Noboru Mizutani

Effects of physiological cardiac pacing on sleep-disordered breathing in patients with chronic bradydysrhythmias

In six patients with chronic bradydysrhythmias, polysomnographies were performed before cardiac pacemaker implantation and over the week following implantation. A patient with third‐degree atrioventricular block (AVB) and two patients with sinus node dysfunction (SND) were associated with sleep‐disordered breathing (SDB). Their cardiac pacemaker therapies, with the increase in the average heart rate, led to a reduction of apnea–hypopnea index and/or an improvement of Cheyne‐Stokes breathing. It seems that chronic bradydysrhythmia is one of the causative factors leading to SDB.

Effect of pacing mode on sleep disturbance.

Abstract 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 ≧ 15 notably ameliorated when DDD mode was chosen; however, the mechanism involved in amelioration is still ambiguous and needs further assessment.

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.

Pacing Therapy for Prevention of Atrial Fibrillation

Nonpharmacological therapy is being evaluated for the prevention of atrial fibrillation (AF). Pacing has been proposed as a one of the option to prevent AF. In patients with bradycardia and requiring pacemaker, physiological pacing such as dual chamber pacing or atrial pacing has an advantage against ventricular pacing in prevention AF. Pacing from novel site like the dual‐site atrium, biatrial, Bachman, and low sepatl pacing may reduce AF burden and new anti‐AF pacemakers with atrial prevention algorithm may decrease AF further. However, selecting the appropriate patients and adopting tailored‐therapy for individual patient is likely to remain one of the difficulties in achieving an advantage. This review discusses the current status of pacing therapy for the prevention of AF. It also discusses the some of merits and limitations of pacing therapy for the treatment of AF.

A survey of the effect of electromagnetic interference on currently marketed pacemakers

It is well known that electromagnetic interference (EMI) generated from various sources can interfere with normal implantable cardiac pacemaker function, and the susceptibility of various generator models to EMI has been studied previously. However, there are no data about the pacemakers currently encountered in the marketplace. In the present study, we examined the influence of EMI on pacemakers in vivo and in vitro, with emphasis on measurements of ambient magnetic and electric fields. Eleven pacemakers from nine manufactures were evaluated under physiological circumstances as close as possible to those of an implanted pacemaker. Pacemaker behavior was monitored with telemetered event markers and intracardiac electrograms. Measured magnetic field strengths from several interference sources encountered in daily life, in the work environment, and in medical practice were too low to result in device inactivation except during use of medical diathermy devices and mobile phones. Medical diathermy produced a noise response in all devices except Medtronic KAPPADR and Vitatron DIAMONDII. During mobile phone use, high levels of the magnetic field were measured only if the phone units were pressed directly on to the pacemaker. However, even this situation did not result in disturbance of the pacemakers sensing function. No pacemaker function changes were seen to be due to electrical interference. During diathermy exposure, high levels of electric fields were measured at distances up to 50cm. Among different exogenous interference sources, no pacemaker currently distributed was found to be influenced in a detrimental way, i.e., oversensing or no output.

Influence of pacing parameters on pacemaker longevity

Abstract This study retrospectively assessed the parameters that affect pulse generator longevity in 78 patients implanted with dual-chamber pacemakers. Longevity was studied in 52 generators: 14 Cosmos II, 17 Relay, 11 Ellite II, and 10 Thera DR. The lifetimes of Cosmos II and Ellite II were significantly prolonged compared to those of Relay and Thera DR. The comparative study was conducted to evaluate the effect of low-impedance leads (ThinLine I, n = 10) on generator longevity compared with a standard lead (Irox, n = 16). No significant variation in pacing threshold was found between the groups. However, the low-impedance group provided significantly lower cell voltage and higher cell impedance during all follow-up periods compared with the standard lead impedance group. The internal current of the pacemaker with rate response and sophisticated diagnostic memory function (Relay, n = 5, and Marathon DR, n = 5) increased significantly compared with the conventional pacemaker (Cosmos II, n = 5). In conclusion, the selection of unnecessary pacing parameters and the selection of low-impedance leads should be avoided in order to extend generator longevity.

The Tokai Pacemaker Register

Abstract The Tokai Working Group on Cardiac Pacemakers was established in 1987 and initiated the Tokai Pacemaker Register in 1993. The register contains data on 1582 patients treated with 1582 generators and 2269 leads. The ECG indications for pacemaker implantation were 49.7% atrioventricular block, 41.1% sinus node dysfunction, and 7.4% atrial fibrillation. Dual-chamber pacing was used in 43.8%, VDD pacing was used in 37.6%, and single-chamber VVI pacing in 18.4% of the patients.

Experimental study for single-pass lead DDD pacing

We investigated the possibility of single-pass lead DDD pacing in animal experiments, using an original double balloon bipolar lead with variable dipole spacing. In the present study, P-wave sensing was best with a narrower dipole spacing, a smaller electrode surface area, and with the placement of atrial electrodes in the upper region of the atrium. The pacing threshold was not significantly different in various atrial sites, whereas the threshold energy increased dramatically under conditions of truly floating atrial pacing. Additionally, our simulation analysis revealed that the pacing thresholds were lower with a smaller electrode surface and the optimal dipole spacing was dependent on the distance between the atrial wall and the stimulating electrodes. Since stimulation at a distance from the atrial wall is barely feasible, further studies are required to achieve single-pass lead DDD pacing.

Problems of single-lead DDD pacing

This paper proposes some questions that remain to be solved for single-pass DDD pacing. These are the possibility of obtaining atrial capture with floating atrial electrodes, the optimal site to obtain atrial capture, the pacing method to ensure atrial pacing, and the possibility of long-term, single-lead DDD pacing. We found that the distance between the proximal electrode and the atrial free wall in the low-threshold group (<5 V/0.5 ms) was 5.8 mm, and in the high-threshold group (>5 V/0.5 ms) it was 10.3 mm. The distance was significantly shorter in the former group. Atrial pacing with OLBI (overlapping biphasic stimulation) provided relatively stable atrial pacing even if the atrial electrode dislodged from a cardiac size reduction following improved cardiac function. In conclusion, single-pass DDD pacing could be achieved if the atrial electrodes are in direct contact with, or in very close proximity to, the free wall of the right atrium, and it would be beneficial if atrial pacing could be achieved by OLBI pacing. However, producing stable single-pass lead DDD pacing is difficult in the long term when the atrial electrodes are floating freely inside the atrium.