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Biomedical subjects

L Bergfeldt

Publications and source records attributed to L Bergfeldt.

At least 19 recordsLinked to original sources
PubMed1998

Changes in human coronary sinus blood flow and myocardial metabolism induced by ventricular fibrillation and defibrillation.

BACKGROUND: During implantation of cardioverter-defibrillators, repeated inductions of ventricular fibrillation and defibrillation are performed. Little is known about the myocardial metabolism associated with ventricular fibrillation and defibrillation in humans. METHODS: Sixteen patients scheduled for transvenous cardioverter-defibrillator implantation were included in the study. In 10 of the patients, blood samples were taken simultaneously in the coronary sinus and radial artery and analyzed for PO2, PCO2, standard bicarbonate, pH, lactate, alanine, glucose, and glycerol. Oxygen saturation, base excess, and oxygen content were calculated. The patients were studied before, shortly after, and 2 and 5 minutes after successful defibrillation. In six of the patients, coronary sinus blood flow was registered continuously. RESULTS: The coronary sinus blood flow declined from a basal value of 93 +/- 16 mL/min to 35 +/- 6 mL/min 14 +/- 2 seconds after induction of ventricular fibrillation. Following termination of ventricular fibrillation, coronary sinus blood flow increased to a peak value of 227 +/- 75 mL/min. Oxygen saturation, PO2, and oxygen content in the coronary sinus increased by approximately 25% shortly after each episode of ventricular fibrillation and defibrillation. The coronary sinus lactate increased and the arterio-coronary sinus lactate difference decreased shortly after each of the four episodes, but was normalized within 2 minutes. CONCLUSIONS: Repeated threshold tests during defibrillator implantation did not cause any long-lasting or cumulative metabolic effects, indicating that the described technique, with a 5-minute recovery period in between episodes, is safe as regards myocardial metabolism.

Adult↗
PubMed1997

Incidence of sudden death after radiofrequency ablation of the atrioventricular junction for atrial fibrillation.

This study assesses the incidence of sudden death and classifies the causes of death following radiofrequency ablation of the atrioventricular (AV) junction. We studied 220 patients with paroxysmal (n = 105) or chronic (n = 115) atrial fibrillation (AF) and a mean age of 64 +/- 12 years. These patients were followed 31 +/- 15 months after radiofrequency ablation of the AV junction and pacemaker implantation. In 86 patients, structural heart disease was identified before the procedure. All patients were traced via the Swedish National Civic Registry and Cause of Death Registry. The cause-of-death was classified according to data from death certificates, autopsy protocols, and medical records. Thirty-one patients (mean age 69 +/- 11 years, 16 men) died 15 +/- 15 months (range 0.2 to 60) after the procedure. There were 6 sudden unexplained deaths, 14 cardiovascular deaths, and 11 deaths from noncardiovascular causes. Eleven patients, all with structural heart disease, died suddenly out of hospital 16 +/- 16 months (range 0.2 to 42) after the procedure. In 6 of these there was no obvious cause of death. Three of these 6 patients underwent autopsy, which showed extensive coronary artery disease (n = 1), severe heart failure (n = 1) and cardiac hypertrophy and dilation (n = 1). The remaining 3 all had depressed left ventricular systolic function and a history of congestive heart failure. Five of the patients who died suddenly from cardiovascular causes had autopsies that revealed acute myocardial infarction (n = 4) and massive pulmonary embolism (n = 1).

Aged↗
PubMed1997

HLA-B27-associated cardiac disease.

