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Biomedical subjects

K Breivik

Publications and source records attributed to K Breivik.

32 records · Page 2Linked to original sources
PubMed1983

Long-term comparison of unipolar and bipolar pacing and sensing, using a new multiprogrammable pacemaker system.

Over a six-month period a comparison was made between uni- and bipolar myocardial stimulation thresholds and R-wave sensitivity in 15 consecutive pacemaker patients. The patients received a new multiprogrammable Cordis 336 A pulse generator, that could be programmed with either uni- or bipolar circuitry. In addition, rate, output, sensitivity and pacing mode could be noninvasively programmed. The occurrence of myopotential interference at different sensitivity levels was also studied. Cordis 325-161 bipolar endocardial leads were used in all patients. In one patient, the current output sometimes had to be programmed higher bipolarly than unipolarly to capture the ventricles, otherwise no differences in threshold were found. Acutely. R-wave sensitivity was superior in 9 patients (60%) in the bipolar mode. Unipolar and bipolar electrograms were equal in 4 (26.7%), whereas unipolar R-wave sensitivity was best in only 2 (13.3%) of the patients. At a six-month follow-up, the same tendency was found. In 5 patients, bipolar sensing was superior to unipolar, while anti- and bipolar sensitivity was equal in the remaining patients. Myopotential inhibition was never seen in the bipolar mode at highest sensitivity (0.8 mV) even during provocative tests (n = 15) or 24-hour Holter monitoring (n = 12). In the unipolar mode, 14/15 patients (93.3%) showed inhibition during provocative tests and 12/12 patients (100%) during monitoring at a programmed sensitivity of 0.8 mV. No patients had myopotential interference at a sensitivity level of 3.5 mV. All patients have their pacemakers programmed in the bipolar mode after six months. This study confirms earlier acute data that the bipolar pacing mode is superior to the unipolar mode for permanent pacemaker therapy.

Aged↗
PubMed1983

Bipolar atrial application of a new temporary pacing lead after cardiac operations.

A new temporary pacing lead. Medtronic Model 6400, with a defined electrode surface area of 7.5 mm2, has been clinically and electrophysiologically evaluated during bipolar atrial application in 20 patients after cardiac operations. A silicon disc was used for fixation of the electrodes to the right atrium in 10 patients, and an atrial plication technique was used in the other 10. Myocardial stimulation threshold and resistance were measured throughout the postoperative period. Atrial electrograms were recorded on magnetic tape for computer analysis of amplitudes, slew rates, and signal source impedance. No significant differences (p greater than 0.1) were found in myocardial stimulation threshold between the two fixation modes. During constant-current pacing, median threshold rose from 0.65 mA to 2.3 mA. Stimulation resistance, measured during constant-voltage pacing, fell from 567 to 365 omega, with a subsequent rise to 425 omega before electrode removal. Again no difference was found between silicon disc and plication fixation of the electrodes. P-wave amplitudes were significantly higher with plication than with silicon disc fixation (2.26 versus 0.86 mV, p less than 0.01), as were slew rates (0.34 versus 0.18 V/s, p less than 0.05). Signal source impedance had a magnitude of 6 k omega. The electrodes were used successfully in 12 (60%) of the patients for diagnosis and/or treatment of arrhythmias. We find the new lead well suited for atrial application.

Aged↗
PubMed1982

Electrophysiological properties of a new permanent endocardial lead for uni- and bipolar pacing.

Unipolar and bipolar electrode systems were compared for electrogram amplitudes and slew rates, signal source impedance, and myocardial stimulation threshold and resistance in 15 consecutive patients who received a new endocardial electrode (Cordis 325-161). The bipolar electrograms showed the highest amplitude in nine of the patients (60%). The unipolar and bipolar electrograms were equal in four patients (26.7%), whereas the unipolar electrograms were highest in only two patients (13.3%). The difference in mean amplitude between bipolar (11.1 mV) and unipolar (10.1 mV) electrograms was statistically significant (p 0.05). Mean slew rates were almost equal (1.7 versus 1.6 V/s; p greater than 0.1). The bipolar electrode system always gave somewhat higher signal source impedance than the unipolar system (p 0.001). The current threshold was significantly lower during bipolar pacing (0.59 mA) in constant current pacing mode, than during unipolar pacing (0.65 mA) (p less than 0.05). No significant differences were found during constant voltage pacing. Stimulation resistance was highest in the bipolar electrode system (p less than 0.001). We conclude that the bipolar electrode system is as good as, or better than, the unipolar system both for ventricular sensing and for pacing.

Aged↗
PubMed1982

Pulse width dependent increase in the pacemaker automatic interval.

