2 research outputs found
From mouse to whale : a universal scaling relation for the PR Interval of the electrocardiogram of mammals
Background—On the ECG, the PR interval measures the time taken by an electrical impulse generated in the sinoatrial
node to propagate from atria to ventricles. From mouse to whale, the PR interval increases 10 fold, whereas body mass (BM) augments a million fold. Scaling of many biological processes (eg, metabolic rate, life span, aortic diameter) is described
by the allometric equation Y = Y0.BMb, where Y is the biological process and b is the scaling exponent that is an integer
multiple of 1/4. Hierarchical branching networks have been proposed to be the underlying mechanism for the 1/4 power
allometric law.
Methods and Results—We first derived analytically the allometric equation for the PR interval. We assumed that the heart
behaves as a set of “fractal-like” networks that tend to minimize propagation time across the conducting system while
ensuring a hemodynamically optimal atrioventricular activation sequence. Our derivation yielded the relationship
PR = BM1/4. We subsequently obtained previously published values of PR interval, heart rate, and BM of 541 mammals
representing 33 species. Double-logarithmic analysis demonstrates that PR interval increases as heart rate decreases, and
both variables relate to BM following the 1/4 power law. Most important, the best fit for PR versus BM is described
by the equation PR=53.BM0.24. Hence, the empirically determined exponent (0.24) is close to 1/4, as predicted.
Conclusions—We have demonstrated that the PR interval of mammals scales as the 1/4 power of the BM, following the universal law for allometric scaling to ensure an optimal atrioventricular activation sequence