PURPOSE: To review the available information about cardiac disease in relation to the immunogenetic marker HLA-B27 and the inflammatory disorders associated with it (seronegative spondyloarthropathies). DATA SOURCES: English-language clinical studies, case reports, and reviews published in 1995 or earlier were identified from a search of the MEDLINE database. These papers, textbooks, and other bibliographic sources were used to identify other relevant publications, enabling collection of references from 1936 through 1995 in a stepwise manner. STUDY SELECTION: Clinical studies, case reports, and topical reviews on the HLA-B27 histocompatibility locus, seronegative spondyloarthropathies, and cardiac disease were selected. DATA EXTRACTION: Information from systemic or hypothesis-driven studies, including those showing clinically and statistically meaningful associations between disorders, and additional relevant information from case reports and reviews is presented. DATA SYNTHESIS: Immunogenetic, histopathologic, clinical, and electrophysiologic evidence was examined to explore the concept of HLA-B27-associated cardiac disease. RESULTS: Relative to the general population (in which the frequency is 6% to 8%), men (but not women) with pacemakers have a significantly increased frequency of HLA-B27. Furthermore, a cardiac syndrome that consists of severe conduction system abnormalities plus aortic regurgitation is associated with HLA-B27, which was present in 67% to 88% of the patients with both of these clinical findings. This proportion of HLA-B27 is similar to that found in patients with ankylosing spondylitis and Reiter disease. Cardiac and aortic tissue both show intimal proliferation of small arteries (obliterative endarteritis) and fibrosis, as seen in tissues adjacent to afflicted joints. Both cardiac conduction abnormalities and aortic regurgitation occur in patients with various HLA-B27-related extracardiac disorders, regardless of the severity of the latter; in about 50% of patients with these cardiac findings, a diagnosis of an HLA-B57-related rheumatic disease has not previously been made. Third-degree (complete) atrioventricular block related to HLA-B57 is located within the atrioventricular node in 95% rather than the expected 20% of cases. CONCLUSIONS: The heart and the joints are both of major importance as targets for the HLA-B57-associated disease process. HLA-B57-related cardiac lesions may be found in the absence of other rheumatologic manifestations. Furthermore, a genetically linked cardiac syndrome has been defined: the combination of conduction system abnormalities and aortic regurgitation.

Arrhythmias, Cardiac↗
PubMed1997

[ECG findings with poor prognosis. Bifascicular block as a warning sign in cases of syncope].

Of 517 emergency room admissions for syncope at four Stockholm hospitals, 36 (7 per cent) were found to be cases of bifascicular block. Of these 36 patients, 34 underwent ambulatory electrocardiography (ECG) in hospital, which showed significant arrhythmia to be present in three cases [high-grade atrioventricular block (n = 2), or sustained ventricular tachycardia (n = 1)]. After a mean follow-up of 32 months, eight more patients had developed high-grade atrioventricular block, and 13 patients had died (eight of them suddenly). It is concluded that patients with bisfascicular block constitute a high-risk category, and would benefit from thorough investigation, including an invasive electrophysiological study, in order to identify those at risk of progression to high-grade atrioventricular block or malignant ventricular arrhythmia.

Aged↗
PubMed1997

Myocardial injury after electrical therapy for cardiac arrhythmias assessed by troponin-T release.

Episodes of ventricular fibrillation with subsequent intracardiac, and to a lesser extent, external defibrillation give rise to a statistically significant increase in S-troponin T, S-CK-MB(mass) and S-myoglobin indicative of a minor myocardial injury or dysfunction. In contrast, no such signs were observed after external direct-current conversion of atrial fibrillation using high energies, or after pace-terminated ventricular tachycardia.

Adult↗
PubMed1997

Left ventricular function after repeated episodes of ventricular fibrillation and defibrillation assessed by transoesophageal echocardiography.

BACKGROUND: Investigators studying the effects of cardioverter-defibrillators on left ventricular systolic function have given only minor attention to the diastolic effects. OBJECTIVES: The purpose of this study was to investigate the impact of repeated episodes of ventricular fibrillation and defibrillation on systolic function and diastolic filling of the left ventricle during non-thoracotomy implantation of a cardioverter-defibrillator. METHODS: Systolic function and diastolic filling of the left ventricle were assessed peri-operatively on a beat-by-beat basis using a transoesophageal echo-Doppler technique in 12 patients during > or = 4 episodes of ventricular fibrillation and defibrillation. Systolic function was assessed from the fractional area change and diastolic filling from the E/A ratio. Arterial blood pressure and the ECG were recorded continuously. RESULTS: Blood pressure and heart rate did not change significantly throughout the procedure. The systolic function, similarly, was not significantly affected; the only changes were seen in the first two beats after defibrillation when the mean fractional area increased from 0.2 +/- 0.01 to 0.4 +/- 0.02 and 0.3 +/- 0.02, respectively (P < 0.001). Diastolic filling was, however, impaired as reflected by a decrease in the E/A ratio from 2.6 +/- 0.5 before to 1.6 +/- 0.4 (P < 0.01) after repeated threshold tests. CONCLUSIONS: While the combined ischaemic and electrical trauma caused by repeated episodes of ventricular fibrillation and defibrillation during the implantation of a cardioverter-defibrillator did not cause any systolic dysfunction, diastolic filling was significantly impaired.

