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Biomedical subjects

L Jordaens

Publications and source records attributed to L Jordaens.

At least 19 recordsLinked to original sources
PubMed2003

Comparison of monophasic and biphasic shocks for transthoracic cardioversion of atrial fibrillation.

OBJECTIVE: To compare the efficacy of cardioversion in patients with atrial fibrillation between monophasic damped sine waveform and rectilinear biphasic waveform shocks at a high initial energy level and with a conventional paddle position. DESIGN: Prospective randomised study. PATIENTS AND SETTING: 227 patients admitted for cardioversion of atrial fibrillation to a tertiary referral centre. RESULTS: 70% of 109 patients treated with an initial 200 J monophasic shock were cardioverted to sinus rhythm, compared with 80% of 118 patients treated with an initial 120 J biphasic shock (NS). After the second shock (360 J monophasic or 200 J biphasic), 90% of the patients were in sinus rhythm in both groups. The mean cumulative energy used for successful cardioversion was 306 J for monophasic shocks and 159 J for biphasic shocks (p < 0.001). CONCLUSIONS: A protocol using monophasic waveform shocks in a 200-360 J sequence has the same efficacy (90%) as a protocol using rectilinear biphasic waveform shocks in a 120-200 J sequence. This equal efficacy is achieved with a significantly lower mean delivered energy level using the rectilinear biphasic shock waveform. The potential advantage of lower energy delivery for cardioversion of atrial fibrillation needs further study.

Atrial Fibrillation↗
PubMed2002

An equine model of chronic atrial fibrillation: methodology.

We describe the development and the different features of an experimental model of chronic atrial fibrillation (AF) in equines. In four healthy ponies a dual-chamber pacemaker, with an adapted pacemaker program, was implanted transvenously in the standing animal. This adapted pacemaker induced episodes of AF by delivering a 2s burst of electrical stimuli (42 Hz) as soon as sinus rhythm was detected. Simultaneous with a surface electrocardiogram, the intra-atrial electrogram could be recorded to determine the atrial electrogram morphology. Programmed electrical stimulation (PES) was used to determine the atrial effective refractory period (AERP) and the rate adaptation of the AERP, the sinus node recovery time (SNRT) and the corrected SNRT, AF vulnerability, AF cycle length and AF duration. This experimental AF model can be used to study the pathophysiology of chronic AF in equines.

Animals↗
PubMed2001

Determinants of sudden death after discharge from hospital for myocardial infarction in the thrombolytic era.

AIMS: The purpose of this study was to assess risk factors for sudden death after discharge from hospital for myocardial infarction in an era in which 50% of patients receive thrombolytic drugs. METHODS AND RESULTS: We prospectively studied 708 consecutive survivors of myocardial infarction admitted to hospitals, which had registered their clinical, functional, and electrical parameters. A total of 83 patients died in the first 2 years (12%) after discharge. Sudden death was only observed in 12 patients. In multivariate analysis only NYHA class >I, and a filtered QRS duration > or =110 ms were important predictive variables for sudden death. A pre-defined high-risk group of 25 patients had no sudden death. When the strongest predictive variables in univariate analysis were combined to increase the positive predictive value for sudden death, we only achieved a maximal value of 27%. CONCLUSIONS: In an unselected infarction population, the risk for sudden death is low in the first 2 years. Therefore, prediction and prophylactic intervention, such as defibrillator therapy become difficult. The event is related to cardiac dysfunction on admission, and with abnormalities in the filtered electrocardiogram.

Adult↗
PubMed2001

Initial clinical experience with a new arrhythmia detection algorithm in dual chamber implantable cardioverter defibrillators.

