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August 1, 1972CirculationOpen Access

Coronary Artery Occlusion in the Conscious Dog

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Why the study?

Do alterations in heart rate and blood pressure affect the degree of ischemic injury during acute coronary occlusion in conscious dogs?

Population

Closed-chest conscious dogs with a balloon cuff previously implanted around the left anterior descending…

Comparison

Alterations in heart rate and blood pressure… vs Control levels of heart rate and blood pressure…

Design

Preclinical

Follow-up

15-minute periods

Authors

DRDavid R. RedwoodESEldon R. SmithSEStephen E. Epstein

Discussion

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Overview

Caution against rate or pressure interventions in human ischemia; extends preclinical data but leaves open clinical translation.

Key Points

  • The study aims to evaluate the effects of heart rate and blood pressure on ischemic injury during acute myocardial infarction.
  • Occlusion of the left anterior descending coronary artery for 15 minutes using an inflatable balloon cuff in conscious dogs.
  • Heart rate was modified using atropine, pacing, and vagus nerve stimulation, while hypotension was induced by venesection.
  • Myocardial ischemia was assessed by measuring S-T elevation from 12 electrodes.
  • There was a positive correlation between heart rate increase and S-T elevation with r = 0.93, P < 0.01.
  • S-T elevation reached 68 mv under hypotension and bradycardia after 15 minutes of ischemia.
  • Increasing heart rate during hypotension resulted in greater S-T elevation (mean difference 29 mv, P < 0.05).

Structured PICO

Do alterations in heart rate and blood pressure affect the degree of ischemic injury during acute coronary occlusion in conscious dogs?

P
Population
Closed-chest conscious dogs with a balloon cuff previously implanted around the left anterior descending coronary artery
I
Intervention
Alterations in heart rate (increased by atropine or pacing, decreased by vagal stimulation) and blood pressure (hypotension via venesection) during 15-minute LAD occlusion
C
Comparator
Control levels of heart rate and blood pressure during ischemia
O
Outcome
Degree of myocardial ischemia estimated by summating S-T elevation recorded from 12 myocardial electrodessurrogate

In a canine model of acute myocardial ischemia, increases in heart rate exacerbate ischemic injury, while bradycardia reduces it, suggesting tachycardia is deleterious to the ischemic myocardium.

Limitations

  • Unclear if hemorrhagic hypotension effects are analogous to hypotension accompanying bradycardia in human acute myocardial infarction

Cite This Study

Redwood et al. (1972) studied this question.

synapsesocial.com/papers/6a20a20c2ad198cbe7f373b5https://doi.org/10.1161/01.cir.46.2.323
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