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R Derksen

Publications and source records attributed to R Derksen.

17 recordsLinked to original sources
PubMed2006

Quantitative acid-base physiology using the Stewart model. Does it improve our understanding of what is really wrong?

Traditional theories of acid-base balance are based on the Henderson-Hasselbalch equation to calculate proton concentration. The recent revival of quantitative acid-base physiology using the Stewart model has increased our understanding of complicated acid-base disorders, but has also led to several new controversies. With the help of three patient histories, we show that the Henderson-Hasselbalch equation should be regarded as a simplified version of the more general Stewart model and not as something completely different. Therefore, both models may be useful at the bedside.

Journal Article↗
PubMed2003

Implantable cardioverter defibrillator recipients: quality of life in recipients with and without ICD shock delivery: a prospective study.

AIMS: The experiences of patients who received shocks from their implantable cardioverter defibrillator (ICD) and how these events affect their overall adjustment are poorly understood. Our goal was to evaluate quality of life and psychological well-being, and the prevalence of, and changes in, depression and anxiety of patients who did or did not experience defibrillatory shocks in the first 12 months after ICD implantation. In total 167 patients were monitored after discharge. Four self-administered questionnaires were used. The first assessment took place before ICD implantation, the remaining three at 1, 6 and 12 months after discharge. RESULTS: We classified patients into three shock groups and one no shock group. A small group of ICD recipients (26%) received ICD shock delivery, usually during the last 6 months of the study. Borderline significant differences were found within the groups over time regarding physical role limitations (P < 0.051). Those who experienced shocks throughout the year (group 1) felt more limited in their daily activities due to physical or mental problems. All groups health (P < 0.001). Overall quality of life did not change significantly after 6 months. Anxiety and depression did not change significantly over time. In total 22-66% of patients reported clinically significant depressive symptoms throughout the first year, and 31-83% clinically significant symptoms of anxiety. ICD recipients who had experienced a shock were significantly more anxious one-year postdischarge than those who had not received a shock. CONCLUSIONS: Overall quality of life and psychological well-being did not change in ICD recipients, irrespective of whether they experienced defibrillatory shocks. The high prevalence of depression and anxiety can be interpreted as a response to the perceived physical and mental problems regarding daily activities. Our data indicate that patients who have experienced an ICD shock do not adapt well to living with an ICD, they are more anxious than ICD recipients who received no shocks. However, the anticipation of having another shock after experiencing one is less stressful than that of the first shock. We conclude that the lasting psychological distress will not dissipate spontaneously or naturally and that psychosocial interventions may be warranted.

Activities of Daily Living↗
PubMed2003

Contrast-enhanced MRA and 3D visualization of pulmonary venous anatomy to assist radiofrequency catheter ablation.

In pulmonary vein isolation as a treatment for atrial fibrillation the proximal part of the pulmonary veins is catheterized. A protocol for preinterventional assessment of pulmonary vein anatomy was developed, based on contrast-enhanced magnetic resonance angiography (MRA) in combination with three-dimensional visualization to tailor periprocedural angiography. The results allow for assessment of the number, morphology, and location of the ostia of the pulmonary veins, as well as complicating anatomical variations, such as common trunks and aberrant courses.

Adult↗
PubMed2002

Brugada syndrome.

Explore the source record for details and available documents.

Bundle-Branch Block↗
PubMed2002

A 12-month quality of life assessment of cardiac arrest survivors treated with or without an implantable cardioverter defibrillator.

BACKGROUND: Previous studies indicate that the implantable cardioverter defibrillator (ICD) has a large impact on the quality of life of patients. The effects of having an ICD over longer periods of times has been less studied. OBJECTIVE: To assess the quality of life and well-being of cardiac arrest survivors who have received an implantable cardioverter defibrillator (ICD) or other treatment. METHODS: 168 patients were monitored for 1 year and completed four questionnaires. RESULTS: No differences were found between the two treatments regarding quality of life (except for pain, ICD patients perceived less pain) and well-being. A significant improvement in physical and social function, and in mental health was found in the first 6 months. Older patients (60 years or older) perceived less improvement in their health than younger patients. Women reported having poorer social function. The prevalence of anxiety and probable depression was high irrespective of the treatment received: anxiety and depressive symptoms did not change significantly between 1 and 12 months after discharge. Patients with higher anxiety scores experienced less improvement in health and patients with more depressive symptoms experienced poorer social function. CONCLUSIONS: The prevalence of anxiety and probable depression was high in cardiac arrest survivors. Probable depression affected social function. Those patients who felt anxious experienced less health improvement. Quality of life and well-being were not affected by the type of treatment. We conclude that surviving an out-of-hospital cardiac arrest has a greater impact on patients than the treatment received.

