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N Edvardsson

Publications and source records attributed to N Edvardsson.

At least 37 records · Page 2Linked to original sources
PubMed1989

Prediction of terminal atrial myocardial repolarisation from incomplete phase 3 data.

The duration of the monophasic action potential (MAP) carries prognostic antiarrhythmic information when the recording is done during sinus rhythm (SR) after DC conversion of atrial fibrillation (AF). This study analyses whether it is possible to predict MAP duration during sinus rhythm by analysing the atrial MAP during AF, even though complete myocardial repolarisation is never reached during this arrhythmia. We have therefore evaluated the estimated duration of the action potential (AP) and MAP by exponential extrapolation of phase 3 data. (1) AP studies were done on 11 human atrial myocardial specimens. Resting membrane potential (RMP) and AP duration were better identified when more data obtained during repolarisation were used for prediction. Thus the predicted RMP deviated on average by -0.4% of AF amplitude from the real RMP level when data to 90% repolarisation were used for extrapolation. AP duration at 90% repolarisation correlated well with the real AP duration (r = 0.88) at this level of data aquisition. (2) Continuous recording of atrial MAPs was done in 15 patients during AF and in 12 of these during SR after DC conversion. Resting myocardial repolarisation level during AF, RP(EST), and estimated MAP duration, MAPD(EST), could be calculated by exponential extrapolation in 12 patients. The actual repolarisation during fibrillation reached below 90% of the RP(EST) level in eight patients and below 70% in all 12. The MAP duration during SR could be predicted with increasing precision when data closer to the RP(EST) were used for calculation of MAPD(EST). Thus MAPD(EST) correlated well with SR MAP duration when data reaching at least 90% of RP were used (r = 0.85).(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1989

Follow-up by repeated signal-averaged surface QRS in patients with the syndrome of arrhythmogenic right ventricular dysplasia.

Repeated signal-averaged surface electrocardiograms were recorded with a mean interval of 32.5 months (range 14 to 55 months) in 12 patients with the syndrome of arrhythmogenic right ventricular dysplasia (ARVD). The mean differences in the amplitude and duration of the filtered QRS complex (FQRS), the root mean square voltage of the last 40 ms of the FQRS and the duration of the terminal potentials of less than 25 microV were not statistically significant between the recordings. A wide spectrum of changes in the voltage and duration of the terminal potentials was observed, irrespective of the clinical susceptibility to ventricular tachycardia. Three patients developed changes suggesting a progression, with a decreased voltage and prolonged duration of the terminal potentials, and four patients showed the opposite pattern. In five patients the signals were stationary. It is concluded that the properties of late potentials may change with time in patients with ARVD. Follow-up by repeated signal-averaged QRS does not appear to be useful in predicting the susceptibility to ventricular tachycardia in ARVD. Its application in predicting and following progressive right ventricular morphological changes remains to be determined.

Adolescent↗
PubMed1989

Torsade de pointes tachycardias induced by overdosage of zimeldine.

Torsade de pointes tachycardias may occur in connection with overdoses, and more rarely with therapeutic doses, of tricyclic antidepressant agents and antiarrhythmic drugs, especially in the presence of hypokalemia. Zimeldine is a selective serotonin reuptake blocker, which according to studies in humans and animals, has no serious cardiovascular side effects in therapeutic doses. We report a patient who was admitted with repeated syncopal attacks resulting from prolonged QT intervals and torsade de pointes tachycardias. She also had hypokalemia, although she had had no treatment known to affect the potassium level. Correction of the potassium level rapidly prevented further tachycardias and led to normalization of the QT interval. Repeated blood samples verified high levels of zimeldine and its metabolites. We conclude that whenever torsade de pointes tachycardias occur, treatment with antidepressant or antiarrhythmic agents should be immediately suspected and verified. In addition, prompt initiation of potassium infusion may dramatically resolve the arrhythmias, even if the serum potassium level is within the lower normal range, and may also potentiate the effect of class I antiarrhythmic drugs such as lidocaine.

Aged↗
PubMed1988

Quantitative analysis of the signal-averaged QRS in patients with arrhythmogenic right ventricular dysplasia.

