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Introduction: This study evaluated the impact of the atrial lead implantation site on the subsequent development of atrial arrhythmias., Method: Dual chamber pacemakers were implanted in 109 consecutive patients. The indication was AV-block in 51 patients, sick sinus syndrome in 58 patients. No patient had chronic atrial fibrillation, but 12 patients (11%) had paroxysmal atrial fibrillation before implantation. Patients were classified according to the atrial lead implantation site: right atrial appendage and right atrial free wall., Results: Preimplant episodes of atrial fibrillation were similar in patients with lead implantation at the free wall and with implantation in the right atrial appendix (13% vs 7.5%, P=0.53). During a mean follow-up of 24+/-13 months, new paroxysmal atrial fibrillation occurred in 5% after lead implantation in the appendix vs 28% of patients after implantation at the right atrial free wall (P = 0.004)., Conclusion: The development of atrial arrhythmias in dual chamber pacing is influenced by the implantation site of the atrial lead. The frequency of atrial arrhythmias during follow-up is higher after atrial lead implantation at the right lateral wall than in the appendix.

A biatrial pacemaker was inserted in a 68-year-old female with paroxysmal atrial fibrillation and atrial flutter refractory to antiarrhythmic drugs based on a sick-sinus-syndrome and concomitant interatrial conduction delay. One electrode positioned in the right atrium and another electrode located in the coronary sinus were connected to a dual-chamber pacemaker. The electrode in the right atrium was connected to the atrial channel, the electrode in the coronary sinus to the ventricular channel. The pacemaker was programmed in DDD-mode with an AV-delay of 30 ms. Under a chronic antiarrhythmic medication with 160 mg sotalol per day there was no evidence for recurrent episodes of atrial tachyarrhythmias in the patient's history, 24-h-Holter-ECG, nor in the memory of the pacemaker during a follow-up of 8 months.

Implantable cardioverter/ defibrillators (ICD) represent in many patients with ventricular tachyarrhythmias the first line treatment. Up to 15% of the patients requiring an ICD need concomitant permanent cardiac pacing for bradyarrhythmias resulting in the need of simultaneous ICD- and antibradycardic pacemaker-therapy. We present four patients with successful implantation of a transvenous ICD-system (Medtronic Jewel 7220 and Micro Jewel 7221; electrode: Medtronic 6939), all of which had an antibradycardic pacemaker (2 unipolar, 2 bipolar) implanted prior to ICD-implantation. Meticulous intraoperative testing in order to avoid adverse interactions between the two systems has been carried out successfully in all cases. Possible adverse interactions comprise oversensing of pacemaker signals by the ICD with subsequent inadequate therapy, inhibition of defibrillation therapy during ventricular fibrillation caused by false detection of pacemaker spikes by the ICD as well as reprogramming of the pacemaker after shock delivery. A review of the published literature yielded 91 reported cases of combined ICD- and pacemaker-therapy. In 16% of the patients, one or more of the mentioned complications have been observed. Those occurred more frequently with unipolar than with bipolar pacemaker-systems. Thus, combined therapy with antibradycardic pacemaker and transvenous ICD-systems can be performed safely.

Unlabelled: Steroid-eluting screw-in leads (CapSure Fix 4068, Medtronic; n = 14) were compared to the same lead as a J-shaped tined electrode (CapSure SP 4524, Medtronic; n = 27, implanted in the atrium in patients receiving dual-chamber pacemakers. Follow-up were at discharge and after 1 month. Implantation (screw-in lead: 84 +/- 18 min; tined lead: 81 +/-29 min) and fluoroscopy times (screw-in lead: 7.3 +/- 4.9 min; tined lead 9.2 +/- 7.0 min) were similar in the two groups. At implant, P-wave amplitudes were similar with 4.8 +/- 1.6 mV (screw-in lead) and 4.0 +/- 2.6 mV (tinted lead), respectively. Compared to tined leads, the screw-in leads had higher pacing thresholds at 0.5 ms pulse duration (screw-in lead: 0.74 +/- 0.32 V; tined lead: 0.55 +/- 0.15 V; p = 0.02) as well as higher impedance (screw-in lead: 566 +/- 93 ohms; tined lead: 470 +/- 99 ohms; p = 0.01). Pulse duration thresholds at 2.5 V pulse amplitude were neither different at discharge (screw-in lead: 0.07 +/- 0.04 ms; tined lead: 0.06 +/- 0.05 ms) nor after 1 month (screw-in lead: 0.09 +/- 0.04 ms; tined lead: 0.06 +/- 0.06 ms). P-wave amplitudes > or = mV were observed at discharge in 14/14 (screw-in lead) 21/27 patients (tined lead), respectively, and after 1 month in 13/14 (screw-in lead) and 22/27 (tined lead) patients, respectively. Impedance of the screw-in lead was significantly higher with 693 +/- 84 ohms at discharge and 691 +/- 79 ohms after 1 month compared to the tined lead with 520 +/- 81 and 574 +/- 62 ohms (p = 0.001). No lead dislodgment was reported during follow-up., Conclusions: For the studied steroid-eluting leads active and passive fixation had neither at implantation nor during 1-month follow up any influence on P-wave amplitude. At similar pulse duration thresholds, impedance of the screw-in lead was significantly higher than for the tined lead. Higher impedance additionally reduces pacing current, if similar pacing impulses are delivered.

