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Wondering Atrial Pacemaker (WAP)

Wandering atrial pacemaker (WAP) is an atrial arrhythmia that occurs when the natural pacemaker site shifts between the SA node, the atria, and the atrioventricular node (AV node). This shifting of the pacemaker from the SA node to adjacent tissues is identifiable by at least three morphological changes in the P-wave (see above). Wandering atrial pacemaker (also termed multifocal atrial rhythm) is when there are three or more signals generated from the atria that serve as the dominant pacemaker site. Since they discharge in random fashion, the pacemaker location is continuously shifting and may be located anywhere in the atrial myocardium. As a result, the conducting signal originates from multiple sites in the atria, which causes a changing P wave morphology and PR intervals. The rate is 60 to 100. If the rate is more than 100, this would be considered Multifocal Atrial Tachycardia (MAT). It is possible for a wandering atrial pacemaker to occur more often in the young and among athletes. The cause usually stems from an augmented vagal tone. An increase in the vagal tone causes a slower heart rate and allows the AV node or the atria to take over the hearts rhythm. When the vagal tone decreases, the heart reverts back to the normal pacemaker (the SA node). It may also be seen in patients with heart disease or COPD. Wandering atrial pacemaker may also be a precursor to multifocal atrial tachycardia. Patients with wandering atrial pacemaker are usually not symptomatic due to a slower controlled heart rate. Treatment for wandering atrial pacemaker is not necessary in most circumstances. The condition can manifest itself during a persons normal sleep cycle. It may also occur as a side effect of some medications, including digitalis. WAP may also be indicative of developing heart disease or a cardiac sinus disorder. It is generally considered benign and is usually transitory. Often it is encountered in association with respiratory effort or strain, due to increased vagal tone, for example during the act of lifting heavy weights. Thus, individuals in whom this condition might occur include construction workers, warehouse workers, janitors, and horticulturists or other professions in which digging is involved.

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