title: Beat-to-beat corrected QT analysis detects corrected QT prolongation in 50 consecutive telemetry-monitored patients.
abstract: BACKGROUND
  The American Heart Association/American College of Cardiology Foundation recommends monitoring for corrected QT (QTc) prolongation. The incidence of QTc prolongation in the general public is unknown. Episodic measurements may miss patients at risk.
  
  
  OBJECTIVE
  The purpose of this study was to determine the incidence of QTc prolongation in hospitalized telemetry patients when beat-to-beat monitoring, confirmed by manual calculation, was used for detection.
  
  
  METHODS
  After institutional review board approval was obtained, waveforms of telemetry-monitored patients were analyzed consecutively until 50 patients with prolonged QTc were identified (QTc >470 milliseconds in men and >480 milliseconds in women). Prolongation was confirmed by manual calculation. Incidence was calculated. Clinical risk factors and the outcomes of torsades de pointe or sudden death were explored.
  
  
  RESULTS
  Telemetry waveforms were evaluated for 192 444 minutes (3207.4 hours) of recordings, yielding 8,076,653 QTc measurements. In 50 consecutive patients (24 [48%] men), 100% had verified episode(s) of QTc prolongation. Home medications that could result in QTc prolongation were identified in 9 patients (18%). Hospital medications with risk of QTc prolongation were administered to 31 patients (62%). Sixteen patients (32%) were not on a QTc-prolonging medication. Corrected QT prolongation risk factors in the history were found in 2 patients (4%) and hypomagnesemia or hypokalemia was seen in 6 patients (12%). Twelve-lead electrocardiogram detected prolonged QTc in 13 of 45 patients (26%). Prolongation of QTc was detected by standard of care manual analysis in 4 patients (8%). No patient experienced torsades de pointe or sudden death.
  
  
  CONCLUSIONS
  With beat-to-beat analysis, QTc prolongation was detected in 100% of 50 consecutive patients where standard of care (nursing manual analysis or 12-lead electrocardiogram) would have detected 28%. Hospital medications were more likely to contribute to QTc prolongation than home medications.
  
  
  CONCLUSIONS
  More specific definitions for determining proarrhythmic risk are needed as automated technology improves the capture rate of QTc prolongation events.
authors.affiliation: Judy E. Davidson, DNP, RN, FCCM Director, Research Integration and Management, Scripps Clinical Research Center, La Jolla, California. Donna Agan, EdD Director of Operations Integration, Scripps Mercy Hospital, San Diego, California. Dan L. Ballard Jr, BS Process Validation Engineer, Welch Allyn Monitoring, Beaverton, Oregon. Huu Tam D. Truong, MD Cardiology Fellow, Cardiology Department, University of Arizona, Sarver Heart Center, Tucson. Christine M. Bridgen, PharmD Clinical Pharmacist, Department of Pharmacy, Scripps Encinitas Hospital, San Diego, California. Steven Rubino Network + Clinical Systems Specialist, Lead, Biomedical Engineering Department, Scripps Mercy Hospital, San Diego, California. Harminder Sikand, PharmD Clinical Director, Department of Pharmacy, Scripps Mercy Hospital, San Diego, California. Joseph Stein, MD, FACC Electrophysiologist, Division of Cardiology/Electrophysiology, Scripps Mercy Hospital, San Diego, California.
authors.forename: Judy E
authors.initials: JE
authors.lastname: Davidson
authors.forename: Donna
authors.initials: D
authors.lastname: Agan
authors.forename: Dan L
authors.initials: DL
authors.lastname: Ballard
authors.forename: Huu Tam D
authors.initials: HT
authors.lastname: Truong
authors.forename: Christine M
authors.initials: CM
authors.lastname: Bridgen
authors.forename: Steven
authors.initials: S
authors.lastname: Rubino
authors.forename: Harminder
authors.initials: H
authors.lastname: Sikand
authors.forename: Joseph
authors.initials: J
authors.lastname: Stein
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001145:Arrhythmias, Cardiac / Q000503:physiopathology*; D053840:Brugada Syndrome; D000075224:Cardiac Conduction System Disease; D005260:Female; D006329:Heart Conduction System / Q000002:abnormalities* / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic; D012189:Retrospective Studies; D012307:Risk Factors; D013686:Telemetry; D055815:Young Adult