AIM: Inappropriate therapy, due to poor discrimination of supraventricular tachycardia (SVT) from ventricular tachycardia (VT) remains a major problem in patients with an implantable cardioverter defibrillator (ICD). Theoretically, the addition of atrial sensing in discrimination algorithms should improve this differentiation. The aim of the study is to evaluate the performance of a new tachycardia discrimination algorithm, SMART Detection. METHODS AND RESULTS: Twenty-six patients received a non-thoracotomy ICD system (Phylax AV, Biotronik, Germany). All documented spontaneous arrhythmia episodes were analyzed. During a mean follow-up of 8 months, a total number of 139 events with stored electrograms were recorded in 12 patients. The final diagnosis was ventricular fibrillation (VF) or polymorphic VT (n=20), monomorphic VT (n=69), SVT (n=26), other ventricular arrhythmia (n=3) and T wave oversensing (n=21). In 6 episodes a dual tachycardia was present. Considering SVT episodes, inappropriate therapy occurred in 2 cases of atrial flutter due to stable ventricular rate (<30 ms), 1 case of atrial tachycardia and 2 cases of sinus tachycardia due to a sudden onset (> 10%). CONCLUSION: With the SMART Detection algorithm, discrimination of VT from SVT achieved a sensitivity of 100%, with an accuracy of 95.6% for all ventricular arrhythmias. In the case of SVT, the algorithm appropriately detected and inhibited therapy in 88% of atrial fibrillation.

Adult↗
PubMed2001

Long term results of cardioverter-defibrillator implantation in patients with right ventricular dysplasia and malignant ventricular tachyarrhythmias.

OBJECTIVE: To study the outcome of patients with arrhythmogenic right ventricular dysplasia treated with an implantable cardioverter-defibrillator (ICD) for ventricular tachyarrhythmias complicated by haemodynamic collapse. DESIGN: Observational study. SETTING: University hospital. PATIENTS: Nine consecutive patients (eight male, one female; mean (SD) age, 36 (18) years) with arrhythmogenic right ventricular dysplasia presenting with ventricular tachycardia and haemodynamic collapse (n = 6) or ventricular fibrillation (n = 3), treated with an ICD. MAIN OUTCOME MEASURES: Survival; numbers of and reasons for appropriate and inappropriate ICD interventions. RESULTS: After a mean (SD) follow up of 32 (24) months, all patients were alive. Six patients received a median of 19 (range 2-306) appropriate ICD interventions for events detected in the ventricular tachycardia window; four received a median of 2 (range 1-19) appropriate ICD interventions for events detected in the ventricular fibrillation window. Inappropriate interventions were seen for sinus tachycardia (18 episodes in three patients), atrial fibrillation (three episodes in one patient), and for non-sustained polymorphic ventricular tachycardia (one episode in one patient). CONCLUSIONS: Patients with arrhythmogenic right ventricular dysplasia and malignant ventricular arrhythmias have a high recurrence rate requiring appropriate ICD interventions, but they also often have inappropriate interventions. Programming the device is difficult because this population develops supraventricular and ventricular tachyarrhythmias with similar rates.

Adult↗
PubMed2001

Effects of intravenous dofetilide on induction of atrioventricular re-entrant tachycardia.

OBJECTIVE: To assess the efficacy and safety of intravenous dofetilide in preventing induction of atrioventricular re-entrant tachycardia. DESIGN: A multicentre, open, dose ranging trial. Fifty one patients with electrically inducible atrioventricular re-entrant tachycardia were allocated to one of five doses of dofetilide (1.5, 3, 6, 9, and 15 microgram/kg), two thirds of the dofetilide dose being given over a 15 minute loading period and the remainder over a 45 minute maintenance period. MAIN OUTCOME MEASURE: Responders were defined as patients in whom dofetilide prevented reinduction of atrioventricular re-entrant tachycardia at the end of the infusion. RESULTS: Intravenous dofetilide had no effect on tachycardia inducibility at the two lower doses (1.5 and 3 microgram/kg) but prevented the reinduction of tachycardia at the three higher doses (6, 9, and 15 microgram/kg) at a rate of 36% (11/31). There was a clear relation between plasma dofetilide concentrations and efficacy (p = 0.009). In non-responders, dofetilide increased the cycle length of induced atrioventricular re-entrant tachycardia. Dofetilide increased the atrial and ventricular effective refractory periods, as well as the antegrade and retrograde effective refractory period of the accessory pathway. Treatment related side effects were reported in four patients, one with a new sustained incessant supraventricular tachycardia. CONCLUSIONS: Dofetilide shows promise as an agent for the prevention of atrioventricular re-entrant tachycardia in patients without structural heart disease.

Adolescent↗
PubMed2000

Infarct size and recurrence of ventricular arrhythmias after defibrillator implantation.