From a total of 51 patients equipped with rate and pulse width adjustable pulse generators (Microlith-P 0505, Microthin-PI 0522) implanted over the last 3 years, 10 (19.6%) showed an unexpected drop in pacemaker pulse rate during pulse width programming. For one of the pulse generators used (Microthin-PI 0522), unexpected rate decrease occurred in 7/13 cases (53.8%). For all except one patient, decrease in pacemaker pulse rate corresponded with the total refractory period of the pulse generator ( 320 ms), at a certain pulse width when rate drop first occurred. In seven of the patients the pulse generator automatic interval was extended from 13 ms to 171 ms beyond the refractory period. In two patients it was necessary to replace the pulse generators. Our study strongly proves that this abnormal pacemaker functioning is a result of sensing of the polarization voltage at the pacemaker electrode/tissue interface and/or the T-wave. The polarization voltage is highly dependent on the total pacemaker electrode/tissue interface impedance. Using typical values for pulse generator output and input resistance and output capacitance, Faraday resistance, Helmholtz capacitance and tissue resistance at the electrode/tissue interface it was shown mathematically that in some cases the polarization voltage alone would be of sufficient amplitude and slew rate for pacemaker inhibition. The study demonstrates an urgent need for change in the filter characteristics by making the pulse generators less sensitive in the low frequency region and reducing the polarization voltage by reducing the output circuit capacitance.

Adult↗
PubMed1982

Clinical and electrophysiological properties of a new temporary pacemaker lead after open-heart surgery.

A new temporary pacemaker lead, Medtronic 6400, with a solid defined electrode surface area of 7.5 mm2, has been implanted in 50 patients after open-heart surgery. One electrode was inserted intramyocardially on the right ventricle, while another was placed extracardially and served as a reference lead. Forty-six of the patients were followed postoperatively with measurements of myocardial stimulation threshold and resistance. In 25 of the patients, electrograms were recorded on magnetic tape for further computer analysis of amplitudes, slew rates, and signal source impedance. During constant current pacing, myocardial stimulation threshold increased from a median of 0.4 mA one hour postoperatively to a maximum value of 2.3 mA. In two patients (4.3%) intermittent pacing failure was seen. Stimulation resistance fell from a median of 875 omega to a minimum of 487 omega, with a subsequent increase of 598 omega before electrode removal. Both mean electrogram amplitude (7.35 mV) and slew rate (0.82 V/s) had their minimum values on the sixth postoperative day. Intermittent sensing failure was observed in 2/25 patients (8%). Signal source impedance was of a magnitude not likely to contribute to sensing failure. No complications were seen from the use of this lead. The new electrode is an important improvement in temporary pacemaker lead design.

Adult↗
PubMed1982

Acute and chronic pulse-width thresholds in solid versus porous tip electrodes.

Sixty-one patients given programmable pacemakers at initial implantation have been followed for a mean of 18 months (3-42) with non-invasive measurements of myocardial pulse-width threshold. Fifty of the patients had CPI 0505/0522 (Microlith-P/Microthin-PI) pacemakers with either Cordis 322-462 8 mm2 ball tip (n=12), Cordis 322-620 17.5 mm2 (n=23), or CPI 4116 porous tip electrodes (stimulation area 7.5 mm2 and sensing area 50 mm2) (n=15). Eleven patients had Medtronic 5985 (Spectrax-SX) pacemakers with either Medtronic 6907-R 8 mm2 ring tip (n=7), 6907 11 mm2 (n=3) or 6917 myocardial electrodes (area 12 mm2) (n=1). At acute implant, the ball tip and porous tip electrodes had the lowest stimulation thresholds, but the differences were only statistically significant in comparison with the 17.5 mm2 electrode (p less than 0.01). Chronically there were no significant differences between the various electrodes (p greater than 0.1), but the ball tip electrode tended to give best long-term results, and the porous tip electrode the poorest. Thirty-eight of the 61 patients (62.3%) had chronic pulse-width thresholds of 0.1 ms or less at approximately equal to 5 V output, indicating that pulse-width programming is a useful way to conserve battery energy. However, at some stage of the study, six of the patients (9.8%) had a pulse-width threshold of 0.5 ms or more. Pulse width should therefore not be set too narrow in standard nonprogrammable pacemakers.

Adolescent↗
PubMed1982

New temporary pacing lead for use after cardiac operations.

A newly designed temporary pacemaker lead (Medtronic Model 6400), which has a solid defined electrode surface area of 7.5 mm2, was compared with a multifilamental stainless steel electrode in common use (Davis & Geck, DG). Thirty-nine patients had both types of electrodes inserted intramyocardially in the right ventricle. A DG electrode fastened to the pericardium served as a reference lead. In addition to the standard Medtronic 7.5 mm2 electrode (n = 11), specially made Medtronic electrodes with areas of 5 mm2 (n = 10), 10 mm2 (n = 10), or 7.5 mm2 with platinum-iridium tips (n = 8) were studied. Measurements of myocardial stimulation threshold and resistance were made in both electrodes throughout the postoperative period. The patients' electrograms were recorded on magnetic tape for computer analysis of amplitudes and slew rates. The Medtronic 7.5 mm2 electrodes showed overall better results than 5 and 10 mm2 leads. Maximum stimulation threshold on the Medtronic 7.5 mm2 electrodes was medium 3.4 mA versus 10 mA on DG electrodes (p less than 0.001). The tissue resistance on Medtronic 7.5 mm2 was almost double than on the Davis & Geck electrodes (median 311 ohms versus 164 ohms on the day of minimum resistance, p less than 0.001). There were no significant differences in electrogram amplitudes between the two electrode types studied (5.52 versus 4.68 mV, p greater than 0.1), but the slew rates were significantly higher on the Medtronic (0.56 versus 0.37 V/sec; p less than 0.01). The new lead is an important innovation in temporary pacemaker lead design compared to the commonly used multifilamental leads.

