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Biomedical subjects

H Lagergren

Publications and source records attributed to H Lagergren.

At least 19 recordsLinked to original sources
PubMed1993

Choosing the stimulation rate in patients with intermittent bradycardia and a single lead pacemaker.

In order to assess the prevalence of intermittent bradycardia in a pacemaker population, we retrospectively evaluated the occurrence of intrinsic heart activity in 229 patients with ventricular pacing. Spontaneous heart activity was recorded in 60% of the patients. However, the stimulation rate had been decreased in only 40% of the patients in order to allow for longer periods of intrinsic heart activity. In the second part of the study we prospectively assessed differences in pacemaker utilization in 19 patients with intermittent bradycardia and single lead pacemakers. All patients were observed over four periods of 14 days, with the following pacing modes: 70 beats/min, 50 beats/min, hysteresis sensing 50 beats/min, and pacing 70 beats/min; and search hysteresis sensing 50 beats/min and pacing 70 beats/min. Search hysteresis pacing is a new feature that theoretically allows for a shorter time of pacing than that of hysteresis pacing. A reduction in the stimulation rate from 70 beats/min to 50 beats/min resulted in a 60% reduction in pacemaker utilization (P < 0.05). Search hysteresis decreased pacemaker utilization by 33% (P < 0.05). There was no statistical difference between conventional hysteresis and fixed rate pacing at 70 beats/min. Most patients found fixed rate pacing preferable to hysteresis pacing. In order to minimize battery consumption and to avoid unfavorable hemodynamics in patients with ventricular pacing, the stimulation mode and rate should be optimized in patients with intermittent bradycardia to allow for longer periods of intrinsic heart activity.

Aged↗
PubMed1988

25 years of implanted intracardiac pacers.

In 1962, a simplified method of transvenously inserting an intracardiac electrode and implanting the whole pacemaker system under local anaesthesia was reported from the Karolinska Hospital in Stockholm. This simplified method has been universally adopted and pacemakers are now probably implanted too freely in many places. In the Stockholm area pacemakers are implanted half as frequently as in the rest of Sweden and as often as in the United Kingdom.

Aged↗
PubMed1985

A comparison between conventional and basket transvenous electrodes.

Three transvenous electrodes, two of a conventional type and one in the shape of a wire basket, were compared. In order to make a valid comparison, the electrodes were all attached to the same kind of lead. The conventional large and small surface electrodes showed no difference in early complication rate. The wire basket electrode, however, had significantly fewer early complications than the others. This was true whether the patients underwent a two- or a one-step procedure, and whether the surgery was done by experienced or inexperienced pacemaker surgeons. When inserted by experienced surgeons in a one-step procedure, the wire basket electrodes had an early complication rate of only 1.2%. Since this unrefined electrode that allows tissue ingrowth for improved anchoring has shown such good results, it is likely that other electrodes that have been perfected, of a hollow or porous design, will also be advantageous to the patients and show good results.

Adult↗
PubMed1985

Valsalva-induced variations in the intracardiac signal.

Variations in the intracardiac signal may substantially affect the sensing function of cardiac pacemakers. As the Valsalva maneuver causes a change in heart volume, its effect on the intracardiac signal was studied in seven patients with an adequate escape rhythm who had permanent ventricular pacemakers. During generator replacement, they were asked to perform a standardized Valsalva maneuver. An increase from the baseline amplitude ranging from 5% to 70% was noted during forced expiration against the closed glottis. There was a decrease from the baseline ranging from 15% to 50% after termination of this maneuver. Similar changes were noted for the rate of voltage change (slew rate). The magnitude of these alterations was most pronounced in patients with comparatively low intracardiac amplitudes. Because marked changes in the intracardiac signal can result from the Valsalva maneuver, it might be an important source of undersensing among patients with permanent pacemakers.

Aged↗
PubMed1984

Paroxysmal complete heart block due to bradycardia-dependent "phase 4" fascicular block in a patient with sinus node dysfunction and bifascicular block.

A 34-year-old man with ankylosing spondylitis was admitted to the hospital because of syncopal attacks and heart block. Standard ECG, telemetry and an invasive electrophysiologic examination demonstrated right bundle branch block with left anterior fascicular block, sinus node dysfunction with spontaneous slowing of the sinus rate and, as a result, complete infrahisian atrioventricular block in the remaining fascicle at sinus rates below 57 beats per minute. Infrequent supraventricular extrasystoles and abruptly terminated atrial pacing led to the same result. Atrioventricular conduction resumed after three-to-four blocked atrial impulses with successively increasing rate. Pacemaker treatment provided complete symptomatic relief.

Adams-Stokes Syndrome↗
PubMed1984

Ten-year follow-up on 1,000 patients with transvenous electrodes.

One thousand patients given a transvenous electrode EMT 588 until mid-January, 1974, were followed up for a minimum of 10 years. Two hundred ninety-six patients survived this time or longer. Fully 30% of them were above the age of 70 when first paced. During the observation period, 34% of the survivors had electrode complications requiring electrode replacement. These occurred in almost 14% during the first year of treatment. Electrode failures during the first year were due mainly to dislocations and rises in the stimulation threshold, while later failures were caused chiefly by damage to the lead, which was caused, in part, by repeated pulse generator replacements and infections. Half of the patients who survived for more than 15 years have the original electrode, the oldest one now exceeding 22 years.

