Abnormal QT interval variability in patients with hypertrophic cardiomyopathy: can syncope be predicted?

Area of Science:

• Cardiology
• Electrophysiology
• Medical Science

Background:

• Hypertrophic cardiomyopathy (HCM) is a genetic heart condition.
• Syncope is a common and serious symptom in HCM patients.
• Altered cardiac repolarization is a potential mechanism for syncope in HCM.

Purpose of the Study:

• To investigate QT interval variability patterns in HCM patients.
• To determine the relationship between QT variability and syncope risk in HCM.
• To explore differences in QT variability between waking and sleeping hours.

Main Methods:

• 24-hour Holter monitoring was used to assess QT interval variability.
• Participants included 10 HCM patients with syncope, 10 HCM patients without syncope, and 10 healthy controls.
• Time-domain and frequency-domain analyses of QT variability were performed.

Main Results:

• QT variability was significantly higher in HCM patients compared to healthy controls.
• HCM patients with a history of syncope exhibited the highest QT variability.
• QT variability did not show diurnal variation in HCM patients, unlike in controls.
• Increased QT Standard Deviation of the Average of Normal to Normal-to-Normal intervals (SDANN) accurately identified HCM patients with syncope (75% accuracy).

Conclusions:

• QT variability is abnormal in patients with HCM.
• Altered cardiac repolarization control, indicated by increased QT variability, may contribute to arrhythmia-related syncope in HCM.
• QT variability metrics, such as SDANN, may serve as potential biomarkers for syncope risk stratification in HCM.