Noise, artifact, and oversensing related inappropriate ICD shock evaluation: ALTITUDE noise study

Brian D. Powell, Samuel J Asirvatham, David L. Perschbacher, Paul W. Jones, Yong-Mei Cha, David A. Cesario, Michael Cao, F. Roosevelt Gilliam, Leslie A. Saxon

Research output: Contribution to journalArticle

38 Scopus citations


Background: Approximately 12-21% of implantable cardioverter defibrillator (ICD) patients receive inappropriate shocks. We sought to determine the incidence and causes of noise/artifact and oversensing (NAO) resulting in ICD shocks. Methods: A random sample of 2,000 patients who received ICD and cardiac resynchronization therapy defibrillator shocks and were followed by a remote monitoring system was included. Seven electrophysiologists analyzed stored electrograms from the 5,279 shock episodes. Episodes were adjudicated as appropriate or inappropriate shocks. Results: Of the 5,248 shock episodes with complete adjudication, 1,570 (30%) were judged to be inappropriate shocks. Of these 1,570, 134 (8.5%) were a result of NAO. The 134 NAO episodes were determined to be due to external noise in 76 (57%), lead connector-related in 37 (28%), muscle noise in 11 (8%), oversensing of atrium in seven (5%), T-wave oversensing in two (2%), and other noise in one (1%). The ICD shock itself resulted in a marked decrease in the level of noise in 60 of 134 (45%) NAO episodes, and the magnitude of this effect varied with the type of NAO (58% for external noise, 35% for muscle, 27% for lead/connector, and 0% for oversensing; P = 0.03). There was no significant difference in NAO likelihood based on type of lead (integrated bipolar 89/1,802 vs dedicated bipolar 9/140, P = 0.67). Conclusions: External noise and lead/connector noise were the primary causes, while T-wave oversensing was the least common cause of NAO resulting in ICD shock. Noise/artifact decreased immediately after a shock in nearly half of episodes. The specific ICD lead type did not impact the likelihood of NAO.

Original languageEnglish (US)
Pages (from-to)863-869
Number of pages7
JournalPACE - Pacing and Clinical Electrophysiology
Issue number7
StatePublished - Jul 2012



  • arrhythmias cardiac
  • artifacts
  • cardiac resynchronization therapy
  • defibrillators
  • electromagnetic fields
  • implantable

ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine

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