Tachycardia mechanisms Automaticity The rate at which the sinus node discharges usually is faster than other latent or subsidiary automatic cardiac pacemakers. Subsidiary pacemakers can become dominant in the settings of acidosis, ischemia, sympathetic stimulation, and use of certain drugs.…
Premature atrial complexes Description Premature atrial complexes (PACs) are supraventricular ectopic depolarizations originating in or near the atria or in the pulmonary veins that supersede activation from the sinus node. The most common sites of origin appear to be in…
Atrioventricular conduction abnormalities Atrioventricular (AV) block occurs when an atrial impulse either is not conducted to the ventricle or is conducted with delay. This assumes that the impulse occurs at a time that conduction would be expected to occur based…
Normal sinus node Description Normal sinus rhythm (NSR) is an atrial rhythm caused by electrical activation that originates from the sinus node, a structure located in the area of the junction of the right atrium and superior vena cava. NSR…