From the Guidelines
The typical ECG findings in patients with hypertrophic cardiomyopathy (HCM) include left ventricular hypertrophy with increased QRS voltage, deep Q waves in the inferior and lateral leads, ST segment and T wave abnormalities, and conduction abnormalities such as left axis deviation and left bundle branch block, as noted in the 2024 AHA/ACC/AMSSM/HRS/PACES/SCMR guideline for the management of hypertrophic cardiomyopathy 1.
ECG Findings in HCM
The ECG is abnormal in 75% to 95% of patients with phenotypic HCM, including evidence for left ventricular hypertrophy (LVH) and repolarization changes, although these abnormalities do not reliably correlate with the severity or pattern of hypertrophy 1.
- Left ventricular hypertrophy is often evident with increased QRS voltage, particularly in the precordial leads.
- Deep Q waves in the inferior (II, III, aVF) and lateral (I, aVL, V5-V6) leads are common, reflecting the abnormal septal depolarization pattern.
- ST segment and T wave abnormalities, including ST depression and T wave inversions, are frequently observed, especially in the lateral leads.
- Left atrial enlargement may be indicated by a prolonged, notched P wave in lead II or a biphasic P wave in V1.
- Conduction abnormalities such as left axis deviation and left bundle branch block can occur.
- Some patients may exhibit signs of ventricular pre-excitation patterns.
Importance of ECG in HCM Diagnosis and Management
The 12-lead ECG is a crucial tool in the initial evaluation and periodic follow-up of patients with HCM, providing valuable information about LVH, repolarization abnormalities, arrhythmias, and conduction abnormalities 1.
- Ambulatory electrocardiographic monitoring is necessary for the evaluation of sudden cardiac death (SCD) risk and for guiding the management of arrhythmias.
- Extended monitoring may be useful for determining the cause of symptoms or diagnosing atrial fibrillation (AF), especially in patients with additional risk factors such as left atrial dilation, advanced age, and New York Heart Association (NYHA) class III to IV heart failure 1.
Clinical Implications
It is essential to note that approximately 5-10% of HCM patients may have a normal ECG, so the absence of these findings does not exclude the diagnosis, particularly in early or localized disease 1.
- Clinical correlation of symptoms with ECG findings is crucial, especially in patients with infrequent symptoms, where portable event monitors or implantable monitors may be warranted.
- The ECG findings should be interpreted in the context of the patient's clinical presentation, family history, and other diagnostic tests, such as echocardiography and genetic testing.
From the Research
ECG Findings in Hypertrophic Cardiomyopathy
The typical ECG findings in patients with hypertrophic cardiomyopathy (HCM) include:
- High QRS voltage, depression of the ST segment, and inversion of the T wave, satisfying the diagnostic criteria of left ventricular hypertrophy 2
- Abnormalities in the mid-precordial leads, with the most striking changes in Lead V4 2
- Depolarization and repolarization abnormalities, such as pathological Q waves, fragmented QRS (fQRS), or repolarization abnormalities 3
- Strain pattern, which is an independent predictor of left ventricular mass (LVM) 3
- Romhilt-Estes score, which is the most sensitive ECG criterion for detecting left ventricular hypertrophy (LVH) in HCM patients 3
Relationship between ECG Findings and HCM Phenotype
There is a direct relationship between the severity of ECG abnormalities and the HCM phenotype, with more severe ECG abnormalities associated with:
- Increased left ventricular mass index 4
- Increased prevalence and extent of late gadolinium enhancement (LGE) 4
- Maximum left ventricular thickness ≥ 30 mm 4
Clinical Implications
A normal ECG has a negative predictive accuracy of 96% for markedly increased left ventricular mass and 100% for maximum left ventricular thickness ≥ 30 mm, suggesting that a normal ECG can be effective in ruling out severe left ventricular hypertrophy 4. However, false negative ECG findings remain a challenge in population screenings for HCM 4. The presence of fQRS and strain pattern predicts myocardial fibrosis, while the Cornell index is a negative predictor of myocardial fibrosis 3.