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S B Olsson

Publications and source records attributed to S B Olsson.

At least 37 records · Page 2Linked to original sources
PubMed2000

Detection of inter-atrial conduction defects with unfiltered signal-averaged P-wave ECG in patients with lone atrial fibrillation.

AIMS: To demonstrate a possible inter-atrial conduction delay in patients with lone paroxysmal atrial fibrillation (PAF) using 'unfiltered' signal-averaged P-wave ECG (PSAECG) and compare these results with those obtained with conventional filter settings. METHODS AND RESULTS: Twenty one patients with lone PAF and 20 healthy volunteers (control group) were enrolled in the study. An orthogonal lead surface ECG was high-pass filtered at 0.8 Hz, averaged with template matching, and combined into a spatial magnitude ('unfiltered' technique). Results were compared with conventionally filtered (40-300 Hz) PSAECG. The filtered technique revealed no differences in P-wave duration between the two groups (121 +/- 12 vs 128 +/- 15 ms, control and PAF groups respectively, ns). Double-peaked P-wave spatial magnitudes (interpeak distance >30 ms) were revealed in 11 of 21 PAF patients but only in two of 18 controls (P<0.01). The nadir in the spatial magnitude was located significantly later in the PAF group (114 +/- 13 vs 103 +/- 9 ms, P<0.01). CONCLUSION: 'Unfiltered' PSAECG revealed significant differences in orthogonal P-wave morphology in patients with lone PAF, indicating the possibility of an inter-atrial conduction delay, while conventional P-wave duration analysis failed to discriminate between the two groups.

Adult↗
PubMed2000

Intravenous MgSO4 alone and in combination with glucose, insulin and potassium (GIK) prolong the atrial cycle length in chronic atrial fibrillation.

AIMS: To investigate the effects of parenteral administration of MgSO4, and glucose, insulin, and potassium (GIK), on the dominant atrial cycle length during chronic atrial fibrillation (CAF). METHODS AND RESULTS: The length of the dominant atrial cycle (DACL) in the power-frequency spectrum of the QRST-suppressed lead V1 ECG was identified before and after intravenous administration of MgSO4 alone and after 5 and 10 h of MgSO4 and GIK infusion, in 13 patients with CAF. The changes in DACL were compared with changes in heart rate (HR), blood pressure and blood parameters. MgSO4 alone increased the DACL from 146(13) (mean(SD)) (control) to 153(14) ms (P < 0.01) and decreased the HR from 102(22) to 95(18) beats x min(-1) (P < 0.05). After 5 h of MgSO4 and GIK infusion the DACL was increased compared with control, from 146(13) to 152(11) ms (P < 0.01), but unchanged compared with that after the bolus infusion of MgSO4. HR was decreased compared with control (102(22)) and the bolus infusion of MgSO4 (95(18)) to 87(15) beats x min(-1) after 5 h of intervention. The DACL was further increased after 10 h of MgSO4 and GIK infusion compared with both control (from 146(13) to 157(11) ms), (P < 0.01) and the 5h infusion (152(11) to 157(11) ms), (P < 0.05). No further changes were seen in HR after 10 h (87(17)) of intervention. There were indications of an inverse relationship between total changes in HR (deltaHR) and DACL (deltaDACL) during the interventions (P < 0.05). CONCLUSION: Bolus infusion of MgSO4 prolongs the DACL and decreases HR in CAF. A further prolongation of DACL was seen after 10 h of MgSO4 and GIK infusion compared with control and with 5 h of intervention. Changes in DACL and HR during the entire intervention period showed an inverse relationship. The antiarrhythmic properties of MgSO4 and the GIK solution in CAF clearly require further attention.

Aged↗
PubMed2000

Recording monophasic action potentials using a platinum-electrode ablation catheter.

