Clinical Quick Reference — Management of Hypertrophic Cardiomyopathy
Published: Journal of the American College of Cardiology, Vol. 83, No. 23 (2024) Societies: AHA/ACC/AMSSM/HRS/PACES/SCMR DOI:10.1016/j.jacc.2024.02.014
The 2024 update introduces significant practice-changing recommendations, particularly around cardiac myosin inhibitors and refined risk stratification approaches.
Key Updates:
Cardiac myosin inhibitors (mavacamten, aficamten) — New Class I/2a recommendations for obstructive HCM; potential paradigm shift away from beta-blockers/verapamil alone
Exercise stress testing — Expanded indications for ESE in diagnosis and prognosis (new Class I/2a recommendations)
Genetic testing — Enhanced cascade screening and variant reclassification protocols
Nonobstructive HCM — New Class 2b recommendations for younger, pathogenic variant carriers
HCM Diagnosis
Diagnostic Criteria
Class I Comprehensive physical examination and imaging (echo/CMR/CT) are recommended in all suspected HCM cases.
Wall Thickness Criteria (per 2D echo):
≥15 mm in any LV segment = diagnostic of HCM in adults (without family hx)
13-14 mm = suggestive with family history or positive genetic test
<13 mm = genotype-positive, phenotype-negative (requires surveillance)
Imaging Approach
Class I Transthoracic echocardiography is the initial diagnostic modality. Class I CMR is recommended if echo is inconclusive or to assess apical hypertrophy, LV apical aneurysm, and extent of LGE.
Pearl: CMR accurately measures maximal LV wall thickness and detects extent of late gadolinium enhancement (LGE), which predicts life-threatening arrhythmias and SCD risk.
Genetic Testing & Counseling
Class I In patients with HCM, evaluation of familial inheritance including 3-generation family history is recommended. Class I Genetic testing is beneficial to facilitate identification of at-risk family members for cascade screening.
Genetic Testing Strategy:
HCM is predominantly autosomal dominant with variable penetrance
Sarcomere gene variants (MYBPC3, MYH7, TNNI2, TNNT2, TPM1, MYL2, MYL3, ACTC1) account for ~60% of familial cases
Gene panels include 8 sarcomere genes; exome/genome sequencing for comprehensive testing
Cascade genetic testing in first-degree relatives (index case identified)
Variant reclassification every 2-3 years as evidence evolves
Genotype-Positive, Phenotype-Negative (GPPN)
Class I Serial clinical assessment (ECG, echo every 1-2 years in children, 3-5 years in adults) is recommended. Class 2b Exercise stress testing may be considered for GPPN individuals to evaluate for latent obstruction.
SCD Risk Stratification
Class I Comprehensive, systematic SCD risk assessment is recommended at initial evaluation and every 1-2 years thereafter.
Major SCD Risk Factors in Adults
Risk Factor Category
Definition/Threshold
Clinical Significance
Prior Cardiac Arrest
Personal history of cardiac arrest or sustained VT
Establishes highest risk; Class I ICD indication
Family History of SCD
SCD in close relative ≤50 years of age
Strong independent risk factor; particularly prognostic if multiple family members affected
Unexplained Syncope
Syncope without clear cause; exertional or recent syncope particularly concerning
Marker of arrhythmogenic substrate; especially if multiple episodes
Massive LVH
Maximal LV wall thickness ≥30 mm in any segment
Structural marker of SCD risk; risk increases with degree of hypertrophy
LV Apical Aneurysm
Discrete apical ballooning or aneurysm by echo or CMR
Marker of focal ischemia and arrhythmogenic substrate
Extensive LGE on CMR
Late gadolinium enhancement ≥15% of LV myocardial mass
Quantifies myocardial fibrosis; predictor of SCD risk and AF
NSVT on Holter/Loop Recorder
>3 consecutive beats at ≥120 bpm on ambulatory ECG monitoring
Marker of enhanced ventricular automaticity; risk proportional to frequency/duration
Abnormal BP Response to Exercise
Failure of SBP to increase ≥25 mmHg or paradoxical decrease during exercise stress test
Associated with inadequate peripheral vasodilation; independent SCD risk marker
LV Systolic Dysfunction
LVEF <50% ("burned-out" HCM)
Indicates disease progression; significantly increases SCD and HF mortality risk
5-Year SCD Risk Estimation
Validated risk calculators combining multiple factors (LV thickness, family hx, syncope, NSVT, BP response, LGE, apical aneurysm) are available for adults (age ≥16) and children. Class 2a For patients ≥16 years with ≥1 major risk factor, discussion of estimated 5-year SCD risk and mortality is recommended to guide shared ICD decision-making.
