Inhibition of demand pacemakers caused by potentials associated with inspiration

Ventricular pacing inhibition by oversensing due to diaphragmatic myopotential during deep inspiration

An 80-year-old man, who had dilated cardiomyopathy with right ventricular (RV) dilatation, underwent implantable cardioverter defibrillator (ICD) implantation for advanced atrioventricular block and primary prevention of sudden cardiac death. Tined and screw-in leads were placed on the right atrial appendage and RV apex, respectively. Ventricular pacing inhibition was detected after surgery due to oversensing by diaphragmatic myopotential occurring only during deep inspiration. We performed re-surgery and switched the screw-in lead for a tined lead. The diaphragmatic myopotential decreased, thereby improving oversensing by diaphragmatic myopotential and ventricular pacing inhibition. It might be beneficial to use a tined lead when placing the ventricular lead at the RV apex for implantation of a pacemaker or ICD if oversensing of diaphragmatic myopotential is observed using a screw-in lead. <Learning objective: Oversensing due to diaphragmatic myopotential is rarely observed. However if it occurs, it becomes a critical problem, which causes pacemaker inhibition or inappropriate ICD shock. However, the method of preventing this problem is unknown. In this case, we demonstrated that a tined-lead may be useful for the prevention of oversensing by diaphragmatic myopotential.>.

Myopotential sensing by a dual chamber implantable cardioverter defibrillator: two case reports

INTRODUCTION

Inappropriate discharges and/or improper inhibition of bradycardia pacing due to oversensing of extraneous signals in implantable cardioverter defibrillators (ICDs) have been described. With one exception, no previous report involving an intact lead system has cited myopotential oversensing as the cause.

METHODS AND RESULTS

Two case reports of myopotential oversensing by a dual chamber ICD system are reported. In the first patient suffering from chronic pulmonary obstructive disease, intermittent myopotential sensing during labored respiration resulted in episodic inhibition of bradycardia pacing. In the second patient, oversensing of sustained myopotentials generated during strenuous isometric activity resulted in an inappropriate ICD discharge. For both, the ICD system consisted of a CPI model 1810 Ventak AV used in conjunction with a model 0125 Endotak lead, incorporating integrated bipolar sensing.

CONCLUSION

Although modern ICDs have proven to be highly effective in detecting and terminating malignant tachyarrhythmias, the opportunity for improving their detection specificity remains.

Oversensing from electrode 'chatter' in a bipolar pacing lead: a case report

An 81-year-old man was treated for high degree AV block and syncope with an AV universal (DDD) pacemaker. Bipolar active fixation atrial and ventricular leads were used. Intermittent oversensing from the ventricular lead was detected on Holter monitoring following implantation. This resulted in inappropriate inhibition of ventricular pacing. Ventricular electrogram showed spurious signals between 5 mV and 15 mV in magnitude coincident with ventricular lead inhibition. Treatment consisted of reprogramming the device to the VVT mode. Six weeks after implantation normal pacemaker function in the DDD mode was demonstrated on Holter monitoring and inappropriate pacer inhibition could not be demonstrated. We postulate that electrode 'chatter' between the cathodal ring electrode and the helix of the ventricular lead resulted in artifactual potentials sufficient to inhibit pacing. We hypothesize that fibrosis and fixation of the ventricular lead tip over a period of weeks eliminated these electromechanical artifacts and resulted in the oversensing problem being self-limited. Physicians should be aware of electrode 'chatter' as a cause of pacemaker oversensing.

Myopotential inhibition of unipolar lithium pacemakers

The effect of isometric upper extremity exercise on pacemaker function was evaluated in 27 patients who remained pacemaker-dependent during testing. Inhibition was demonstrated in eight (31 percent) of which five were symptomatic. Based on design of the sensing amplifier and return to an all-metal housing in the unipolar lithium pulse generators, myopotential inhibition is being recognized as one cause of symptomatic pacemaker inhibition that is more common than generally appreciated. A method of evaluation and management options for symptomatic patients are discussed. Routine testing of all patients should be performed at the time of a regular office evaluation. If one model pulse generator appears to be particularly prone to myopotential inhibition, this knowledge should be considered in the choice of future pacing systems.

Inhibition of programmable demand pacemaker by pacemaker-induced myopotentials

Pacemaker-induced myopotentials caused inhibition of a demand pacemaker in two cases in which the unipolar partially encapsulated pacemaker flipped over in its pocket and directly stimulated the muscles of the chest wall. This pacemaker-induced muscular stimulation, possibly combined with afterpotential sensing or T-wave sensing (or both), caused the rate of the demand pacemaker to fall when the output of the programmable pacemaker was set to deliver high energy charges. By programming the unit to deliver a lower charge (shorter width of pulse), the rate rose appropriately to the programmed rate. Likewise, manual rotation of the unipolar pacemaker into proper orientation with the active uninsulated surface directed towards the skin also solved the problem temporarily.

Suppression of an external demand pacemaker by diaphragmatic myopotentials: a sign of electrode perforation?

Transient pacemaker inhibition was observed in a patient with an external bipolar demand pulse generator. Recordings of the proximal, distal and bipolar electrograms showed extracardiac myopotentials only in the unipolar distal and bipolar configuration. These myopotentials which caused inhibition of the pulse generator were related to respiration and other maneuvers that resulted in active contraction of the diaphragm, thus proving their diaphragmatic origin.

Risks of delayed potentials in pacemaker patients prone to ventricular tachycardia

Late potentials occurring after completion of the QRS complex have been observed in patients prone to ventricular tachycardia. They were recorded either during epicardial studies or in the catheterization laboratory. This paper describes such abnormal myocardial activity and discusses their potential effects on cardiac pacemakers.

Apparent malfunction of demand pacemakers due to spurious potentials generated by contact between two endocardial electrodes

Malfunction of both temporary and permanent demand transvenous pacemakers was caused by contact between the two endocardial electrodes. Contact between these electrodes created spurious potentials which resulted in irregular inhibition of both demand units. The potentials were demonstrated by recording from the temporary wire. There was no interference with either pacemaker in the fixed rate mode and malfunction ceased when the temporary wire was removed.

Inhibition of bipolar demand pacemaker by diaphragmatic myopotentials

This report describes inhibition of a normally functioning bipolar demand pulse generator by diaphragmatic myopotentials. Transient pacemaker suppression occurred repeatedly with deep respiration, straining, the Valsalva maneuver, coughing, sneezing and laughing. When the magnet was applied, none of these maneuvers inhibited the pacemaker. Extensive investigations ruled out an intermittent electrode problem such as a wire fracture or insulation break. Sensing of diaphragmatic myopotentials should be considered in the differential diagnosis of unexplained pacemaker pauses.