AIMS: The monophasic action potential (MAP) is conventionally recorded using Ag-AgCl electrodes which are not suitable for delivering radiofrequency currents. To be able to use the sharp MAP upstroke for identifying the local activation, as a step towards the development of a MAP-guided catheter ablation technique, the possibility of recording MAP via platinum electrodes of an ordinary ablation catheter was explored. METHODS AND RESULTS: One hundred and forty-two MAP recordings from the endocardium were obtained via an ablation catheter in 40 patients undergoing electrophysiological study/catheter ablation. During sinus rhythm and pacing, 90% of the ventricular and 100% of the atrial MAPs had stable baselines. The amplitudes were 13 +/- 4.2 mV for ventricular and 2.4 +/- 0.8 mV for atrial MAPs. During mapping and ablation, MAPs and uni- and bipolar electrograms were recorded simultaneously using the same tip electrode in eight patients. The MAPs provided more distinct local activation than the electrograms. During 17 MAP recordings, additional MAPs were recorded simultaneously using an Ag-AgCl electrode catheter in the immediate vicinity of the ablation catheter. The MAPs taken with the ablation catheter had characteristics consistent with those taken with the Ag-AgCl catheter. CONCLUSIONS: (1) Platinum electrodes can be used for timely recording of MAPs in patients. (2) It is feasible to record MAPs and deliver radiofrequency currents via the same platinum-tip electrode. These findings suggest that MAP-guided catheter ablation is technically possible.

Action Potentials↗
PubMed1999

[Atrial fibrillation--new knowledge yields new therapeutic possibilities].

Atrial fibrillation (AF) is the most common cardiac arrhythmia prompting treatment. Advances in our knowledge of the pathophysiology of AF provide the basis for new and improved treatment modalities. Thus, focal excitation and localised impulse conduction defects are possible trigger factors which can be counteracted by focal ablation and pacing synchronisation, respectively. Perpetuation of AF, caused by continuous multisite re-entry, is promoted by successive shortening of repolarisation. Internal defibrillation and anatomical limitation of re-entry are treatments that counteract perpetuation of the arrhythmia. Current knowledge of AF and the application of new treatments are discussed by the Lund AF research group.

Atrial Fibrillation↗
PubMed1999

[Atrial fibrillation--epidemiological and electrophysiological aspects].

Atrial fibrillation is a common and therapy-requiring cardiac arrhythmia. The chronic form becomes identified in population studies from the age of 50 and increases with age. The number of Norwegian individuals with this arrhythmia is estimated to be slightly in excess of 40,000 and it will increase approximately by another 5,000 until the year 2010. Mechanisms responsible for initiation and maintenance of the arrhythmia are increasingly better understood. The paroxysmal form often has a focal origin, allowing curative treatment, but can also be associated with signs of deficient interatrial conduction. The chronic form is perpetuated partly by a shortening of atrial myocardial refractoriness, attributed to a failure in the intracellular turnover of Ca-ions due to the high excitation rate. Ongoing studies are expected to illustrate the clinical benefit of Ca-blockers prior to cardioversion of chronic atrial fibrillation. The further relapse rate is low in patients who have maintained sinus rhythm more than 1-2 months following conversion. It is therefore possible that, following a successful conversion to sinus rhythm, aggressive antiarrhythmic treatment should be given during a limited period only--a strategy which has to be evaluated in prospective studies.

Adult↗
PubMed1999

Effect of cardiac exposure by median sternotomy on atrial fibrillation cycle length.

BACKGROUND: Epicardial mapping is a powerful tool that has enabled us to gain insight into the electrical phenomena perpetuating atrial fibrillation and has guided the design of surgical and catheter-based therapeutic strategies. However, epicardial data are acquired during abnormal physiological conditions; the patients are anaesthetized, their chests opened, dislocating the heart and exposing it to air of room temperature, and the autonomic tone is modulated due to the surgery. The effect of intra-operative conditions on atrial electrophysiological properties have not been investigated before. Thus in the present study we assessed the atrial cycle length, shown to be an index of atrial refractoriness, and the ventricular rate before and during open-heart surgery in 10 patients with chronic atrial fibrillation and an underlying heart disease. METHODS AND RESULTS: Using a newly introduced and validated ECG method known as frequency analysis of fibrillatory ECG (FAF-ECG), the atrial cycle length and the ventricular rate were determined just before surgery. After anaesthesia and median sternotomy, epicardial mapping of the entire right atrial free wall was performed. The mean ventricular rate as well as the dominant atrial fibrillation cycle length consistently increased, the former from 71 to 92 beats x min(-1) (mean of all patients, P<0.05) and the latter from 156 to 172 ms (P<0.05). CONCLUSIONS: Atrial fibrillation cycle length, an index of atrial refractoriness, is increased as an effect of anaesthesia and heart exposure during open-heart surgery in patients with chronic atrial fibrillation, implying that atrial activation might be altered, which must be considered when interpreting data from epicardial conduction analysis.