Prior cardiac arrest or sustained VT: ICD Class I indication regardless of calculated risk
Pitfall: Do not rely on wall thickness alone. Integrate clinical history (syncope, family hx), echo findings (apical aneurysm, LVEF), ECG (NSVT), and CMR (LGE extent) for comprehensive risk assessment. Risk is multifactorial and cumulative; presence of multiple factors significantly elevates risk beyond individual factor contribution.
ICD Placement for Primary Prevention
Class I Indication
Class I ICD is recommended in patients with prior cardiac arrest or hemodynamically significant sustained VT.
Class 2a Indication (Reasonable)
Class 2a ICD is reasonable in patients with HCM and ≥1 major SCD risk factor. The 5-year SCD risk estimate and clinical profile should guide shared decision-making, with discussion of estimated risks, benefits, and estimated ICD longevity.
ICD Primary Prevention Algorithm
Step 1: Identify patients with prior sustained VT or cardiac arrest → Class I for ICD
Step 2: Assess for ≥1 major SCD risk factor (family hx, syncope, wall thickness ≥30 mm, apical aneurysm, NSVT, abnormal BP response, LGE, LVEF <50%)
Step 3: Calculate 5-year SCD risk using validated calculator
Step 5: ICD placement if patient desires, or continued surveillance if declined
Pediatric ICD Placement
Class 2a ICD placement is reasonable in children with ≥1 major SCD risk factor after comprehensive evaluation and shared decision-making. Consider device complications (lead failure, growth issues) in younger patients.
Management of Obstructive HCM
Pharmacologic Therapy Overview
Class I For patients with obstructive HCM and symptoms, nonvasodilating beta-blockers (titrated to effectiveness or maximally tolerated dose) are recommended as first-line therapy.
Class I For patients with obstruction unresponsive to beta-blockers, nondihydropyridine calcium channel blockers (verapamil, diltiazem) are recommended as second-line agents.
Class I For patients with persistent symptoms despite beta-blockers or calcium channel blockers, adding a myosin inhibitor (mavacamten) or disopyramide (in combination with atrioventricular nodal blocking agents) is recommended.
LVOT Obstruction Management Algorithm:
Step 1: Initial Assessment - Confirm LVOT obstruction (resting or provoked gradient ≥30 mmHg); assess severity and symptoms
Step 2: First-Line Pharmacotherapy - Start beta-blocker (e.g., metoprolol 50-200 mg daily) or combination with rate-limiting agent
Step 3: Optimize First-Line Agent - Titrate to maximum tolerated dose; assess response at 2-4 weeks
Step 4: If Inadequate Response - Add nondihydropyridine CCB (verapamil 120-480 mg daily or diltiazem 180-360 mg daily)
Step 5: Persistent Symptoms Despite Dual Agent Therapy - Consider addition of myosin inhibitor (mavacamten starting 5 mg daily) or disopyramide (200-400 mg daily with AV nodal blocking agent)
Step 6: Drug-Refractory Symptoms - Refer for septal reduction therapy (myectomy preferred; ASA if myectomy contraindicated)
Dehydration: Decreases LV cavity size and increases gradient; counsel on adequate fluid intake
Cardiac Myosin Inhibitors
Paradigm shift in 2024: Mavacamten is now recommended as a first-line option for drug-refractory obstructive HCM.
Mavacamten (Camzyos®) — Pharmacology & Dosing
Class I For patients with obstructive HCM and persistent symptoms despite beta-blockers or calcium channel blockers, adding a myosin inhibitor is recommended.