Adult↗
PubMed1996

The effect of ventricular activation sequence on cardiac performance during pacing.

The aim of this study was to evaluate the importance of a normal ventricular activation pattern for cardiac performance. In nine mongrel dogs, atrial pacing was compared to AV synchronous pacing at three different AV delays (150, 100, and 60 ms). In six dogs, proximal septal AV synchronous pacing was compared to apical AV synchronous pacing at three different AV delays. AV synchronous pacing was performed after RF induced complete heart block. Hemodynamics were evaluated by assessment of positive and negative dP/dt, cardiac output, and left ventricular and pulmonary pressures. Atrial pacing was superior to AV synchronous pacing with respect to positive and negative dP/dt and cardiac output. This difference was present at all AV delays. Proximal septal pacing was associated with a higher positive and negative dP/dt compared to apical pacing at all AV delays. Left ventricular activation time was significantly shorter during proximal septal pacing than during apical pacing (88 +/- 4 vs 115 +/- 4 ms, P < 0.001). We conclude that atrial and proximal septal pacing improves cardiac function and shortens the ventricular activation time compared to apical AV synchronous pacing independent of the AV interval.

Animals↗
PubMed1996

Sinus node recovery time assessment revisited: role of pharmacologic blockade of the autonomic nervous system.

Sinus node recovery time assessment is used to diagnose clinically significant sinus node dysfunction (SND) when Holter has failed to prove a relationship between sinus bradyarrhythmias and symptoms, but consensus has not been reached as to the value of including assessment after pharmacologic blockade of the autonomic nervous system. This issue was addressed in the present study performed on 52 patients with syncope or presyncope/dizziness (n = 48), sinus bradyarrhythmias (n = 45), or both (n = 41). Group 1 consisted of 13 patients with a proven relationship between symptoms and sinus bradyarrhythmias. Group 2 consisted of 39 patients with suspected SND. The protocol included three pacing periods at two pacing rates and was performed at baseline (n = 52), after single doses of atropine and propranolol (0.02 mg/kg and 0.1 mg/kg, respectively) (n = 41), and again after a second dose (n = 29). The sensitivity of prolonged recovery times was 77% in group 1. Among group 2 patients, 56% had prolonged recovery times at baseline (79% when including the results after the first dose of drugs). The second dose did not contribute diagnostic information, but it caused significant adverse reactions in 7 of 29 patients (P < 0.001). These 7 patients were all older than 60 years. Assessment of sinus node recovery time after pharmacologic blockade of the autonomic nervous system thus increases the sensitivity of the method in patients with suspected SND and normal baseline results. However, only 50% of the initially suggested doses of atropine and propranolol is sufficient and eliminates the risk for significant adverse reactions.

Adult↗
PubMed1995

Diagnostic value of programmed ventricular stimulation in patients with bifascicular block: a prospective study of patients with and without syncope.