Aged↗
PubMed1999

Attenuation of electrical remodelling in chronic atrial fibrillation following oral treatment with verapamil.

AIMS: Electrical remodelling with shortening of the atrial refractory period and increased fibrillatory rate occurs after onset of atrial fibrillation and can be attenuated by pre-treatment with intravenous verapamil. The aim of the present study was to investigate whether already established fibrillatory-induced shortening of atrial fibrillatory cycle length could be reversed with oral verapamil. METHODS AND RESULTS: Thirteen patients (nine men; mean age 67 years) with chronic atrial fibrillation (CAF) were studied. The dominant atrial cycle length (DACL) was estimated non-invasively using the frequency analysis of fibrillatory ECG (FAF-ECG) method. Measurements were repeated following treatment with slow release oral verapamil. DACL increased from 147 +/- 13 ms to 156 +/- 21 ms after 1 day (P=0.02), to 164 +/- 18 ms after 5 days (P=0.005) and finally to 160 +/- 16 ms after 6 weeks (P=0.008). CONCLUSION: Long-term oral treatment with verapamil increases the DACL significantly in patients with CAF. The prolongation is evident after 1 day and is further developed during the first 5 days of treatment. Since DACL is believed to be an index of refractoriness, the findings of the present study suggest that this treatment increases the atrial refractory period in patients with CAF.

Aged↗
PubMed1999

The optimal oesophageal pacing technique--the importance of body position, interelectrode spacing, electrode surface area, pacing waveform and intra-oesophageal local anaesthesia.

In order to improve the technique of transoesophageal atrial stimulation (TAS), the effects of body position, interelectrode spacing and electrode surface area on pacing threshold were assessed in two substudies. The effects of intra-oesophageal local anaesthesia and of two different pacing wave configurations on pacing threshold and discomfort were also assessed. Substudy I comprised 16 subjects (3 patients with a history of paroxysmal supraventricular tachycardia and 13 healthy volunteers) and substudy II comprised 16 healthy volunteers. TAS was performed using a hexapolar luminal prototype oesophageal electrode catheter. In substudy I bipolar pacing was performed in the semi-supine and left decubitus body positions for different pulse durations (20, 10, 6 and 2 ms), interelectrode pole distances (10 to 24 mm) and electrode pole surface areas (0.22 to 0.66 cm2). In substudy II TAS was performed with square wave and triangular waveform pulses after intra-oesophageal saline and lidocaine 20 mg/ml. These solutions were given in random order. Neither the interelectrode distance nor electrode surface areas had any significant influence on pacing thresholds. Stimulation thresholds were not affected by body position. Intraoesophageal lidocaine did not affect the discomfort experienced. Peak pacing thresholds using a triangular waveform were significantly higher than thresholds using a square waveformn (p < 0.001). The optimal pacing technique for TAS remains to be defined. The TAS-induced pain is probably not generated from the oesophageal mucous membrane. There is a significant difference in pacing thresholds between triangular and square waveforms.

Adult↗
PubMed1999

Atrial fibrillation and flutter: aeromedical considerations. New strategies for management and intervention.

Few cases of atrial fibrillation can be completely excused from the possibility of having some impact of potential importance in the aviation environment. The clinical pattern in paroxysmal disturbance is very wide and possible incapacitating phenomena are mainly haemodynamic. In contrast, chronic atrial fibrillation is mostly well-tolerated with only minimal haemodynamic effect, but there is a risk of thromboembolism, suggesting the need for anti-thromboembolic treatment. A subgroup with chronic atrial fibrillation with a very low risk may be defined, allowing avoidance of anti-thromboembolic treatment and a positive attitude towards aeromedical certification. Such individuals are likely to be normotensive males, under the age of 60 years, with a normal left (and right) heart configuration on electrocardiography.