Mechanism & Clinical Pharmacology:
Mechanism of action: First-in-class cardiac selective myosin inhibitor; directly inhibits cardiac myosin ATPase motor protein, reducing myosin-actin cross-bridge cycling
Result: Decreased cardiac contractility and LVOT gradient; improved symptoms without affecting systemic blood pressure or heart rate significantly
Starting dose: 5 mg once daily (with or without food)
Titration protocol: Dose adjustments every 12 weeks based on LVOT gradient reduction, symptom response, and LVEF. Maximum approved dose: 10 mg daily
LVEF monitoring requirement: Must assess LVEF at baseline and before each dose escalation. LVEF must remain ≥50% to continue therapy
Discontinuation criteria: If LVEF declines to <50%, mavacamten must be stopped; may restart at lower doses if EF subsequently recovers
Clinical efficacy: EXPLORER-HCM trial: ~90% achieved ≥10 mmHg gradient reduction; ~60% became asymptomatic on monotherapy; median LVOT gradient reduction ~35-45 mmHg
Aficamten & Other Myosin Inhibitors
Aficamten is a second-generation cardiac myosin inhibitor in clinical development. Class 2b May be considered as alternative to mavacamten in eligible patients pending broader clinical experience and regulatory approval.
Monitoring & Safety
Parameter
Baseline
Dose Titration (Q12w)
Ongoing
LVEF assessment
Required (echo or CMR)
Before each dose increase
Every 6-12 months
LVOT gradient
Required (echo)
Assess response
Annually with symptoms
Clinical symptoms
Baseline
At each visit
Regular follow-up q3-6 mo initially
Pearl: Myosin inhibitors are now preferred over high-dose disopyramide for drug-refractory obstructive HCM due to better tolerability profile (disopyramide has anticholinergic side effects). If LVEF declines but improves on lower therapy, mavacamten can be cautiously restarted at reduced doses.
Septal Reduction Therapy (SRT)
Surgical Myectomy
Class I SRT is recommended in symptomatic patients with obstructive HCM who remain symptomatic despite guideline-directed medical therapy (GDMT). SRT should be performed at experienced HCM centers.
Transaortic extended septal myectomy (ESM): Gold standard for broad LV obstruction; 1-3% mortality in experienced centers
Outcomes: >90% success rate; symptom relief in ~85% of obstructive patients
Concomitant procedures: Mitral valve repair/replacement if intrinsic MV disease; coronary angiography to exclude CAD
Alcohol Septal Ablation (ASA)
Less effective than myectomy but acceptable alternative for select patients with high operative risk or comorbidities.
Mortality ~1%; significant recidivism and need for repeat procedures
Consider when myectomy contraindicated or risk unacceptable to patient
AF Management in HCM
Class I In patients with HCM and clinical AF, anticoagulation is recommended with direct-acting oral anticoagulants (DOACs) as first option and vitamin K antagonists as second-line, independent of CHA₂DS₂-VASc score.
Anticoagulation Key Points:
DOACs preferred over warfarin in HCM with AF (better efficacy, lower bleeding)
Anticoagulation regardless of CHA₂DS₂-VASc ≥2 or any CHA₂DS₂-VASc risk
Device-detected AF (subclinical) requires anticoagulation if episode >24 hours
Rate vs Rhythm Control
Class I For AF with rapid ventricular response, rate control with beta-blockers, verapamil, or diltiazem is recommended. Class 2a Rhythm control strategy may be beneficial in selected patients.
Catheter Ablation for AF
Class 2a Catheter ablation for AF is reasonable when drug therapy is ineffective or patient preference. Success rates lower than general AF population; repeat procedures often needed.
Nonobstructive HCM with Preserved EF
Nonobstructive HCM affects approximately 30-35% of symptomatic patients. Management focuses on symptom relief, SCD prevention, and prevention of AF complications.
Pharmacologic Management
Class I Beta-blockers or nondihydropyridine calcium channel blockers are recommended for symptom management in nonobstructive HCM. Class 2a Low-dose diuretics may be added for symptomatic volume overload.
Key Strategies:
Avoid positive inotropic agents and excessive vasodilation
Use diuretics cautiously; overly aggressive diuresis worsens diastolic dysfunction
Consider myosin inhibitors in pathogenic variant carriers with mild phenotype
Monitor for AF development; anticoagulate if AF occurs
Class 2b In younger pathogenic variant carriers (age ≤45 years) with mild or absent phenotype, valsartan may be beneficial to slow adverse cardiac remodeling (preliminary data from clinical trials). Class I Serial clinical assessment (ECG, echo every 1-2 years in children, 3-5 years in adults) is recommended.
HCM with Advanced Heart Failure
HCM progression to "burned-out" HCM (LVEF <50%) occurs in 5-10% of patients. Management shifts to HFrEF paradigm with both similarities and unique considerations versus dilated cardiomyopathy.