Temporal signal averaging of the surface QRS (V1 + V3 + V5) was performed in 16 patients with arrhythmogenic right ventricular dysplasia and in 16 normal subjects. The differences between ARVD patients and normals were large for the filtered QRS duration (FQRSd) (146.2 +/- 18.9 ms vs. 91.8 +/- 4.1 ms, P less than 0.000001), the late potential duration (LPd) (83.5 +/- 23.3 ms vs. 23.6 +/- 4.6 ms, P less than 0.00001), the LPd/FQRSd ratio (53.9 +/- 10.1% vs. 25.8 +/- 5.1%, P less than 0.00001), the filtered QRS amplitude (234.0 +/- 61.1 microV vs. 429 +/- 94.2 microV, P less than 0.001), and the root mean square voltage of the signals in the terminal 40 and 50 ms of the FQRS (RMS40 and RMS50) (18.4 +/- 10.0 microV vs. 118.4 +/- 49.8 microV, P less than 0.0005 and 27.9 +/- 19.2 microV vs. 217.0 +/- 66.3 microV, P less than 0.000002). RMS50 less than 40 microV discriminated best between ARVD and normals (81% sensitivity and 100% specificity). The right-sided predominance of the abnormalities in ARVD was demonstrated by the significantly longer FQRSd and LPd, and the higher ratio LPd/FQRSd in right than in left precordial leads. The arrhythmia susceptibility did not seem to influence the presence of or properties of LP in the ARVD group. Patients with multiple QRS morphologies during ventricular tachycardia (VT) had, compared with patients with only one type of VT, longer LPd (108.3 +/- 46.4 ms vs. 64.2 +/- 31.7 ms, P less than 0.02) and lower RMS40 voltage (9.4 +/- 9.9 microV vs. 25.4 +/- 21.6 microV, P less than 0.05). The relative heart volume was positively correlated with delayed activity, but an enlarged heart was not a pre-requisite for the presence of LP. The method thus identifies changes which are specific to ARVD. The findings indicate that certain electrical or morphological conditions are required for the occurrence of arrhythmias.

Adolescent↗
PubMed1987

Arrhythmogenic right ventricular dysplasia presenting with ventricular tachycardia in a father and son.

A father and his son presented with ventricular tachycardia of left bundle-branch block configuration, two years apart. The patients had no clinical signs of right or left ventricular dysfunction. The diagnosis of arrhythmogenic right ventricular dysplasia was based on right ventricular angiographic and radionuclide findings. Microscopic sections obtained at surgery for the ventricular tachycardia in the father revealed abnormal infiltration of fat and focal fibrosis in the right ventricular myocardium, confirming the diagnosis. The importance of thorough evaluation of right and left ventricular function and structure in patients with ventricular tachycardia of right ventricular origin is emphasized. Currently available diagnostic techniques and management are presented.

Adolescent↗
PubMed1987

Clinical value of plasma concentrations of antiarrhythmic drugs.

The clinical use of plasma concentrations of antiarrhythmic agents suffers from important limitations. Any factor changing the protein binding capacity affects the free, clinically active, fraction of the drug. Most antiarrhythmic agents attach to the acute phase alpha-1-acid glycoprotein, varying during conditions such as acute myocardial infarction, leading to changes in the plasma binding capacity for e.g. lidocaine. Several pharmacodynamic factors may counteract or potentiate the electrophysiological or haemodynamic action of antiarrhythmic agents. Active metabolites contribute to the clinical efficacy or to the side-effects. The induction of metabolizing enzymes of some drugs and the inhibition of hepatic metabolism of others may change the free drug fraction in plasma. While many studies show a good correlation between plasma levels and antiarrhythmic effect, few imply a correlation between plasma levels and a decrease in mortality. However, in spite of these limitations, plasma levels may be useful in guiding treatment with high dosages, with drugs with long elimination half-lives, in treatment failures due to true failure of the drug, changes in pharmacokinetics or because of poor patient compliance, and may be of particular interest when side-effects and/or intoxication are suspected.

Anti-Arrhythmia Agents↗
PubMed1987

Precision of preoperative electrophysiological study in predicting the intraoperatively defined location of single left-sided accessory pathways.

In 34 patients with a left-side anomalous pathway (AP) considered for arrhythmia surgery, the atrial insertion of the anomalous pathway in the preoperative investigation was determined by using three different techniques. The atrial activation sequence during orthodromic tachycardia or ventricular stimulation was recorded in the coronary sinus by using either (a) unipolar leads from an eight-polar electrode catheter with an interelectrode distance of 1 cm, (b) bipolar leads from consecutively positioned pairs of electrodes on the same electrode catheter or (c) bipolar leads recorded at one centimeter intervals by withdrawal of the electrode catheter. The corresponding location at surgery was obtained by atrial epicardial mapping during ventricular stimulation. Each way of recording the atrial activation sequence in the coronary sinus during orthodromic tachycardia or ventricular stimulation was compared with regard to their predictive value in assessing the corresponding location by intraoperative mapping. At surgery, a visual grid system was used to define the anatomical landmarks which were located 20 mm apart. When the unipolar technique was used to assess the anomalous pathway location, there was a difference corresponding to a distance of 2-2.5 anatomical landmarks (48 mm) between the preoperative and intra-operative assessments. With the bipolar technique the difference was up to 3 anatomical landmarks (60 mm) while it was up to 4.5 anatomical landmarks (90 mm) when the withdrawal technique was employed. The unipolar technique was superior in differentiating a left lateral from a left posterior or a septal location.

Adolescent↗
PubMed1987

Clinical course, serum concentrations and elimination rate in a case of massive sotalol intoxication.