Aerospace Medicine↗
PubMed1998

Non-invasive assessment of the atrial cycle length during atrial fibrillation in man: introducing, validating and illustrating a new ECG method.

OBJECTIVES: Atrial fibrillation (AF) in man has previously been shown to include a wide variety of atrial activity. Assessment of the characteristics of this arrhythmia with a commonly applicable tool may therefore be important in the choice and evaluation of different therapeutic strategies. As the AF cycle length has been shown to correlate locally with atrial refractoriness and globally with the degree of atrial organization, with, in general, shorter cycle length during apparently random AF compared to more organized AF, we have developed a new method for non-invasive assessment of the AF cycle length using the surface and the esophagus (ESO) ECG. METHODS AND RESULTS: From the frequency spectrum of the residual ECG, created by suppression of the QRST complexes, the dominant atrial cycle length (DACL) was derived. By comparison with multiple intracardiac simultaneously acquired right and left AF cycle lengths in patients with paroxysmal AF, we found that the DACL in lead V1, ranging from 130 to 185 ms, well represented a spatial average of the right AF cycle lengths, whereas the DACL in the ESO ECG, ranging from 140 to 185 ms, reflected both the right and the left AF cycle length, where the influence from each structure depended on the atrial anatomy of the individual, as determined by MRI. In patients with chronic AF, the method was capable of following changes in the AF cycle length due to administration of D,L-sotalol and 5 min of ECG recording was sufficient for the DACL to be reproducible. CONCLUSIONS: We conclude that this new non-invasive method, named 'Frequency Analysis of Fibrillatory ECG' (FAF-ECG), is capable of assessing both the magnitude and the dynamics of the atrial fibrillation cycle length in man.

Adult↗
PubMed1998

Modification of intrinsic AV-nodal properties by magnesium in combination with glucose, insulin, and potassium (GIK) during chronic atrial fibrillation.

OBJECTIVE: To explore the effects of MgSO4 in combination with glucose, insulin, and potassium (GIK) on intrinsic AV-nodal properties during chronic atrial fibrillation. METHODS: The study included two patient groups--(a) control and intervention and (b) intervention--with different infusion times and concentrations of MgSO4. Ambulatory electrocardiographic recordings were analyzed using modified heart-rate stratified histogram (HRSH) analysis allowing detailed observation of the RR distribution at different average heart rate levels. The two RR-interval populations observed in most patients were characterized by analyzing the relationship between the summits of the peaks of the bimodal histograms. RESULTS: A bimodal RR distribution with a shorter and a longer RR-interval population was observed in 9 of 11 (control), 9 of 11 (intervention) in group (a), and 11 of 13 in group (b) patients. No significant changes in the two RR populations were seen in the control registration (group a). There were, however, indications of a conduction delay in the longer RR intervals in group (a), which received a low concentration of MgSO4, when control was compared with intervention recordings. In group (b), receiving a high MgSO4 concentration, a conduction delay was seen in both the shorter and longer RR populations, being most pronounced for the longer RR population. CONCLUSION: High MgSO4 levels caused a delay in both the shorter and longer RR intervals. The conduction delay in the longer RR population was most pronounced, indicating that MgSO4 differently affected the two corresponding AV-nodal pathways.

Aged↗
PubMed1998

Effects of magnesium and glucose, insulin, potassium (GIK) solution on the action potential parameters of guinea-pig atrial muscle.

