

AHA Scientific Statements · athlete · atrial fibrillation · cardiac myosin inhibitors · cardiovascular magnetic resonance imaging · diastolic dysfunction · echocardiography · exercise · family screening · genetics · hypertrophic cardiomyopathy · implantable cardioverter-defibrillator · left ventricular outflow tract obstruction · occupation · physical activity · pregnancy · rhythm monitoring · risk stratification · sarcomeric genes · septal alcohol ablation · septal reduction therapy · shared decision-making · sports · sudden cardiac death · surgical myectomy · systolic dysfunction · ventricular arrhythmias

Key Takeaways

Section 2 — Definition, Etiology, Clinical Course, and Natural History

• Prevalence of unexplained asymptomatic hypertrophy in young US adults: ~1:500; symptomatic HCM by claims data: <1:3000 adults (true burden higher due to unrecognized disease).
• Equal sex distribution but women diagnosed less often; Black patients diagnosed younger (~40 vs 45.5 years), more likely symptomatic HF, less likely to receive genetic testing — likely reflects structural inequities in access to care.
• Adult diagnostic criterion: LV wall thickness ≥15 mm in any segment in absence of another cause; ≥13–14 mm acceptable with positive family history or pathogenic/likely pathogenic variant.
• Pediatric diagnostic criterion: z-score >2.5 for asymptomatic children with no family history; z-score >2 when definitive family history or positive genetic test.
• ~30–60% of patients have an identifiable pathogenic/likely pathogenic sarcomeric variant; up to 40% have no family history ("nonfamilial").
• Primary sarcomeric genes: MYH7, MYBPC3 (most common together), TNNI3, TNNT2, TPM1, MYL2, MYL3, ACTC1; each non-MYH7/MYBPC3 gene accounts for 1–5%.
• Natural history shift: SCD reduction from ICDs has shifted dominant morbidity to HF complications and AF stroke risk.
• Cardiometabolic risk factors (obesity, HTN, diabetes, sleep apnea) are common in HCM and worsen prognosis — intensive risk factor modification recommended.

Section 3 — Pathophysiology

• LVOTO: obstruction present if peak gradient ≥30 mmHg; resting or provoked gradient ≥50 mmHg is the treatment threshold. Dynamic — varies with preload, afterload, contractility, medications, food, and alcohol.
• SAM of the mitral valve is the primary cause of LVOTO; MR from SAM is mid-to-late systolic, typically posteriorly directed.
• Diastolic dysfunction: impaired relaxation, ↑stiffness, ↓compliance; contributes to symptoms independent of LVOTO.
• Myocardial ischemia: microvascular dysfunction with impaired coronary flow reserve, medial hypertrophy of intramural arterioles; apical ischemia may contribute to apical aneurysm formation.
• Autonomic dysfunction: abnormal blood pressure response to exercise in ~25% of patients.

Section 4 — Shared Decision-Making

• Class I, Level B-NR: Shared decision-making for all major HCM decisions including genetic evaluation, activity, therapy, and ICD placement.
• Key domains: genetic testing, ICD implantation, advanced LVOTO therapies, and sports/exercise participation.

Section 5 — Multidisciplinary HCM Centers

• Class I, Level C-LD: SRT should be performed at experienced (comprehensive or primary) HCM centers with demonstrated outcomes.
• Class IIa, Level C-LD: Referral to HCM centers for complex decisions (weak-evidence recommendations, genetic counseling, pediatric ICD, SRT, advanced HF).
• Outcome benchmarks for SRT: 30-day mortality ≤1%, symptomatic improvement >90%, rest/provoked LVOT gradient <50 mmHg >90%.

Section 6 — Diagnosis, Initial Evaluation, and Follow-Up

6.1 Clinical Diagnosis

• Initial evaluation: comprehensive physical examination + complete medical + 3-generation family history (Class I, Level B-NR).
• Classic exam findings: harsh crescendo-decrescendo systolic murmur, abnormal carotid pulse, S4; LVOTO maneuvers (Valsalva, squat-to-stand, standing).