This prospective cross-sectional study include 100 consecutive patients (56 males, 44 females, 29 to 86 (mean = 67.5 +/- 12.2) years) with ventricular inhibited demand pacemakers 0.1 to 94.7 (mean 23.3 +/- 25.4) months after pacemaker implantation. Fifty-two patients were free of symptoms, whereas 48 patients were still complaining of syncope, dizziness, or palpitations. After history, physical examination, and 12-lead standard ECG all patients underwent 24-h Holter monitoring. A computer-aided analysis of spontaneous arrhythmias was done first. In a second run computed-aided analysis of transient pacemaker dysfunctions was performed with a specially designed pacemaker module. There were no significant differences between asymptomatic and symptomatic patients with regard to the incidence of transient pacemaker dysfunctions, with regard to defined types of pacemaker dysfunctions, spontaneous ventricular arrhythmias, and with regard to supraventricular tachycardias. A significant difference between asymptomatic and symptomatic patients was found, however, regarding the Lown classification of ventricular arrhythmias, because asymptomatic patients showed class 0 and I/II arrhythmias more frequently (p < 0.025). In the 100 patients a total of 6609 pacemaker dysfunctions were observed, 5104 failures to sense and 1505 inappropriate inhibitions. Most patients showed up to 240 pacemaker dysfunctions per 24 h. There were no failures to capture. Different types of pacemaker dysfunctions were found with different clinical implications. Due to the Holter findings in nine patients pacemakers were reprogrammed or replaced. After pacemaker implantation the number of patients with severe symptoms significantly decreased compared to the number of patients before pacemaker implantation. Nonetheless, there was a number of patients still complaining of symptoms after pacemaker implantation. In only a few patients did pacemaker implantation worsen symptoms . Our data show that with use of long-term ECG transient pacemaker dysfunctions and spontaneous arrhythmias are more frequent than patients' history and common standard techniques in the pacemaker clinic may suggest Holter monitoring, therefore, is a useful diagnostic tool, not only in symptomatic, but also in asymptomatic pacemaker patients. It allows to obtain a reliable survey of the real amount of transient pacemaker dysfunctions in the individual patient, which is the base for further therapeutic decisions.