The present paper aims to explore the effects of [Mg2+]o and glucose, insulin and K+ (GIK) on action potential parameters in guinea-pig atrial muscle. Specimens of atrial appendages were taken from guinea-pig hearts. Action potentials were recorded in isolated atrial trabeculae. Resting potential (RP) and action potential duration at 90% repolarization (APD90) were measured with conventional microelectrode techniques. [Mg2+]o at 6 and 12 mmol L-1 depolarized the RP and prolonged the APD90, whereas 4 mmol L-1 had no effect at all. Glucose alone or in combination with insulin had no effect on action potential parameters. GIK solution with supernormal [K+]o at 6 mmol L-1 depolarized the RP and decreased the APD90. Intervention with [Mg2+]o at 4 mmol L-1 in combination with GIK solution with supernormal [K+]o of 6 mmol L-1, reversibly depolarized the RP, whereas the APD90 was not significantly changed. [Mg2+]o at 12 mmol L-1 in combination with GIK solution with a physiological [K+]o of 4 mmol L-1 prolonged the APD90 whereas the RP was unaffected. [Mg2+]o at 6 and 12 mmol L-1 slightly depolarized the RP and prolonged the APD90. The action potential of normally polarized atrial muscle was not sensitive to supernormal levels of glucose alone or in combination with insulin. The effects of [Mg2+]o in combination with the GIK solutions on action potential parameters seemed to be attributable to the supernormal [Mg2+]o and [K+]o alone, while these seemed to have opposite effects on APD90.

Action Potentials↗
PubMed1998

Right atrial free wall conduction velocity and degree of anisotropy in patients with stable sinus rhythm studied during open heart surgery.

AIMS: Although the perpetuation of several supraventricular arrhythmias is critically dependent upon intra-atrial conduction, the literature lacks detailed information on normal values of conduction velocity and degree of anisotropy. In order to explore these factors further, we have measured conduction velocities at the right atrial free wall during sinus rhythm and during atrial pacing in four directions parallel and perpendicular to the atrioventricular groove in patients with normal atria and stable sinus rhythm. METHODS AND RESULTS: Using a Bard Cardiac Mapping System, atrial ECGs were recorded using a 3 x 4 cm electrode array with 56 equally spaced bipolar electrodes in 12 patients undergoing open heart surgery due to ischaemic heart disease or Wolf-Parkinson-White syndrome. A bipolar pen probe connected to a Medtronic 5328 stimulator was used for pacing at a 10% higher rate than sinus rhythm. The local activation times were manually set and isochronal activation maps were created for each recording. The conduction velocities were calculated from the activation maps over a distance ranging from 2.2 to 4.2 cm. The majority of the activation maps showed no signs of anisotropy; the others had less than 15% spatial inhomogeneity of conduction. Mean conduction velocity, calculated from five consecutive beats, was 88 +/- 9 cm.s-1 (mean +/- SD), ranging between 68 +/- 4 and 103 +/- 3 cm.s-1 during sinus rhythm. Mean conduction velocity during atrial pacing was 81 +/- 16 cm.s-1 at a propagation direction of 0 degree, 74 +/- 14 cm.s-1 at a 90 degrees direction, 79 +/- 12 cm.s-1 at 180 degrees and 78 +/- 20 cm.s-1 at 270 degrees, where 0 degree was parallel to the atrioventricular groove in the cranial direction and the angle increased counter-clockwise. Mean conduction velocity during sinus rhythm was significantly higher (P < 0.05) than during atrial pacing at the 90 degrees and 180 degrees directions but not compared to atrial pacing at 0 degree or 270 degrees. There was no significant difference in mean conduction velocity in different directions during atrial pacing. CONCLUSION: Although anisotropy was documented during conduction velocity in individual cases, conduction velocity was not dependent on propagation direction at the epicardial right atrial free wall in patients with stable sinus rhythm. These findings do not exclude the presence of internodal preferential pathways as these are located sub-epicardially and a marked transmural discordance in activation has previously been documented in the vicinity of such pathways.

Adult↗
PubMed1998

Non-invasive assessment of magnitude and dispersion of atrial cycle length during chronic atrial fibrillation in man.