Aged↗
PubMed1979

Long-term observation of pacemaker electrodes. A follow-up study of 328 consecutive patients treated between 1959 and 1967.

Epicardial electrodes implanted in 20 patients between 1959 and 1962 had a short-term effectiveness. A change to endocardial stimulation was later necessary in 15 of these patients. Endocardial electrodes inserted between 1962 and 1967 in 306 patients were included in this study; 121 (40%) of these patients survived for 10 years or more. Seventy-five (62%) of the long-term survivors had no problems with their electrodes. In 39 of these patients the stimulation thresholds were measured after both 5 and 10 years and found to be 2.3 +/- 0.6 volts and 2.2 +/- 0.8 volts, respectively. Hence, long-term complication-free endocardial pacing can be accomplished.

Adult↗
PubMed1978

Influence of output capacitor, electrode and pulse width on power consumption in cardiac pacing.

Three different types of unipolar endocardial electrodes--47 in all--were compared in regard to power consumption at stimulation threshold with six different output capacitors and seven pulse widths. Fifteen were conventional large surface electrodes (area 47 mm2); 18 were conventional small surface electrodes (area 6 mm2), and 14 had a specially designed tip with a large area but small active surface of 8 mm2. Pulse widths ranged from 0.15 to 2.0 msec and output capacitors from 1.0 to 22.0 microFarads. All in all about 2,000 measurements were performed. The average current drain to the pacemaker output stage was measured and power consumption was calculated for each electrode--pulse width--output capacitor combination. In all combinations, the two small surface electrodes consumed approximately the same amount of power and, in both cases, significantly less than the larger one. With regard to power economy at stimulation threshold, the pulse width of choice was about 0.5 msec and, furthermore, power consumption decreased with increasing capacitor size. The optimal combination was a small surface electrode, an output capacitor of 22 microF and a pulse width of 0.5 msec.

Adult↗
PubMed1977

Prevention of platelet adhesion and aggregation by a glutardialdehyde-stabilized heparin surface.

A stable heparinized surface was prepared by sequential treatment of polyethylene with water solutions of hexadecylamine hydrochloride, heparin and glutardialdehyde. In order to explain the "non-thrombogenic" properties of this surface, it was evaluated with regard to prevention of platelet adhesion and aggregation. Human heparinized blood (2 and 10 IU/ml) with 51Cr-labelled autologous platelets was rotated for 60 minutes in untreated and heparin-treated circular tubings. The surface area/blood volume ratio was varied and an air-blood interface was present. In untreated tubings, platelet adhesion and aggregation increased in proportion to the size of the surface area/blood volume ratio, irrespective of the heparin concentrations of the blood. In the heparin-treated tubings, there was no measurable platelet adhesion to the surface and no platelet aggregation in the blood. The difference between the heparinized and the untreated surfaces with regard to platelet adhesion was discernible even after 10 minutes storage of stagnant blood. It is concluded that platelet adhesion and aggregation induced by exposure of blood to a foreign surface in an in vitro experimental model can be prevented by a stable heparin coating of the surface.

Aldehydes↗
PubMed1977

Deleterious effects of cardiac pacing in a patient with mitral insufficiency.

A 70-year-old, artificially paced women with dizziness and extremely low physical capacity exhibited a systolic BP varying from one moment to another; in standing position it was not measurable. With the aid of a strain gauge technique, the amplitude of the pulse wave of her left thumb was recorded and shown to vary widely. The variations were correlated to synchrony or asynchrony between atrial and ventricular activity. Pronounced decreases in stroke volume and peripheral pulse volume were recorded with pacemaker-induced beats compared with idioventricular beats. With artifical stimulation at a rate of 45/min, thus avoiding competition but still protecting her from syncopes, she was free from symptoms.

Aged↗
PubMed1976

Effect of low-dose heparin prophylaxis on arterial oxygen tension after high laparotomy.

The effect of low doses of heparin (5000 units of sodium heparin every 12 hours for 5 days) on arterial oxygenation was studied in 24 patients in the postoperative period after upper abdominal surgery. Another 24 patients served as a control group. The arterial oxygen tension was the same in both groups preoperatively and was equally significantly reduced during the 1st postoperative day. During the 2nd day, oxygen tension rose in the heparin-treated group to values which no longer differed significantly from the peroperative level. In the control group the significant reduction persisted until the 4th postoperative day. The arterial carbon-dioxide tension did not differ between the groups, neither did it vary significantly between days. There were no clinical signs of large pulmonary embolism during the postoperative period, chest X-ray was normal in all patients examined and a photoscan was normal in 23 of 24 subjects studied. Low-dose heparin treatment may apparently shorten the period of postoperative hypoxaemia, probably by counteracting both large pulmonary emboli and microthromboembolism.

Adult↗