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Decrease in repetitive extrasystole threshold during epinephrine infusion is enhanced in conscious dogs with

J M Pinto1, D A Kirby, B Lown

  • 1Department of Nutrition, Cardiovascular Laboratories, Harvard School of Public Health, Boston, MA 02115.

Physiology & Behavior
|February 1, 1991
PubMed
Summary

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Hypertension increases the risk of dangerous heart rhythms. In hypertensive dogs, low-dose epinephrine significantly worsened electrical instability, suggesting enhanced vulnerability to ventricular arrhythmias.

Area of Science:

  • Cardiovascular Physiology
  • Cardiac Electrophysiology

Background:

  • Hypertension is linked to myocardial hypertrophy and increased adrenergic responsiveness.
  • These factors can predispose individuals to malignant ventricular arrhythmias.

Purpose of the Study:

  • To investigate the effects of subpressor doses of epinephrine on ventricular arrhythmia vulnerability.
  • To compare these effects in normotensive versus hypertensive canine models.

Main Methods:

  • Two groups of dogs (normotensive and hypertensive) were instrumented with aortic catheters and right ventricular pacing catheters.
  • Mean arterial pressure and repetitive extrasystole threshold (ventricular fibrillation vulnerability index) were measured.
  • Subpressor doses of epinephrine (0.15 and 0.3 µg/kg/min) were infused for 30 minutes.

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Main Results:

  • In normotensive dogs, low-dose epinephrine (0.15 µg/kg/min) had no significant effect on hemodynamic parameters or arrhythmia threshold.
  • In hypertensive dogs, the same epinephrine dose significantly increased heart rate by 39% and decreased the repetitive extrasystole threshold by 41%.

Conclusions:

  • Epinephrine infusion enhances myocardial electrophysiological vulnerability in hypertensive animals.
  • Hypertension exacerbates the pro-arrhythmic effects of adrenergic stimulation.