Published Online
on October 18, 2004

A more recent version of this article appeared on October 26, 2004

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Submitted on July 8, 2003
Revised on June 16, 2004
Accepted on June 17, 2004

Diagnosis of Sleep-Related Breathing Disorders by Visual Analysis of Transthoracic Impedance Signals in Pacemakers

Christoph Scharf MD^*, Yong K. Cho PhD, Konrad E. Bloch MD, Corinna Brunckhorst MD, Firat Duru MD, Kryzstof Balaban MD, Nancy Foldvary DO, Lynn Liu MD, Richard C. Burgess PhD, MD, Reto Candinas MD, and Bruce L. Wilkoff MD

From University Hospital of Zurich, Department of Internal Medicine, Division of Cardiology and Pneumology, Zurich, Switzerland (C.S., K.E.B., C.B., F.D., R.C.); the Cleveland Clinic Foundation, Departments of Cardiovascular Medicine and Pulmonary Medicine, Cleveland, Ohio (K.B., N.F., L.L., R.C.B., B.L.W.); and Medtronic Inc, Minneapolis, Minn (Y.K.C.).

^* To whom correspondence should be addressed. E-mail: christoph.scharf{at}usz.ch.

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.

Methods and 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 5 h^-1 and 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 reliability coefficient, 0.85; intraclass correlation, 0.73). Event-by-event comparison within ±15 seconds revealed agreement in 81% (, 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.

Key words: pacemakers • diagnosis • sleep apnea syndromes

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