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April 1, 1978Circulation ResearchOpen Access

Segment lengthening accelerates early repolarization and produces afterdepolarizations during late repolarization, which can reach threshold for a propagated action potential.

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Why the study?

Does segment lengthening alter action potentials in isolated frog ventricles?

Population

Isolated, intact frog ventricles and frog ventricular strips

Comparison

Segment lengthening vs Isotonic beats (where segment shortens)

Design

Preclinical

Authors

MLM J Lab

Discussion

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Overview

May link stretch to triggered activity in ischemia; leaves open translation from frog models to mammalian hearts.

Key Points

  • The aim is to investigate how mechanical changes in frog ventricle affect action potentials during contraction.
  • Isolated frog ventricle preparations were used to record monophasic action potentials and segment lengths.
  • Microelectrode and insulated gap recordings were employed to assess electrical activity.
  • Isovolumic and isotonic beats were compared to analyze repolarization and afterdepolarization changes.
  • During isovolumic beats, early repolarization phase accelerated with significant changes in segment length.
  • An afterdepolarization occurred related to later phases of repolarization, reaching threshold for action potential.
  • Accelerated repolarization was evident as a shortening of the Q-T interval in the ventricular electrogram.

Structured PICO

Does segment lengthening alter action potentials in isolated frog ventricles?

P
Population
Isolated, intact frog ventricles and frog ventricular strips
I
Intervention
Segment lengthening (during isovolumic beats or via intraventricular injections of Ringer's solution)
C
Comparator
Isotonic beats (where segment shortens)
O
Outcome
Changes in action potentials (early repolarization acceleration, afterdepolarizations)surrogate

Mechanoelectrical feedback from segment lengthening alters action potentials and can trigger propagated action potentials, providing a potential mechanism for extrasystoles in myocardial ischemia.

Cite This Study

M J Lab (1978) studied this question.

synapsesocial.com/papers/6a2077afca38d7025f780351https://doi.org/10.1161/01.res.42.4.519
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Also Consider

Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context:

  1. 1Transient depolarisation and action potential alterations following mechanical changes in isolated myocardium1980 · 82 citations
  2. 2Effect of heart electric stimulation on repolarization of ventricular myocardium of fish and amphibians2013 · 3 citations
  3. 3Regenerative repolarization of the frog ventricular action potential: a time and voltage‐dependent phenomenon.1977 · 17 citations
  4. 4Components of the cardiac action potential1962 · 30 citations
  5. 5Intracellular and external recording from frog ventricular fibers during hypertonic perfusion1960 · 42 citations