title: Diagnosis of sleep-related breathing disorders by visual analysis of transthoracic impedance signals in pacemakers.
abstract: BACKGROUND
  Minute ventilation sensors of cardiac pacemakers measure ventilation by means of transthoracic impedance changes between the pacemaker case and the electrode tip. We investigated whether this technique might detect sleep-related breathing disorders.
  
  
  RESULTS
  In 22 patients, analog waveforms of the transthoracic impedance signal measured by the pacemaker minute ventilation sensor over the course of a night were visualized, scored for apnea/hypopnea events, and compared with simultaneous polysomnography. Analysis of transthoracic impedance signals correctly identified the presence or absence of moderate to severe sleep apnea (apnea/hypopnea index, AHI >20 h(-1)) in all patients (receiver operating characteristics, ROC=1.0). The ROC for AHI scores of > or =5 h(-1) and > or =10 h(-1) showed an area under the curve of 0.95, P<0.005, and 0.97, P<0.0001, respectively. Accuracy over time assessed by comparing events per 5-minute epochs was high (Cronbach alpha reliability coefficient, 0.85; intraclass correlation, 0.73). Event-by-event comparison within +/-15 seconds revealed agreement in 81% (kappa, 0.77; P<0.001).
  
  
  CONCLUSIONS
  Detection of apnea/hypopnea events by pacemaker minute ventilation sensors is feasible and accurate compared with laboratory polysomnography. This technique might be useful to screen and monitor sleep-related breathing disorders in pacemaker patients.
authors.affiliation: Cardiovascular Center, University Hospital Zurich, Department of Internal Medicine, Division of Cardiology and Pneumology, Rämistrasse 100, CH-8091 Zürich, Switzerland. christoph.scharf@usz.ch
authors.forename: Christoph
authors.initials: C
authors.lastname: Scharf
authors.forename: Yong K
authors.initials: YK
authors.lastname: Cho
authors.forename: Konrad E
authors.initials: KE
authors.lastname: Bloch
authors.forename: Corinna
authors.initials: C
authors.lastname: Brunckhorst
authors.forename: Firat
authors.initials: F
authors.lastname: Duru
authors.forename: Kryzstof
authors.initials: K
authors.lastname: Balaban
authors.forename: Nancy
authors.initials: N
authors.lastname: Foldvary
authors.forename: Lynn
authors.initials: L
authors.lastname: Liu
authors.forename: Richard C
authors.initials: RC
authors.lastname: Burgess
authors.forename: Reto
authors.initials: R
authors.lastname: Candinas
authors.forename: Bruce L
authors.initials: BL
authors.lastname: Wilkoff
mesh_terms: D000368:Aged; D002307:Cardiography, Impedance; D005260:Female; D006801:Humans; D008297:Male; D010138:Pacemaker, Artificial; D017286:Polysomnography; D012891:Sleep Apnea Syndromes / Q000175:diagnosis*; D014785:Vision, Ocular