Related Experiment Video
Updated: Aug 7, 2026

Electrophysiological Assessment of Murine Atria with High-Resolution Optical Mapping
Published on: February 22, 2018
Scaling of atrioventricular transmission in mammalian species: an evolutionary riddle!
Frits L Meijler1, Jan Strackee, Arnold A Stokhof
1Interuniversity Cardiology Institute (ICIN) of the Netherlands, Utrecht. denham@euronet.nl
Abstract:
"Scaling deals with the structural and functional consequences of changes in size or scale among otherwise similar organisms." It plays a key role in all studies on comparative mammalian physiology and morphology. Heart weight is proportionally related to body weight and can be described by a straightforward, so-called allometric equation. We studied scaling of AV transmission times (PR intervals on the ECG) in 375 mammals of different dimensions and species. Scaling of AV transmission times versus heart length (third root of weight) is statistically best described by a S-shaped curve. This implies that AV transmission time in mammals is not linearly related to heart length and does not depend solely on the length of the AV transmission system. The AV node fine-tunes AV transmission times at rest and during exercise in individuals; it protects the ventricles against high-rate atrial arrhythmias such as atrial fibrillation; and it regulates basal AV transmission times in mammalian species of varying sizes. We call the "how" and "why" of the scaling of AV transmission time in mammals an evolutionary riddle that deserves further study.
Related Concept Videos
The Cardiac Cycle
The Process
Electrical signals—sent from the sinoatrial (SA) node in the right atrial wall to the atrioventricular (AV) node between the right atrium and right ventricle—cause both atria to simultaneously contract. When the signal reaches the AV node, it pauses for approximately a tenth of a second, allowing the atria to contract and empty blood into the...
Synteny and Evolution
Around 80 million years ago, the human and mice lineages diverged from the common ancestor. During the course of evolution, the ancestral chromosome underwent...
Electrophysiology of Normal Cardiac Rhythm
Conduction System of the Heart
The pacemaker cells are located in two primary nodes: the sinoatrial (SA) node and the atrioventricular (AV) node. The SA node pacemaker cells can autonomously depolarize, triggering an action potential that leads to the...
Development of the Heart
As the embryo undergoes lateral folding, these paired tubes approach each other, merging into a single primitive heart tube by...
Conduction System of the Heart
This system relies on the unique properties of nodal and Purkinje cells:...

