Suppression of a ventricular-inhibited bipolar pacemaker by skeletal muscle activity

Comparison of myopotential interference in unipolar-bipolar programmable DDD pacemakers

Myopotential interference (MPI) can inhibit or trigger single and dual chamber unipolar pacemakers while bipolar pacemakers are resistant. Twenty units of two different models of dual chamber pacemaker, each capable of being programmed to single chamber or dual chamber and unipolar or bipolar function were tested to provoke myopotential interference. No patient had evidence of myopotential interference at any sensitivity setting in the bipolar configuration either in atrium or in ventricle. All patients (20/20) interfered with pacemaker function at the highest atrial or ventricular sensitivity settings in the unipolar configuration. T wave sensing occurred at the 0.25 mV sensitivity setting in four patients in pacemaker model 925, in both bipolar and unipolar configurations. Twenty-five percent of patients had myopotential interference at the unipolar atrial sensing threshold and did not allow a setting which would reject myopotential interference while providing satisfactory atrial sensing. Twenty percent (2/10) had myopotential caused ventricular inhibition at the least sensitive ventricular channel setting in model 240G so that myopotential interference could not be avoided in that unit no matter how large the electrogram.

Myopotential interference inducing pacemaker tachycardia in a DVI programmed pacemaker

A 67-year-old male, suffering from ventricular tachycardia unresponsive to drug therapy, received a universal AV sequential pacemaker (DDD,M). The pacemaker was programmed in the DVI mode, pacing rate 100 bpm, AV interval 250 ms. After implantation, the patient experiences two episodes of tachycardia that proved to be pacemaker tachycardia with a rate of 150 bpm. The first period was self-terminating, and the second had to be stopped by reprogramming the pulse generator. Pacemaker tachycardia could easily be provoked by instructing the patient to contract the pectoral muscle adjacent to the pulse generator. To our knowledge, this is the first report of pacemaker tachycardia provoked by myopotentials in a pulse generator programmed in the DVI mode.

Prevention of myopotential inhibition of unipolar QRS-inhibited demand pacemakers

Seventy-two unipolar QRS-inhibited demand pacemakers were examined by provoking myopotential interference by exercise. Filter characteristics of 5 kinds of generators were tested by the use of sin wave pulse. Each myosignal of the major pectoral muscle and the abdominal rectus muscle was subjected to Fourier transform for analyses of amplitude and frequencies. Pacemaker inhibition was observed in 42 (58 per cent) of 72 with the highest frequency in the push up test. In this test, the incidence of myopotential inhibition was significantly lower (p less than 0.01) on the pacemaker implantations in the abdominal wall than that in the anterior chest wall. The myosignals of the major pectoral muscle had sufficient frequency and power density for triggering the QRS sensing mechanism but the abdominal muscular signals did not. To avoid myopotential inhibition of unipolar ventricular inhibited demand pacemakers it is most effective to implant multiprogrammable pacemakers subcutaneously in the abdominal wall and to select the optimal sensitivity according to the myopotential inhibition tests.

Self-inhibition of an AV sequential demand (DVI) pulse generator due to polyurethane lead insulation disruption

Self-inhibition of bipolar DVI AV-sequential pacemakers has been attributed to electrode malposition, although the potential for self-inhibition due to current leakage has been recognized. Previous cases of current leakages due to insulation defects in bipolar VVI ventricular demand systems have usually presented as abnormal sensing or pacing function without a change to actual unipolar sensing and pacing. This article describes a case of disruption of the insulation of polyurethane bipolar atrial and ventricular leads by silk ligatures, resulting in unipolar atrial and ventricular pacing and self-inhibition of ventricular output of a DVI pulse generator. This case emphasizes the importance of avoiding any application of suture material directly to polyurethane leads. This case also emphasizes the importance of monitoring pacemaker artifact amplitude and axis in patient follow-up.

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.

