Class 1 antiarrhythmic drugs--characteristic electrocardiographic differences when assessed by atrial and ventricular...

Area of Science:

• Cardiology
• Pharmacology
• Electrophysiology

Background:

• Class 1 antiarrhythmic drugs are categorized into subgroups 1a, 1b, and 1c based on their impact on action potential duration.
• Understanding the surface electrocardiogram (ECG) effects of these drug classes is crucial for clinical application.

Purpose of the Study:

• To investigate and differentiate the specific electrocardiographic effects of representative drugs from Class 1a, 1b, and 1c antiarrhythmic subgroups.
• To determine if characteristic ECG changes support the established classification of these antiarrhythmic agents.

Main Methods:

• Nine patients underwent electrocardiographic recordings during both sinus rhythm and controlled atrial/ventricular pacing.
• The effects of Disopyramide (1a), Lignocaine (1b), and Flecainide (1c) on QT interval, QRS duration, and JT interval were analyzed.

Main Results:

• Disopyramide (1a) significantly prolonged the QT interval by increasing both QRS and JT durations.
• Lignocaine (1b) significantly reduced the QT interval by decreasing the JT interval, with no effect on QRS duration.
• Flecainide (1c) prolonged QRS duration but not QTc during sinus rhythm; however, it prolonged the QT interval at paced rates due to increased QRS duration, without affecting the JT interval.

Conclusions:

• Distinct electrocardiographic alterations produced by Disopyramide, Lignocaine, and Flecainide support their classification into Class 1a, 1b, and 1c antiarrhythmic subgroups.
• These characteristic ECG findings are valuable for differentiating between Class 1 antiarrhythmic drug subclasses.