Adult↗
PubMed1981

Spontaneous heart activity in pacemaker treated patients with high-grade atrioventricular block. A Holter monitor study.

A Holter monitor study was performed to assess the occurrence of spontaneous heart activity in 70 pacemaker treated patients (mean age 72.1 years) with high-grade atrioventricular (AV) block, who have been treated with permanent pacemakers for a mean of 60 months (range 5-161). Nineteen patients had asynchronous (VOO), and 51 QRS-inhibited (VVI) pacemakers. The patients were monitored for a mean of 23 hours (range 15.5-26). Twenty-five patients were re-studied for day-by-day variations in spontaneous heart activity. At clinical observation, thirty-eight patients had some kind of spontaneous cardiac activity, mostly ventricular ectopic beats. Three patients had short episodes of sinus rhythm of more than 70 beats/min. Patients in functional class III-IV (NYHA) or with an enlarged heart had the most spontaneous heart activity. No tachyarrhythmias precipitated by interference between intrinsic heart beats and asynchronous pacemakers were seen. Twenty patients studied twice had a relatively stable occurrence of spontaneous heart activity, while five (20%) varied considerably. On the basis of these long-term observations it is difficult to predict when interference rhythm will occur, and asynchronous pacemakers therefore cannot be recommended for the first implantation.

Adult↗
PubMed1980

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.

Action Potentials↗
PubMed1979

Sick sinus syndrome treated with permanent pacemaker in 109 patients. A follow-up study.

During the last decade implantation of permanent pacemakers has become the treatment of choice for patients suffering from the sick sinus syndrome (SSS). We have followed up 112 SSS patients treated with permanent pacemakers in Haukeland Hospital in the period 1966--76. The pacemakers were later removed from three of the patients. In the remaining 109 patients the SSS was characterized by tachy-bradyarrhythmias (TBA) in 44 and bradyarrhythmias (BA) in 65. Before implantation, 68 patients had syncopes and 27 severe dizziness. After implantation, symptomatic improvement was apparent in 104 patients; only three still had syncopes. During the follow-up period (mean 34.4 months), 29 patients died (yearly mortality 9.3%). There was no significant difference in total mortality between patients with TBA and with BA. Concomitant disturbances in atrioventricular (AV) conduction occurred in 35.8% of the patients. Among 79 of 80 patients still alive, five had developed total AV block, 19 had stable atrial fibrillation, 12 of these were possibly pacemaker-independent (ventricular rate greater than 60/min). Systemic embolization was observed in 16 patients, more frequently in the TBA (12/44) than in the BA group (4/65) (p less than 0.001). It is concluded that permanent pacemakers have an excellent symptomatic effect in patients with SSS. The prognosis is mainly determined by the presence or absence of coronary heart disease and/or heart failure.

Adolescent↗
PubMed1978

Patients with high-grade atrioventricular block treated and not treated with a pacemaker.

One-hundred and eighty-one patients with chronic and with intermittent high-grade atrioventricular block (AVB) were studied retrospectively. Seventy-one were treated with fixed-rate, 51 with demand-type pacemaker, 59 were treated conservatively. Observation time was three years minimum and 14.5 years maximum. The mean age was about seven years higher, and 8.7% more patients had chronic AVB in the conservatively treated than in the pacemaker-treated group. About 12% more patients had Adams-Stokes attacks in the pacemaker group than in the conservatively treated group. There were 7% more patients with coronary heart disease (CHD) in the pacemaker group, and 10% more with aortic valve disease among the conservatively treated. Totally 4.4% of the patients had a calcification of the mitral annulus fibrosus. The two groups were comparable as regards functional class (NYHA) and heart size. Survival showed 31% more sudden deaths in the conservatively treated than in the pacemaker group. Sudden deaths were not more frequent among the patients with CHD than in those without. Long-term survival showed the more favourable result for the patients with than without pacemaker treatment. There were eight (11.3%) unexplained sudden deaths among the patients treated with fixed-rate pacemaker, only three (5.9%) among those treated with a demand unit. The fixed-rate and the demand units showed a mean longevity of 37.2 and 34.6 months, respectively.

Age Factors↗