6.2 Echocardiography

• TTE recommended at initial evaluation (Class I, Level B-NR); repeat every 1–2 years in stable patients; with any change in clinical status.
• Provocative TTE (Valsalva, standing): if resting gradient <50 mmHg (Class I, Level B-NR).
• Exercise TTE: for symptomatic patients without resting/provocable gradient ≥50 mmHg by standard maneuvers (Class I); reasonable in asymptomatic patients (Class IIa).
• Intraoperative TEE: mandatory for surgical myectomy (Class I); with intracoronary contrast for alcohol ablation (Class I).
• Post-SRT TTE at 3–6 months (Class I).

6.3 CMR Imaging

• Indicated when echocardiography inconclusive (Class I, Level B-NR).
• Useful to differentiate HCM from mimics (infiltrative disease, athlete's heart) (Class I).
• Beneficial for SCD risk when risk remains uncertain after echo + Holter: assesses max LV wall thickness, EF, apical aneurysm, LGE (Class I, Level B-NR).
• Indicated to plan SRT when obstruction mechanism is unclear (Class I).
• Periodic CMR every 3–5 years for longitudinal SCD risk surveillance (Class IIb, Level C-EO).
• LGE ≥15% of LV mass = ~2-fold increase in SCD risk; no consensus on optimal quantification method.

6.4 Cardiac CT

• May be considered if echocardiography non-diagnostic and CMR unavailable (Class IIb, Level C-LD).

6.5 Heart Rhythm Assessment

• 12-lead ECG at initial evaluation and every 1–2 years (Class I, Level B-NR).
• 24–48h ambulatory monitoring at initial evaluation and every 1–2 years (Class I, Level B-NR).
• Extended monitoring for palpitations or lightheadedness (Class I).
• Extended ambulatory monitoring annually: Class I (upgraded from 2a in 2020) for patients at high AF risk (risk factors or validated HCM-AF score) eligible for anticoagulation.
• Extended monitoring in adults without AF risk factors: Class IIb.
• HCM-AF score: validated in 1900 patients; high-risk patients developed AF at 3.4%/year (development cohort) and 2.7%/year (external validation).

6.6 Angiography and Invasive Assessment

• Cardiac catheterization for uncertain LVOTO severity on noninvasive imaging (Class I).
• Coronary angiography (CT or invasive) for myocardial ischemia symptoms or coronary risk factors before myectomy (Class I).

6.7 Exercise Stress Testing

• Exercise TTE for symptomatic patients without confirmable LVOTO on standard echo (Class I).
• CPET for NYHA III–IV nonobstructive HCM: selection for transplant/mechanical support (Class I).
• Pediatric HCM regardless of symptoms: exercise stress testing recommended for functional capacity and prognosis (Class I, Level B-NR) — NEW 2024.
• Adult HCM: exercise stress testing reasonable at initial evaluation (Class IIa).

6.8 Genetics and Family Screening

• 3-generation family history essential at initial assessment (Class I).
• Genetic testing recommended to identify at-risk family members (Class I); pre/post-test genetic counseling by cardiovascular genetics expert (Class I).
• First-tier gene panel: MYH7, MYBPC3, TNNI3, TNNT2, TPM1, MYL2, MYL3, ACTC1 — identifies pathogenic variant in ~30% sporadic and ~60% familial HCM.
• Larger panels do not add diagnostic value.
• Cascade genetic testing of first-degree relatives when pathogenic/likely pathogenic variant identified (Class I).
• Serial variant reclassification every 2–3 years (Class I, Level B-NR) — pathogenicity can change; 11% of HCM variants reclassified over 6 years in one study.
• Postmortem genetic testing valuable after sudden unexplained death with HCM (Class I).
• Usefulness of genetic testing for adult SCD risk assessment: uncertain (Class IIb) — genotype does NOT independently guide ICD decisions in adults.
• If no pathogenic variant found in proband: cascade family genetic testing NOT useful (Class III: No Benefit).

6.9 Genotype-Positive, Phenotype-Negative

• Serial ECG and cardiac imaging every 1–2 years (children/adolescents) or 3–5 years (adults) (Class I).
• Competitive sports of any intensity: reasonable (Class IIa, Level B-NR) — SCD is rare in phenotype-negative individuals.
• ICD NOT recommended for primary prevention in phenotype-negative individuals (Class III: No Benefit).

