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Factors associated with elevated impedance with a nonthoracotomy defibrillation lead system
M C Kontos1, K A Ellenbogen, M A Wood
1Division of Cardiology and Cardiothoracic Surgery, Medical College of Virginia, Virginia Commonwealth University, Richmond, USA.
The American Journal of Cardiology
|January 1, 1997
Summary
Elevated impedance in implantable defibrillator patients using nonthoracotomy leads is linked to smaller heart volumes. However, higher impedance does not predict greater defibrillation energy needs.
Area of Science:
- Cardiology
- Biomedical Engineering
- Medical Devices
Background:
- Implantable defibrillator success depends on peak current, inversely related to electrode impedance.
- Factors influencing elevated impedance in nonthoracotomy lead systems require further investigation.
Purpose of the Study:
- To identify clinical and echocardiographic factors associated with elevated lead impedance in patients undergoing nonthoracotomy implantable defibrillator lead system implantation.
Main Methods:
- Analyzed clinical and echocardiographic data from 41 patients attempting nonthoracotomy lead system implantation.
- Measured lead impedance at end-expiration using 5-J monophasic shocks.
- Grouped patients into low (<47 ohms) and high (>47 ohms) impedance groups.
Main Results:
- Significantly smaller mean left ventricular end-diastolic and end-systolic volumes in the low-impedance group compared to the high-impedance group (p=0.01).
- Lead impedance significantly correlated with both end-diastolic and end-systolic volumes (r=0.44, p<0.005).
- No significant difference in impedance between patients requiring transvenous leads alone versus those needing subcutaneous or epicardial patches.
Conclusions:
- Lead impedance in nonthoracotomy systems correlates with left ventricular volumes.
- Elevated impedance does not predict increased defibrillation energy requirements in this patient cohort.