What question did this study set out to answer?

The effects of tension on acetylstrophanthidin-induced transient depolarizations and aftercontractions in canine myocardial and Purkinje tissues.

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Population

Isolated canine Purkinje and ventricular muscle preparations

Design

Preclinical

Authors

Mechanical stretch may promote digitalis-related arrhythmias in animal models; leaves open human relevance and clinical translation.

To evaluate how resting mechanical tension affects acetylstrophanthidin-induced transient depolarizations and aftercontractions in isolated canine Purkinje and ventricular tissues.
Isolated canine Purkinje and ventricular muscle preparations (including N=11 muscle preparations) were exposed to acetylstrophanthidin.
Preparations were placed under resting tension at 80% of peak developed tension while measuring transmembrane potentials and contractile responses across varied basic cycle lengths.
Acetylstrophanthidin elicited aftercontractions in all Purkinje tissues and in 11 muscle preparations, with 7 muscle preparations demonstrating concurrent transient depolarizations.
Amplitudes of aftercontractions and transient depolarizations peaked at coupling intervals between 600 and 700 ms and directly correlated with the preceding basic cycle length.
Resting tension increased transient depolarization amplitudes in Purkinje tissue and provoked depolarizations in muscle that occasionally reached threshold.

Population

Isolated canine Purkinje and ventricular muscle preparations

Intervention

Acetylstrophanthidin (AS) exposure combined with resting tension equal to 80% of that required to elicit peak developed tension

Outcome

Transmembrane potentials and contractile activity (transient depolarizations and aftercontractions)surrogate

Stretch or increased resting tension may promote cardiac arrhythmias related to digitalis-induced transient depolarizations.

Gregory R. Ferrier (1976) studied this question.

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