GDMT for HF with Reduced EF
Class I GDMT per current HF guidelines is recommended (ACE-I/ARB/ARNI, beta-blocker, MRA). Class I Diagnostic testing for other causes of reduced EF is recommended (CAD, myocarditis, valvular disease).
HFrEF Management Principles:
GDMT Optimization: Titrate ACE-I/ARB to target dose; beta-blockers reduce mortality in HFrEF
Aldosterone antagonists: Spironolactone or eplerenone reduce mortality in HFrEF
ARNI (sacubitril/valsartan): Consider in patients intolerant of ACE-I/ARB or as alternative
SGLT2 inhibitors: Now emerging as beneficial class in HFrEF for symptom and hospitalization reduction
Special Considerations in HCM-Derived HFrEF
Discontinue myosin inhibitors: If LVEF <50%, stop mavacamten and reassess at lower doses only if EF recovers
CRT consideration:Class 2a In patients with HCM, LVEF <35%, and QRS ≥120 ms despite GDMT, CRT may be considered for symptomatic HF
Heart transplant/LVAD: Refer for advanced therapies if GDMT fails and EF severely reduced; post-transplant survival in HCM comparable to other cardiomyopathies
ICD therapy: Continues to be indicated for SCD prevention even with reduced EF
Pearl: HCM patients with "burned-out" phenotype show excellent response to GDMT. Reassessment at intervals may reveal LVEF improvement, in which case myosin inhibitors can be restarted at lower doses.
Exercise & Competitive Sports
Recreational Exercise
Class I Mild- to moderate-intensity recreational exercise is beneficial for cardiorespiratory fitness and overall health in patients with HCM.
Competitive Sports
Class I For athletes with HCM, comprehensive evaluation and shared decision-making with an expert is recommended before return to play.
Risk Stratification for Competitive Sports:
Prior cardiac arrest, sustained VT → restrict from competitive sports
Single SCD risk factor → shared decision-making; annual reevaluation recommended
Genotype-positive, phenotype-negative → reasonable for any intensity without restriction
Pitfall: ICD placement for primary prevention is NOT an indication for competitive sports restriction alone. Underlying SCD risk determines sports eligibility, independent of ICD.
Pregnancy is generally well-tolerated in HCM with low maternal mortality (<1%). Multidisciplinary coordination (cardiology + maternal-fetal medicine) is essential.
Anticoagulation in Pregnancy
Class I In pregnant women with HCM and AF or other indication for anticoagulation, low-molecular-weight heparin or vitamin K antagonist (at maximum therapeutic dose ≤5 mg daily) is recommended for stroke prevention.
Beta-Blockers in Pregnancy
Class I Selected beta-blockers are safe for symptom management; metoprolol and propranolol have the most data. Class I Vaginal delivery is recommended as first-choice delivery method.
Mavacamten Contraindicated
Class 3: Harm Mavacamten is contraindicated in pregnancy due to potential teratogenic effects (animal data). Discontinue before conception.
Shared Decision-Making
Class 2a For women with clinically stable HCM wishing to become pregnant, shared discussion of maternal and fetal risks, benefits of GDMT, and initiation of GDMT is reasonable.
Pediatric HCM
Children with HCM differ from adults in risk markers, phenotype onset, and device implications. Pediatric risk stratification requires age-adjusted approaches due to different disease progression patterns.
Pediatric SCD Risk Assessment
Class I Comprehensive, systematic SCD risk assessment at initial evaluation and every 1-2 years is recommended. Class 2a For children <16 years with ≥1 major SCD risk factor, discussion of estimated SCD risk is reasonable for ICD decision-making.
Pediatric SCD Risk Factors:
Family history of SCD (especially in first-degree relatives <50 years)
Personal history of syncope (unexplained, exertional)
Maximal LV wall thickness (adjusted for body surface area; >2.5 SD above mean)
NSVT on ambulatory ECG monitoring
Abnormal BP response to exercise
Extensive LGE on CMR imaging
LV apical aneurysm
Systolic dysfunction (LVEF <50%)
Pediatric ICD Placement
Class 2a ICD placement is reasonable in children with ≥1 major SCD risk factor after comprehensive evaluation and shared decision-making. Consider long-term device complications (lead failure, growth issues, multiple replacements) in pediatric population.