The purpose of this study was to assess cardiopulmonary exercise capacity, variation in heart rate during everyday activities, frequency of atrial arrhythmias and quality-of-life during accelerometer-based rate modulated dual-chamber pacing. Nine chronotropically incompetent and 14 chronotropically competent patients (mean age 51 years) were randomly assigned to DDD and DDDR mode and evaluated by a semisupine bicycle exercise testing exceeding the anaerobic threshold, 24-h Holter monitoring and a quality-of-life questionnaire. In the subgroup of patients with chronotropic incompetence, defined by a HR/VO2-ration, 2 beats/ml/kg, during DDDR pacing, compared to DDD, maximum heart rate increased from 83 +/- 13 to 132 +/- 7 beats/min (p < 0.01), maximum oxygen uptake from 12.7 +/- 3.1 to 15.3 +/- 3.2 ml/kg/min ( p < 0.05) and the VO2/WR-ratio from 8.1 +/- 1.0 to 9.0 +/- 0.9 ml/min/watts (p < 0.05). Exercise duration lengthened from 252 +/- 59 to 301 +/- 96 s (p < 0.05). During the 24-h Holter recordings the average maximum heart rate rose form 69 +/- 7 in the DDD mode to 78 +/- 9 beats/min in the DDDR mode significantly (p < 0.05). DDDR pacing did not result in an increased number of atrial salvos (2.6 atrial events/24 h) when compared to DDD pacing (2.5 atrial events/24 h, N.S.). These objective results were confirmed by the quality-of life assessment due to a symptom questionnaire. The symptom score declined from 20 +/- 10 in the DDD mode to 16 +/- 7 in the DDDR mode (p < 0.01). In the patients with chronotropic competence, however, cardiopulmonary exercise capacity did not improve in the DDDR mode: maximum heart rate was 120 +/- 21 versus 130 +/- 24 beats/min (N.S.), maximum oxygen uptake 17.7 +/- 5.9 versus 16.8 +/- 5.9 ml/kg/min (N.S.), The VO2/WR-ratio 9.8 +/- 2.3 versus 9.2 +/- 2.5 ml/min/watts (N.S.) and the exercise duration 407 +/- 159 versus 406 +/- 165 s (N.S.). The average maximum heart rate was 80 +/- 15 in the DDD mode and 83 +/- 16 beats/min in the DDDR mode (N.S.). Significantly more atrial arrhythmias occurred in the DDDR pacing mode: 1.6 atrial salvos per 24 h in the DDD mode versus 4.8 atrial salvos per 24 h in the DDDR mode (p < 0.05). This patient subgroup experienced a significant worsening of his quality-of-life. The symptom score rose from 20 +/- 9 in the DDD mode to 28 +/- 11 in the DDDR mode (p < 0.05). In conclusion, DDDR pacing improved cardiopulmonary exercise capacity, normalized heart rate variation over 24 h and increased quality-of-life in patients with chronotropic incompetence. On the contrary, since the DDDR pacing more could not improve cardiopulmonary exercise capacity, increased atrial arrhythmias and worsened the patient's quality-of-life, patients with chronotropic competence should not be programmed in the DDDR pacing mode.

Twenty patients (complete AV block n = 13, sick sinus syndrome n = 4 (replacement of a VVI system), bradyarrhythmia n = 3) with rate-adaptive pacemakers (respiration volume guided n = 10, QT-driven n = 1, dual sensor (QT/activity) system n = 9) were randomly assessed by ergospirometry after 4 weeks of VVI- (70 bpm), VVIR1-(70-110 bpm, low upper rate) and VVIR2-pacing (70-130 bpm, high upper rate). Oxygen uptake (VO2), work load (W), and heart rate were determined at peak exercise (max) and at the anaerobic threshold (AT). In the whole population, rate adaptation led to a significantly higher VO2-max than VVI-pacing for both VVIR1- (15.5 +/- 5.1/12.6 +/- 4.1 ml/kg/min, 28 +/- 37%, p < 0.01) and VVIR2-pacing (14.8 +/- 4.4/12.6 +/- 4.1 ml/kg/min, 20 +/- 23%, p < 0.01). At the AT, however, VO2 was significantly improved only by the VVIR1 mode (low upper rate, 9.8 +/- 2.5/8.0 +/- 2.1 ml/kg/min, 28 +/- 36%, p < 0.01). Regarding only patients with moderately limited exercise capacities (Weber class C, n = 11), rate adaptive VVIR1 and VVIR2 pacing could not produce a significant increase of VO2-max and VO2-AT. In contrast, patients with severely reduced exercise capacities (Weber class D, n = 9) significantly profited from the rate adaptation, but only in the VVIR1 mode (VO2-max 48 +/- 45%, VO2-AT 51 +/- 38%, p < 0.01). Thus, in the whole population an increase of oxygen uptake and of exercise workload at the anaerobic threshold could only be achieved by pacing with the low upper rate of 110 bpm. By this, particularly patients with heart failure and a severely limited exercise tolerance (Weber D) had a significant benefit. Therefore, the upper rate should be programmed in a lower range in patients with heart failure, at least for rate-adaptive ventricular pacemaker systems.

