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The changing base line of complex ventricular arrhythmias. A new consideration in assessing long-term antiarrhythmic
Insights
Ventricular arrhythmia frequency can spontaneously decrease over time, even without treatment. This natural variability may falsely suggest treatment success, impacting clinical trial accuracy and patient care.
Area of Science:
- Cardiology
- Clinical Electrophysiology
Background:
- Baseline electrocardiograms (ECGs) are standard for assessing antiarrhythmic drug efficacy.
- This method assumes stable arrhythmia frequency without intervention.
Purpose of the Study:
- To evaluate the assumption of constant arrhythmia frequency over time in stable patients.
- To determine the impact of spontaneous variability on treatment efficacy assessment.
Main Methods:
- Studied 26 patients with symptomatic, non-life-threatening ventricular arrhythmias.
- Compared arrhythmia frequency during two placebo treatment periods separated by 17 months.
Main Results:
- Significant reductions observed in the second placebo period: ventricular premature depolarizations (50%), pairs (65%), and ventricular tachycardia (83%).
- Over one-third of patients appeared to respond to therapy during placebo, considering spontaneous variability.
Conclusions:
- Long-term spontaneous changes in arrhythmia frequency can mislead efficacy assessments.
- Annual reassessment of arrhythmia frequency during placebo is recommended for similar patients.
- This recommendation excludes patients with life-threatening ventricular arrhythmias.
Abstract:
Initial base-line electrocardiograms are used to assess the efficacy of treatment for ventricular arrhythmias. This approach assumes that in the absence of treatment the frequency of arrhythmia would remain constant. To test the validity of this assumption, we studied 26 clinically stable patients with symptomatic but not life-threatening ventricular arrhythmias, during two periods of placebo treatment separated by a mean of 17 months. As compared with the initial placebo period, there were significant reductions in ventricular premature depolarizations (50 per cent), pairs (65 per cent), and ventricular tachycardia (83 per cent) during the second period of placebo administration (P less than or equal to 0.05 for all comparisons). Over one third of the patients gave the appearance of receiving successful therapy during the second placebo period, even when the reported spontaneous variability of ventricular arrhythmia was taken into consideration. If unrecognized, these long-term spontaneous changes in the frequency of arrhythmia could result in continuation of unnecessary and potentially toxic therapy and lead to incorrect conclusions regarding the efficacy of antiarrhythmic drugs in clinical trials. We therefore recommend that the frequency of arrhythmia be reassessed annually in the absence of treatment in patients similar to those in our study. These recommendations should not be applied to patients with life-threatening ventricular arrhythmias.