What question did this study set out to answer?

To determine how abrupt cycle length shortening alters the spatial inhomogeneity and dispersion of repolarization across ventricular myocardium under normoxic and hypoxic conditions.

September 1, 1991CirculationOpen Access

Repolarization inhomogeneities in ventricular myocardium change dynamically with abrupt cycle length shortening.

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Why the study?

Does abrupt cycle length shortening alter spatial inhomogeneity of repolarization in normoxic and hypoxic guinea pig hearts?

Population

Langendorff-perfused guinea pig hearts

Comparison

Abrupt cycle length shortening from 500 to 300… vs Normoxic controls versus 30 minutes of hypoxia

Design

Preclinical

Authors

DRDavid RosenbaumGeneral Cardiology DKDaniel T. KaplanRutgers Sexual and Reproductive Health and Rights AKAnthony KanaiForest Institute

Discussion

Member takes

Implication

Blunted DI adaptation during hypoxia may heighten arrhythmia vulnerability; leaves open mechanistic relevance to human ischemia.

Key Points

To determine how abrupt cycle length shortening alters the spatial inhomogeneity and dispersion of repolarization across ventricular myocardium under normoxic and hypoxic conditions.
Simultaneously recorded 124 action potentials in Langendorff-perfused guinea pig hearts using high-resolution optical mapping with a voltage-sensitive dye.
Calculated mean action potential duration (APD) and dispersion index (DI; variance of APD distribution) across cycles following an abrupt cycle length shortening from 500 to 300 msec under normoxia and after 30 minutes of hypoxia.
In normoxic controls, abrupt cycle length shortening exponentially decreased mean APD by 23 +/- 3 msec (p < 0.0001) with synchronized beat-to-beat APD oscillations across ventricular sites.
Normoxic hearts exhibited a transient 51.0 +/- 6.8% reduction in DI by the sixth beat post-shortening (p < 0.01) before recovering by 15-20 beats, driven by synchronous APD oscillations and transient reduction of the apical-to-basal gradient.
Following hypoxia, baseline mean APD dropped from 175.0 +/- 13.3 to 76 +/- 25.7 msec; subsequent cycle length shortening lowered APD by only 6 +/- 6 msec, desynchronized oscillations, and failed to suppress DI (+7.1 +/- 23%).

Structured PICO

Does abrupt cycle length shortening alter spatial inhomogeneity of repolarization in normoxic and hypoxic guinea pig hearts?

Population

Langendorff-perfused guinea pig hearts

Intervention

Abrupt cycle length (CL) shortening from 500 to 300 msec

Comparator

Normoxic controls versus 30 minutes of hypoxia

Outcome

Mean action potential duration (APD) and repolarization dispersion index (DI)surrogate

Abrupt cycle length shortening dynamically changes ventricular repolarization inhomogeneity, a protective response that is lost during hypoxia, potentially increasing arrhythmia vulnerability.

Cite This Study

Rosenbaum et al. (1991) studied this question.

synapsesocial.com/papers/69f14b962811130d0cde222d https://doi.org/10.1161/01.cir.84.3.1333

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Repolarization inhomogeneities in ventricular myocardium change dynamically with abrupt cycle length shortening.

Discussion

Member takes

Implication

Key Points

Structured PICO

Cite This Study

Repolarization inhomogeneities in ventricular myocardium change dynamically with abrupt cycle length shortening.

Discussion

Member takes

Implication

Key Points

Structured PICO

Cite This Study

Also Consider

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