What question did this study set out to answer?

To evaluate how physiological contractions and inotropic interventions influence the end-systolic length-force relationship in ventricular muscle.

August 1, 1987Cardiovascular Research

Effects of inotropic interventions on end systolic length-force curve of cat ventricular muscle

Q: What is the clinical evidence from this study?

Study design: Other. Intervention: Inotropic interventions (increase in stimulus frequency, increasing calcium concentration, exposure to isoprenaline) vs. Baseline/isometric length-force curve. Primary outcome: End systolic length-force curve (slope and intercept).

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Key result

Inotropic interventions (increased stimulus frequency, calcium, or isoprenaline) increased the slope of the end systolic length-force curve and decreased its intercept in cat papillary muscles.

Population

Cat papillary muscles (ventricular muscle)

Comparison

Inotropic interventions vs Baseline/isometric length-force curve under…

Design

Preclinical

Authors

BJB. R. JewellUniversity of Leeds DHDorothy A. HanckElectrophysiology

Discussion

Member takes

Implication

In cat papillary muscle, inotropes modify end-systolic length-force relations; leaves open relevance to intact human myocardium.

Key Points

To evaluate how physiological contractions and inotropic interventions influence the end-systolic length-force relationship in ventricular muscle.
Simulated physiological cardiac cycles in cat papillary muscles at 37 °C using a computer-controlled servosystem that permitted net external work.
Constructed end-systolic length-force curves by altering the setpoint force against which the contracting muscle shortened.
Tested responses to inotropic interventions, specifically increased stimulation frequency, elevated extracellular calcium concentration, and isoprenaline exposure.
End-systolic length-force curves under physiological contractions closely matched isometric length-force curves established under comparable conditions.
All three inotropic interventions increased the slope of the length-force curve and decreased its extrapolated intercept on the length axis.
The consistent shift in curve kinetics demonstrates that length dependence of activation occurs in the actively working myocardium.

Structured PICO

Population

Cat papillary muscles (ventricular muscle)

Intervention

Inotropic interventions (increase in stimulus frequency, increasing bathing calcium concentration, and exposure to isoprenaline)

Comparator

Baseline/isometric length-force curve under comparable experimental conditions

Outcome

End systolic length-force curve (slope and intercept on the length axis)surrogate

Inotropic interventions alter the end-systolic length-force curve in cat ventricular muscle, providing evidence for length dependence of activation in the working myocardium.

Cite This Study

Jewell et al. (1987) studied this question. Inotropic interventions (increase in stimulus frequency, increasing calcium concentration, exposure to isoprenaline) vs. Baseline/isometric length-force curve was evaluated on End systolic length-force curve (slope and intercept). Inotropic interventions (increased stimulus frequency, calcium, or isoprenaline) increased the slope of the end systolic length-force curve and decreased its intercept in cat papillary muscles.

synapsesocial.com/papers/6a9bdd370b073dbbe4b2114c https://doi.org/10.1093/cvr/21.8.559

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