What question did this study set out to answer?

This study aims to understand how hyperkalemia, acidosis, and hypoxia affect the maximum rate of depolarization in guinea pig myocardium when treated with class I antiarrhythmic drugs.

July 1, 1991Journal of Cardiovascular Pharmacology

Effects of Hyperkalemia, Acidosis, and Hypoxia on the Depression of Maximum Rate of Depolarization by Class I Antiarrhythmic Drugs in Guinea Pig Myocardium

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This study aims to understand how hyperkalemia, acidosis, and hypoxia affect the maximum rate of depolarization in guinea pig myocardium when treated with class I antiarrhythmic drugs.
Performed standard microelectrode methods to record intracellular action potentials from guinea pig myocardium strips.
Superfused myocardium with solutions inducing hyperkalemia, acidosis, and hypoxia while applying therapeutic concentrations of lidocaine, flecainide, and encainide.
Assessed effects across four different drive rates of action potential.
In hyperkalemia, resting potential decreased from -87.9 mV to -74.6 mV, with maximum rate of depolarization dropping from 316 V/s to 240 V/s.
Lidocaine showed greater enhancement of Vmax depression compared to flecainide or encainide under hyperkalemia conditions (p < 0.001).
Acidosis resulted in a 3.5 mV depolarization and 19% reduction in Vmax, with lidocaine again showing more pronounced effects than the other drugs (p < 0.01).

Structured PICO

Population

Guinea pig right ventricular myocardium strips

Intervention

Lidocaine, flecainide, and encainide (three therapeutic concentrations) under conditions of hyperkalemia ([K+] = 11.2 mM), acidosis (pH = 6.3), or hypoxia (PO2 = 60 mm Hg) at four different drive rates (interstimulus interval = 2,400, 1,200, 600, and 300 ms)

Comparator

Standard physiological saline (pH 7.3; PO2 greater than 650 mm Hg; [K+] = 5.6 mM) with the same drugs

Outcome

Maximum rate of depolarization (Vmax)surrogate

Hyperkalemia and acidosis, but not hypoxia, significantly enhance the depressant effect of lidocaine on the maximum rate of depolarization in guinea pig myocardium compared to flecainide and encainide.

Discussion

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Implication

Caution against extrapolating guinea pig Vmax effects to human antiarrhythmic selection in hyperkalemia or acidosis; leaves open clinical translation.

Cite This Study

Campbell et al. (1991) studied this question.

synapsesocial.com/papers/6a7771bcdf493903fd1eef33 https://doi.org/10.1097/00005344-199107000-00008

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Implication

Caution against extrapolating guinea pig Vmax effects to human antiarrhythmic selection in hyperkalemia or acidosis; leaves open clinical translation.

Effects of Hyperkalemia, Acidosis, and Hypoxia on the Depression of Maximum Rate of Depolarization by Class I Antiarrhythmic Drugs in Guinea Pig Myocardium

Key Points

Structured PICO

Discussion

Implication

Cite This Study

Effects of Hyperkalemia, Acidosis, and Hypoxia on the Depression of Maximum Rate of Depolarization by Class I Antiarrhythmic Drugs in Guinea Pig Myocardium

Key Points

Structured PICO

Discussion

Implication

Cite This Study

Also Consider

Also Consider