Mechanical restitution during alternans in guinea pig papillary muscles

Cardiovascular Research
C I SpencerW A Seed

Abstract

The aim was to investigate alternate acceleration and retardation of mechanical restitution as a possible mechanism for mechanical alternans in isolated myocardium. Mechanical alternans was induced in papillary muscles from the right ventricles of 11 guinea pigs (200-300 g) by rapid pacing under hypothermic conditions (T = 27 degrees C). Mechanical restitution curves were constructed by measuring the force responses to stimuli applied following variable test intervals during steady state pacing. Curves were obtained under control conditions (steady state stimulation interval 3 s), and for the beats following the large and small contractions during mechanical alternans. Monoexponentials were fitted to the restitution curves. The mean rate constant for restitution following the large beat in alternans was found to be slightly but significantly smaller than that following the small. Both rate constants obtained during alternans were significantly larger than the control rate constant (restitution was faster in alternans). In addition, as the alternation widened, the restitution curve of the beat following the small contraction developed a higher plateau than that following the large. The results confirm that the small beat in alte...Continue Reading

Related Concepts

Myocardial Contraction
Calcium [EPC]
PIGS
Calcium
Cavia
Right Ventricular Structure
Protoplasm
Isolated Noncompaction of the Ventricular Myocardium
Biomechanical Compliance
Contraction (Finding)

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