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Biomedical subjects

S B Olsson

Publications and source records attributed to S B Olsson.

At least 127 records · Page 7Linked to original sources
PubMed1981

Effect of intravenous melperone on atrial repolarization in man.

The effect of 10 mg of melperone intravenously on the duration of the right atrial monophasic action potential was studied in seven patients and one healthy volunteer. Melperone induced an increase of the atrial monophasic action potential duration by 13%, 15 min after intravenous injection of the drug. This prolongation was a consistent finding but was within the limits of normal intra-individual variation and considerably smaller than normal inter-individual differences. However, the observations warrant studies to evaluate the effect of the drug in different cardiac arrhythmias.

Action Potentials↗
PubMed1980

Spontaneous reversion from long-lasting atrial fibrillation to sinus rhythm.

We have collected 23 cases with atrial fibrillation (AF) of 3-29 years' duration with spontaneous reversion to sinus rhythm (SR). We have also identified 22 similar cases in the literature. Several of our patients spent several years with different atrial arrhythmias before a stable SR was established. Of all the 45 cases, 39 had significant rheumatic mitral valve disease. In the majority of these patients the ECG shows first degree AV block after return to SR and a low-amplitude P-wave--as if the left atrial P component was lacking. There are no signs of left atrial mechanical activity after re-establishment of SR in our mitral valve disease group, as judged from phonocardiograms, apexcardiograms, echocardiograms and left atrial pressure recordings in selected patients. Heart muscle biopsy was obtained from two patients who underwent mitral valve surgery. Left atrial speciments showed almost complete lack of all muscle structures. There is thus electrical, mechanical and histological evidence of left atrial muscle deterioration. It is likely that the electrophysiological factors responsible for initiation and maintenance of AF have disappeared with this deterioration, thereby allowing SR to be re-established. The return of SR might indicate a progress of the heart disease although the patient may benefit from normalization of cardiac rate and regularity. The easy identification of our 23 patients makes us believe that the phenomenon of appearance of late SR is far more common than suggested up to now.

Aged↗
PubMed1979

Effect of mexiletine on monophasic action potentials recorded from the right ventricle in man.

The effect of mexiletine, a new antiarrhythmic agent, on ventricular refractoriness and monophasic action potentials recorded from the right ventricle was studied in nine subjects. The effective refractory period of the right ventricle was determined by the extra stimulus technique using a pacing electrode situated at the right ventricular apex. Following this determination the right ventricular apex was paced at a constant cycle length and premature stimuli were introduced starting at a coupling interval of 2 ms greater than the ventricular refractory period and then at progressively increasing coupling intervals of 5 ms increments. Simultaneous recordings of monophasic action potentials of both the regular paced beats and the induced premature beats were made using a specially designed suction electrode catheter. The monophasic action potential durations were measured at 50% and 90% repolarisation. All these control measurements were repeated after an intravenous dose of 2 mg.kg-1 body wt. of mexiletine. The results showed that mexiletine did not significantly change the effective ventricular refractory period nor did it alter the monophasic action potential duration of the regular paced beat. The drug did, however, significantly prolong the monophasic action potential duration of the early induced premature beats and it is possible that this property of the drug may be related to its antiarrhythmic activity.

Action Potentials↗
PubMed1979

Effect of mexiletine on conduction of premature ventricular beats in man: a study using monophasic action potential recordings from the right ventricle.

Ventricular conduction intervals between a stimulating pacemaker electrode at the right ventricular apex and an impulse detecting monophasic action potential electrode at the right ventricular septum were measured in nine subjects. The right ventricle was paced at a constant rate and programmed premature ventricular stimuli were introduced after every eighth paced beat beginning at the refractory period. The ventricular conduction intervals were measured from the pacemaker artefact to the onset of depolarisation of the MAP recording. In the control recordings a short period of prolonged (subnormal) conduction lasting for 5 to 26 ms after the refractory period was present in six of the nine subjects. In eight subjects a period of 'supernormal' conduction lasting from 50 to 180 ms was present. The effect of mexiletine was to increase the subnormal conduction and to abolish the supernormal conduction. It is concluded that a small degree of supernormal conduction occurs in the normal human ventricle possibly as a result of phase 4 depolarisation of cells of the specialised conducting system.

Action Potentials↗
PubMed1979

Verapamil-induced ventricular regularity in atrial fibrillation. Effects of exercise, isoproterenol, atropine and conversion to sinus rhythm.

The effects of physical exercise, isoproterenol and atropine upon the ventricular rate and regularity were studied in 12 patients with atrial fibrillation (AF) during verapamil-induced regular ventricular rhythm. Physical exercise, isoproterenol and atropine all caused a gradual loss of ventricular regularity during AF. Verapamil caused a reduction of exercise heart rate during AF and, to a minor extent, even during sinus rhythm. The regular ventricular rhythm induced by verapamil during AF is interpreted as a total AV-nodal block with nodal escape rhythm. Possible clinical benefits of this rhythm are discussed.

Adult↗
PubMed1978

Effects of metoprolol on heart rate in patients with digitalis treated chronic atrial fibrillation.

