Downward gradient in action potential duration along conduction path in and around the sinoatrial node

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Abstract
Regional differences in electrical activity in rabbit sinoatrial node have been investigated by recording action potentials throughout the intact node or from small balls of tissue from different regions. In the intact node, action potential duration was greatest at or close to the leading pacemaker and declined markedly in all directions from it, e.g., by 74 ± 4% (mean ± SE, n = 4) to the crista terminalis. Similar data were obtained from the small balls. The gradient is down the conduction pathway and will help prevent reentry. In the intact node, a zone of inexcitable tissue with small depolarizations of