Infarct size as determined by perfusion imaging is an independent predictor of mortality after implantable cardioverter defibrillator (ICD) implantation in patients with coronary artery disease (CAD) and life-threatening ventricular arrhythmias (VA). However, its value as a predictor of VA recurrence and hospitalisation after ICD implantation is unknown. Therefore, the objective of this study was to evaluate whether infarct size as determined by perfusion imaging can help to identify patients who are at high risk for recurrence of VA and hospitalisation after ICD implantation. We studied 56 patients with CAD and life-threatening VA. Before ICD implantation, all patients underwent a uniform study protocol including a thallium-201 stress-redistribution perfusion study. A defect score as a measurement of infarct size was calculated using a 17-segment 5-point scoring system. Study endpoints during follow-up were documented episodes of appropriate anti-tachycardia pacing and/or shocks for VA and cardiac hospitalisation for electrical storm (defined as three or more appropriate ICD interventions within 24 h), heart failure or angina. After a mean follow-up of 470+/-308 days, 22 patients (39%) had recurrences of VA. In univariate analysis, predictors for recurrence were: (a) ventricular tachycardia (VT) as the initial presenting arrhythmia (86% vs 59% for patients without ICD therapy, P=0.04), (b) treatment with beta-blockers (36% vs 68%, P=0.03) and (c) a defect score (DS) > or = 20 (64% vs 32%, P=0.03). In multivariate analysis, VT as the presenting arrhythmia (chi2=5.51, P=0.02) and a DS > or = 20 (chi2=4.22, P=0.04) remained independent predictors. Cardiac hospitalisation was more frequent in patients with a DS > or = 20 (44% vs 13% for patients with DS < 20, P=0.015) and this was particularly due to more frequent hospitalisations for electrical storm (24% vs 3% for patients with DS < 20, P=0.037). The extent of scarring determined by perfusion imaging can separate patients with CAD into high- and low-risk groups for recurrence of VA and cardiac hospitalisation after ICD implantation.

Adrenergic beta-Antagonists↗
PubMed2000

Spontaneous episodes of atrial fibrillation after implantation of the Metrix Atrioverter: observations on treated and nontreated episodes. Metrix Investigators.

OBJECTIVES: We sought to evaluate the number and duration of device-treated and self-terminating, nontreated episodes of atrial fibrillation (AF) after implantation of the Metrix Atrioverter. BACKGROUND: A recent study has shown that the Atrioverter can rapidly restore sinus rhythm in patients with AF; however, the effect of the device on the clinical course of the arrhythmia in these patients is unknown. METHODS: The Atrioverter was implanted in 51 patients with symptomatic, recurrent, drug-refractory AF. The device was programmed to periodically monitor the cardiac rhythm. Defibrillation of AF episodes was performed under physician observation. RESULTS: During a mean follow-up of 260 +/- 144 days, 1,161 episodes of AF were observed during valid monitoring periods in 45 of 51 patients. Forty-one patients experienced 231 episodes for which they sought defibrillation therapy. The average duration of the treated episodes during valid monitoring periods (190 of 231 episodes in 39 of 41 patients) was significantly longer than that of the nontreated episodes (38 +/- 44 vs. 10 +/- 8 h; p < 0.05). The time between episodes requiring Atrioverter therapy increased, and the risk of having an episode requiring treatment decreased. No changes were observed in the number and duration of the short-lasting, nontreated episodes as time since implantation of the device increased. CONCLUSIONS: In patients with symptomatic, recurrent, drug-refractory AF, the frequency of long-lasting episodes, which were treated under observation with repeated defibrillation using the Atrioverter, decreased. The number and duration of short-lasting, nontreated episodes did not change during the 20-month study period. The effect of ambulatory use of the device on the recurrence of short-lasting episodes needs to be evaluated.

Adult↗
PubMed2000

Lipid lowering drugs and recurrences of life-threatening ventricular arrhythmias in high-risk patients.

