ISSN:
1432-2013
Keywords:
Key words Contractility
;
Left ventricle
;
End-systolic pressure-volume relationship
;
Conductance catheter
;
Neonate
;
Experimental
;
Sarcoplasmic reticulum
;
Ryanodine
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract We investigated the relationship between heart rate and contractility in seven anaesthetized young piglets by measuring contractility at different atrial pacing rates. To study the origin of this relationship we repeated the measurements after blocking the sarcoplasmic reticulum calcium release channel with ryanodine. We assessed contractility using indices derived from instantaneous left ventricular pressure and volume measured by micromanometric and conductance catheters during rapid inferior vena cava occlusion, thus generating the end-systolic pressure-volume relationship, which was characterized by its slope E es, and the maximum rate of change of ventricular pressure (dP/dt max)/end-diastolic volume relationship, also charaterized by its slope. All animals showed an increase in contractility with increasing heart rate (intact force/frequency relationship) which was abolished after ryanodine. The most striking effect of ryanodine on baseline haemodynamics was the dramatic decrease of dP/dt max to about 50% of its original value, while peak developed pressure and E es did not change. We conclude that the young piglet, despite its immaturity, has a functional sarcoplasmic reticulum, illustrated by an intact force/frequency relationship. In addition, blockade of the sarcoplasmic reticulum in vivo has profoundly different effects during early and late systole, indicating that indices of contractility derived during different parts of the cardiac cycle represent different aspects of systole.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s004240050492
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