Influence of electromagnetic interference on implanted cardiac arrhythmia devices in and around a magnetically levitated linear motor car.

This study was designed to determine the susceptibility of implanted cardiac arrhythmia devices to electromagnetic interference in and around a magnetically levitated linear motor car [High-Speed Surface Transport (HSST)]. During the study, cardiac devices were connected to a phantom model that had similar characteristics to the human body. Three pacemakers from three manufacturers and one implantable cardioverter-defibrillator (ICD) were evaluated in and around the magnetically levitated vehicle. The system is based on a normal conductive system levitated by the attractive force of magnets and propelled by a linear induction motor without wheels. The magnetic field strength at 40 cm from the vehicle in the nonlevitating state was 0.12 mT and that during levitation was 0.20 mT. The magnetic and electric field strengths on a seat close to the variable voltage/variable frequency inverter while the vehicle was moving and at rest were 0.13 mT, 2.95 V/m and 0.04 mT, 0.36 V/m, respectively. Data recorded on a seat close to the reactor while the vehicle was moving and at rest were 0.09 mT, 2.45 V/m and 0.05 mT, 1.46 V/m, respectively. Measured magnetic and electric field strengths both inside and outside the linear motor car were too low to result in device inactivation. No sensing, pacing, or arrhythmic interactions were noted with any pacemaker or ICD programmed in either bipolar and unipolar configurations. In conclusion, our data suggest that a permanent programming change or a device failure is unlikely to occur and that the linear motor car system is probably safe for patients with one of the four implanted cardiac arrhythmia devices used in this study under the conditions tested.

Comparative study of the effect of pacing mode on the interaction of the right and left ventricles.

This study was designed to evaluate ventricular dyssynchrony from the viewpoint of the interaction of right and left ventricular contractions. Forty-three patients, 24 with sick sinus syndrome, 9 with complete atrioventricular block, and 10 with normal sinus rhythm were involved in this study. Microtip transducer catheters were advanced into both the left and right ventricles and ventricular pressure and the associated dp/dt were recorded simultaneously. Hemodynamic differences in various pacing modes were analyzed using pressure and dp/dt recordings obtained from the left and right ventricles. When an asynchrony between the right and left ventricular contractions existed, the right ventricular positive peak dp/dt developed a dual-peak waveform, the second peak corresponding in time to the peak of the left ventricular positive peak dp/dt. This dual-peak dp/dt waveform was seen with ventricular (VVI) and atrioventricular sequential (DVI) pacing, whereas a single-peak waveform was seen with atrial (AAI) pacing or sinus rhythm. In cases where DVI or VVI pacing modes are selected, an asynchronous effect between contractions of the right and left ventricles may occur, with dual-peak dp/dt of the right ventricle. Because the dual-peak dp/dt waveform indicates ventricular dyssynchrony, reducing the distance from peak I to peak II could maintain the synchronization of the right and left ventricles. It is considered particularly vital to give sufficient consideration to this point in chronic heart failure patients with left bundle branch block requiring biventricular pacing.

Effect of pacing mode on sleep disturbance.

The relationship between pacing mode and sleep is not yet known, and therefore polysomnography was used to evaluate the effect. A total of 16 patients (8 men and 8 women; mean age, 72 +/- 9 years) with DDD pacemakers made up the study population. Of these 16 patients, 8 patients had complete AV block and 8 patients had sick sinus syndrome. The recording was done twice in VVI and DDD modes. Between VVI mode and DDD mode, sleep latency time (VVI mode: 38 +/- 25, DDD mode 23 +/- 27 min), frequency of temporary waking (8.3 +/- 6.7, 3.7 +/- 2.9 times), the number of episodes of apnea (59 +/- 84, 36 +/- 55 times, the apnea-hypopnea index (AHI) (15 +/- 18, 10 +/- 13), and efficacy of sleep (72% +/- 10%, 81% +/- 11%) were significantly different. Also, the apnea index improved significantly in DDD mode. There was no significant difference in total sleep time and in total duration of temporary waking between the two groups. From the study results, a reduction in sleep disturbance was achieved when DDD pacing mode was chosen, rather than VVI mode. Furthermore, efficacy of sleep also improved significantly compared with VVI mode. Interestingly, sleep apnea syndrome in four patients with AHI > or = 15 notably ameliorated when DDD mode was chosen; however, the mechanism involved in amelioration is still ambiguous and needs further assessment.