Fibrosis and wall thickness affect ventricular repolarization dynamics in hypertrophic cardiomyopathy

Area of Science:

• Cardiology
• Electrophysiology
• Genetics

Background:

• Hypertrophic cardiomyopathy (HCM) is linked to ventricular repolarization abnormalities and arrhythmia risk.
• Understanding the relationship between HCM phenotype and repolarization dynamics is crucial for risk stratification.

Purpose of the Study:

• To investigate the association between hypertrophic cardiomyopathy (HCM) phenotype and ventricular repolarization dynamics.
• To determine how hypertrophy and fibrosis influence repolarization parameters in HCM patients.

Main Methods:

• 24-hour ambulatory ECG recordings were performed on HCM patients (n=46) with specific mutations and control subjects (n=35).
• Key repolarization parameters including rate-adapted QT (QTe), maximal QT, T-wave apex to wave end (TPE) intervals, and QTe/RR slope were measured.
• Findings were correlated with echocardiographic and cardiac magnetic resonance imaging (CMRI) data, including late gadolinium enhancement (LGE).

Main Results:

• Rate-adapted QTe intervals were longer in HCM patients with slower heart rates compared to controls.
• Increased myocardial hypertrophy correlated with longer QTe values.
• HCM patients with significant hypertrophy (wall thickness > 20.6 mm) and LGE exhibited prolonged QTe, TPE intervals, and steeper QTe/RR slopes compared to controls and those with milder hypertrophy.
• Late gadolinium enhancement (LGE) on CMRI was identified as an independent predictor of QTe/RR slope.

Conclusions:

• Ventricular repolarization dynamics in HCM are significantly influenced by the degree of myocardial hypertrophy and the presence of fibrosis.
• Late gadolinium enhancement (LGE) plays an independent role in altering QT dynamics, potentially contributing to an increased arrhythmogenic substrate in hypertrophic cardiomyopathy.