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Biomedical subjects

R Candinas

Publications and source records attributed to R Candinas.

At least 19 recordsLinked to original sources
PubMed2003

[Catheteer ablation technique of atrial fibrillation].

Atrial fibrillation is the most frequent arrhythmia with a prevalence of 1.7% in the general population and 5% in the population over 65 year old [1], the prevalence in men over 65 years is even 9.1% [2]. Atrial fibrillation is divided dependent on its frequency in intermittent, persisting and chronic. The symptoms and the clinical course are individually very different. Responsible for the initiation of atrial fibrillation are triggers, which initiate atrial fibrillation, and a substrate, that means an atrial myocardium altered by remodelling, which maintains atrial fibrillation. A curative treatment was not available until recently. Different ablation techniques were developed: Linear, focal ablation techniques and the isolation of pulmonary veins. The observation that atrial fibrillation will maintain only in large atria, led to the linear ablation techniques with the goal of reducing the atria functionally. The linear ablations have however a small value because of low success rates and high complication rates. Arrhythmogenic foci are of crucial importance in the initiation of atrial fibrillation, these foci are mostly located in the pulmonary veins. This observation led to the focal ablation in the pulmonary veins, which was left again because of the limitations, however. For some years the isolation of pulmonary veins is performed at some large centers. This paper summarizes the most important techniques, success rates and complications of the pulmonary vein isolation. The present indication and the preinterventional diagnostics are discussed. Due to the constantly improving success rates and decreasing complication rates (pulmonary vein stenosis, thrombembolie, cardiac tamponades, mortality practically) the pulmonary vein isolation is an alternative possibility of treatment which can be considered for a subgroup of patients with drug-resistant, symptomatic atrial fibrillation.

Atrial Fibrillation↗
PubMed2002

[Radiofrequency catheter ablation of ventricular tachycardias].

Management of patients with ventricular tachycardia (VT) is often difficult. Drug therapy is often ineffective. Implantable cardioverter defibrillators (ICDs) can terminate VT episodes but do not prevent them. Radiofrequency (RF) catheter ablation can suppress arrhythmias in selected patients. However, the procedure is often challenging and success rates lower than for ablation of supraventricular tachycardias. The mapping and ablation approach depends on the VT mechanism. Monomorphic VT in patients without structural heart disease is referred to as idiopathic and has a focal origin. These VTs can be abolished by ablation in most of the patients. In VT due to reentry within an area of scar from an old myocardial infarction or cardiomyopathic process, critical parts of the circuit may be difficult to localize, rendering RF ablation challenging. In patients with monomorphic VT, prevention of VT recurrence can be achieved in 55% to 80% of patients. Multiple morphologies of VTs and circuits that are located deep in the endocardium are common problems that reduce efficacy. Furthermore, mapping to identify target regions for ablation can be more difficult if VT is rapid and not tolerated, or not inducible. Recently, multisite mapping of the arrhythmia substrate during sinus rhythm or multisite activation mapping of a few VT beats were shown to be effective for ablation of these "unmappable VTs". Bundle branch reentry tachycardia occur in patients with nonischemic cardiomyopathies, mostly valvular heart disease and can be successfully abolished with RF ablation of the right bundle. However, some of these patients may develop recurrences due to other types of VT. Recent technical developments have increased efficacy and simplified the approach of RF ablation of VT in patients with structural heart disease. However, long-term efficacy is not accurately predictable and implantation of an ICD is mandatory in most of the patients with severely depressed left ventricular function.

Cardiomyopathy, Dilated↗
PubMed2002

ICD implantation with and without combined myocardial revascularisation--incidence of ICD therapy and late survival.

