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July 1, 1989Circulation

Electropharmacology of amiodarone therapy initiation. Time courses of onset of electrophysiologic and antiarrhythmic effects.

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Why the study?

What is the time course of onset of electrophysiologic and antiarrhythmic effects of amiodarone in patients with inducible ventricular tachycardia?

Population

34 patients with inducible ventricular tachycardia

Comparison

Amiodarone oral loading dosage vs Baseline (pre-treatment)

Design

Cohort

Follow-up

Up to 20 weeks

Authors

LML. Brent MitchellWinnipeg Regional Health AuthorityDWD. George WyseElectrophysiologyAGAnne M. GillisElectrophysiology

Discussion

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Implication

Differential onset may inform loading duration before VT reassessment; leaves open optimal timing in prospective trials.

Key Points

  • This research aims to determine the time courses of onset for electrophysiologic and antiarrhythmic effects of amiodarone in patients with ventricular tachycardia.
  • 34 patients were enrolled and received a standardized oral loading dosage of amiodarone over a specified period.
  • Electrophysiologic studies were performed serially at various time points: baseline, 2 weeks, 6 weeks, 10 weeks, and 20 weeks.
  • Changes in atrial, sinus, and atrioventricular nodal properties were monitored along with conduction intervals.
  • Atrioventricular nodal properties showed maximal changes within 2 weeks, with significant increases in cycle length (from 369 +/- 80 msec to 498 +/- 78 msec, p < 0.001).
  • Ventricular Class III effects reached peak after 10 weeks, with the QT interval increasing from 355 +/- 36 msec at baseline to 436 +/- 45 msec at 10 weeks (p < 0.001).
  • Suppression of ventricular tachycardia rate was not maximized until 10 weeks, unlike suppression of ventricular premature beats which peaked at 2 weeks.

Structured PICO

What is the time course of onset of electrophysiologic and antiarrhythmic effects of amiodarone in patients with inducible ventricular tachycardia?

P
Population
34 patients with inducible ventricular tachycardia
I
Intervention
Amiodarone oral loading dosage (1,200 mg/day for 14 days; 800 mg/day for 7 days; and 400 mg/day thereafter)
C
Comparator
Baseline (pre-treatment)
O
Outcome
Time courses of onset of electrophysiologic and antiarrhythmic effects (changes in atrial, sinus, and atrioventricular nodal properties, conduction intervals, and ventricular tachycardia inducibility)surrogate

Amiodarone exhibits a differential time course of electrophysiologic effects, with atrial and AV nodal effects peaking at 2 weeks, while maximal ventricular Class III and antiarrhythmic effects against VT require up to 10 weeks of loading.

Cite This Study

Mitchell et al. (1989) studied this question.

synapsesocial.com/papers/6a1bd121ea84844e355f0529https://doi.org/10.1161/01.cir.80.1.34
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Also Consider

Synapse has enriched 3 closely related papers on similar clinical questions. Consider them for comparative context:

  1. 1Relation between amiodarone and desethylamiodarone plasma concentrations and electrophysiologic effects, efficacy and toxicity1987 · 52 citations
  2. 2Class 3 antiarrhythmic action in man. Observations from monophasic action potential recordings and amiodarone treatment.1973 · 92 citations
  3. 3A Randomized Clinical Trial of the Noninvasive and Invasive Approaches to Drug Therapy of Ventricular Tachycardia1987 · 189 citations