What are the ECG findings and management options for a patient with Hypertrophic Obstructive Cardiomyopathy (HOCM)?

ECG Findings and Management in Hypertrophic Obstructive Cardiomyopathy (HOCM)

The 12-lead ECG is abnormal in 75-95% of patients with HOCM, showing characteristic findings including left ventricular hypertrophy, repolarization abnormalities, abnormal Q waves, and ST-T wave changes that are essential for diagnosis and risk stratification. 1, 2

ECG Diagnostic Findings in HOCM

Common ECG Abnormalities

• Left ventricular hypertrophy (LVH) - present in most patients
• Repolarization abnormalities - ST-segment depression and T-wave inversions, particularly in lateral and inferior leads
• Abnormal Q waves - especially in inferolateral and anterior leads
• Left atrial enlargement - indicating increased risk of atrial fibrillation
• Conduction disturbances - including bundle branch blocks

Key Diagnostic Features

• Pathological Q waves ≥40 ms in duration and/or ≥25% of the R wave in depth and/or ≥3 mm in depth in at least two contiguous leads 2
• Marked repolarization abnormalities help distinguish HOCM from hypertensive heart disease
• Q waves in V1-V4 are associated with areas of myocardial fibrosis and asymmetrical distribution of LVH 2

Limitations

• ECG abnormalities do not reliably correlate with severity or pattern of hypertrophy 1
• 5-25% of patients may have normal ECGs, which does not exclude HOCM 2
• ECG voltage criteria alone have limited sensitivity and specificity 2

Management Algorithm for HOCM

Initial Evaluation

1. 12-lead ECG - recommended in initial evaluation and periodic follow-up every 1-2 years 1
2. 24-48 hour ambulatory ECG monitoring - recommended in initial evaluation and follow-up every 1-2 years to identify risk for SCD 1
3. Extended monitoring (>24 hours) - for patients with palpitations or lightheadedness 1

Risk Stratification

1. Identify risk factors for sudden cardiac death (SCD):

   • Non-sustained ventricular tachycardia (NSVT) on ambulatory monitoring 1
   • Family history of SCD
   • Unexplained syncope
   • Massive LVH (≥30 mm)
   • Abnormal blood pressure response to exercise
   • LV apical aneurysm
   • Extensive LGE on CMR

2. Identify risk factors for atrial fibrillation:

   • Left atrial dilatation
   • Advanced age
   • NYHA class III-IV heart failure 1

Management Based on ECG Findings

For Patients with NSVT on Monitoring

• Risk stratification for SCD
• Consider ICD implantation if high risk 1
• Serial ambulatory ECG monitoring every 1-2 years for patients without ICDs 1

For Patients with Risk Factors for Atrial Fibrillation

• Extended ambulatory monitoring to screen for AF 1
• Anticoagulation if AF detected to prevent stroke 3
• More frequent assessment for patients with left atrial dilatation, advanced age, and NYHA class III-IV HF 1

For Symptomatic Patients

• Extended monitoring until symptoms occur during monitoring 1
• Consider portable event monitors or implantable monitors for infrequent symptoms 1

Treatment Options

1. First-line therapy for symptomatic patients with LVOT obstruction:

   • Non-vasodilating beta-blockers or non-dihydropyridine calcium channel antagonists 4
   • Mavacamten (myosin inhibitor) - newer option that lowers LVOT gradient and improves quality of life 4

2. Septal reduction therapy if drug therapy fails:

   • Surgical myectomy - procedure of choice with <1% mortality at experienced centers 5
   • Alcohol septal ablation - alternative for high-risk surgical patients

3. ICD implantation for high-risk patients 1

4. Anticoagulation for patients with atrial fibrillation 3

Important Considerations and Pitfalls

• ECG abnormalities may be the only manifestation of disease at an early stage 6
• Ethnicity affects ECG patterns, with black patients having more pronounced voltage criteria 2
• Specific electrical anomalies may help differentiate HOCM from phenocopies such as cardiac amyloidosis 6
• Recurrent obstruction after successful myectomy is rare 5
• Extended monitoring is crucial as asymptomatic AF is present in up to 50% of patients 2

Family Screening

• 12-lead ECG is recommended as a component of screening for first-degree relatives of patients with HOCM 1
• Consider genetic testing as HOCM is often inherited in an autosomal dominant pattern 2

By following this comprehensive approach to ECG interpretation and management in HOCM, clinicians can effectively diagnose, risk stratify, and treat patients to reduce morbidity and mortality associated with this condition.