High heart rate associated early repolarization causes J ‐waves in both zebra finch and mouse

Zebra finches, a bird species with high heart rates, have a J ‐wave on the ECG, which results from early repolarization, This supports the notion that J‐waves are a common phenomenon in endothermic animals with high heart rates. AbstractHigh heart rates are a feature of small endothermic —or warm‐blooded—mammals and birds. In small mammals, the QT interval is short, and local ventricular recordings reveal early repolarization that coincides with the J‐wave on the ECG, a positive deflection following the QRS complex. Early repolarization contributes to short QT‐intervals th ereby enabling brief cardiac cycles and high heart rates. We therefore hypothesized high hearts rates associate with early repolarization and J‐waves on the ECG of endothermic birds. We tested this hypothesis by comparing isolated hearts of zebra finches and mice and recorded pseudo‐ECGs and opt ical action potentials (zebra finch,n = 8; mouse,n = 8). In both species, heart rate exceeded 300 beats per min, and total ventricular activation was fast (QRS <  10 ms). Ventricular activation progressed from the left to the right ventricle in zebra finch, whereas it progressed from apex‐to‐base in mouse. In both species, the early repolarization front followed the activation front, causing a positive J‐wave in the pseudo‐ECG. Inhibition of early repolarization by 4‐aminopyridine reduced J‐wave amplitude in both species. Action potential duration was similar between ventricle...
Source: Physiological Reports - Category: Physiology Authors: Tags: ORIGINAL ARTICLE Source Type: research