Sinus node dysfunction (SND) is a rare cause of bradycardia in children without structural heart disease. The clinical and diagnostic findings in 4 children with this condition are described. Two of them presented with symptoms, in one arrhythmias had been noted before birth, and a routine physical examination had revealed bradycardia in another. Age at onset of either clinical symptoms or bradycardia ranged from 0 to 11 1/2 years. Routine and 24-h-electrocardiograms showed atrioventricular junctional rhythms with minimal rates of 25/min and episodes of asystole with a maximal duration of 10.3 s. Other electrocardiographic abnormalities such as first degree atrioventricular block, ventricular extrasystoles or tachycardia were common findings. Electrophysiological studies were performed in 3 cases and confirmed the diagnosis of SND. A permanent pacemaker was inserted in 2 children; medical treatment did not have any long-term effect. During a follow-up period of 5 to 13 years there were no complications. In summary, SND in childhood can be assessed by Holter monitoring with high reliability. Electrophysiological studies are not necessary and of limited value. Therapeutic policies and prognostic statements are difficult to establish due to the small number of cases so far described. Permanent cardiac pacing, however, is unavoidable in symptomatic children.

The pathological reactions of the tissue under the picture of a circumscriptive erythema above the pacemaker-pouch of a 35-year-old patient was noticed and documented for more than 10 years. Repeated appearance of a painful and fluctuating swelling above the silicone-containing implant, as well as non-symptomatic intervals during times without application of silicone-material led to the assumption of an allergic contact dermatitis to the silicone components of the pacemaker. However, patch-testing of the pacemaker's constituents remained negative and could not verify this supposition. The diagnosis of a foreign-body-reaction was histologically set up. In its progress a stenosis of vessels as well as an activation of the T-cell-system can follow. Therefore, it might be possible that different factors meshing with each other can modify the cause-consequence-structure and can lead to the erythematic changes.

This study used ergospirometry with quantification of gas exchange parameters to analyze the beneficial effects of two sensors for rate responsive pacing: QT-interval and minute ventilation (MV). Bicycle exercise testing was performed with modulating VVIR pacing modes in random sequence. Rate responsiveness effected a mean increase of exercise tolerance of 31.1% in the QT group and 22.6% in the MV group. With both systems maximal oxygen uptake increased by 29.4% (QT) and 28.3% (MV). Oxygen consumption at the anaerobic threshold was improved by 28.3% (QT) and 32.1% (MV). The increase of cardiopulmonary parameters achieved by rate responsiveness was significant (p < 0.05) without significant difference in comparison between both groups. Despite the initially delayed rate increase at the onset of exercise mediated by the QT-interval, the programmed upper rate limit was satisfactorily attained by both principles. Thus, both sensors--minute ventilation and QT-interval--provide an adequate rate modulation in response to exercise and a marked improvement of cardiopulmonary work capacity.

New activity pacemaker systems with the principle of sensing low-frequency acceleration in the anterior-posterior axis are currently under clinical evaluation. We compared the pacemaker system Relay, which represents this new generation of accelerometer controlled devices, with conventional activity systems sensing pressure and vibration. Ten pacemaker patients with implanted Activitrax, Sensolog or Relay pacemakers and 10 healthy volunteers with externally strapped-on pacemakers were studied. The aim was to evaluate the systems' ability to distinguish different workloads during graded treadmill testing with changes in speed and/or slope. The rate adaption of the new acceleration sensing pacemakers was found to be more adequate compared to vibration and pressure-sensing pacemakers when only the slope of the treadmill was varied. The acceleration-sensing pacemaker adjusted its rate according to the workload largely independent from the type of stress (n.s.). With the vibration and pressure-sensing pacemakers, however, significant differences (p < 0.05) were seen between rate adaption in the two stress test modes. The new generation of acceleration-sensing pacemakers has certain advantages over conventional vibration-sensitive systems in terms of a higher sensitivity to varying workloads and higher specificity to the type of exercise performed.