OBJECTIVES: The aim of this study was to examine the inducibility of ventricular arrhythmias in patients with bifascicular block both with and without a history of syncope and to relate the findings to clinical events during follow-up. BACKGROUND: Patients with bifascicular block have an increased risk of sudden death that is not reduced by pacemaker treatment. This risk could be related to a high incidence of ventricular arrhythmias. METHOD: Programmed ventricular stimulation was performed in 101 patients with bifascicular block: 41 had a history of unexplained syncope, and 60 were asymptomatic. RESULTS: Programmed ventricular stimulation resulted in a sustained ventricular arrhythmia in 18 patients (18%), 8 in the syncope group and 10 in the nonsyncope group (p = NS). Three patients in each group had an inducible sustained monomorphic ventricular tachycardia. During a mean follow-up of 21 months, 10 patients experienced a clinical event defined as sudden death (n = 4), syncope (n = 5) or appropriate discharges from an implantable cardioverter-defibrillator (n = 1). Only one of these patients had an inducible ventricular arrhythmia at baseline. CONCLUSIONS: The inducibility of ventricular arrhythmias is high in patients with bifascicular block and of the same magnitude in patients with and without a history of syncope. Clinical events during follow-up were not predicted by programmed ventricular stimulation in either of the two groups. The finding of inducible ventricular arrhythmia in patients with bifascicular block should therefore be interpreted with caution.

Adolescent↗
PubMed1995

"Normal" response of the QT interval and QT dispersion following intravenous injection of the sodium channel blocker disopyramide: methodological aspects.

Measurement of the QT dispersion (the maximal interlead difference) on the surface electrocardiogram has been suggested for assessing the risk for ventricular arrhythmias and for examining drug effects and their proarrhythmic potential. The acute response of QT dispersion was assessed in 10 healthy subjects receiving disopyramide, which is known to delay repolarization and to prolong global measures thereof. The QRS, JT, and QT intervals and their dispersion were assessed at spontaneous rhythm and at atrial pacing at baseline and after an intravenous injection of disopyramide 2 mg/kg over 5 minutes. The short-term (within 30 minutes) and long-term (> or = 2 weeks) variabilities of the QT interval and the QT dispersion, expressed as the coefficient of variation, were also analyzed. At spontaneous rhythm the group average QT interval was between 369 and 375 msec, and the QT dispersion was between 33 and 37 msec; both were relatively stable over time. All subjects responded homogeneously to disopyramide with a significant QT prolongation (p < 0.001), but no consistent response of the QT dispersion was observed. This discrepancy reflects the significant difference in time-dependent variability with a coefficient of variation of spontaneous, paced, and heart rate-corrected QT dispersion between 25% and 42%, 8-42 times greater than the corresponding values of 1-4% for the QT intervals. The individual response of the QT dispersion to drug challenge should therefore be interpreted with caution. Furthermore and as a consequence, QT dispersion is less sensitive for assessing drug effects on ventricular depolarization and repolarization than the QT interval.

Adult↗
PubMed1995

Electrophysiological evaluation of the sodium-channel blocker carbamazepine in healthy human subjects.

Carbamazepine (CBZ) is a sodium-channel blocker used mainly for the treatment of epileptic seizures and neuralgias. It may impair the function of the cardiac conduction system in susceptible patients, but its electrophysiological effects have not been thoroughly assessed in the normal heart, which was the aim of the present study. Ten healthy volunteers, mean age 32 years, underwent two electrophysiological investigations at baseline and three at different dose levels of CBZ. The transesophageal atrial stimulation technique was used to evaluate sinus node function, refractoriness of the atrial myocardium, atrioventricular conduction, and ventricular depolarization and repolarization (as reflected by the QRS, JT, and QT intervals) at spontaneous rhythm and after atrial pacing. Atropine was administered to facilitate 1:1 conduction and assessment of rate-dependent effects. At the highest CBZ dose (800 mg/day), which gave plasma concentrations within the upper therapeutic range, the PQ interval was mildly prolonged (151 vs. 159 msec; p < 0.01). In addition, the shortening of the JT interval normally seen at higher pacing rates was counteracted by high-dose CBZ, as demonstrated by a lower mean slope of the regression line after atropine and CBZ than after atropine alone (0.17 vs. 0.20; p < 0.05). No other effects were detected. At therapeutic levels CBZ had minimal effects on the healthy conduction system, supporting its safe use in the absence of cardiac disease.

Administration, Oral↗
PubMed1995

Cardiac release of histamine after ventricular fibrillation and defibrillation during insertion of implantable cardioverter defibrillators (ICD).