A young woman had been on antiarrhythmic treatment with sotalol 80-160 mg daily for three years because of ventricular tachycardia. After a quarrel she ingested an overdose of sotalol, estimated to be 13-14 g, and was immediately brought to hospital, where the first ECG was taken 25 minutes after the ingestion. The clinical course, including the relationship over time between pronounced bradycardia, QT prolongation and malignant ventricular tachyarrhythmias is described. Serum concentrations were obtained regularly between 11 and 54 hours after the ingestion. After initially very high levels, the concentrations decreased in a strictly exponential manner to arrive at therapeutic concentrations 39 hours after the ingestion. Calculations revealed that over 12 g of sotalol was absorbed into the circulation, while the half life was 9.2 h and the oral clearance 294 mg min-1. The heart rate normalized about 24 hours after the repolarization variables, which supports the opinion that the class III action of sotalol is unrelated to the beta-blockade. In sotalol intoxication, malignant tachyarrhythmias appearing during excessive prolongation of the QT interval, most often in combination with hypokalemia, ethanol intoxication or concomitant antiarrhythmic treatment, may need emergency defibrillation but seem to disappear within a few hours. Thus, while massive sotalol intoxication may be fatal, early treatment promotes a successful outcome even when very high doses have been ingested.

Adult↗
PubMed1987

Transesophageal versus intracardiac atrial stimulation in assessing electrophysiologic parameters of the sinus and AV nodes and of the atrial myocardium.

Electrophysiological parameters of the sinus and AV nodes and of the atrial myocardium were assessed with both transesophageal atrial stimulation (TAS) and intracardiac atrial stimulation (ICS) in the same patient during the same study. The study group was comprised of nine men and seven women, aged 45 to 79 years, referred for the evaluation of syncope of possible arrhythmogenic origin. Twelve patients were included for analysis. Autonomic inhibition (AI) was obtained in five patients. The most striking result was the significantly longer AERP with TAS (mean 286 +/- 9 ms) than with ICS (mean 244 +/- 12 ms; p than 0.02). After AI, the AERP was even more prolonged with TAS (mean 332 +/- 20 ms) than with ICS (mean 237 +/- 8 ms; p less than 0.01). Intraatrial and AV nodal conduction times assessed at multiple paced cycle lengths were significantly shorter with TAS than with ICS. There was no difference between TAS and ICS with regard to AVERP, Wenckebach periodicity and H-V intervals. Although a tendency towards shorter sinus node recovery time (SNRT) and sinoatrial conduction time (SACT) was observed with TAS, the difference was not statistically significant. Possible mechanisms of the differences are discussed. It seemed clear that the site of origin of an atrial impulse can have definite effects upon excitability and conduction properties of atrial and AV nodal fibers. Enhanced sympathetic activity during TAS was also suggested. The electrophysiological properties inherent in the TAS technique warrant further elucidation.

Aged↗
PubMed1986

Surgical treatment of the WPW-syndrome--experience in 30 initial cases.

Between May 1980 and February 1985, 30 patients were operated upon at Sahlgren's Hospital for life-threatening or disabling arrhythmias, caused by Kent's bundles. Two surgical methods were used. The outcome of surgery was fully satisfactory in 19 patients, whereas 4 patients continued to have arrhythmias after surgery. Six patients had a modified delta-wave in the ECG after surgery, but their arrhythmias could be controlled by antiarrhythmic medication. One patient died after surgery due to an undiagnosed cerebral tumor. There were 2 late deaths, between 6 and 12 months postoperatively; neither of these was caused by arrhythmias.

Adolescent↗
PubMed1986

Effect of long term treatment with metoprolol and sotalol on ventricular repolarisation measured by use of transoesophageal atrial pacing.

The effects of long term (4 weeks) treatment with oral metoprolol (100 mg twice daily) and sotalol (160 mg twice daily) on ventricular repolarisation time were compared in a double blind crossover study in 20 patients post-infarction. For QT interval studies transoesophageal atrial pacing was performed at a cycle length of 800 ms. Sotalol prolonged the QT interval by 5-7% compared with metoprolol. The prolongation reflects a change in the repolarisation time because there was no change in the QS interval. Measurements of heart rate at rest and during bicycle exercise indicated that metoprolol and sotalol in the doses selected were equipotent as beta blockers. Transoesophageal atrial pacing is a simple non-invasive method with few and mild side effects that is well suited to drug studies.

Aged↗
PubMed1985

Paroxysmal vagally mediated AV block with recurrent syncope.

Paroxysmal complete atrioventricular (AV) block without associated electrocardiographic (ECG) abnormality is not a well recognized entity. A mother and her daughter had recurrent syncopal episodes, but a normal ECG. The episodes were preceded by nausea and vomiting. ECG during these episodes revealed complete heart block. In the mother, one episode was promptly reversed by atropine. Electrophysiological evaluation of the sinus and AV nodal function and atrial and ventricular effective refractory periods before and after autonomic blockade was normal. Provocative manoeuvres failed to induce AV block. Paroxysmal AV block was vagally mediated in one of the patients, as indicated by prompt response to atropine. In the second case, the vagal dependence could not be proved but appears to be the most likely explanation. It thus appears that paroxysmal, vagally mediated complete AV block should be seriously considered in patients with unexplained syncope.

Adult↗
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↗