Exercise Recommendations in Children
Class I Exercise stress testing is recommended in all symptomatic children and in asymptomatic children to assess exercise tolerance and detect latent LVOT obstruction.
Genetic Screening in Pediatrics
Class I Genetic testing is recommended in all children with HCM to identify pathogenic variants and facilitate cascade genetic testing in family members. Class I Serial clinical assessment (ECG, echo every 1-2 years) is recommended in GPPN children.
Pearl: Pediatric patients may have disease manifesting later in childhood or adolescence. Genotype-positive relatives should begin screening in childhood and continue at regular intervals even if initially phenotype-negative, as disease penetrance increases with age.
Multidisciplinary HCM Centers
Class I In patients with HCM requiring septal reduction therapy or complex management decisions, consultation with or referral to a comprehensive HCM center is recommended.
Comprehensive vs Primary HCM Centers
Comprehensive HCM Centers Should Provide:
Advanced echocardiography and CMR imaging expertise
Experienced interventional cardiologists for alcohol septal ablation
Cardiac surgeons experienced in septal myectomy
Cardiac geneticists and genetic counselors for family screening
Electrophysiologists for ICD and AF ablation
Heart failure specialists for advanced HF management
SCD risk stratification algorithms and shared decision-making framework
Research infrastructure for participation in clinical trials
Indications for Referral to HCM Center
Complex LVOT obstruction anatomy or severe symptoms despite GDMT
Consideration of septal reduction therapy (myectomy or ablation)
High SCD risk requiring expert shared decision-making
Complex AF management or need for catheter ablation
Systolic dysfunction with advanced HF
Recurrent VT despite ICD therapy
Pregnancy planning or peripartum management
Participation in clinical trials for new therapies
Comorbidities in HCM
Many HCM patients have comorbid conditions (hypertension, obesity, sleep apnea, diabetes) that impact symptom burden, arrhythmia risk, and prognosis. Integrated management is essential.
Hypertension
Class I Lifestyle modifications and medical therapy for hypertension are recommended. Class I In obstructive HCM, beta-blockers and nondihydropyridine calcium channel blockers are preferred; ACE inhibitors/ARBs should be used cautiously (may worsen LVOT gradient in some patients).
Obesity
Class I Counseling and comprehensive lifestyle interventions for weight loss are recommended. Obesity increases symptom burden, LVOT gradient, AF risk, and adverse remodeling, particularly in pathogenic variant carriers.
Sleep Apnea
Class I Assessment for sleep-disordered breathing is recommended. CPAP or other sleep apnea treatment can reduce symptoms and arrhythmia burden in HCM patients.
Diabetes and Metabolic Disease
Class I Adherence to ACC/AHA primary prevention guidelines is recommended in HCM patients with diabetes or other metabolic disease to reduce ASCVD risk. Class 2a SGLT2 inhibitors may be beneficial in HCM patients with diabetes and/or HF.
Pearl: Environmental and behavioral factors (obesity, hypertension, sleep apnea) are modifiable and significantly impact HCM progression. Intensive risk factor modification can reduce SCD risk, reduce AF incidence, and improve functional status.
Septal Reduction Therapy Outcomes
Surgical Myectomy Results
Extended Septal Myectomy (ESM) Outcomes:
Mortality: 1-3% in experienced high-volume centers; higher in low-volume institutions
Conduction abnormalities: Complete heart block occurs in ~1-5% of cases; permanent pacemaker required
Symptom improvement: Variable; ~70% achieve functional improvement but lower success than myectomy
Pitfall: Outcomes strongly depend on operator/center experience and procedural volume. SRT should be performed at comprehensive HCM centers with demonstrated excellence and low complication rates. Patient outcomes are significantly worse at low-volume centers.
Evidence Quality & Level Summary
Class of Recommendation (COR):
Class I Benefit >>> Risk. Recommended (should be performed)
Class 2a Benefit >> Risk. Reasonable (can be useful)
Class 2b Benefit ≥ Risk. May be considered (usefulness/efficacy uncertain)
Class 3 Risk ≥ Benefit. Not recommended (harm or ineffective)
Level of Evidence (LOE):
Level A: Multiple RCTs or meta-analysis of RCTs (high-quality evidence)
Level B-R: Single RCT or meta-analysis of RCTs with limitations (randomized)
Level B-NR: Nonrandomized observational studies or registries (nonrandomized)
Level C-LD: Limited data or nonrandomized/observational studies (limited data)
Note: Many HCM management decisions rely on expert opinion and observational studies due to the rarity of the disease and difficulty conducting large RCTs. Shared decision-making incorporating patient preferences and clinical judgment is essential, particularly for ICD placement and exercise recommendations.