BACKGROUND: Our aim was to evaluate the occurrence of implanted cardioverter-defibrillator (ICD) shock and antitachycardia pacing (ATP), the effect of ICD therapies on mortality and the impact of revascularisation strategies on arrhythmic events. PATIENTS AND METHODS: We investigated 130 CAD patients undergoing ICD implantation between 1984 and 1999. RESULTS: Freedom of shock was 66 +/- 7 %, 48 +/- 9 % and 48 +/- 9 % after 1, 3 and 5 years in patients with revascularisation and 62 +/- 8 %, 43 +/- 8 % and 23 +/- 11 % in patients without revascularisation, respectively; p = n. s. Freedom from ATP was similar in both groups - in patients with revascularisation, 64 +/- 6 %, 58 +/- 7 % and 58 +/- 7 % and without revascularisation 56 +/- 8 %, 51 +/- 9 % and 38 +/- 10 %, respectively; p = n. s. There were no significant differences in cumulative survival between patients with and without revascularisation; p = n. s. CONCLUSIONS: CAD patients with VT/VF and with implanted ICD have, despite successful revascularisation, the same rate of device therapy and mortality as patients without an indication of revascularisation. This implies that patients with chronic ischemic heart disease and ventricular tachyarrhythmias continue to be at risk of sudden death after CABG/PTCA; evaluation for ICD implantation is warranted.

Angioplasty, Balloon, Coronary↗
PubMed2001

[Ventricular tachycardia].

In patients with ventricular tachycardias, various structural and functional conditions can be influenced by certain triggers, initiating the mechanism of the arrhythmia. Thorough understanding of these different factors is paramount for the appropriate choice of treatment. Several options are available for the management of ventricular tachycardias: antiarrhythmic drugs, ICD implantation and catheter ablation or a combination of the above. The prognosis of an individual patient is determined by the underlying disease, the mechanism of tachycardia and the selected therapy. The complexity of several conditions requires a specialized diagnostic approach and tailored medical management. Therefore the patients with the following diagnoses should be referred to a specialized electrophysiology center: survivors of sudden cardiac death old infarct scar, reduced ejection fraction and complex ectopy Cardiomyopathy with syncope or ventricular tachycardias Long QT-Syndrome Brugada Syndrome Right Ventricular Dysplasia recurrent syncopes of unclear etiology.

Anti-Arrhythmia Agents↗
PubMed2001

Endothelin and cardiac arrhythmias: do endothelin antagonists have a therapeutic potential as antiarrhythmic drugs?

Endothelin-1 (ET-1), the predominant isoform of the ET peptide family and a potent vasoconstrictor, has been shown to aggravate ischemia-induced ventricular arrhythmias. However, there is also evidence that ET-1 may have a direct arrhythmogenic action that is not solely attributable to myocardial ischemia. Proposed mechanisms for the arrhythmogenic effects of ET-1 are prolongation or increased dispersion of monophasic action potential duration, QT prolongation, development of early afterdepolarizations, acidosis, and augmentation of cellular injury. As for an ionic basis for the observed electrophysiologic effects, ET-induced Ca(2+) release from intracellular stores, generation of inositol triphosphate, inhibition of delayed rectifier K(+) current, and stimulation of the Na(+)/H(+) exchanger may be involved. Recently, some studies have shown that ET receptor antagonists, which promise to be powerful tools in cardiovascular medicine, may also demonstrate antiarrhythmic properties. This review describes the current state of knowledge on the interactions between the ET system and cardiac arrhythmias, and discusses the therapeutic potential of ET antagonists as antiarrhythmic drugs.

Action Potentials↗
PubMed2001

Sudden cardiac death after coronary artery bypass grafting is not predicted by signal-averaged ECG.

BACKGROUND: Sudden cardiac death (SCD) is a major cause of death despite successful revascularization in patients with coronary artery disease. The signal-averaged ECG (SAECG) is a sensitive predictor of SCD and could be used in the screening strategy to select patients for prophylactic cardioverter implantation. METHODS: The SAECG was recorded in 561 patients (mean age: 60 +/- 8.8 years) within 10 days of coronary artery bypass grafting. Signal-averaged ECG was performed with a bandpass filtering of 40 to 250 Hz for more than 250 beats until a noise level of 0.6 microV was achieved. All patients were followed for 5.5 +/- 1.2 years after the procedure. RESULTS: Preoperative angiographic ejection fraction was at least 60% in 393 patients (72%), 40% to 60% in 126 patients (23%), and 40% or less in 28 patients (5%). There were 34 deaths, 10 of which were SCD. Late potentials were found in a total of 150 patients (27%) and were equally frequent preoperatively and postoperatively and among patients with (30%) and without (27%) SCD. The only predictors for overall mortality were age and a reduced ejection fraction. CONCLUSIONS: Signal-averaged ECG did not predict prognosis in low-risk patients undergoing coronary artery bypass grafting.