Adult↗
PubMed2001

Activation delay after premature stimulation in chronically diseased human myocardium relates to the architecture of interstitial fibrosis.

BACKGROUND: Progressive activation delay starting at long coupling intervals of premature stimuli has been shown to correlate with sudden cardiac death in patients with hypertrophic cardiomyopathy. The purpose of this study was to elucidate the mechanism of increased activation delay in chronically diseased myocardium. METHODS AND RESULTS: High-resolution unipolar mapping (105, 208, or 247 recording sites with interelectrode distances of 0.8, 0.5, or 0.3 mm, respectively) of epicardial electrical activity was carried out during premature stimulation in 11 explanted human hearts. The hearts came from patients who underwent heart transplantation and were in the end stage of heart failure (coronary artery disease, 4; hypertrophic cardiomyopathy, 1; and dilated cardiomyopathy, 6). Eight hearts were Langendorff-perfused. Epicardial sheets were taken from the remaining hearts and studied in a tissue bath. Activation maps and conduction curves were constructed and correlated with histology. Conduction curves revealing prominent increase of activation delay were associated with zones of dense, patchy fibrosis with long fibrotic strands. Dense, diffuse fibrosis with short fibrotic strands only marginally affected conduction curves. The course of conduction curves in patchy fibrotic areas greatly depended on the direction of propagation relative to fiber direction. CONCLUSIONS: The study demonstrates that in chronically diseased human myocardium, nonuniform anisotropic characteristics imposed by long fibrotic strands cause a progressive increase of activation delay, starting at long coupling intervals of premature stimuli. The increase strongly depends on the direction of the wave front with respect to fiber direction and the architecture of fibrosis.

Adult↗
PubMed2001

Sequential map-guided endocardial resection for ventricular tachycardia improves outcome.

OBJECTIVE: Surgery for ventricular tachycardias late after myocardial infarction is frequently associated with high mortality including sudden death, and arrhythmia recurrences. We examined our results of sequential map-guided endocardial resection at normothermia in patients with ventricular tachyarrhythmias late after myocardial infarction to assess the efficacy of this technique as well as the early and long-term outcome. METHODS: From 1995 to 1999, 22 patients underwent normothermic sequential map-guided endocardial resection for ventricular tachyarrhythmias late after myocardial infarction. Mean age was 61.2+/-6.5 years and left ventricular ejection fraction 32.5+/-8.7%. Adjunctive procedures included endoventricular patch repair of left ventricular aneurysm in 21 patients, coronary artery bypass grafting in 15 patients, and mitral valve replacement in one patient. Inducibility of ventricular tachycardia was evaluated postoperatively and patients were treated with sotalol or defibrillator implantation. RESULTS: The intraoperative number of inducible different ventricular tachycardia morphologies was 4.0+/-2.7. More than one mapping-resection sequence was needed in ten patients. In only one patient, sustained ventricular tachycardia was induced postoperatively, sotalol was not tolerated and a defibrillator was implanted. Five patients with inducible non-sustained ventricular tachycardia became non-inducible while on sotalol. There was one operative death (4.5%). During a median follow-up of 26 (1--62) months, there were neither cardiac deaths nor ventricular tachycardia recurrences. Two patients died from non-cardiac causes. Cumulative probability of survival at 5 years was 0.83+/-0.09. CONCLUSIONS: Sequential map-guided endocardial resection at normothermia was associated with low operative mortality and low postoperative inducibility of sustained ventricular tachycardia. The selected therapeutic approach resulted in freedom of arrhythmia recurrence and cardiac mortality including sudden death, during long-term follow-up.