The reduction of electrode surface area leads to an increase of pacing impedance which may be caused either by higher tissue resistance or by greater polarization occurring at the electrode-myocardium interface. The impedance of steroid-eluting leads with both 8 mm2 surface area (CapSure 4003, Medtronic n = 12) and with 4 mm2 (030-368, Telectronics, n = 8) were compared to the impedance of a high polarizing Elgiloy lead (PE 60/4 DN, Biotronik; n = 7). All leads were connected to the same unipolar VVI pacemaker (Pasys 8329, Medtronic). Pacing impedance was measured at 0.8, 1.6, 2.5, 5.0, and 8.0 volts pulse amplitude and at 0.05, 0.25, 0.5, 1.0, 2.0 msec pulse duration. Impedance of the Elgiloy lead was constant at 0.05 and 0.25 msec, but increased at longer pulse durations for pulse amplitudes below 5.0 volts. Both steroid-eluting leads had constant impedance at each pulse duration. The impedance of the 4 mm2 lead was significantly higher than of the 8 mm2 lead. In contrast to the Elgiloy lead, impedance of the steroid-eluting leads is not influenced by pulse-dependent factors such as polarization, indicating that the higher impedance of the 4 mm2 steroid-eluting lead is caused by a higher tissue resistance and not by greater polarization.

In the past, the most important feature in the development of rate-responsive pacemaker systems was ensuring an adequate rate response to physical exercise. But there are other variables that modulate the rate of the healthy heart; examples include postural changes in heart rate in order to prevent orthostatic reactions, and the nightly decrease in intrinsic pacemaker rate. Therefore, we developed a sensor that could distinguish, not only rest and activity, but also discriminate between a supine and an upright position. This sensor is a multicontact tilt switch, which contains a small mercury ball. By measuring the number of openings and closures within the sensor as the ball touches the numerous sensor contacts it is possible to discriminate between different levels of exercise; the contact pins are circled around the base plate. There is an almost linear increase in the number of changes per time with increasing exercise. Besides measuring body activity from the number of contact changes per time, it is also possible to determine the body's posture from the count and positioning of the closed contacts within the casing. Based upon the results of 12 volunteers and nine pacemaker patients, a new algorithm is being prepared which enables the pacemaker to decrease stimulation rate in the supine position, to increase it in the upright position, and to correlate pacing rate with the increase in physical exercise. There is a good correlation between number of contact changes and the intrinsic heart rate (r = 0.87).

Antibradycardiac pacemaker therapy has become established as one of the most effective forms of cardiological therapy for the indications AV-block, sick sinus syndrome, bradyarrhythmia, and hypersensitive carotid sinus. About 220,000 systems are implanted per year worldwide, about 32,000 in West Germany. Of the pacing modes, the fixed-rate ventricular single chamber systems (VVI) dominate with a share of almost 90%. Prognostic importance: For AV-block, the improvement of the prognosis by pacemaker therapy is unquestionable, since it increases the cumulative survival rates to 81% and 95% after 1 year and 50% to 65% after 5 years. For sick sinus syndrome, VVI-pacing proves to be a symptomatic measure, no prognostic importance can be proven. It is not conclusively clarified at present whether physiological pacing modes (AAI, DDD) have any such importance. Pacemaker therapy also has no prognostic importance for bradyarrhythmia. Hemodynamic importance: Numerous hemodynamic studies show that fixed-rate VVI-pacing fails to produce a long-term hemodynamic improvement for either an AV-block or a sick sinus syndrome. In sick sinus syndrome hemodynamic improvement can only be achieved by physiological pacing modes (AAI, DVI, DDD), whereby the increase in cardiac output is between 11% to 30%. For AV-block a long-term hemodynamic improvement can only be obtained by atrial triggered pacing modes (VAT, VDD, DDD); this is higher than the values of fixed-rate VVI-pacing by 7-25% at rest, or 10-40% under exercise. Similar results with improvements of the exercise hemodynamics between 22% and 66% are reported for rate-modulated single-chamber pacing (VVIR) for AV-block. Future trends: In the fourth decade of pacemaker therapy, developments point toward the "smart pacemaker", toward rate-modulated systems with combinations of parameters, toward rate-modulated dual-chamber systems and universal antibradycardiac and antitachycardiac systems.

The individual programming of cardiac pacemakers to pulse amplitudes of 2.5 volts and less reduces unnecessary energy consumption by the pacing impulse. In order not to impair the safety margin, electrodes must reveal a low chronic pacing threshold associated with a small standard deviation. For 3 months after implantation we investigated these conditions in 10 patients with a steroid-eluting lead and in 10 patients with a conventional elgiloy lead. During the study period patients with a steroid-eluting lead had a significantly lower pacing threshold. Twelve weeks after implantation all steroid-patients had 0.8 volts pacing threshold at 0.5 ms pulse width. In contrast to the conventional lead the steroid-eluting lead had a significantly lower impedance. Since voltage enters squared into the energy consumption formula, patients with a steroid-eluting lead needed significantly less energy for an effective stimulation of the myocardium 4 and 12 weeks after implantation. R-wave amplitude was not different in both groups. Our investigation demonstrates that immediately after implantation all patients with a steroid-eluting lead can be programmed at 2.5 volts pulse voltage or individually even lower. The saved energy results either in an extended pulse generator longevity or allows the implantation of a smaller pulse generator with a reduced battery capacity.

