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Ebook Implantable cardioverter - Defibrillators step by step: Part 2

(BQ) Part 2 book "Implantable cardioverter - Defibrillators step by step" includes: Cardiac tachyarrhythmias, ICD function with emphasis on stored electrograms, indications for ICD, ICD implantation and lead systems, cardiac resynchronization, complications of ICD therapy,. | 220 iCD TROUBLESHOOTING TESTING FOR LEAD PROBLEMS Comparing near-fleld and lar-fleld EGMs can help determine which conductor Is affected-Noise only on the far-held EGM suggests that the defect involves the shocking lead and not the sensing lead. Look for abnormalities with changes in body position deep respiration coughing movement of the ipsilateral arm pocket manipulation and Valsalva maneuver. Differentiate myopotentials from false signals but the two may Coexist. A slight decrease in sensitivity 0.3 to 0.45 mV may eliminate myopotentials but is unlikely to eliminate false signals. Note that an Ensulation dcfect may set the stage for oversensing pectoral myopotcntials. Verify the pacing impedance and the high-voltage shocking pathway impedance. The HVshocking impedance measures between 20 and 1Ũ0 ohms. This shocking impedance is always recorded when a shock is delivered. A high value Indicates a fracture a low value an insulation defect. In the past this was determined by deliberate delivery of a small shock. In contemporary devices Et is a painless measurement with a small test pulse in some LCDs lhese painless pulses are delivered periodically to construct a trend plot- The pacing fmpedanoa is related to lead design. Values lower than 2Ơ0 ohms indicate an in-5Illation defect while values higher than 2000 ohms indicate a fracture a loose set screw or a defective adapter Note that high impedance leads do not cause pacing impedances above 20Ũ0 ohms . A change In impedance larger than 30 in a mature lead suggests malfunction. The trend of lead impedance can be useful in the diagnosis of fracture. Occasionally a lead problem is associated with a normal impedance. 13 Remember Numerous aborted shocks due to oversensing suggest a lead problem. Multiple shocks without prior symptoms may also be caused by lead problems Ineffectual shocks for VT VF may occur if the problem involves the shocking electrode. Audible Patient Alert system may be activated by a lead problem. .