Spontaneous variability in ventricular ectopic activity during chronic antiarrhythmic therapy

Area of Science:

• Cardiology
• Clinical Electrophysiology

Background:

• Previous studies on ventricular arrhythmia variability relied on recordings without therapy.
• Evaluating variability during effective antiarrhythmic drug treatment is crucial for accurate assessment.

Purpose of the Study:

• To assess the variability in premature ventricular complexes (PVCs) suppression during effective antiarrhythmic drug therapy.
• To determine the confidence limits for spontaneous variability in PVC frequency during treatment.

Main Methods:

• Analyzed ambulatory electrocardiographic recordings from 55 patients with chronic arrhythmias undergoing effective antiarrhythmic therapy.
• Defined effective therapy as ≥70% reduction in total PVCs or ≥90% reduction in repetitive forms.
• Examined variability in suppression across patient subgroups based on age, gender, etiology, cardiac function, and medication.

Main Results:

• Significant variability in PVC suppression was observed, with substantial declines in effectiveness over time.
• Nineteen percent of patients experienced a loss of suppression to below 60% for total PVCs, and 16% had PVC frequency increases above baseline.
• Variability was greater in subgroups with higher PVC frequency, beta-blocker use, and non-coronary artery disease, but clinical loss of suppression was more common in older patients and those with poorer cardiac function.

Conclusions:

• Substantial variability in arrhythmia frequency occurs during effective antiarrhythmic therapy.
• Broad 95% confidence limits for spontaneous variability necessitate careful interpretation of single Holter tests.
• Changes in arrhythmia frequency should be cautiously attributed to treatment failure, especially in specific patient subgroups.