Caused by the defect of a Lem-Dynacor pacemaker, a critical diminution of the period time till 20 ms developed. Fortunately, ventricular fibrillation did not occur because of diminution of the impulse amplitude beyond the threshold value of ventricular stimulation. Recognition of the defect with the ECG is possible if considered. It is easy to confuse with overlapping of alternating current.

136 patients were followed after implantation a DDD pacemaker (PM) for a total of 1,919 patient-months (m = 14.1 months/patient). 22/136 patients had one or more episodes of atrial flutter or fibrillation (AF) postoperatively. In 121/136 patients (group A) AF had not been documented before, in 4 it was unknown at the time of implantation, but was verified retrospectively (group B). 11 patients (group C) had a positive history of previous AF. Post implantation 7.4% in group A and 81.8% in group C developed AF. In patients with sick sinus syndrome (SSS) the incidence was 10/37 (27%), in those with AV block (AV) 6/77 (7.8%) and in cases with both SSS and AV 6/22 (27.3%). The first AF episode occurred during the implantation itself (n = 2) or during the hospital course in 9/22 patients (A: 11%, B/C: 64% early attacks), and later on in 13 with a time delay of 1-24 months (m = 8.5, 8 patients) in group A and 2-15 months (m = 6.6, 4 patients) in groups B/C. 2 patients of group C had no AF episodes post implantation. In the individual patient the number of attacks ranged from 1 to 3 (10.4/100 patient-months) in group A and from 1 to 6 (20.1/100 patient-months) in groups B/C. During AF 16/22 patients had a ventricular rate of 110-185, m = 132 bpm. In 6 patients the tachycardia was mediated by the PM and in 10 by fast intrinsic AV conduction. 1 patient with SSS, 2 with SSS + AV (spontaneous ventricular rate less than 45 bpm) and 3 with AV needed ventricular backup-pacing during AF. In 7 patients a total of 15 attacks of atrial flutter could be terminated by atrial overdrive pacing, in 5 of these episodes by temporary high rate A00 stimulation via the implanted pacemaker lead system. Otherwise AF was converted to sinus rhythm by antiarrhythmic drugs. After termination AF often recurred, but only 3 patients developed chronic atrial fibrillation. In 2 patients a ventricular rate greater than 180 bpm during AF reverted the PM to asynchronous mode, a possible cause of ventricular fibrillation in one. No other complications due to the PM itself have been encountered. AF, therefore, common during DDD pacing, even in patients without any AF history before implant. Both the incidence and the recurrence of AF depend on the presence or absence of previous atrial arrhythmias.(ABSTRACT TRUNCATED AT 400 WORDS)

Although an exercise-induced increase in blood temperature has been well-known for some time, there was still some doubt whether the change in central venous blood temperature with short-lasting and repetitive physical exercise can be measured and utilized by a temperature controlled pacing system. We studied the central venous blood temperature with short-lasting and repetitive exercise in ten healthy young volunteers and in ten pacemaker patients. The blood temperature was measured intracardially while they walked upstairs. A height of 20 m was covered within 100 +/- 5 s. An oxygen uptake of 27 ml/min/kg was calculated for this level of exercise. After walking upstairs once, the volunteers had an increase in central venous blood temperature of 0.3 degrees C and the pacemaker patients of 0.37 degrees C. After walking upstairs three times, the volunteers had an overall rise in blood temperature of 0.67 degrees C and the pacemaker patients of 0.86 degrees C. Thus, the central venous blood temperature shows a pronounced, measurable increase with short-lasting exercise as well. However, the rises in blood temperature accumulate with repetitive exercise, as the duration of exercise (100 s) when walking upstairs once is not sufficient for a new level of temperature to be reached according to the level of exercise. Thus, a temperature controlled pacing system should take these complex changes into consideration.