Section 7 — SCD Risk Assessment and Prevention

7.1.1 SCD Risk — Adults

• Comprehensive noninvasive SCD risk assessment at initial evaluation and every 1–2 years (Class I, Level B-NR).
• Major risk factors:
  1. Personal history of cardiac arrest or sustained VT
  2. Arrhythmic syncope (especially within 6 months; >5 years prior carries little significance)
  3. Family history of premature HCM-related SCD in first-degree or close relatives ≤50 years
  4. Massive LVH ≥30 mm (any segment); borderline consideration ≥28 mm
  5. LV apical aneurysm with transmural scar/LGE
  6. LV systolic dysfunction (EF <50%)
  7. Extensive LGE ≥15% of LV mass
  8. NSVT: ≥3 beats at ≥120 bpm; greater weight for frequent (≥3 runs), longer (≥10 beats), or faster (≥200 bpm) runs
• CMR beneficial when SCD risk uncertain after standard assessment (Class I, Level B-NR).
• 5-year SCD risk estimate (HCM Risk-SCD calculator) using left atrial diameter and maximal LVOT gradient: reasonable aid for shared decision-making (Class IIa, Level B-NR). Not threshold-driven.

7.1.2 SCD Risk — Children and Adolescents

• Same comprehensive assessment framework; pediatric-specific tools available (Class I).
• HCM Risk-Kids calculator uses: age, LV wall z-scores, left atrial diameter z-score, maximal LVOT gradient, unexplained syncope, NSVT, ± genotype (Class IIa, Level B-NR).
• Genotype-positive status is incorporated in pediatric risk calculators (unlike adult tools).

7.2 ICD Placement

• Class I: ICD for previous cardiac arrest or sustained VT (secondary prevention).
• Class IIa: ICD reasonable for adults with ≥1 major SCD risk factors (see list above).
• Class IIa: ICD reasonable for children with ≥1 conventional risk factors (unexplained syncope, massive LVH, NSVT, family history of early HCM-related SCD), accounting for higher complication rates in young patients.
• Class IIb: ICD may be considered in adults without major risk factors but with extensive LGE or NSVT on monitoring.
• Class III: Harm: ICD without risk factors; ICD solely for competitive sports participation.
• Prespecified risk score thresholds should NOT be the sole arbiter of ICD decisions.

7.3 ICD Device Selection

• Single-chamber transvenous or subcutaneous ICD recommended after shared decision-making (Class I).
• Single-coil leads preferred over dual-coil if defibrillation threshold adequate (Class I).
• Dual-chamber ICD reasonable if pacing needed or to attempt symptom relief in obstructive HCM ≥65 years (Class IIa).
• CRT reasonable in nonobstructive HCM + LBBB + LVEF <50% + NYHA II–IV (Class IIa).

Section 8 — Management of HCM

8.1.1 Pharmacological Management — Obstructive HCM

• Step 1 (Class I): Non-vasodilating beta-blockers, titrated to maximum tolerated dose.
• Step 2 (Class I): Verapamil or diltiazem if beta-blockers ineffective or not tolerated.
• Step 3 (Class I, Level B-R): Add cardiac myosin inhibitor (adult patients only), OR disopyramide (with AV nodal blocker), OR SRT at experienced centers — NEW: myosin inhibitor elevated from prior guideline.
• Vasodilators (ACEi, ARBs, dihydropyridine CCBs) and digoxin: discontinuation may be reasonable as they can worsen LVOTO (Class IIb).
• Low-dose diuretics may be cautiously added for volume overload (Class IIb).
• Class III: Harm: Verapamil in severe dyspnea at rest, hypotension, very high resting gradients (>100 mmHg), or all children <6 weeks of age.
• Mavacamten (adults only): Improves LVOT gradients and symptoms in 30–60% of patients; REMS required (LVEF <50% in 5.7–10% attributable to drug); MUST be discontinued if persistent LVEF <50%.