Aged↗
PubMed2001

Catheter ablation of incisional atrial tachycardia using a novel mapping system: LocaLisa.

Incisional atrial tachycardia occurs due to reentry around surgical scars. Pharmacological therapy is often ineffective. This study assessed the efficacy of a novel mapping system (LocaLisa) in facilitating catheter ablation of incisional atrial tachycardia circuits. Eight consecutive patients (four men, four women) with incisional atrial tachycardia (median age 23.5 years, range 9-44) following previous repair of congenital heart defects underwent transcatheter mapping and ablation of the arrhythmogenic substrate using a mapping system (LocaLisa) that allows localization of endocardial electrodes in a three-dimensional space. Critical isthmuses for the tachycardia circuits were identified by demonstrating concealed entrainment using standard pacing and mapping techniques. Scars and natural anatomic barriers were marked on the LocaLisa image. Lines of block were created by radiofrequency current application between scars and natural anatomic barriers, or between two scars, to close isthmuses demonstrated to be critical for the reentrant circuit. All lines of block were verified in both directions. All reentrant circuits around incisions were successfully ablated. Seven additional tachycardia mechanisms were identified in four patients (common atrial flutter [n = 4], atrioventricular nodal [AVN] reentry [n = 2], ectopic atrial tachycardia [n = 1]) and were also ablated in a single session. The mean fluoroscopy time was 28.4 +/- 13.8 minutes. All patients are arrhythmia-free at a median follow-up of 20 (6-22) months. The LocaLisa mapping system is effective for identification of scars and ablation targets, for confirming lines of block, and facilitating ablation of complex reentrant circuits.

Adult↗
PubMed2001

Diagnosis and long-term follow-up of the Brugada syndrome in patients with idiopathic ventricular fibrillation.

AIMS: Some patients with idiopathic ventricular fibrillation may suffer from the Brugada syndrome. The diagnostic criteria for the Brugada syndrome are uncertain and arbitrarily set. Therefore, we studied the prevalence of the Brugada syndrome using various diagnostic criteria and long-term follow-up in 37 idiopathic ventricular fibrillation patients. METHODS AND RESULTS: Idiopathic ventricular fibrillation was diagnosed after thorough clinical evaluation in 37 survivors of an out-of-hospital cardiac arrest referred to our institute (UMC Utrecht). Retrospectively, nine patients (24%, group I) were classified as potentially having the Brugada syndrome based on the presence of (in)complete right bundle branch block and ST-segment elevation in leads V(1)-V(3)of > or =1 mm. Only three patients (8%, group II) showed (in)complete right bundle branch block and > or =2 mm ST-segment elevation. With the intermittent presence of these ECG features and/or their (re)appearance with class I antiarrhythmic drugs included as criteria, the percentage of the Brugada syndrome was attenuated in group I (2/37; 5%) and group II (1/37; 3%). Sixteen (43%) of all idiopathic ventricular fibrillation patients (mean follow-up 77+/-41 months) had a recurrent episode of syncope, ventricular tachyarrhythmias or sudden death. Recurrence rate was 3/9 (33%) in Brugada patients group I, 2/3 (66%) in group II and 13/28 (46%) in patients without the Brugada syndrome (P=ns). CONCLUSIONS: Depending on the diagnostic criteria used, the Brugada syndrome was observed in 3% to 24% of patients with idiopathic ventricular fibrillation, underlining the importance of defining the precise diagnostic criteria in these patients. For all idiopathic ventricular fibrillation patients, the ventricular tachyarrhythmia recurrence rate was substantial during an average follow-up of more than 6 years.

Adolescent↗
PubMed2001

Persistent increase in plasma thrombomodulin in patients with a history of lupus nephritis: endothelial cell activation markers.