Special Clinical Scenarios
HCM with Concurrent CAD
HCM patients may develop atherosclerotic coronary artery disease (CAD). When both present, management becomes complex due to overlapping mechanisms of ischemia (both LVOT obstruction and CAD-induced).
Class I Coronary angiography (invasive or CTA) is recommended before surgical myectomy to exclude CAD
When concurrent CAD and LVOT obstruction present, aggressive lipid lowering and CAD risk factor management recommended
PCI or CABG may be needed; CABG often preferred when combined with septal myectomy
Beta-blockers provide dual benefit (reduce LVOT gradient and myocardial oxygen demand)
HCM in Hypertensive Patients
Hypertension is common in HCM and worsens diastolic dysfunction and AF risk. Management requires careful drug selection.
Class I Beta-blockers and nondihydropyridine CCBs are preferred antihypertensive agents in obstructive HCM
ACE inhibitors/ARBs should be used cautiously; may worsen LVOT gradient in some patients with dynamic obstruction
Dihydropyridine CCBs and vasodilators contraindicated in obstructive HCM
Aggressive BP control beneficial for symptoms and progression prevention
HCM in Patients with Pacemakers or Other Implanted Devices
Some HCM patients may have prior pacemakers for bradycardia. ICD placement requires device upgrade decisions.
ICD upgrade or replacement recommended for primary SCD prevention in eligible HCM patients with pacemakers
Cardiac resynchronization therapy (CRT) may benefit select HCM patients with advanced HF and QRS prolongation
Device lead management important in HCM due to potential for mechanical obstruction of LVOT
HCM with Severe Mitral Regurgitation
Secondary MR is common in obstructive HCM but resolves with gradient reduction. Primary MV disease requires targeted approach.
Severe secondary MR usually improves significantly after septal reduction therapy
Consider GDMT and gradient reduction before recommending MV intervention
MV repair preferred over replacement when intervention necessary
Primary MV disease (elongated leaflets, chordal abnormalities) may require concomitant repair during myectomy
Clinical Pearls & Key Takeaways
Pearl 1 — Shared Decision-Making is Essential: HCM management increasingly requires patient engagement in decision-making, particularly for ICD placement, exercise/sports participation, invasive procedures, and pregnancy planning. Use validated risk calculators and discuss benefits/risks transparently.
Pearl 2 — Mavacamten Represents a Paradigm Shift: Cardiac myosin inhibitors are now Class I/2a for drug-refractory obstructive HCM, offering an alternative to beta-blockers/CCBs/disopyramide and sometimes avoiding need for invasive SRT. Monitor LVEF carefully (maintain ≥50%).
Pearl 3 — Genetic Testing is Essential but Not Definitive: ~60% of familial HCM has identifiable sarcomere variants; ~40% remain genotype-negative. Absence of identified variant does not exclude HCM or reduce need for family screening. Cascade genetic testing and serial phenotypic surveillance are recommended.
Pearl 4 — Multifactorial Risk Assessment Beats Single Markers: Do not use wall thickness, NSVT, or LGE in isolation for SCD risk stratification. Integrate multiple risk markers (clinical history, echo findings, ECG, CMR) using validated risk calculators for individualized patient risk estimation.
Pearl 5 — AF Requires Anticoagulation Regardless of CHA₂DS₂-VASc: Unlike general population, HCM patients with AF should be anticoagulated regardless of CHA₂DS₂-VASc score. DOACs are preferred; rate control is key goal initially, with rhythm control individualized.
Pearl 6 — Multidisciplinary Referral for Complex Cases: SRT outcomes depend heavily on procedural volume and center expertise. Refer symptomatic HCM patients with LVOT obstruction to experienced HCM centers for optimal outcomes and complications prevention.
Pearl 7 — Pregnancy Generally Safe but Requires Planning: HCM is compatible with pregnancy and vaginal delivery in most women. Avoid mavacamten (teratogenic); use LMWH or warfarin for anticoagulation if indicated; coordinate care between cardiology and OB/GYN.