8.1.2 Invasive Treatment — Obstructive HCM

• Class I: SRT (myectomy or ASA) when symptomatic despite GDMT.
• Class I: Surgical myectomy when associated cardiac disease requiring surgery (papillary muscle anomaly, intrinsic MV disease, multivessel CAD, aortic stenosis).
• Class I, Level C-LD: ASA in adults where surgery contraindicated or high-risk.
• Class IIb: Early myectomy at comprehensive HCM centers with NYHA class II + pulmonary hypertension from LVOTO, left atrial enlargement + AF, poor functional capacity on treadmill, or children/young adults with very high resting LVOT gradient >100 mmHg.
• Class III: Harm: SRT for asymptomatic patients with normal exercise capacity; mitral valve replacement as sole treatment for LVOTO.
• Extended septal myectomy (ESM): mortality <1%, success >90–95%; long-term survival comparable to age-matched general population.
• ASA: avoids sternotomy, shorter hospital stay; higher risk of pacemaker (vs myectomy), higher repeat intervention rate; at 10 years, survival may be lower than ESM.

8.2 Nonobstructive HCM with Preserved EF

• Beta-blockers or nondihydropyridine CCBs for exertional angina/dyspnea (Class I, Level C-LD).
• Oral diuretics if persistent dyspnea despite above (Class IIa).
• Valsartan (NEW Class IIb, Level B-R): For patients ≤45 years with nonobstructive HCM due to pathogenic/likely pathogenic sarcomeric variant, mild phenotype (NYHA I–II, max wall thickness 13–25 mm, no secondary prevention ICD, no AF) — may slow adverse cardiac remodeling.
• ACEi/ARBs: usefulness not well established (Class IIb).

8.3 Advanced Heart Failure

• GDMT for HFrEF when LVEF <50% (Class I, Level C-LD).
• Class I, Level B-R: Cardiac myosin inhibitors MUST be discontinued if persistent LVEF <50% — NEW explicit requirement.
• CPET for NYHA III–IV nonobstructive HCM (Class I).
• Heart transplant evaluation for NYHA III–IV nonobstructive HCM refractory to GDMT (Class I); posttransplant survival comparable to other etiologies; 20–50% of HCM advanced HF has preserved EF — does not preclude transplant listing.
• LVAD as bridge to transplant in NYHA III–IV (Class IIa); post-LVAD survival better with LV cavity >46–50 mm.

8.4 HCM and AF

• Class I, Level B-NR: DOACs (first-line) or warfarin (second-line) for clinical AF, independent of CHA2DS2-VASc score.
• Class I, Level C-LD: Same anticoagulation for device-detected subclinical AF >24 hours duration.
• Class IIa: Anticoagulation for device-detected AF >5 minutes but <24 hours (considering total burden, risk factors, bleeding risk).
• Rhythm control preferred for poorly tolerated AF (Class IIa); amiodarone is the most used antiarrhythmic.
• AF catheter ablation when antiarrhythmic drugs ineffective, contraindicated, or not preferred (Class IIa); less effective in HCM than general population (2× higher relapse); more extensive ablation often required.
• Concomitant surgical AF ablation at the time of myectomy (Class IIa).
• HCM AF stroke risk is independent of CHA2DS2-VASc score — a significant number of strokes occur in patients with score of 0.

8.5 Ventricular Arrhythmias (Management)

• Management follows SCD risk stratification framework; ICD for high-risk patients.
• Antiarrhythmic drugs (amiodarone, sotalol) for symptomatic VT not amenable to ablation or as adjunct to ICD.

Section 9 — Lifestyle Considerations

9.1 Exercise and Sports

• Class III: No Benefit (NEW 2024): Universal restriction from vigorous physical activity or competitive sports is NOT indicated for most patients with HCM.
• Class IIa: Participation in vigorous recreational activities is reasonable after annual evaluation + shared decision-making.
• Class IIb: Competitive sports may be considered after review by HCM expert with annual evaluation + shared decision-making.
• Genotype-positive, phenotype-negative: competitive sports of any intensity reasonable (Class IIa) — no arrhythmic events observed in a prospective registry of 126 individuals.
• Light (<3 METs), moderate (3–6 METs), and vigorous (>6 METs) exercise not associated with increased ventricular arrhythmia events in short-term studies.

9.3 Pregnancy

• Class III: Harm (NEW 2024): Mavacamten is contraindicated in pregnancy due to potential teratogenic effects.
• Multidisciplinary HCM center involvement recommended for managing HCM through pregnancy.

