title: Failure to sense P waves during DDD pacing.
abstract: ECG tracings of three patients in whom AV universal (DDD) pacemakers were implanted intermittently demonstrated dropped P waves. In one patient, true atrial undersensing was present; in the others, sensing of the atrial electrode was appropriate, but sensing of sinus P waves was intermittently blocked by normal pacemaker operation. In this report we discuss the electrocardiographic diagnosis of atrial undersensing in order to avoid unnecessary reinterventions.
mesh_terms: D000368:Aged; D004562:Electrocardiography; D005260:Female; D006325:Heart Atria; D006327:Heart Block / Q000175:diagnosis / Q000503:physiopathology / Q000628:therapy; D006801:Humans; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic; D010138:Pacemaker, Artificial / Q000009:adverse effects*