AIMS: Atrial fibrillation cycle lengths can be assessed from right precordial ECG leads and the unipolar oesophageal ECG using a non-invasive method called Frequency Analysis of Fibrillatory ECG. The purpose of this report is to present the results from application of this method in a large group of patients with long-term atrial fibrillation and to examine the differences between patients with 'coarse' and 'fine' atrial fibrillation. METHODS AND RESULTS: Simultaneous 15 min recordings from V1, V2 and an oesophageal lead at a position behind the posterior atrium were obtained in 28 patients, aged 41 to 78 years, with long-term (> 1 month) atrial fibrillation. In each lead, using the time averaging technique, the QRST complexes were suppressed. Thereafter, the frequency distribution of the residual ECG was estimated by means of Fast Fourier Transform. In the 3-12 Hz range of each lead, the dominant atrial cycle length, the power maximum and the spectral width were calculated. In 26 patients (93%), frequency spectra in the 3-12 Hz range could be obtained. The dominant atrial cycle length ranged from 120 to 175 ms, mean 150+/-16 (SD) ms in V1, and from 120 to 190 ms, mean 150+/-16 in an oesophageal lead (ns). The absolute difference in the dominant atrial cycle length between V1 and the oesophageal lead was 10.4+/-7.7 ms. There was no significant difference in the dominant atrial cycle length in V1 between patients with coarse and fine atrial fibrillation. The power maximum in V1 was significantly greater in patients with coarse compared to fine atrial fibrillation (P=0.01). The spectral widths ranged from 10 to 55 ms and demonstrated significantly higher mean values in lead V2 compared to V1 (P=0.001). Compared to V1, the mean values tended to be smaller in the oesophageal lead (P=0.05). CONCLUSIONS: Using the Frequency Analysis of Fibrillatory ECG method, the dominant atrial cycle length, power maximum and spectral width can be estimated from the frequency spectra in the majority of patients with atrial fibrillation. Spatial dispersion of the dominant atrial cycle length occurs in some patients and may be an important proarrhythmic marker. The distinction between coarse and fine atrial fibrillation cannot be used as a marker of the atrial cycle length.

Aged↗
PubMed1998

Aortic valve replacement in patients older than 85 years: outcomes and the effect on their quality of life.

PURPOSE: The aim of this study was to investigate the outcome of aortic valve replacement (AVR) and the effect on quality of life in patients aged over 85 who had symptomatic aortic stenosis. METHODS: We performed a retrospective analysis of 21 patients, aged 85-91 years (mean age 86.5), who underwent AVR, 10 of whom underwent concomitant coronary artery bypass grafting (CABG) between 1989 and 1995. All patients were categorized as New York Heart Association (NYHA) functional class III and IV. A questionnaire was used to evaluate heart symptoms and quality of life among the 13 patients who were alive at follow-up (9-83 months). RESULTS: Eighteen patients were categorized as NYHA functional class I and II for 1 year (9 months for one patient) after AVR. Three patients, all undergoing concomitant CABG, died early. The overall 1-, 2- and 3-year actuarial survival rate was 85%, 64% and 53% (among the patients undergoing only AVR the figures were 100%, 100% and 85%). Follow-up questionnaire results showed an improvement in the patients' symptoms of heart disease, dyspnea (P = 0.017) and angina (P = 0.03). An improvement in the patients' physical functioning (P = 0.025), satisfaction with physical ability (P = 0.005), sleep (P = 0.025), health status (P = 0.025) and perception of general health (P = 0.005) was also observed. CONCLUSIONS: Our results show that AVR can be performed on patients > or = 85 years of age or older, with an improvement in heart symptoms and quality of life.

Aged↗
PubMed1998

Ultrasound enhanced thrombolysis in experimental retinal vein occlusion in the rabbit.

AIMS: To investigate if it was possible to lower the dose of streptokinase and maintain an effective thrombolysis by adding pulsed low energy ultrasound. METHODS: 53 retinal veins in 27 rabbits were occluded by rose bengal enhanced laser treatment. Six rabbits were treated with streptokinase (50,000 IU/kg), 10 rabbits were treated with a low dose of streptokinase (25,000 IU/kg), and 11 rabbits were treated with a low dose of streptokinase (25,000 IU/kg) and pulsed ultrasound during 1 hour. Fluorescein angiography was performed immediately before the thrombolytic treatment and after 12 hours. RESULTS: In the group treated with streptokinase (50,000 IU/kg) all vessels were open. In the group that was given streptokinase (25,000 IU/kg), 21% of the vessels were open. In the group that was treated with streptokinase (25,000 IU/kg) and ultrasound, 64% of the vessels were open. The difference between groups 2 and 3 is statistically significant (p = 0.011) CONCLUSION: Adding pulsed low energy ultrasound makes it possible to lower the dose of streptokinase while maintaining a good thrombolytic effect.

Animals↗