Copyright © 1993 by the European Society of Cardiology.
© 1993 The Europen Society of Cardiology
Electrophysiology of the ageing rabbit and cat sinoatrial node — a comparative study
Department of Physiology, Academic Medical Centre, University of Amsterdam The Netherlands
accepted 21 April 1993.
Correspondence Dr Alings, Department of Physiology, University of Amsterdam, Academic Medical Centre, Meibergdreef 15, 1105 AZ Amsterdam, The Netherlands
Abstract
Intrinsic properties of the human sinoatrial (SA) node have been shown to decline with age. In the present study we aimed at investigating the underlying mechanisms of age-dependent changes in intrinsic cycle length and sinoatrial conduction time. To this end, the cycle length and transmembrane potentials of the SA nodes of rabbits (2 days–5.6 years) and cats (6 weeks–1.8 years) were recorded and nodal conduction was reconstructed. The size of the SA nodes was measured in Sirius Red stained sections.
Cycle length increases with age in both the rabbit and cat SA node, and in both species cycle length is dependent on diastolic depolarization rate and action potential duration. Nodal action potential duration increases with age in both rabbit and cat, whereas diastolic depolarization rate decreases in the cat only.
The location of the primary pacemaker is not related to age. With age, sinoatrial conduction time increases in both species as a result of an enlargment of the area with low phase 0 upstroke velocities. The size of the SA node of adult animals does not increase with age.
Key Words: Ageing • sinoatrial node • pacemaker fibres • intrinsic cycle length • sinoatrial conduction time • action potential parameters
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