Pearl 8 — Exercise is NOT Contraindicated in HCM: Mild-to-moderate recreational exercise is beneficial for all HCM patients. Competitive sports require individualized risk assessment; ICD placement for SCD prevention is NOT an indication for sports restriction alone.
Clinical Do's & Don'ts
DO:
Obtain family history (3-generation) in all HCM patients
Perform cascade genetic screening in at-risk relatives
Use beta-blockers or verapamil as first-line agents for obstructive HCM
Consider mavacamten for drug-refractory symptoms (new Class I/2a)
Assess SCD risk systematically at baseline and every 1-2 years
Use shared decision-making for ICD placement (discuss risks, benefits, alternatives)
Anticoagulate AF in HCM regardless of CHA₂DS₂-VASc (Class I DOACs)
Encourage mild-to-moderate recreational exercise
Refer symptomatic patients with LVOT obstruction to experienced HCM centers for SRT
DON'T:
Use ACE inhibitors, ARBs, or dihydropyridine CCBs in obstructive HCM (worsen gradient)
Rely on wall thickness alone for SCD risk stratification
Defer ICD discussion in high-risk patients; use validated risk calculators
Restrict all competitive athletes with HCM universally; individualize decision
Use mavacamten in pregnancy (teratogenic potential)
Delay genetic counseling and family screening
Perform SRT at low-volume centers; outcomes depend on operator/center expertise
Ignore AF in HCM; even subclinical AF (>24 hours) requires anticoagulation
Family Screening & Cascade Testing
Class I First-degree relatives of HCM patients should undergo ECG and 2D echocardiography as part of initial family screening. Class I Genetic testing and cascade screening in at-risk relatives is beneficial for identification and management.
ECG: 12-lead standard ECG for arrhythmias, LVH, T-wave inversions
Echocardiography: 2D echo to assess wall thickness, LVOT, MV, EF
Genetic testing: Recommended in pathogenic variant-identified families for cascade testing
Follow-up Screening Intervals
Population
Status
Recommended Interval
Tests
Pediatric relatives (symptomatic)
Phenotype-positive (HCM diagnosed)
Every 1-2 years
Echo, ECG, stress test if symptoms
Pediatric relatives (asymptomatic)
Phenotype-negative (at-risk)
Every 1-2 years until age 21, then every 3-5 years
Echo, ECG; stress test if genotype+
Adult relatives (symptomatic)
Phenotype-positive
Every 1-2 years or sooner if changes
Echo, ECG, stress test, CMR if indicated
Adult relatives (asymptomatic)
Phenotype-negative, genotype-positive
Every 3-5 years
Echo, ECG; CMR if risk factors develop
Genotype-positive, phenotype-negative
No HCM features on imaging
Every 3-5 years; more frequent if variant known to cause early onset
Echo, ECG, stress test in athletes
Pearl: Approximately 10-30% of GPPN relatives will develop phenotypic HCM over 5 years. Close surveillance is essential, particularly in younger relatives and those with high-penetrance variants. Stress testing can unmask latent obstruction in GPPN relatives.
Research & Evidence Gaps
While the 2024 HCM guidelines represent significant advances, several areas require further investigation to refine management approaches.
Key Research Priorities
Areas Identified for Future Study:
Myosin inhibitors: Long-term safety/efficacy of mavacamten and aficamten; optimal dosing strategies; impact on progression to HFrEF; use in nonobstructive HCM
SCD risk stratification: Refinement of pediatric risk models; genetic modifiers of risk; novel CMR metrics (texture analysis, T1 mapping)
AF in HCM: Better prediction of AF development; optimal rate vs rhythm control strategy; efficacy and safety of newer antiarrhythmic agents
Exercise in HCM: Role of exercise training in symptom reduction and outcome prevention; interaction with genetic/structural markers
Nonobstructive HCM: Disease mechanisms and management approaches; role of novel therapies in preventing progression
Gene therapy: Potential for correcting pathogenic variants or modulating disease progression
Advanced HF management: Optimal GDMT strategies for burned-out HCM; timing and patient selection for advanced therapies
Ongoing Clinical Trials
Multiple trials are currently enrolling HCM patients to evaluate myosin inhibitors, gene therapy, and other novel interventions. Referral to HCM centers with research infrastructure can identify appropriate trial participation opportunities.
Clinical Calculators
Use these validated tools to support shared decision-making and risk stratification.