Coronary Artery Bypass↗
PubMed2001

Force and torque effects of a 1.5-Tesla MRI scanner on cardiac pacemakers and ICDs.

Magnetic resonance imaging (MRI) is a widely accepted tool for the diagnosis of a variety of disease states. However, the presence of an implanted pacemaker is considered to be a strict contraindication to MRI in a vast majority of centers due to safety concerns. In phantom studies, the authors investigated the force and torque effects of the static magnetic field of MRI on pacemakers and ICDs. Thirty-one pacemakers (15 dual chamber and 16 single chamber units) from eight manufacturers and 13 ICDs from four manufacturers were exposed to the static magnetic field of a 1.5-Tesla MRI scanner. Magnetic force and acceleration measurements were obtained quantitatively, and torque measurements were made qualitatively. For pacemakers, the measured magnetic force was in the range of 0.05-3.60 N. Pacemakers released after 1995 had low magnetic force values as compared to the older devices. For these devices, the measured acceleration was even lower than the gravity of the earth (< 9.81 N/kg). Likewise, the torque levels were significantly reduced in newer generation pacemakers (< or = 2 from a scale of 6). ICD devices, except for one recent model, showed higher force (1.03-5.85 N), acceleration 9.5-34.2 N/kg), and torque (5-6 out of 6) levels. In conclusion, modern pacemakers present no safety risk with respect to magnetic force and torque induced by the static magnetic field of a 1.5-Tesla MRI scanner. However, ICD devices, despite considerable reduction in size and weight, may still pose problems due to strong magnetic force and torque.

Contraindications↗
PubMed2001

Correlation of impedance minute ventilation with measured minute ventilation in a rate responsive pacemaker.

Although rate responsive pacing based on impedance minute ventilation (IMV) is now standard, there is almost no data confirming the relationship between IMV from an implanted pacemaker and measured minute ventilation (VE) during exercise. Nineteen completely paced adults implanted with Medtronic Kappa 400 pacemakers underwent symptom-limited maximal metabolic treadmill testing using a modified Minnesota Pacemaker Response Protocol. Minute ventilation (VE, L/min) was simultaneously measured using the flowmeter of a respiratory metabolic gas analysis system and the transthoracic impedance minute ventilation circuitry of the pacemaker. Correlation coefficients (r) were used to find the best fit line to describe the relationship between the two measurements. Mean (+/- SD) r values for the first, second, and third order polynomial equations and for log and exponential equations were: 0.92 +/- 0.08, 0.94 +/- 0.04, 0.95 +/- 0.04, 0.91 +/- 0.06, and 0.91 +/- 0.07, respectively. None of the r values were statistically different from the first order equation. Transthoracic IMV as measured by the Medtronic Kappa 400 is closely correlated to measured minute ventilation and is represented well by a first order (linear) equation.

Adult↗
PubMed2001

Avoiding inappropriate ventricular tachycardia detection due to T-wave oversensing in an implantable cardioverter defibrillator: a novel application of the electrogram width criterion.

Appropriate sensing is an essential function of an implantable cardioverter defibrillator (ICD). T-wave oversensing by an ICD can be a serious problem in some patients, causing overestimation of the heart rate, inappropriate tachyarrhythmia detection and therapy delivery. Decreasing the sensitivity or programming longer refractory periods can sometimes overcome T-wave oversensing, but these measures may interfere with the ability of the ICD to correctly detect tachyarrhythmias. This report proposes a novel application of the electrogram (EGM) width criterion using a recently introduced detection enhancement algorithm intended to improve the specificity of ventricular tachycardia detection, to avoid T-wave oversensing. Based on the course of a case with persistent T-wave oversensing and review of previously published reports, oversensing problems in ICDs and management strategies are discussed.

Defibrillators, Implantable↗
PubMed2001

How different from pacemaker patients are recipients of implantable cardioverter-defibrillators with respect to psychosocial adaptation, affective disorders, and quality of life?

