Hypertrophic Cardiomyopathy (HCM) Guideline-Based Practical Review
Evidence-based update for physicians, cardiology trainees, and electrophysiologists
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What is Hypertrophic Cardiomyopathy?
Hypertrophic cardiomyopathy (HCM) is the most common inherited cardiomyopathy, affecting approximately 1 in 500 individuals. It is characterized by otherwise unexplained left ventricular hypertrophy, most commonly due to pathogenic sarcomeric gene mutations.
The 2024 AHA/ACC Multisociety Guideline emphasizes early diagnosis, multidisciplinary care, genetic evaluation, shared decision-making, and individualized treatment rather than universal restrictions.
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Diagnostic Criteria
Diagnosis is established when:
LV wall thickness ≥15 mm in adults without another cause of hypertrophy
Wall thickness 13–14 mm may be diagnostic in first-degree relatives or genotype-positive individuals
Exclude secondary causes such as:
Hypertension
Aortic stenosis
Athlete's heart
Cardiac amyloidosis
Fabry disease
Danon disease
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Initial Evaluation
Every patient with suspected HCM should undergo:
Detailed medical history
Three-generation family history
Physical examination
12-lead ECG
Transthoracic echocardiography
Cardiac MRI when needed
Ambulatory ECG monitoring
Genetic counseling
Repeat echocardiography every 1–2 years or earlier if symptoms change.
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Role of Echocardiography
Assess:
Maximum LV wall thickness
LVOT obstruction
Mitral valve abnormalities
Systolic anterior motion (SAM)
Diastolic function
Left atrial size
LV systolic function
If resting LVOT gradient is <50 mmHg:
Perform Valsalva maneuver
Exercise stress echocardiography if obstruction remains absent
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Role of Cardiac MRI
CMR is recommended when:
Echocardiography is inconclusive
Better definition of hypertrophy pattern is required
Apical HCM is suspected
Planning septal reduction therapy
Assessing myocardial fibrosis (late gadolinium enhancement)
Sudden cardiac death (SCD) risk assessment
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Ambulatory ECG Monitoring
Recommended for:
Initial evaluation
Every 1–2 years
Symptomatic palpitations
Screening for atrial fibrillation
Detection of nonsustained VT
Extended monitoring is advised in patients at higher risk for atrial fibrillation.
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Genetic Testing
Recommended for:
Confirmed HCM patients
Family screening
Identification of phenocopies
If a pathogenic mutation is identified:
Offer cascade testing to first-degree relatives.
Genotype-positive, phenotype-negative individuals require periodic surveillance but generally do not need prophylactic ICD implantation solely because of genotype.
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Family Screening
Children
Echocardiography every 1–2 years
Adults
Echocardiography every 3–5 years
Earlier evaluation is warranted if symptoms develop.
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Pharmacologic Treatment of Obstructive HCM
First-line
Non-vasodilating beta-blockers
Examples:
Metoprolol
Atenolol
Bisoprolol
Nadolol
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If beta-blockers are ineffective or not tolerated
Use non-dihydropyridine calcium channel blockers:
Verapamil
Diltiazem
Avoid verapamil in patients with:
Hypotension
Resting LVOT gradient >100 mmHg
Severe heart failure symptoms
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Persistent Symptoms
Options include:
Cardiac myosin inhibitor (e.g., Mavacamten)
Disopyramide (with AV nodal blocker)
Septal reduction therapy
Routine combination of beta-blocker plus verapamil/diltiazem is not supported.
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Septal Reduction Therapy
Indications:
Severe symptoms despite optimal medical therapy
Significant LVOT obstruction (typically ≥50 mmHg)
Options:
Surgical Septal Myectomy
Preferred when:
Additional cardiac surgery is required
Younger patients
Mitral valve abnormalities
Alcohol Septal Ablation
Suitable for:
High surgical-risk patients
Patients unsuitable for surgery
Both procedures should be performed at experienced HCM centers.
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Sudden Cardiac Death Risk Stratification
Assess every 1–2 years.
Major risk markers include:
Previous cardiac arrest
Sustained ventricular tachycardia
Arrhythmogenic syncope
Family history of premature SCD
Massive LV hypertrophy
LV apical aneurysm
Nonsustained VT
Extensive myocardial fibrosis (CMR)
Reduced LVEF (<50%)
Patients with prior sustained VT or cardiac arrest should receive an ICD.
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Atrial Fibrillation
All HCM patients with:
Clinical AF
Or subclinical AF lasting >24 hours
Should receive lifelong anticoagulation regardless of CHA₂DS₂-VASc score.
Preferred:
DOACs
Alternative:
Warfarin
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Heart Failure in HCM
Patients with LVEF <50% should receive standard guideline-directed therapy for heart failure with reduced ejection fraction.
If receiving mavacamten, discontinue the drug if systolic dysfunction develops.
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Exercise Recommendations
A major change in the 2024 guideline:
Mild-to-moderate recreational exercise is encouraged.
Universal restriction from exercise is no longer recommended.
Competitive sports may be considered after individualized assessment and shared decision-making.
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Pregnancy
Recommendations include:
Continue beta-blockers when indicated with maternal and fetal monitoring.
Vaginal delivery is generally preferred.
Mavacamten is contraindicated because of teratogenicity.
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Key Guideline Pearls
HCM is a genetic disease requiring family evaluation.
Echocardiography remains the cornerstone of diagnosis.
Cardiac MRI improves diagnosis and SCD risk assessment.
Beta-blockers remain first-line therapy for obstructive HCM.
Cardiac myosin inhibitors are now guideline-recommended for persistent symptomatic obstructive HCM.
Septal reduction therapy should be performed only at experienced HCM centers.
Anticoagulate all HCM patients with AF regardless of CHA₂DS₂-VA
Sc score.
Encourage regular recreational exercise instead of blanket activity restriction.
Reassess SCD risk every 1–2 years.
Shared decision-making is central to modern HCM care.
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References
1. 2024 AHA/ACC/AMSSM/HRS/PACES/SCMR Guideline for the Management of Hypertrophic Cardiomyopathy.
2. ACC Guideline-at-a-Glance: 2024 Hypertrophic Cardiomyopathy Guideline.
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