OBJECTIVE: To investigate the presence of continuing endothelial cell activation in patients with systemic lupus erythematosus (SLE) and its relationship with lupus nephritis. METHODS: We measured plasma concentrations of soluble thrombomodulin (sTM), vascular cellular adhesion molecule-1 (sVCAM-1), von Willebrand factor (vWf), sP-selectin, and ED1-fibronectin in 75 SLE patients with a median SLE disease activity index (SLEDAI) of 4. Forty patients with a history of lupus nephritis, confirmed by renal biopsy in 33, were compared with 35 patients without lupus nephritis and 25 controls. For subgroup analysis in patients with clinically stable remission we excluded patients with a SLEDAI > 6 or with evidence of renal disease activity. RESULTS: In the total SLE patient group sTM, sVCAM-1, vWf, and sP-selectin were significantly elevated compared with controls. In patients with a history of lupus nephritis plasma levels of sTM and vWf were significantly increased compared with SLE patients without nephritis. After adjustment for significantly associated variables, especially creatinine clearance and age, in a multivariate linear regression analysis, sTM remained significantly elevated in patients with a history of lupus nephritis (difference 28.9 ng/ml, 95% CI 11.5-46.4). In the subgroup analysis of 57 patients, the results remained unchanged. CONCLUSION: The increase of sVCAM-1, sP-selectin, sTM, and vWf reflects a state of persistent endothelial cell activation. Multivariate regression analysis shows that the elevated sTM levels are strongly associated with a history of lupus nephritis, independent of creatinine clearance or disease activity, suggesting endothelial cell activation specifically localized in the kidneys.

Adolescent↗
PubMed2000

Ventricular tachycardia as a complication of atrial flutter ablation.

A 61-year-old woman with dilated cardiomyopathy, who previously underwent successful radiofrequency catheter ablation for atrial flutter, developed monomorphic ventricular tachycardia (VT). The site of VT origin was the inferobasal right ventricle adjacent to the previous atrial isthmus ablation area. The most likely mechanism for the VT was scar-related reentry, the scar being the result of previous radiofrequency lesions in the atrial isthmus. The VT was successfully ablated.

Atrial Flutter↗
PubMed1999

LocaLisa: new technique for real-time 3-dimensional localization of regular intracardiac electrodes.

BACKGROUND: Estimation of the 3-dimensional (3D) position of ablation electrodes from fluoroscopic images is inadequate if a systematic lesion pattern is required in the treatment of complex arrhythmogenic substrates. METHODS AND RESULTS: We developed a new technique for online 3D localization of intracardiac electrodes. Regular catheter electrodes are used as sensors for a high-frequency transthoracic electrical field, which is applied via standard skin electrodes. We investigated localization accuracy within the right atrium, right ventricle, and left ventricle by comparing measured and true interelectrode distances of a decapolar catheter. Long-term stability was analyzed by localization of the most proximal His bundle before and after slow pathway ablation. Electrogram recordings were unaffected by the applied electrical field. Localization data from 3 catheter positions, widely distributed within the right atrium, right ventricle, or left ventricle, were analyzed in 10 patients per group. The relationship between measured and true electrode positions was highly linear, with an average correlation coefficient of 0.996, 0.997, and 0.999 for the right atrium, right ventricle, and left ventricle, respectively. Localization accuracy was better than 2 mm, with an additional scaling error of 8% to 14%. After 2 hours, localization of the proximal His bundle was reproducible within 1.4+/-1.1 mm. CONCLUSIONS: This new technique enables accurate and reproducible real-time localization of electrode positions in cardiac mapping and ablation procedures. Its application does not distort the quality of electrograms and can be applied to any electrode catheter.

Bundle of His↗
PubMed1999

Accuracy of the LocaLisa system in catheter ablation procedures.

Estimation of the 3-dimensional (3D) position of ablation electrodes from fluoroscopic images is inadequate in the ablation of complex arrhythmogenic substrates. We developed a new technique for real-time 3D localization of intracardiac electrodes. Regular catheter electrodes are used as sensors for a high-frequency transthoracic electrical field, which is applied via standard skin electrodes. We investigated localization accuracy by comparing measured and true interelectrode distances between the tip and the 10th electrode of a decapolar catheter, and the tip and the 4th electrode of a quadripolar catheter during catheter ablation procedures. Long-term stability was analyzed by localization of the proximal His bundle before and after slow pathway ablation. Accuracy achieved with the 54-mm distance between the two outer electrodes of the decapolar catheters was 101% +/- 15%, 95% +/- 10%, and 97% +/- 8% in the right atrium, right ventricle, and left ventricle, respectively. During catheter ablation procedures, the measured distance between the tip and 4th electrode of the mapping catheter was 100% +/- 15% in atrial flutter, 100% +/- 12% in slow pathway ablation, and 100% +/- 14% in ablations for left ventricular tachycardia. After 2 hours, localization of the proximal His bundle was reproducible within 1.4 +/- 1.1 mm. The LocaLisa technique allows for reproducible, real-time nonfluoroscopic 3D visualization of standard mapping and ablation catheters and is sufficiently accurate for the creation of linear radiofrequency lesions. The freedom of catheter choice makes the LocaLisa system an invaluable tool in catheter mapping and ablation procedures.