OBJECTIVE: To assess differences in psychosocial adaptation, quality of life, and incidence of affective disorders between patients with pacemakers and those with implantable cardioverter-defibrillators (ICDs). DESIGN: Patients aged 40-70 years who underwent a first pectoral implantation of a pacemaker or an ICD system were studied. All subjects were asked to complete the hospital anxiety and depression scale (HAD), the short form general health survey (SF-36), and a specially designed device related questionnaire. Data analysis was performed for three patient groups: pacemaker (n = 76), ICD patients who received therapeutic shocks (n = 45), and ICD patients who did not receive shocks (n = 31). RESULTS: There were no differences between the three patient groups in HAD scores or in any of the SF-36 subscales or summary ratings. Probable depressive disorder (depression score > 10) was observed in 5.2%, 6.5%, and 6.6%, and probable anxiety disorder (anxiety score > 10) in 13.1%, 9.7%, 13.3% of the pacemaker, non-shocked ICD, and shocked ICD patients, respectively. There were no sex differences. However, patients in the shocked ICD group were more likely than those in the other groups to report limitations in their leisure activities, to perceive their device as a "life extender," and to admit anxiety about battery depletion and technical problems. Forty per cent of shocked ICD patients would be interested in joining a support group. CONCLUSIONS: Despite having distinctly different medical histories and treatments, patients with pacemakers and ICDs responded similarly to validated tools of health status assessment. ICD patients who had received shocks perceived their device as prolonging their life and had greater anxiety about technical problems. Their endorsement of the potential benefits of a support group warrants further investigation.

Adaptation, Psychological↗
PubMed2000

[Maternal cardiac arrhythmias in pregnancy].

During pregnancy an increased incidence of maternal cardiac arrhythmias is observed. These include a wide spectrum, from clinically irrelevant isolated premature beats to debilitating supraventricular and ventricular tachycardias. In principle, management of arrhythmias during pregnancy is similar to that in non-pregnant patients. However, special consideration should be given to foetal age and potential teratogenic and haemodynamic adverse drug effects on the foetus. Therapeutic strategy should be guided by interdisciplinary consulting (i.e. cardiology, obstetrics, neonatology). Diagnostic evaluation must rule out underlying cardiovascular, pulmonary, endocrine or metabolic diseases. Additionally, precipitating factors such as excessive caffeine and/or alcohol ingestion and cigarette smoking should be avoided. For benign arrhythmias a conservative approach is appropriate. Antiarrhythmic drug selection depends on the specific arrhythmia being treated and the cardiac condition of the mother and the foetus. Some antiarrhythmic agents, such as propranolol, metoprolol, digoxin and quinidine, have been extensively tested during pregnancy and have proven to be safe; they should therefore, whenever possible, be used as firstline. For supraventricular tachycardia, intravenous adenosine may be used to terminate the arrhythmia if vagal manoeuvres fail. In emergency situations cardioversion may be performed with relative safety. Implantable cardioverter defibrillators as a preventive measure for life-threatening arrhythmias in pregnant patients do not seem to increase the risk of major complications.

Adult↗
PubMed2000

Threshold tracking pacing based on beat by beat evoked response detection: clinical benefits and potential problems.

Continuous monitoring of pacemaker stimulation thresholds and automatic adjustment of pacemaker outputs were among the longstanding goals of the pacing community. The first clinically successful implementation of threshold tracking pacing was the Autocapture feature which has accomplished automatic ventricular capture verification for every single stimulus by monitoring the Evoked Response (ER) signal resulting from myocardial depolarization. The Autocapture feature not only decreases energy consumption by keeping the stimulation output slightly above the actual threshold, but also increases patient safety by access to high-output back-up pulses if there is loss of capture. Furthermore, it provides valuable documentation of stimulation thresholds over time and serves as a valuable research tool. Current limitations for its widespread use include the requirements for implantation of bipolar low polarization leads and unipolar pacing in the ventricle. Fusion/pseudofusion beats with resultant insufficient or even non-existent ER signal amplitudes followed by unnecessary delivery of back-up pulses and a possible increase in pacemaker output is not an uncommon observation unique to the Autocapture feature. The recent incorporation of the Autocapture algorithm in dual chamber pacemakers has been challenging because of more frequent occurrence of fusion/pseudofusion beats in the presence of normal AV conduction. Along with a review of the previously published studies and our clinical experience, this article discusses the clinical advantages and potential problems of Autocapture.

Algorithms↗