Quantitative electrocardiography and vectorcardiography in postnatally developing rats

Postnatal anatomical and functional development of the heart: A species comparison

“…As in the case in humans, shorter QRS intervals are noted and horizontal QRS loops change from clockwise, figure-of-eight to counterclockwise loop oriented toward the left, as observed in the adult, during the early postnatal period in rats (Diez and Schwartze, 1991). QRS intervals are considerably shorter than in the adult, even at Day 53.…”

“…The heart rate in neonatal rats increases during the early postnatal period and then remains relatively constant into adulthood (Kyrieleis, 1963;Diez and Schwartze, 1991;Quigley et al, 1996). This increase in rate seems to be inversely proportional to the decrease in QT interval seen during this period, and may be explained by the increasing influence of the sympathetic system (Table 6).…”

“…In the rat, the PQ interval decreases between 6 and 14 days of age and reaches adult values at 53 days of age (Yamori et al, 1976;Diez and Schwartze, 1991). The QT interval also decreases during the first 3 week of life and reaches adult values later than 53 days of age.…”