9.4 Comorbidities

• Intensive management of cardiometabolic risk factors (obesity, HTN, diabetes, obstructive sleep apnea) is a critical component of HCM management.

Section 10 — Evidence Gaps and Future Directions

• Refining HCM diagnosis (distinguishing HCM from phenocopies, hypertensive cardiomyopathy, athlete's heart).
• Disease-modifying therapies to attenuate or prevent progression (valsartan is promising — broader trial data needed).
• Improving care for nonobstructive HCM (very few RCTs; no validated therapies for diastolic dysfunction).
• Improving risk stratification (integration of LGE, apical aneurysm, EF into validated risk tools; pediatric tools need further validation).
• Arrhythmia management (optimal AF ablation strategies; ventricular arrhythmia management).
• Expanding genetic architecture understanding (up to 40% without identifiable variant; polygenic contributions).

Key Concepts Mentioned

• concepts/LVOTO — central pathophysiologic mechanism; treatment target
• concepts/HCM-Risk-SCD — SCD risk quantification for adults and pediatric patients
• concepts/Septal-Reduction-Therapy — invasive LVOTO treatment; updated outcome benchmarks
• concepts/Late-Gadolinium-Enhancement — CMR-based fibrosis marker; ≥15% LV mass = ↑SCD risk
• concepts/Cascade-Family-Screening — clinical + genetic screening of first-degree relatives
• concepts/Exercise-in-HCM — updated exercise and sports participation framework

Key Entities Mentioned

• entities/HCM — primary subject
• entities/Mavacamten — Class I second-line obstructive HCM; contraindicated in pregnancy
• entities/MYBPC3 — most common HCM gene
• entities/MYH7 — second most common HCM gene
• entities/Atrial-Fibrillation — major morbidity in HCM; anticoagulation required regardless of CHA2DS2-VASc

Limitations of the Document

• AHA 2024 vs ESC 2023 — ICD approach: AHA 2024 uses a major risk factor framework (ICD reasonable with ≥1 major risk factor); ESC 2023 mandates HCM Risk-SCD calculator with thresholds (≥6% = Class IIa). Neither approach is validated in randomized trials.
• AHA 2024 vs ESC 2023 — LV apical aneurysm: AHA 2024 lists apical aneurysm as a Class IIa ICD indication (major risk factor); ESC 2023 considers it insufficient as sole ICD indication.
• AHA 2024 vs ESC 2023 — mavacamten positioning: AHA 2024 elevates mavacamten to Class I (step 3 therapy equivalent to disopyramide/SRT); ESC 2023 positions mavacamten as Class IIa (step 4, below disopyramide).
• SCD 5-year risk tool not threshold-driven (AHA 2024): AHA 2024 uses the calculator as an aid to shared decision-making rather than a decision threshold — diverges from ESC 2023 which uses specific thresholds.
• Genotype for adult SCD risk: Genetic variant status does NOT independently guide ICD decisions in adults (Class IIb, uncertain). Pediatric risk tools do include genotype.
• Valsartan for nonobstructive HCM: Only one small RCT (n=178); long-term outcomes unknown.
• LGE quantification: No consensus on optimal method; ≥15% threshold promoted but not universally validated.
• Alcohol septal ablation — long-term survival: 5-year survival similar to myectomy; 10-year data suggests lower survival with ASA vs ESM. Conflicting data from large registries.

Wiki Pages Updated

• sources/HCM-AHA-2024 (this file — created)
• entities/HCM (updated: AHA 2024 clinical criteria, risk factors, exercise paradigm, valsartan)
• entities/Mavacamten (updated: Class I AHA 2024, pregnancy contraindication, REMS, discontinuation rule)
• concepts/LVOTO (updated: AHA 2024 step 3 algorithm, verapamil contraindication rule)
• concepts/HCM-Risk-SCD (updated: AHA 2024 major risk factor approach, pediatric tools, apical aneurysm as Class IIa)
• concepts/Septal-Reduction-Therapy (updated: AHA 2024 outcome benchmarks, indication criteria, ASA long-term data)
• concepts/Exercise-in-HCM (created: new exercise/sports paradigm)
• wiki/index.md (updated)
• wiki/log.md (updated)