Histamine has inotropic, chronotropic, arrhythmogenic, and vasoactive effects, and is released from the heart in ischaemia-reperfusion injury. The effect of ventricular fibrillation (VF) and defibrillation (DEF) on histamine release was investigated in 9 anaesthetized patients undergoing transvenous implantation of ICD. Concomitant arterial and coronary sinus (CS) blood samples were drawn before induction of VF (duration 20 seconds), immediately after, and 2 and 5 min after DEF (18-24 Joules). Basal arterial histamine was 2.5 +/- 6 nmol/l, and did not increase after VF. The histamine level in CS was 1.1 +/- 0.2 nmol/l before VF (p < 0.008 compared to arterial), and increased to 2.5 +/- 0.6 nmol/l immediately after (p < 0.045 compared to basal), to 3 +/- 1.1 nmol/l 2 min after (p < 0.45), and to 2.4 +/- 0.8 nmol/l 5 min after VF. In the basal state there was an uptake of histamine across the coronary circulation. After VF/DEF the level of histamine increased in coronary venous blood, suggesting cardiac release of histamine.

Aged↗
PubMed1995

Screening for sinus node dysfunction by analysis of short-term sinus cycle variations on the surface electrocardiogram.

A new noninvasive screening method for diagnosing sinus node dysfunction (SND) was evaluated. Sinus cycle variations from 1-minute electrocardiograms (ECG) were described by two variables: the variation range around the mean cycle length (percentage) and the maximal change between any two consecutive cycles (milliseconds). SND was diagnosed when both variables were increased. Part 1: Validation of this method against Holter and sinus node recovery time assessment in 69 patients with proven or possible sick sinus syndrome (SSS). Part 2: Application of the method to 60 patients with clinically significant cardiovascular and pulmonary disorders (group 3), but without any pretest suspicion of SND. Part 1: Sinus cycle variations and sinus node recovery times were abnormal in similar proportions, 55% and 63%, respectively. The sensitivities in proven SSS were 72% and 71%, respectively. Sinus node function was concordantly classified in 80% of 64 patients undergoing both tests. When sinus cycle variations were abnormal the probability of a prolonged recovery time was 89%. Part 2: Asymptomatic SND was found in 12% of patients in group 3. Thus, analysis of short-term beat-to-beat variations in the surface ECG has a sensitivity of approximately 70% and a specificity of 100% for diagnosing SND.

Adolescent↗
PubMed1995

Use of signal-averaged electrocardiography for predicting inducible sustained monomorphic ventricular tachycardia in patients with bundle branch block with and without a history of syncope.

The aim of this study was to examine the utility of signal-averaged electrocardiography in relation to inducible sustained monomorphic ventricular tachycardia in patients with bundle branch block. One hundred fourteen patients with bundle branch block underwent signal-averaged electrocardiography in the time domain and programmed ventricular stimulation. Sustained monomorphic ventricular tachycardia was induced in 17 patients. The mean values of the three signal-averaged electrocardiographic variables analyzed differed significantly between the inducible and the noninducible group. The filtered QRS duration showed the most prominent difference between the two groups, and a filtered QRS duration > or = 155 msec had a sensitivity of approximately 80%, a specificity of 60%, and a total predictive value of 65%. In the subgroup of patients with syncope, a combination of these criteria with a history of coronary artery disease had a sensitivity of 100% and a specificity of 90%.

Aged↗
PubMed1995

Cardiac outflow of endothelin, neuropeptide Y and noradrenaline in relation to hyperaemia in coronary sinus flow following electrical conversion of induced ventricular fibrillation in man.

