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Biomedical subjects

N Edvardsson

Publications and source records attributed to N Edvardsson.

At least 91 records · Page 5Linked to original sources
PubMed1985

Induction of delayed repolarization during chronic beta-receptor blockade.

The development of delayed ventricular repolarization was studied in eight patients with clinical indication for chronic beta blockade. Their mean age was 74 years (range 69-81 years) and they all had permanent pacemakers for syncope. The ventricular repolarization time was assessed by means of the Q-T top interval during ventricular stimulation at different paced heart rates. In a group of seven other patients there was a close relationship between the right ventricular monophasic action potential duration at 90% repolarization (RV MAPD90) and the paced Q-T top interval (r = 0.90). After three weeks of treatment with 200 mg metoprolol daily, the paced Q-T top interval increased significantly (3-4%, P less than 0.001) at all paced heart rates, while after about two weeks of treatment a significant increase was seen only at the paced heart rate of 130 beats min-1 (P less than 0.01). Thus, the present study confirmed the development of delayed ventricular repolarization within three weeks of treatment with 200 mg metoprolol daily. The onset of this effect was first noticeable after about two weeks of treatment. Furthermore, the close relationship between the RV MAPD90 and the paced Q-T top interval implies that the paced Q-T top interval may be a reliable and useful feature to detect changes in the ventricular repolarization time.

Aged↗
PubMed1985

Estimation of ventricular repolarization in man by monophasic action potential recording technique.

Myocardial monophasic action potentials (MAP) can be recorded with the aid of suction or contact electrodes applied endocardially via a catheter. The technique necessitates high input impedance amplifiers with infinite time constant. A bipolar technique improves signal quality with regard to electrical contamination around the rapid upstroke of the MAP. Mechanical artefacts in the recordings are common and may be explained by catheter movement induced by atrial or ventricular contractions. The MAP signal can be used for a precise measurement of time of local excitation and for the study of atrial as well as ventricular repolarization. The technique has mostly been applied in the exploration of atrial and ventricular repolarization in healthy hearts and during different cardiac arrhythmias. Furthermore, several studies have documented the electrophysiological action of antiarrhythmic drugs upon the human heart. Concluding from 576 different investigations we consider the technique to have no serious side-effects.

Cardiac Catheterization↗
PubMed1985

Effects of lidocaine, procainamide, metoprolol, digoxin and atropine on the conduction of premature ventricular beats in man.

The acute electrophysiologic effects of clinical doses of procainamide, lidocaine, metoprolol, digoxin and atropine upon the conduction of ventricular premature beats, were studied in 48 healthy volunteers. The conduction time of the first premature beat, induced 1 ms after the ventricular effective refractory period (VERP) was longer than that of the basic paced beats in 41 of the 48 subjects (85%); in 31 (65%) the delay was greater than 5 ms, indicating subnormal conduction. Digoxin decreased the delay so that it became insignificant, while, after procainamide, the delay increased significantly. The other agents did not significantly affect the subnormal conduction. The mean conduction times of premature beats, induced 30-50 ms after the VERP, were shorter than the basic conduction time in 43 of the 48 subjects (90%), and in 25 (52%) the decrease was greater than 5 ms, showing supernormal conduction. Lidocaine abolished the supernormal conduction. The other agents did not significantly alter the supernormal conduction. In the healthy heart, sub- and supernormal conduction of premature beats seem to be common phenomena, and seem, with few exceptions, to be largely unaffected by clinical doses of procainamide, lidocaine, metoprolol, digoxin and atropine.

Action Potentials↗
PubMed1984

Göteborg Metoprolol Trial: effects on arrhythmias.

During the initial hospitalization, ventricular fibrillation (VF) developed in 6 metoprolol-treated patients (0.9%) vs 17 placebo-treated patients (2.4%) after inclusion in the study (p = 0.035). There were 6 episodes of VF in the metoprolol group compared with 41 episodes in the placebo group (p less than 0.001). During the same period, 14 metoprolol-treated patients had treated ventricular tachycardia vs 26 placebo-treated patients (p = 0.076). Similar favorable results were found when the incidence of severe ventricular arrhythmias during the first rehospitalization within the 3-month double-blind treatment period was analyzed.