Atrial Flutter↗
PubMed1996

Can implantable cardioverter-defibrillator therapy reduce healthcare costs?

This article presents a comparison of the costs and the cost effectiveness of defibrillator implantation in a hypothetical scenario for the years 1996-2000, with recently reported actual data from the Dutch prospective study over the years 1989-1993. Recently, technological advances in pulse generator and leads have revolutionized implantable cardioverter-defibrillator (ICD) therapy. Major advances include (1) transvenous single lead positioning and (2) tremendously reduced size, combined with prolonged longevity of the pulse generator. Both have simplified implantation technique and provided for superior effectiveness and lower costs. This suggests that a more favorable cost-effectiveness is to be expected. The study group reported here consisted of patients successfully resuscitated after cardiac arrest due to malignant ventricular tachyarrhythmias in the chronic stage of myocardial infarction. During a mean follow-up of 27 months, starting on the day of therapeutic decision making, total costs and the cost-effectiveness ratio were estimated. Actual data from the prospective study in 1989-1993 are compared with a hypothetical scenario for 1996-2000. Mortality and costs for hospitalization per day, per procedure, and per device are taken from the prospective study and equalized for both scenarios. Transthoracic lead positioning and abdominal implantation of a Ventak P (CPI) defibrillator with +/- 3 years longevity were characteristic of the recently completed prospective study. The hypothetical future scenario uses the Ventak Mini-2 with assumed 5 years longevity, implanted pectorally and connected to a single transvenous lead. Implantation will be carried out in the catheterization laboratory and as first-choice treatment. Due to prolonged longevity of the device and shorter hospitalization, a cost reduction of US $11,530 per patient is expected. Total costs per patient in the 1989-1993 prospective study in the (1) conventional arm (drugs first choice), (2) early ICD arm (ICD first choice), and (3) early ICD arm in the 1996-2000 study (ICD first choice) are $63,032, $56,067, and $44,537, respectively. The corresponding cost-effectiveness ratios are $87, $64, and $51 per day alive, respectively. Thus, it appears that modem ICD technology will be associated with an increasing reduction in healthcare costs, at least in selected patients. This reduction is associated with a more favorable cost-effectiveness ratio.

Cost Control↗
PubMed1995

Prevention of relapses in systemic lupus erythematosus.

Many relapses of systemic lupus erythematosus (SLE) are preceded by a rise in antibodies against double-stranded DNA (anti-dsDNA). We investigated whether these relapses can be prevented by giving prednisone when a rise in anti-dsDNA occurs. 156 patients with SLE were studied. Anti-dsDNA was measured by Farr assay monthly. When a rise in anti-dsDNA was found, patients were randomly assigned either conventional treatment or 30 mg prednisone added to the current daily dose and tapering off to baseline over 18 weeks. A rise in anti-dsDNA was detected in 46 patients (24 assigned conventional treatment and 22 prednisolone). The relapse rate was higher in the conventional group than in the prednisolone group (20 vs 2, p < 0.001). Although rises in anti-dsDNA in the prednisone group were treated with additional prednisone, the cumulative oral doses of prednisone in the two groups did not differ significantly (p = 0.025). 7 major relapses requiring additional cytotoxic immunosuppressive treatment occurred in the conventional group versus 2 in the prednisone group. Treatment with prednisone as soon as a significant rise in anti-dsDNA occurs prevents relapse in most cases, without increasing the cumulative dose of prednisdone given.

Adult↗