Acute evaluation of transthoracic impedance vectors using ICD leads.
BACKGROUND
Minute ventilation (MV) has been proven to be very useful in rate responsive pacing. The aim of this study was to evaluate the feasibility of using implantable cardioverter-defibrillator (ICD) leads as part of the MV detection system.


METHODS
At implant in 10 patients, the transthoracic impedance was measured from tripolar ICD, tetrapolar ICD, and atrial lead vectors during normal, deep, and shallow voluntary respiration. MV and respiration rate (RespR) were simultaneously measured through a facemask with a pneumotachometer (Korr), and the correlations with impedance-based measurements were calculated. Air sensitivity was the change in impedance per change in respiratory tidal volume, ohms (Omega)/liter (L), and the signal-to-noise ratio (SNR) was the ratio of the respiratory and cardiac contraction components.


RESULTS
The air sensitivity and SNR in tripolar ICD vector were 2.70 +/- 2.73 ohm/L and 2.19 +/- 1.31, respectively, and were not different from tetrapolar. The difference in RespR between tripolar ICD and Korr was 0.2 +/- 1.91 breaths/minute. The regressed correlation coefficient between impedance MV and Korr MV was 0.86 +/- 0.07 in tripolar ICD.


CONCLUSIONS
The air sensitivity and SNR in tripolar and tetrapolar ICD lead vectors did not differ significantly and were in the range of the values in pacemaker leads currently used as MV sensors. The good correlations between impedance-based and Korr-based RespR and MV measurements imply that ICD leads may be used in MV sensor systems.
Gottfridsson
Christer
C
Department of Molecular and Clinical Medicine/Cardiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden. christer.gottfridsson@medicine.gu.se
Daum
Douglas
D
Kennergren
Charles
C
Ramuzat
Agnès
A
Willems
Roger
R
Edvardsson
Nils
N
D000328:Adult; D000368:Aged; D000465:Algorithms; D002307:Cardiography, Impedance / Q000295:instrumentation* / Q000379:methods*; D017147:Defibrillators, Implantable; D003936:Diagnosis, Computer-Assisted / Q000295:instrumentation / Q000379:methods*; D017097:Electric Impedance; D004567:Electrodes, Implanted; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012129:Respiratory Function Tests / Q000295:instrumentation* / Q000379:methods; D015656:Respiratory Mechanics; D012680:Sensitivity and Specificity; D055815:Young Adult