OBJECTIVES: To evaluate a possible effect of lipid lowering drugs on recurrences of ventricular arrhythmias (VA) after implantable cardioverter defibrillator (ICD) implantation. BACKGROUND: In patients with coronary artery disease (CAD), lipid lowering drugs reduce total and sudden cardiac death. Because the mechanism is not completely understood, we studied whether these drugs have a favorable influence on the occurrence of life-threatening VA in patients with CAD and ICD implants. METHODS: We conducted an observational study in 78 patients with CAD and life-threatening VA, treated with an ICD. After ICD implantation, 27 patients were on treatment with lipid lowering drugs (group I) and 51 were not (group II). Patients were studied for the following end points: recurrences of VA requiring ICD intervention, cardiac death and hospitalization. RESULTS: After a mean follow-up of 490 +/- 319 days, 35 patients (45%) had recurrences of VA requiring ICD intervention. In multivariate analysis, the use of lipid lowering drugs (chi-square 6.33, p = 0.012) and poorly tolerated sustained monomorphic ventricular tachycardia as initial presentation (chi-square 4.84, p = 0.028) remained as independent predictors of recurrences of VA. Patients in groups I and II had similar baseline clinical characteristics, but patients in group I had a lower incidence of recurrences of VA (6/27 or 22% vs. 29/51 or 57%, p = 0.004) and of the combined end points of cardiac death and hospitalization (4/27 or 15% vs. 23/51 or 45%, p = 0.015) compared with patients in group II. CONCLUSIONS: This is the first observation that the use of lipid lowering drugs is associated with a reduction of recurrences of VA in patients with CAD and ICD implants. These data require confirmation in a prospective randomized trial.

Aged↗
PubMed2000

Pacing induced sustained atrial fibrillation in a pony.

A transvenous, screw-in electrode was implanted in the right atrium of a healthy pony and connected with an implantable pulse generator programmed to deliver bursts of electrical stimuli to the atrium. Initially, cessation of burst pacing resulted in short (less than 1 minute), self-terminating episodes of atrial fibrillation. As burst pacing continued, the episodes of induced atrial fibrillation became longer. After 3 weeks of continuous atrial pacing, atrial fibrillation became sustained (56 hours). This model of pacing induced atrial fibrillation can be used to study the mechanisms leading to atrial fibrillation, its perpetuation and therapy. Our preliminary observations support the concept that once atrial fibrillation starts, it sets up changes in the electrical characteristics of the atrium that favor its own perpetuation.

Animals↗
PubMed2000

[Clinical evaluation of a dual chamber implantable cardioverter-defibrillator].

Single-chamber ventricular cardioverter-defibrillator (ICD) has been shown to significantly reduce the incidence of sudden cardiac death due to malignant ventricular arrhythmias. However, inappropriate therapy due to supraventricular tachyarrhythmias (mainly atrial fibrillation) affects up to 34% of patients. Moreover, it has been estimated that up to 20% of ICD patients are in the need of physiological antibradycardia pacing. Use of dual-chamber ICD offers an atrial signal for better ability to discriminate atrial from ventricular tachyarrhythmias as well as a maintenance of AV synchrony, what may be of critical importance for patients with a compromised left ventricular function. In the present study we describe our preliminary clinical experience with a dual-chamber ICD's implanted in 20 patients. During the implantation and in-hospital testing, 95 induced VT/VF episodes were correctly diagnosed by ICD, as well as 28 induced FA episodes. Over a mean follow-up period of 10 +/- 6 months, 98 tachycardia episodes were recorded. All 76 VT/VF episodes were correctly diagnosed, as were 18 of 22 FA. Four FA episodes were diagnosed as VT/VF and treated by antitachycardia pacing in 2 cases and by shock in 2. Thus, sensitivity and specificity of VT/VF detection are 100% and 82% respectively. A dual-chamber ICD appears to improve discrimination of atrial from ventricular tachyarrhythmias without loss of sensitivity and to decrease occurrence of inappropriate therapy. AV synchrony, by improving the hemodynamic status of the patient (mainly in those with impaired left ventricular function), may demonstrate better survival and comfort of life.

Aged↗
PubMed2000

[Ventricular repolarization and Holter monitoring. Effect of sympathetic blockage on the QT/RR ratio].

Circadian variations of the QT interval and its heart rate dependency have been established. However, the respective roles of the sympathetic and parasympathetic nervous systems in their regulation are still undetermined. Eighteen healthy volunteers (average age 39 +/- 7 years, 10 men) were recruited and selected randomly to receive either placebo or atenolol (100 mg/day). The treatments were crossed after 7 days. The rate dependency of the QT was assessed by day and by night by 24 hour Holter ECG monitoring. The effects of atenolol on the rate dependency of the QT interval depend on the time of day. During the daytime, the QT rate dependency was reduced by atenolol (0.180 (0.162:0.198) versus 0.216 (0.195:0.236) with placebo, p < 0.01) whereas during the night, the QT rate dependency was the same in both groups. Therefore, the betablocker is associated with an inversion of the daily modulation of the QT rate dependency. The daytime rate-dependency of the QT interval in decreased with betablocker therapy. This result suggests a direct or indirect influence of the sympathetic nervous system on the rate dependency of ventricular repolarisation.

