What is the clinical evidence from this study?

Study design: Other. Population: Automaticity of sheep cardiac Purkinje fibers. Intervention: Pharmacological agents and altered ionic concentrations. Primary outcome: Induction of spontaneous and repetitive activity.

What question did this study set out to answer?

To determine the role and ionic mechanisms of subthreshold oscillatory potentials in initiating spontaneous automaticity and repetitive discharge in cardiac Purkinje fibers.

August 1, 1995Canadian Journal of Physiology and Pharmacology

Role of voltage oscillations in the automaticity of sheep cardiac Purkinje fibers

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Key result

In sheep Purkinje fibers, diastolic depolarization initiated spontaneous activity by reaching the action potential threshold through the depolarizing phase of a tetrodotoxin-sensitive ThVos.

Population

Sheep cardiac Purkinje fibers superfused in vitro

Comparison

Various pharmacological and ionic interventions… vs Quiescent fibers or baseline conditions

Design

Preclinical

Authors

PSPeter SpieglerIsland Hospital MVMario VassalleState University of New York

Discussion

Member takes

Implication

Extends mechanistic insight into Purkinje fiber automaticity in sheep; leaves open translation to human arrhythmias.

Key Points

To determine the role and ionic mechanisms of subthreshold oscillatory potentials in initiating spontaneous automaticity and repetitive discharge in cardiac Purkinje fibers.
Superfused isolated sheep cardiac Purkinje fibers in vitro under conditions of altered extracellular potassium and calcium concentrations.
Assessed electrical activity and overdrive excitation during electrical drive and during exposure to barium, acetylcholine, cesium, tetrodotoxin, lidocaine, and caffeine.
In low extracellular potassium, threshold voltage oscillations (ThVos) emerged during quiescence and progressively grew until reaching the threshold required to fire action potentials.
Tetrodotoxin and lidocaine selectively suppressed ThVos without blocking driven action potentials, confirming the depolarizing phase depends on a tetrodotoxin-sensitive sodium current.
ThVos demonstrated distinct voltage sensitivity, being triggered by barium- or acetylcholine-induced resting depolarization, suppressed by cesium-induced hyperpolarization, and operating independently of calcium overload.

Structured PICO

Population

Sheep cardiac Purkinje fibers superfused in vitro

Intervention

Various pharmacological and ionic interventions (low extracellular potassium, barium, acetylcholine, cesium, tetrodotoxin, lidocaine, low potassium plus high calcium) and electrical drive

Comparator

Quiescent fibers or baseline conditions

Outcome

Induction of spontaneous and repetitive activity and characteristics of voltage oscillations (ThVos)surrogate

In sheep Purkinje fibers, voltage oscillations near the fast sodium current threshold (ThVos) play a key role in initiating spontaneous and repetitive activity via a tetrodotoxin-sensitive sodium component.

Cite This Study

Spiegler et al. (1995) studied Automaticity of sheep cardiac Purkinje fibers. Pharmacological agents and altered ionic concentrations was evaluated on Induction of spontaneous and repetitive activity. In sheep Purkinje fibers, diastolic depolarization initiated spontaneous activity by reaching the action potential threshold through the depolarizing phase of a tetrodotoxin-sensitive ThVos.

synapsesocial.com/papers/6a9de21726da45658790ce27 https://doi.org/10.1139/y95-166

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Role of voltage oscillations in the automaticity of sheep cardiac Purkinje fibers

Discussion

Member takes

Implication

Key Points

Structured PICO

Cite This Study

Role of voltage oscillations in the automaticity of sheep cardiac Purkinje fibers

Discussion

Member takes

Implication

Key Points

Structured PICO

Cite This Study

Also Consider

Also Consider