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A-V NODAL RHYTHM
In this disorder of the cardiac mechanism, the pacemaker of the heart is located in the A-V node. Automatism of the A-V node is thereby established. At a slow regular rate of about 40 to 45 per minute, it sends out impulses to both auricles and ventricles. Usually a normal Q-R-S complex occurs first, followed by an inverted P wave, which is superimposed on the end of the Q-R-S complex, on the T wave, or between the two waves. In some cases of nodal rhythm the P wave may come early, so that it falls with the Q-R-S wave and is concealed therein. Finally, it may precede the Q-R-S wave by a very short interval when the pacemaker is located high up in the A-V node (figs. 100 and 101). Although the P wave in nodal rhythm, as ordinarily considered, should be inverted, it has occasionally been
CARTER JB. THE FUNDAMENTALS OF ELECTROCARDIOGRAPHIC INTERPRETATION. JAMA. 1932;99(18):1503-1510. doi:10.1001/jama.1932.27410700006011