Adult↗
PubMed1984

Acute effects of lignocaine, procainamide, metoprolol, digoxin and atropine on human myocardial refractoriness.

The acute intravenous effects of therapeutic doses of procainamide, lignocaine, metoprolol, digoxin and atropine on the monophasic action potentials (MAP) and effective refractory periods of the right ventricle (VERP) were studied in 48 healthy volunteers. Procainamide prolonged the VERP in the apex region. Lignocaine shortened the MAP duration at 90% repolarisation. Metoprolol did not affect any of the measured variables in spite of a significant decrease in heart rate. Digoxin produced a significant increase in the VERP at the outflow tract, but not in the apex region and the MAP variables did not change. Following atropine, the VERP at both recording sites decreased but the MAP signal was unaffected. In summary, the effects of procainamide, lignocaine, metoprolol and digoxin were in good agreement with previous studies in normal ventricular muscle cells in vitro. In addition, the findings following atropine, digoxin and procainamide are indicative of a parasympathetic innervation of the endocardial surface of the right ventricle.

Action Potentials↗
PubMed1984

Amiodarone in atrial fibrillation.

Twenty-seven patients with atrial fibrillation without any concomitant conduction abnormality have been treated with oral amiodarone in a daily maintenance dose of 200 mg. The drug has been used for three purposes: 1) to block atrioventricular conduction, thereby decreasing the ventricular rate during atrial fibrillation (9 patients), 2) as prophylaxis against paroxysmal atrial fibrillation (8 patients), 3) as prophylaxis against recurrence of atrial fibrillation after DC conversion to sinus rhythm (13 patients). All patients were considered refractory to other antiarrhythmic drugs in these respects. In the second group, 4 of the 8 patients reported complete cessation of attacks and the others a marked reduction of the attack rate. In the third group, 10 of the 13 patients have maintained sinus rhythm for a longer period on treatment with amiodarone than with other drugs, resulting more than a triple prolongation of the time in sinus rhythm. In 3 patients the drug has been discontinued because of side-effects. In conclusion, amiodarone affords protection from episodes of paroxysmal atrial fibrillation, as well as from recurrence of atrial fibrillation after DC conversion to sinus rhythm. If the drug is ineffective in either of these respects, it may still be useful as a means of moderating the ventricular response in atrial fibrillation.

Adult↗
PubMed1984

Right ventricular monophasic action potentials in healthy young men.

The right ventricular repolarization phase was studied in 48 healthy men between 20 and 40 years of age. The assessment of the repolarization time included the measurement of ventricular effective refractory periods and monophasic action potentials during constant ventricular stimulation. Computer-based analysis of the monophasic action potential allowed the duration at 90% and 50% repolarization, the amplitude, the maximal upstroke velocity and the total rise time of the depolarization to be determined. These results may serve as reference values in further studies on ventricular repolarization using the same monophasic action potential recording technique.

Action Potentials↗
PubMed1984

Spatial vectorcardiography in the Wolff-Parkinson-White syndrome: correlation with epicardial mapping findings.

The spatial vectorcardiograms (VCG) of 13 patients with WPW syndrome due to single accessory pathways were analyzed and correlated with the excitation analysis obtained on epicardial mapping. The azimuth angle of the initial 10 ms cardiac vector was greater than + 90 degrees (directed right and anteriorly) in patients with a left ventricular free wall; it ranged between 0 degree to 90 degrees (left and anteriorly) in those with a left or right paraseptal free wall and was -30 degrees (left and posteriorly) in one patient with a right ventricular free wall location. The elevation angle of the initial 10 and 20 ms cardiac vector was either zero or positive (inferiorly directed) in those with right and left ventricular free wall pathway. Among six patients with a paraseptal location, the elevation angle was negative (superiorly directed) in four and positive in two. Both the patients with a clockwise inscription of a QRS loop in the horizontal plane (HP) had pathways located to the left ventricle. Among the paraseptal group, at surgery, the accessory pathway could not be excised in two in spite of dissection very close to the IV (interventricular) septum. The elevation angle in both these patients was markedly negative (-45 degrees and -62 degrees) in contrast to the other in whom surgical excision was successful.+

Adolescent↗
PubMed1984

Pacemaker dependence in patients with bifascicular block during acute anterior myocardial infarction.

