Pacemaker-Mediated Tachycardia Differential Diagnoses

Updated: Apr 15, 2022
  • Author: Brian Olshansky, MD, FESC, FAHA, FACC, FHRS; Chief Editor: Jose M Dizon, MD  more...
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Diagnostic Considerations

Any rapid atrial rhythm, such as atrial tachycardia, atrial flutter, or atrial fibrillation, sensed by the atrial lead, can then be tracked by the pacemaker to the upper rate limit. [8] This is confirmed when intracardiac electrograms are examined or by evaluation of the underlying rhythm. In unipolar pacemakers, myopotentials from the chest wall muscles or electromechanical signals from an electrocautery device in the operating room may be oversensed and also may drive the pacemaker to the upper rate limit. [9]

Extremely rare, but of concern, in older pacemakers, the pacemaker circuitry may malfunction, resulting in a runaway pacemaker in which the pacemaker paces the heart at a very rapid rate and this cannot be programmed off. [10] All the above problems require active involvement of the pacemaker to maintain the tachycardia but are not reentrant in nature and so not considered classic pacemaker-mediated tachycardia.