The implanted cardioverter defibrillator represents an alternative therapy for patients with drug-refractory malignant ventricular arrhythmias. Implantation and testing of the device requires that ventricular fibrillation be evoked and converted, thus providing a situation in which cardiovascular haemodynamics can be studied. In this study we have evaluated the effects of electrically induced ventricular fibrillation, followed by defibrillation, on coronary sinus blood flow and cardiac outflow of endothelin- and neuropeptide Y-like immunoreactivity (-LI) and of noradrenaline. Twelve patients were studied during implantation of a defibrillator. Ventricular fibrillation was induced and terminated after 17 +/- 1 s 5 +/- 1 times in each patient. In six patients coronary sinus blood flow was measured continuously. Plasma samples were obtained from four of these patients and another six patients, from the coronary sinus, radial artery and central vein before and during fibrillation and at two time points ( < 30 s and 5 min). Basal coronary sinus blood flow decreased to 38% at 14 +/- 2 s of ventricular fibrillation. Immediately following defibrillation there was a short-lasting increase in coronary sinus blood flow to 244% and a significant increase in the levels of neuropeptide Y-LI (146%) and noradrenaline (158%) in the coronary sinus while endothelin-LI remained unchanged (97%). Neither fibrillation nor defibrillation evoked any changes in the peripheral arterial and venous levels of endothelin-, neuropeptide Y-LI or noradrenaline. It is concluded that coronary sinus blood flow is markedly reduced during fibrillation and that restoration of normal impulse activity is followed by short-lasting hyperaemia. There was no evidence for effects on the vascular endothelium as assessed by endothelin levels.

Adult↗
PubMed1995

Spectral turbulence analysis of the signal-averaged electrocardiogram for predicting inducible sustained monomorphic ventricular tachycardia in patients with and without bundle branch block.

Spectral turbulence analysis of the signal-averaged electrocardiogram is a new method for identifying patients prone to sustained monomorphic ventricular tachycardia. In contrast to analysis in the time domain, it has been claimed to be applicable in patients with bundle branch block. The aim of this study was to assess the predictive value of spectral turbulence analysis, in relation to the inducibility of sustained monomorphic ventricular tachycardia, in patients with and without bundle branch block. One hundred and sixty nine patients, of whom 120 had a QRS duration > or = 120 ms, were studied. Forty-seven patients had inducible sustained monomorphic ventricular tachycardia and were compared to 122 control patients. The overall sensitivity of the spectral turbulence analysis for predicting inducible ventricular tachycardia was 77%, the specificity 35% and the total predictive accuracy 47%. The limited predictive accuracy was mainly due to a lack of difference between patients with and without ventricular tachycardia in patients with a QRS duration > or = 120 ms. In patients with QRS < 120 ms, however, there were significant differences in all spectral turbulence parameters and the method had a sensitivity of 75%, a specificity of 72% and a total predictive accuracy of 73%. The diagnostic usefulness of spectral turbulence analysis is dependent upon normal QRS duration and the method is applicable only to patients without bundle branch block.

Adult↗
PubMed1995

Long-term follow-up of patients treated by radiofrequency ablation of the atrioventricular junction.

Radiofrequency ablation of the AV conduction tissue (His-bundle ablation) is an accepted treatment for therapy resistant atrial fibrillation/flutter. However, data on the long-term effects of the procedure are limited. We followed 50 patients for a mean of 17 months after AV junction ablation. The indication was treatment resistant atrial fibrillation or flutter. The patients underwent a standardized interview performed by two nurses. Health care was studied via the in-patient register. Subjective improvement was reported by 88% and the number of days in hospital per year was reduced from 17 to 7. The use of antiarrhythmic drugs was reduced by 75%. If the reduction in costs of drugs and days in hospital is compared with the cost of the ablation and the pacemaker implantation, breaking even is achieved after 2.6 years. We could not confirm that patients with paroxysmal atrial fibrillation note less improvement than those with chronic fibrillation. CONCLUSION: Ablation of the AV junction is a cost effective treatment with good long-term results and relatively few complications. RECOMMENDATIONS: Chronic atrial fibrillation: If sinus rhythm cannot be established and in cases in which heart rate regulating drugs have been ineffective, ablation of the AV junction with implantation of a VVIR pacemaker is recommended. PAROXYSMAL ATRIAL FIBRILLATION: If the patient despite treatment with antiarrhythmic drugs continues to have symptomatic episodes of atrial fibrillation, then AV junction ablation with implantation of a permanent pacemaker is recommended. Patients who have self-limiting episodes of atrial fibrillation should be given a DDDR pacemaker with an automatic mode switch. Patients who do not have self-limiting attacks and require DC conversion, should receive a VVIR pacemaker.

Adult↗