What question did this study set out to answer?

This study aims to determine how apex rotation relates to volume, contractility, and heart rate during cardiac cycles.

July 1, 1995Circulation

Effects of Load Manipulations, Heart Rate, and Contractility on Left Ventricular Apical Rotation

Q: What is the clinical evidence from this study?

Study design: Other. Population: Left ventricular twist dynamics (n=12). Intervention: Load manipulations, heart rate, and contractility changes vs. Baseline/different loading conditions. Primary outcome: Relation between apex rotation and volume, contractility, and heart rate.

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Key result

In open-chest dogs, left ventricular twist at end-diastole and end-systole is primarily a function of volume, with changes in load, contractility, and heart rate altering torsion amplitude and dynamics.

Population

12 open-chest dogs

Comparison

Manipulations of load, contractility, and heart… vs Baseline/control conditions before manipulations

Design

Preclinical

Authors

CKCarol A. Gibbons KroekerUniversity of Calgary JTJohn V. TybergUniversity of Calgary RBRafael BeyarRambam Health Care Campus

Discussion

Member takes

Implication

Does not support clinical LV twist assessment from animal data; leaves open volume dependence in intact human hearts.

Key Points

This study aims to determine how apex rotation relates to volume, contractility, and heart rate during cardiac cycles.
12 open-chest dogs were used to measure apex rotation with a specialized optical device.
Measurements included LV pressure, ECG, LV segment length, and minor-axis diameters via sonomicrometry.
Vena caval occlusion and volume loading were utilized to assess changes in apex rotation.
Apex rotation was significantly affected by volume changes, with specific slopes for end-diastolic (0.61 degrees/percent) and end-systolic (1.36 degrees/percent) phases.
Increased contractility led to a 42% rise in apex rotation amplitude, delaying untwisting until isovolumic relaxation.
Higher heart rates over 150 bpm resulted in decreased apex rotation amplitude and delayed twist relaxation into isovolumic relaxation.

Structured PICO

Population

12 open-chest dogs

Intervention

Manipulations of load (vena caval occlusion, volume loading, single-beat aortic occlusion), contractility (paired pacing), and heart rate

Comparator

Baseline/control conditions before manipulations

Outcome

Left ventricular apex rotation (amplitude and dynamics of torsion)surrogate

Left ventricular twist at end-diastole and end-systole is primarily a function of volume, and this relationship appears unaltered by heart rate, afterload, and contractility.

Cite This Study

Kroeker et al. (1995) studied Left ventricular twist dynamics (n=12). Load manipulations, heart rate, and contractility changes vs. Baseline/different loading conditions was evaluated on Relation between apex rotation and volume, contractility, and heart rate. In open-chest dogs, left ventricular twist at end-diastole and end-systole is primarily a function of volume, with changes in load, contractility, and heart rate altering torsion amplitude and dynamics.

synapsesocial.com/papers/6a0fa2c22badbc352afe7673 https://doi.org/10.1161/01.cir.92.1.130

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Effects of Load Manipulations, Heart Rate, and Contractility on Left Ventricular Apical Rotation

Discussion

Member takes

Implication

Key Points

Structured PICO

Cite This Study

Effects of Load Manipulations, Heart Rate, and Contractility on Left Ventricular Apical Rotation

Discussion

Member takes

Implication

Key Points

Structured PICO

Cite This Study

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