What question did this study set out to answer?

This research aims to investigate the effects of beta-adrenergic receptor stimulation on contractile responses in dogs susceptible to lethal arrhythmias.

October 1, 2001Journal of Applied Physiology

Enhanced in vivo and in vitro contractile responses to β₂-adrenergic receptor stimulation in dogs susceptible to lethal arrhythmias

Q: What is the clinical evidence from this study?

Population: Susceptibility to ventricular fibrillation (n=27). Intervention: Isoproterenol and beta-adrenergic receptor antagonists vs. Resistant dogs / before myocardial infarction. Primary outcome: Velocity of circumferential fiber shortening (Vcf), heart rate response, and single-cell isotonic shortening response.

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Key result

Myocardial infarction provoked an enhanced beta2-adrenergic receptor contractile response in dogs susceptible to ventricular fibrillation, but not in resistant animals.

Why the study?

Does beta-AR stimulation elicit different contractile responses in dogs susceptible vs resistant to lethal arrhythmias before and after myocardial infarction?

Population

Dogs susceptible or resistant to ventricular fibrillation induced by a 2-min coronary occlusion during the…

Comparison

Isoproterenol with or without beta1-AR… vs Baseline vs after infarction; Susceptible vs…

Design

Preclinical

Authors

MHMelanie S. HouleBrooke Army Medical Center RARuth A. AltschuldUniversity of Maryland, Baltimore GBGeorge E. BillmanElectrophysiology

Discussion

Member takes

Implication

May inform beta2-AR targeting in post-MI arrhythmia research; hypothesis-generating in animal models and should not yet change practice.

Key Points

This research aims to investigate the effects of beta-adrenergic receptor stimulation on contractile responses in dogs susceptible to lethal arrhythmias.
Evaluated contractile responses using echocardiography in 27 dogs before and after myocardial infarction.
Assessed single-cell responses from isolated cardiomyocytes treated with isoproterenol.
Comparative analysis of responses between susceptible and resistant dogs was performed.
Before infarction, contractile responses to isoproterenol were similar in both groups.
After infarction, susceptible dogs exhibited a significantly larger circumferential fiber shortening (Vcf) response (specific metrics not provided).
In susceptible dog myocytes, isoproterenol induced a 48% increase in isotonic shortening, significantly higher than the 15% in resistant dogs, both affected by beta(2)-AR blockade.

Structured PICO

Does beta-AR stimulation elicit different contractile responses in dogs susceptible vs resistant to lethal arrhythmias before and after myocardial infarction?

Population

27 dogs susceptible or resistant to ventricular fibrillation induced by coronary occlusion during exercise, evaluated before and after myocardial infarction.

Intervention

Isoproterenol (beta-AR stimulation) with or without beta1-AR antagonist (bisoprolol) or beta2-AR antagonist (ICI-118551).

Comparator

Baseline (before infarction) vs after infarction; Susceptible vs Resistant dogs.

Outcome

Contractile response (velocity of circumferential fiber shortening, Vcf) and heart rate in intact animals; single-cell isotonic shortening in isolated cardiomyocytes.surrogate

Myocardial infarction provokes an enhanced beta2-adrenergic receptor contractile response in dogs susceptible to lethal arrhythmias, suggesting a mechanism for arrhythmogenesis.

Cite This Study

Houle et al. (2001) studied Susceptibility to ventricular fibrillation (n=27). Isoproterenol and beta-adrenergic receptor antagonists vs. Resistant dogs / before myocardial infarction was evaluated on Velocity of circumferential fiber shortening (Vcf), heart rate response, and single-cell isotonic shortening response. Myocardial infarction provoked an enhanced beta2-adrenergic receptor contractile response in dogs susceptible to ventricular fibrillation, but not in resistant animals.

synapsesocial.com/papers/6a211ba238e3bbbbff02be05 https://doi.org/10.1152/jappl.2001.91.4.1627

Topics

Echocardiography

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Enhanced in vivo and in vitro contractile responses to β₂-adrenergic receptor stimulation in dogs susceptible to lethal arrhythmias

Discussion

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Implication

Key Points

Structured PICO

Cite This Study

Topics

Enhanced in vivo and in vitro contractile responses to β₂-adrenergic receptor stimulation in dogs susceptible to lethal arrhythmias

Discussion

Member takes

Implication

Key Points

Structured PICO

Cite This Study

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