They found that intrinsic heart rate (IHR) could be described by the equation IHR (beats/minute) = 118 — 0.57 x age (years), revealing that intrinsic heart rates are generally faster than resting heart rates. This reflects the fact that there is relatively little resting sympathetic tone and a relatively great resting vagal tone. An increased sinus heart rate (as seen in the pigs) could be explained by an increased intrinsic heart rate, increased sympathetic tone, or decreased vagal tone. buy cheap antibiotics
Our studies reveal that AV conduction is more rapid in the pig. The shorter PR interval reflects a significantly reduced H-V interval, as well as low normal HRA-LRA and LRA-H intervals. The shorter length of the penetrating AV bundle undoubtedly results in the shorter H-V interval, although conduction velocity through the atrial myocardium, AV node, and AV bundle may be increased as well. The relatively shorter SACT could also reflect increased conduction velocity through the sinoatrial junction. The similarities between the pig and human of CSNRT, AERP, and AVERP suggest no differences in the intrinsic (unction of the structures.