We report on 3 cases of right bundle branch block configuration in the ECG after pacemaker implantation. In case 1 it was not noticed that the catheter had been directed through an unknown sinus venosus defect into the left atrium and the left ventricle. In case 2 the catheter reached the left ventricle via an iatrogenic perforation of the lower part of the atrial septum. In case 3 the catheter was situated correctly in the right ventricle, but the tip was penetrating the septum. Different possibilities of interpretation of this phenomenon are discussed, and a description of further pacemaker catheter misplacements which may be responsible for a right bundle branch block configuration is given. The authors take the view that a pacemaker catheter should not remain in the arterial area, in the pericardial space and in the coronary sinus. A lateral radiograph, a 12-lead ECG and an echocardiographic study are helpful for detecting and interpreting an unusual catheter position or a right bundle branch block configuration in the pacemaker ECG.

The implantation of an atrial pacing device represents an established mode of therapy for bradycardia in sinus node dysfunction. However, controversial views remain concerning the safety of this type of pacing. To investigate this, we retrospectively analysed data from 81 patients, all of whom received an AAI pacing device between 1972 and 1984. Complete AV-block developed in two out of 81 patients (cumulative incidence after 10 years was 5 +/- 3%). Atrial fibrillation developed in three out of 81 patients (cumulative incidence after 10 years was 10 +/- 5%). Lead-related complications were strongly related to the type of lead tip and the mode of fixation. The overall incidence of lead-related problems was 20 +/- 5% after 5 years and 38 +/- 12% after 10 years. 82 +/- 6% of patients survived the first 5 years, 52 +/- 14% survived for 10 years. The 5 years' survival rate was not different from that of the normal population. From this we conclude that atrial pacing can be safely done with an AAI system as long as there are no signs of an AV-block. Atrial fibrillation develops less often on AAI pacing than on VVI pacing. The risk of developing an AV-block seems rather low.

In order to compare bi- (b) and unipolar (u) stimulation, sensing and electrical interference, twelve patients were followed over a period of ten months. The implanted device was the CPI Delta 925, programmable to the bi- and unipolar mode in the atrium (a) as well as in the ventricle (v). A CPI-4266 screw-in lead positioned in the atrium and a CPI-4260 hook lead placed in the ventricle were connected to the pacemaker. Intraoperatively determined were: (1) the threshold at pulse durations of 0.1 ms, of 0.5 ms and of 1.0 ms, (2) the P/QRS-amplitude, (3) the slew-rate and (4) the resistance in both the bi- and unipolar mode. Having programmed the atrial sensitivity to 0.25 mV or to 0.75 mV and the ventricular sensitivity to 0.5 mV or to 1.5 mV, we postoperatively examined and compared in the two modes of polarity the threshold (2.2 V and 5 V), the P/QRS-amplitude and finally the electrical interference triggered with the help of chest wall stimulation. All measurements were performed one day, four weeks and four months after implantation.(ABSTRACT TRUNCATED AT 250 WORDS)

This article compares the rate behavior of the activity-triggered pacemakers, the Activitrax (A) and the Sensolog (S), during bench tests as well as in patients under defined ergometric conditions and during every day life with special reference to the susceptibility of both systems to external noise. In the bench tests both pacemakers were mounted on a swingbord and subjected to controlled vibrational force. In the first experiment the frequency, in the second experiment the energy was varied. In two groups, one with S, one with A implanted, each consisting of 10 patients, the discriminating power of workload changes was examined under defined treadmill exercise. Furthermore in 5 patients of each group the rate behavior of S and A under daily life conditions and during common environmental noise was registered using Holter-ECG. In the bench tests S and A displayed a frequency-selective mode of operation between 2 Hz and 70 Hz with the highest sensitivity (resonance frequency) at 10 Hz. In patients, S showed a significantly higher discriminating power to changes of workload under treadmill exercise. According to y = 0.27x + 85.8 (r = 0.92) the relationship between the pacing rate of S and the power was linear whereas with y = 0.04x + 89.8 (r = 0.2) the pacing rate of A was almost independent of the given power. The susceptibility to external noise occurring during riding a car, streetcar or train with rate increases between 7 ppm and 12 ppm did not significantly differ in both systems.(ABSTRACT TRUNCATED AT 250 WORDS)