Adult↗
PubMed1999

Heart rate dynamics before spontaneous onset of ventricular fibrillation in patients with healed myocardial infarcts.

The traditional methods of analyzing heart rate (HR) variability have failed to predict imminent ventricular fibrillation (VF). We sought to determine whether new methods of analyzing RR interval variability based on nonlinear dynamics and fractal analysis may help to detect subtle abnormalities in RR interval behavior before the onset of life-threatening arrhythmias. RR interval dynamics were analyzed from 24-hour Holter recordings of 15 patients who experienced VF during electrocardiographic recording. Thirty patients without spontaneous or inducible arrhythmia events served as a control group in this retrospective case control study. Conventional time- and frequency-domain measurements, the short-term fractal scaling exponent (alpha) obtained by detrended fluctuation analysis, and the slope (beta) of the power-law regression line (log power - log frequency, 10(-4)-10(-2) Hz) of RR interval dynamics were determined. The short-term correlation exponent alpha of RR intervals (0.64 +/- 0.19 vs 1.05 +/- 0.12; p <0.001) and the power-law slope beta (-1.63 +/- 0.28 vs -1.31 +/- 0.20, p <0.001) were lower in the patients before the onset of VF than in the control patients, but the SD and the low-frequency spectral components of RR intervals did not differ between the groups. The short-term scaling exponent performed better than any other measurement of HR variability in differentiating between the patients with VF and controls. Altered fractal correlation properties of HR behavior precede the spontaneous onset of VF. Dynamic analysis methods of analyzing RR intervals may help to identify abnormalities in HR behavior before VF.

Aged↗
PubMed1999

Report of a study group on ablate and pace therapy for paroxysmal atrial fibrillation. Barcelona Discussion Group. Working Group on Arrhythmias of the European Society of Cardiology.

Atrioventricular junctional (AVJ) catheter ablation followed by pacemaker implantation is now widely accepted for patients affected by paroxysmal atrial fibrillation (PAF) not controlled by antiarrhythmic drugs. However, few data exist on its indications, optimal methodology and complications. Therefore a study group examined current practice in Europe and North America, using a questionnaire, followed by a Study Group Meeting to discuss the results. Based upon this, class I, class II and class III indications were proposed. Class I indications (for which general agreement existed) include drug-refractory PAF, correlating with important symptoms, the bradycardia tachycardia syndrome already treated with a pacemaker, and continued PAF. Large differences exist in the current methodology, but consensus was reached on the technical approaches of right and left-sided AVJ ablation, and on the timing of pacemaker implant in relation to ablation. No complete agreement was reached on technical features such as catheter choice and heparin use. The recommended pacing mode was DDDR with mode switching.

Atrial Fibrillation↗
PubMed1999

Quality of life in patients with complete heart block and paroxysmal atrial tachyarrhythmias: a comparison of permanent DDIR versus DDDR pacing with mode switch to DDIR.

A prospective double-blind randomized crossover study was done in 15 patients with complete heart block and intermittent ATs. The pacemaker was randomly programmed to dual chamber inhibited rate responsive pacing (DDIR) and to DDDR with mode switch, for 1 month each. An event recorder was given to the patients and after each period, a QOL questionnaire was obtained. Based on telemetric data, all but two patients had AT during follow-up. The duration and frequency of these episodes were not related to mode settings. AV synchrony was better preserved in DDDR (P < 0.05). Most symptom-related event recordings during DDIR showed loss of AV synchrony; DDDR with mode switch caused symptoms due to tracking of ST. Overall the QOL score was not different between the modes. Fewer somatic complaints were noted during DDDR pacing than during baseline. DDIR stimulation showed no difference. Twelve patients preferred the period of DDDR pacing; one experienced severe symptoms during DDIR. In conclusion, patients with paroxysmal AT, DDDR with mode switch, and DDIR had no influence on the occurrence, nor on the duration of AT episodes. AV synchrony was better preserved in DDDR, which was also associated with fewer somatic complaints compared to the baseline. In DDDR, symptoms were observed when ST was tracked. QOL was comparable, although more patients preferred DDDR.

Adult↗