Eleven patients with bifascicular block complicating anteroseptal acute myocardial infarction were studied to determine the effect of prophylactic permanent pacing; eight of them also had transient high grade atrioventricular block during the acute phase of the infarction. One month after the infarction an electrophysiological study was performed and a bradycardia indicating pacemaker implanted. All the patients were followed for two years. Six had bradycardia detected, two of whom did not have high grade atrioventricular block during the index infarction. Seven patients died, four of them suddenly. There was no correlation between the electrophysiological findings and subsequent development of bradycardia. Thus pacemaker dependence seems to be common in patients with bifascicular block complicating acute myocardial infarction. Mortality is, however, also high in patients treated with pacemakers. Prospective studies to determine the predictive factors in those patients with an anterior acute myocardial infarction and who benefit from a combination of permanent pacemaker treatment and antiarrhythmic treatment are needed.

Aged↗
PubMed1984

Identification of multiple pathways in the Wolff-Parkinson-White syndrome. Diagnostic problems and therapeutic implications.

With advanced electrophysiological methods evaluation of functional properties and location of accessory pathways has become possible. Multiple pathways may, however, be difficult to outline with regard to localization and electrophysiological properties due to differences in refractoriness and/or fusion of conduction between the pathways. The investigational procedures in patients with multiple accessory pathways are described and discussed in connection with an illustrative patient with three accessory pathways, two of which are Kent's bundles and one most probably a Mahaim's bundle.

Adolescent↗
PubMed1983

Electrophysiological effects of lidocaine in acute myocardial infarction with bifascicular block or complete A-V block.

Electrophysiological effects of lidocaine were studied in 27 patients with acute myocardial infarction complicated by bifascicular block (group I: 20), and complete A-V block (group II: 7). Lidocaine was administered intravenously in bolus doses of 100 mg each at intervals of 10 min. In group I, there was no significant change in the heart rate (Before (B) = 84.85 +/- 24.19, After (A) = 87.25 +/- 20.26 beats/min) intra-atrial (PA) conduction time (B = 25 +/- 6.18, A = 27.22 +/- 6.69 ms), A-V nodal (AH) conduction (B = 111.5 +/- 56.12, A = 111.5 +/- 56.5 ms) or His bundle to ventricular (HV) activation time (B = 59.5 +/- 19.32, A = 61.25 +/- 18.62 ms) after lidocaine administration. In group II, 2 patients reverted to sinus rhythm, one with 1:1 conduction and the other with type II Wenckebach's block, with being prepared for the study, but both had complete A-V block within 1 h of the His bundle electrogram recordings. Of the remaining 5 patients, 4 had supra and 1 infra His A-V block. After lidocaine, 2 patients developed asystole. In the remaining 4 patients, there was no change in the escape rate or various conduction intervals.

Aged↗
PubMed1982

A case of arrhythmogenic right ventricular dysplasia with ventricular fibrillation.

A case of repeated attacks of ventricular fibrillation is described. The patient suffered from an arrhythmogenic right ventricular dysplasia (ARVD) documented by right and left ventriculograms and myocardial biopsies obtained during surgical treatment of the arrhythmia. The histological changes were interpreted as being signs of fresh myocardial damage of unknown origin in addition to a replacement of the normal myocardium by adipose and fibrotic tissue. The repeated attacks of ventricular fibrillation in this patient contrast to the arrhythmia spectrum noted in the available literature on ARVD, mostly stable chronic ventricular tachycardias.

Adult↗
PubMed1981

Effects of acute and chronic beta-receptor blockade on ventricular repolarisation in man.

The right ventricular repolarisation phase was studied electrophysiologically after an injection of 15 mg metoprolol in 16 healthy volunteers. Eight of them were restudied after chronic treatment with 400 mg metoprolol daily for five weeks. The assessment of the repolarisation time included ventricular effective refractory periods, monophasic action potential duration, and the QT interval measured during atrial stimulation at different driving frequencies. The acute administration of 15 mg metoprolol intravenously had no detectable effect on the repolarisation phase, while chronic treatment caused a significant increase of the ventricular effective refractory periods, monophasic action potential duration, and the QT interval during atrial stimulation. Thus the study confirmed the contrasting effect of acute and chronic beta-receptor blockade on the ventricular repolarisation time in man.

Action Potentials↗
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↗