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Cardiac cycle length modulates cardiovascular regulation that is dependent on previous beat contraction history

B K Slinker1

  • 1Department of Medicine, University of Vermont, Burlington 05405.

Circulation Research
|July 1, 1991
PubMed

Insights

Left ventricular performance is influenced by previous heartbeats, especially at higher heart rates. This study demonstrates that increased heart rate prolongs this "previous beat contraction history" to multiple beats.

Area of Science:

  • Cardiovascular Physiology
  • Cardiac Mechanics

Background:

  • Left ventricular performance is regulated beat-to-beat.
  • Previous beat contraction history influences current ventricular function.

Purpose of the Study:

  • Investigate if previous beat contraction history is due to biochemical processes with long time courses.
  • Determine if this history dependence extends to multiple previous beats as heart rate increases.

Main Methods:

  • Measured hemodynamic responses in anesthetized dogs under right heart bypass.
  • Utilized random preload and afterload changes at three paced heart rates.
  • Employed multiple linear regression to analyze hemodynamic sequences and identify history dependence.

Main Results:

  • Baseline conditions showed one beat of history dependence in all hearts.
  • At the highest heart rate, dependence extended to two beats in 10/11 hearts and three beats in 4/11 hearts.
  • This history dependence was statistically significant (p < 0.05) at higher heart rates.

Conclusions:

  • Previous beat contraction history is interval-dependent and linked to mechanical restitution.
  • Biochemical processes with time courses longer than a cardiac cycle likely mediate this phenomenon.
  • Increased heart rate significantly enhances the duration of left ventricular mechanical history dependence.

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