Myopotential inhibition of unipolar AV sequential (DVI) pacemaker

Whereas myopotential inhibition of QRS-inhibited (VVI) pacemakers is well known, its occurrence in patients with AV sequential (DVI) pacemakers has not been reported. The present communication deals with spontaneous and induced myopotential inhibition of a multiprogrammable Intermedics unipolar AV sequential (DVI) pacemaker. The bedside maneuvers that were performed in the patient exposed the problem, therefore serving to establish the diagnosis. Although external adjustment of the sensitivity was the simple, non-invasive solution in this case, more studies are required to determine the success rate of this approach as well as the incidence and clinical significance of myopotential inhibition of unipolar DVI pacemakers.

Myopotential inhibition of unipolar QRS-inhibited (VVI) pacemakers, assessed by ambulatory Holter monitoring of the electrocardiogram

Seventy-four patients with unipolar QRS-inhibited pacemakers (VVI) were Holter monitored to assess the occurrence of pacemaker inhibition caused by skeletal muscle potentials during daily activities. Fifty patients had high-grade atrioventricular block and 24 had sinoatrial disease. Chest wall stimulation prior to monitoring revealed asystole of > 4 seconds duration in 22 patients, and ventricular rates between 25 and 56 beats per minute in 52 patients. Fifty-one patients (69%) had one or more episodes of pacemaker inhibition from myopotentials. Inhibition occurred in all types of pacemakers studies, but was most frequent and of longest duration in patients with Siemens-Elema 207/70 (13/14 patients), Cordis Omni-Stanicor (6/7 patients), CPI Microlith (5/6 patients), and Medtronic 5945 (8/10 patients). This was not unexpected considering the filter characteristics of the pacemakers. Nine patients (12%) presented symptoms which might be ascribed to pacemaker inhibition. The longest asystole observed was 3.2 s. Seven patients had pacemakers spikes falling on or near T-waves of spontaneous heart beats because their pacemakers had been rendered refractory by myopotentials. No serious arrhythmias were seen during episodes of pacemaker inhibition or interference. More emphasis should be put on the improvement of filter characteristics of unipolar VVI-pacemakers. Pacemaker patients with symptoms of myopotential inhibition should be equipped with either a bipolar or ventricular triggered (VVT) pacemaker or with a sensitivity and/or pacing mode programmable pacemaker.

Myopotential inhibition of demand pacemakers: etiologic, diagnostic, and therapeutic considerations

Myopotential inhibition of demand pacemakers is a common phenomenon and is responsible for a greater degree of morbidity and possible mortality in patients with pacers. Significant electrical potentials generated by contracting muscle mass gain entry into the pacemaker circuitry causing inhibition of pacemaker activity. Intraoperative and bedside maneuvers can readily precipitate the problem and allow for accurate diagnosis. Holter monitoring frequently can also serve to establish the diagnosis. Pacemaker repositioning, replacement with a bipolar system, use of a fixed-rate pacemaker, and pacemaker "sleeves" are possible intraoperative therapeutic methods. External sensitivity adjustable pacemakers would seemingly allow for noninvasive solutions to the problem.

Myopotential inhibition of a bipolar pacemaker caused by electrode insulation defect

A patient is described in whom myopotentials orginating from the anterior abdominal wall muscle suppressed the implanted demand pacemaker despite its bipolar mode of action. This phenomenon was shown by simultaneous recording of the electrocardiogram the electromyogram. At operation, a defect in the insulation of a previously repaired epicardial electrode was found lying in close proximity to these muscles. After repair of the insulation defect, normal pacemaker function was restored. It is suggested that the myopotentials leaked into the pacing system through the insulation defect, thereby suppressing the demand unit, which maintained its bipolar mode of pacing throughout.

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.

Fluoroscope-generated electromagnetic interference in an external demand pacemaker: report of a case

Electromagnetic interference presented as inhibition and resetting of the demand circuitry of a ventricular-inhibited temporary external pacemaker in a 70-year-old man undergoing surgical implantation of a permanent bipolar pacemaker generator and lead. The arrhythmia was found to be due to oversensing of waveforms modulated to simulate myocardial potentials emitted by a faulty fluoroscopy unit used in the vicinity of external temporary transvenous pacing equipment. The documentation of this disruption of pacemaker rhythm reinforces the need for continuous monitoring of patients treated with external demand pacemakers and for the careful maintenance of all electrical equipment.