QTc interval measurement in patients with right bundle branch block: A practical method.

Area of Science:

• Cardiology
• Electrophysiology
• Medical Devices

Background:

• Prolonged QT interval in right bundle branch block (RBBB) complicates repolarization time estimation.
• Depolarization changes in RBBB can affect QT interval measurements, posing clinical challenges.

Purpose of the Study:

• To develop a practical formula for eliminating depolarization effects on QT interval in RBBB patients.
• To provide electrophysiologists with a simplified tool for accurate QT interval assessment in RBBB.

Main Methods:

• Prospective study involving patients with accidentally induced RBBB during electrophysiological studies.
• ECG parameters (QRS duration, QT interval, cycle length) were recorded by expert electrophysiologists.
• A novel formula was derived based on QT interval differences and QRS duration proportion.

Main Results:

• The study included 96 patients, with a mean QT interval increase of 34.83 ± 17.61 after RBBB induction.
• The ratio of QT interval change to QRS duration in RBBB was approximately 23%.
• A formula (QT with RBBB - 23% × QRS) was proposed, with a suggested practical adjustment to 25% for ease of use.

Conclusions:

• Existing QT correction formulas are often impractical or not specific for RBBB.
• The newly developed formula offers a rapid and clinically applicable method for QT correction in RBBB.
• This formula aids in predicting corrected QT (QTc) intervals using established methods like Bazzet, Rautaharju, and Hodge.