Adequate control of ventricular rate in patients with chronic atrial fibrillation (AF) may not be achieved with digitalis alone. In the present study the additional effect of two different doses (50 mg and 50 +/- 50 mg) of oral metoprolol, a new selective beta-blocking agent, on ventricular rate in patients with longstanding AF has been studied. A decrease in the mean ventricular rate during rest and during exercise at various work loads was observed after both doses. The effect was more pronounced at the highest work load of 80 W, both after 50 mg (p less than 0.002) and after 50 +/- 50 mg (p less than 0.01) of the drug. A high initial heart rate at rest or during exercise was reduced more by the drug than a lower one. Exercise tolerance was reduced in 2 patients. These results suggest that patients with AF in whom satisfactory control of heart rate cannot be achieved with digitalis alone may benefit from addition of individualized metoprolol therapy.

Adult↗
PubMed1977

Right atrial monophasic action potential in patients with paroxysmal supraventricular tachyarrhythmias.

Thirteen patients with paroxysmal atrial tachyaarhthmias (six atrial supraventricular tachycardia, six atrial fibrillation, and one atrial flutter) have been investigated by recording of monophasic action potentials (MAP) during a period free from arrhythmias. None of the patients differed from healthy individuals with respect to any of the MAP variables. Occasional recordings showed values not found in healthy individuals, such as prolonged duration of the MAP or slow phase 4 depolarization. The atrial effective refractory period (AERP) was determined in two patients. One AERP was short compared with values found in healthy individuals. Thus some MAP recordings gave a possible explanation for the mechanism behind the arrhythmias, while other recordings showed no differences from results in healthy individuals.

Action Potentials↗
PubMed1977

Human atrial conduction with reference to heart rate and refractory periods.

Atrial conduction time (ACT) between a stimulating pacemaker electrode and an "impulse-detecting" monophasic action potential (MAP) electrode has been determined in 20 healthy males. A small increase in ACT was found with increasing paced heart rates. Using the extra stimulus technique, ACT was found to increase when the early ectopics approached the atrial effective refractory period (AERP). The degree of ACT prolongation was similar at long and short basic ACTs, indicating that the slowing of impulse propagation probably occurred near the simulating electrode and presumably within 1/2-1 cm from that electrode. The increase in ACT close to the AERP was of importance when determining the atrioventricular refractory period. In three recordings a supernormal phase of conduction was found. The small errors of the MAP recordings in detecting the time of excitation make the method sensitive enough to detect small differences in ACT.

Action Potentials↗
PubMed1977

The effect of mexiletine on the electrophysical properties of the intact human heart.

The effect of an intravenous dose of mexiletine, a new anti-arrhythmic agent, on the electrophysiological properties of the intact human heart was studied in ten subjects with no evidence of cardiovascular disease. Mexiletine produced no significant changes in the sinus node recovery time, the corrected sinus node recovery time or in the atrial, atrio-ventricular and ventricular effective refractory periods. In addition mexiletine had no significant effect on proximal atrioventricular conduction. The drug did, however, prolong atrio-ventricular conduction distal to the bundle of His in all ten subjects by an average of 6 msec. This change was statistically significant (P less than 0.01). The drug is recommended to be used with caution in patients with conduction disturbances.

Adult↗
PubMed1976

Right atrial monophasic action potential in healthy males. Studies during spontaneous sinus rhythm and atrial pacing.

Right atrial monophasic action potentials (MAP) have been recorded in 40 healthy males. At least one MAP recording was performed in each individual during spontaneous sinus rhythm. Right atrial pacing and simultaneous MAP recording were performed in 25 of the 40 individuals. The paced cycle length was successively decreased in steps of 100 msec between 800 and 400 msec. The durations of the MAP at 50 and 90% repolarization and the relative repolarization rate during phase 3 (RRR ph 3) were calculated and normal values for the variables are given. A correlation was demonstrated between the duration of the MAP and the cycle length-the longer the cycle length, the longer the duration of the MAP-both during sinus rhythm and during the atrial pacing. A significant correlation was also shown between the RRR ph 3 and the duration of the MAP at 90% repolarization-the shorter the MAP, the faster the RRR ph 3. One age group (45-54 years) deviated significantly from the rest in some respects, but in general there was no age trend in the whole material.

Action Potentials↗
PubMed1976

Atrial repolarization in healthy males. Studies with programmed stimulation and monophasic action potential recordings.

Right atrial effective refractory periods (AERP) and monophasic action potentials (MAP) have been determined in 29 healthy males in four different age groups between 25 and 64 years. One age group (45-54 years) showed a significantly longer AERP than the others, with a mean of 283 msec compared with 230-238 msec in the other groups. However, no age trend was found in the total material. The AERP decreased at higher paced heart rates, the decrease between paced cycle lengths of 800 and 600 msec amounting to 13 msec. When the MAP and the AERP were determined in the same position of the atrium, they showed no statistically significant correlation. A possible explanation is that the cells contributing to the AERP and the MAP are not altogether the same. The MAP and the AERP determinations have a similar degree of reproducibility but possibly mirror different kinds of repolarization phenomenon.

Action Potentials↗