Wandering atrial pacemaker
Wandering atrial pacemaker | |
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ECG showing differing P-wave morphologies | |
Specialty | Cardiology |
Wandering atrial pacemaker (WAP) is an
Pathophysiology
The SA node is considered the primary pacemaker of the heart. In wandering atrial pacemaker, there are other locations within the atria besides the SA node that are responsible for each heartbeat. This is unusual because the SA node, AV node, bundle of His, bundle branches, and Purkinje fibers are the structures that have pacemaking capability. The atrial and ventricular muscle tissue do not have this capability.
Originally, it was believed that the
Causes
Wandering atrial pacemaker may be seen in young, healthy individuals as well as in the elderly and those with lung disease.[2] The cause of wandering atrial pacemaker is unclear.
Increased tone from the vagus nerve may factor into the rhythm appearing in young, healthy individuals who exercise. The vagus nerve is a part of the parasympathetic nervous system that helps control heart rate and contractility of the heart. Through exercise, there is increased input to the heart from the vagus nerve, which causes the heart to beat at a slower rate. This is manifested by a lower resting heart rate than may be seen in the average person. For elderly individuals, the rhythm may be caused by sinus node dysfunction. This is where the heart's pacemaker, the SA node, has become damaged. For individuals with lung disease, the rhythm could be related to the underlying lung pathology. In rare cases, digoxin toxicity can cause wandering atrial pacemaker.
Symptoms
Wandering atrial pacemaker doesn't usually have symptoms because it is commonly a benign rhythm. It is usually found incidentally on an ECG for other medical indications that require a heart rhythm screening. If a patient does have symptoms, it may manifest as skipped heartbeats. Upon physical examination, it can be found by having an irregularly irregular rhythm, similar to how atrial fibrillation is described.[4] An ECG would then be performed to find the underlying cause of the rhythm disturbance.
Diagnosis
The
Another heart rhythm similar to wandering atrial pacemaker is multifocal atrial tachycardia. Both arrhythmias have at least 3 different P-wave morphologies in a single ECG lead, but the heart rate is different. When the heart rate is lower than 100 beats per minute, the heart rhythm is considered wandering atrial pacemaker. When the heart rate is greater than 100 beats per minute, the heart rhythm is considered multifocal atrial tachycardia.[2]
Treatment
Treatment is rarely required because, in most cases, it is asymptomatic. If symptoms develop, medication can be pursued for symptomatic relief. In the setting of suspected sinus node dysfunction manifesting as wandering atrial pacemaker, evaluation for pacemaker placement may be done due to sinus node damage.[2] In cases of digoxin toxicity, a physician may decrease the dose, change medications, or cease digoxin therapy.