Oversensing of Diaphragmatic Miopotentials in Patients with Implantable Cardioverter Defibrillators

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Abstract

The oversensing phenomenon in implantable cardioverter defibrillators (ICD) may cause unnecessary activation or inhibition of the incorporated pacemaker, generating a potential risk of inappropriate therapy and early draining of the battery. The purpose of this publication was to evaluate the over-sensing prevalence of diaphragmatic myopotentials in patients with implantable cardioverter defibrillators. Every ICD used had the capacity to store electrograms. Although the electrogram is only stored in the memory when an arrhythmia appears and before the delivery of therapy, we have observed that in some patients, under certain circumstances, the memory storage may occur without any previous arrhythmic event. It seems that the factor involved in some of these cases is the over sensing of diaphragmatic myopotentials. Forty-four patients of both sexes were studied (74%men) range 35-73 years old with the cardioverter defibrillator CPIV entak and Endotak catheter implanted (device with electrogram storage capacity). Every patient made isometric, postural and breathing manouvers to induce diaphragmatic myopotentials, including Valsalva manouvers in all of the cases. The stored memory and/or the therapy activation was observed in all of them, 39 patients with arrhythmia, but in five the storage occured in the absence of arrhythmia. In one of the patients the oversensing was dueto lead dislodgment, and in another one due to the T wave sensing. In three patients (6.8%) we have ob-served oversensing after making the Valsalva manouver. Simultaneous analysis of RR intervals and storedECG helped for the diagnosis. The diaphragmatic myopotentials detection may deliver unnecessary shocks. Having this in mind all patients should be evaluated periodically.