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Further observations on the electrophysiologic effects of oral amiodarone therapy
Insights
Amiodarone can cause reversible heart block in the His bundle, even without pre-existing conduction issues. Discontinuing the drug resolved the block, highlighting the need for caution with long-term amiodarone use.
Area of Science:
- Cardiology
- Electrophysiology
- Pharmacology
Background:
- Amiodarone is a widely used antiarrhythmic drug.
- Intraventricular conduction abnormalities can be a side effect of amiodarone.
- The potential for amiodarone to induce conduction delays in patients without pre-existing defects is less understood.
Observation:
- A case study involving a patient treated with amiodarone for atrial tachycardia.
- The patient developed a reversible intra-Hisian block.
- His bundle recordings revealed prolonged BH and HV intervals during amiodarone therapy.
Findings:
- Amiodarone treatment led to intermittent exit block and significantly prolonged His bundle (BH) and ventriculo-Hisian (HV) intervals.
- Discontinuation of amiodarone resulted in resolution of the intra-Hisian block and normalization of electrophysiological parameters.
- Electrophysiology normalized, showing atrial flutter without intra-Hisian or infra-Hisian delay.
Implications:
- Amiodarone necessitates cautious long-term oral use, even in patients lacking overt intraventricular conduction defects.
- Clinicians should monitor for potential cardiac conduction abnormalities during amiodarone therapy.
- This case underscores the importance of considering drug-induced effects on cardiac electrophysiology.
Abstract:
A case is presented of a reversible intra-Hisian block occurring under amiodarone treatment for atrial tachycardia in a patient without clear intraventricular conduction abnormalities. His bundle recordings showed an atrial tachycardia with intermittent exit block and greatly prolonged BH and HV intervals (40 and 100 msec, respectively). Thirty days after amiodarone discontinuation, His bundle electrograms showed atrial flutter without intra-Hisian or infra-Hisian delay. Amiodarone should be used with caution during long-term oral therapy in patients with or without clear intraventricular conduction defects.