PubMed Health⌕ Search

Biomedical subjects

Christoph Kaiser

Publications and source records attributed to Christoph Kaiser.

17 recordsLinked to original sources
PubMed2006

Separated local field NMR experiments on oriented samples rotating at the magic angle.

Biophysical studies on membrane proteins by solid state NMR (SSNMR) can be carried out directly in a membrane environment. Samples are usually prepared in form of multi-lamellar dispersions for magic angle sample spinning or as aligned multi-layers for orientation dependent NMR experiments without sample rotation. A new development is the application of MAS NMR to aligned samples (MAOSS; Magic Angle Oriented Sample Spinning). In combination with separated local field (SLF) experiments, size and orientation of heteronuclear dipolar couplings may be extracted from two-dimensional experiments which correlate dipolar couplings with isotropic chemical shifts. The orientation of these (1)H-X dipolar couplings can be directly related to the orientation of molecular groups in the sample. Here, we demonstrate the feasibility of these experiments on highly ordered polyethylene fibers which serve as model compound. Based on these data, the experiment is also applied to ordered multi-layers of bacteriorhodopsin (purple membrane) which is used as a model for aligned membrane proteins. We present a detailed analysis of different experimental designs with respect to angular sensitivity and the influence of residual sample disorder ("mosaic spread"). The results of the MAOSS-SLF experiment are discussed within the context of established solid state NMR experiments which are usually performed without sample rotation and we compare the data to orientation information obtained from X-ray diffraction.

Bacteriorhodopsins↗
PubMed2006

Late clinical events after clopidogrel discontinuation may limit the benefit of drug-eluting stents: an observational study of drug-eluting versus bare-metal stents.

OBJECTIVES: We sought to define the incidence of late clinical events and late stent thrombosis in patients treated with drug-eluting (DES) versus bare-metal stents (BMS) after the discontinuation of clopidogrel as well as their timing and outcome. BACKGROUND: There is growing concern that delayed endothelialization after DES implantation may lead to late stent thrombosis and related myocardial infarction (MI) or death. However, event rates and outcomes after clopidogrel discontinuation versus BMS are unknown. METHODS: A consecutive series of 746 nonselected patients with 1,133 stented lesions surviving 6 months without major events were followed for 1 year after the discontinuation of clopidogrel. Patients were assigned randomly 2:1 to DES versus BMS in BASKET (Basel Stent Kosten Effektivitäts Trial). The primary focus of this observation was cardiac death/MI. RESULTS: Rates of 18-month cardiac death/MI were not different between DES and BMS patients. However, after the discontinuation of clopidogrel (between months 7 and 18), these events occurred in 4.9% after DES versus 1.3% after BMS implantation. Target vessel revascularization remained lower after DES, resulting in similar rates of all clinical events for this time period (DES 9.3%, BMS 7.9%). Documented late stent thrombosis and related death/target vessel MI were twice as frequent after DES versus BMS (2.6% vs. 1.3%). Thrombosis-related events occurred between 15 and 362 days after the discontinuation of clopidogrel, presenting as MI or death in 88%. CONCLUSIONS: After the discontinuation of clopidogrel, the benefit of DES in reducing target vessel revascularization is maintained but has to be balanced against an increase in late cardiac death or nonfatal MI, possibly related to late stent thrombosis.

Aged↗
PubMed2006

Coronary artery imaging with contrast-enhanced MDCT: extracardiac findings.

OBJECTIVE: The purpose of our study was to evaluate the incidence of extracardiac findings on contrast-enhanced MDCT of the coronary arteries and to assess the effect of different field-of-view settings. SUBJECTS AND METHODS: Patients with suspected coronary artery disease (n = 166) were examined with contrast-enhanced MDCT (16 x 0.75 mm focused on the heart) during injection of contrast material (80 mL injected at a rate of 4 mL/sec) followed by saline (20 mL injected at 4 mL/sec). Retrospectively gated images were reconstructed at a 1-mm slice thickness and a 0.5-mm increment with isotropic voxels of 1 mm3. Images were reviewed for extracardiac findings, which were then classified as none, minor, or major with respect to their impact on patient management and treatment. In a different group of patients (n = 20), chest scans (16 x 1.5 mm) were used for measuring volumes of displayed body structures on wholechest scans, coronary artery MDCT images, and coronary artery MDCT images reconstructed with the maximum field of view. RESULTS: Extracardiac findings were detected in 41 patients (24.7%). Findings were classified as minor (19.9%) or major (4.8%). Among the major findings, which had an immediate impact on patient management and treatment, were bronchial carcinoma and pulmonary emboli. Volume analysis revealed that 35.5% of the total chest volume was displayed on dedicated coronary artery MDCT focused on the heart, whereas 70.3% of the chest was visible when coronary artery MDCT raw data were reconstructed with the maximal field of view (p < 0.001). CONCLUSION: Coronary artery MDCT can reveal important findings and disease in extracardiac structures. Thus, the entire examination should be reconstructed with the maximum field of view and should be reviewed by a qualified radiologist.

Adult↗
PubMed2005

Coronary stent infection: a rare but severe complication of percutaneous coronary intervention.

During the last two decades, the number of percutaneous coronary interventions (PCI) has steadily increased in Switzerland, as has the use of coronary stents. However, reports of coronary stent infections are very rare. In the present article we review all published cases of coronary stent infections. All patients presented with symptoms of infection within the first four weeks after PCI. Clinical hallmarks of stent infection were fever and chest pain. Blood cultures were positive in all patients. Despite the use of intravenous antibiotics in all except one patient and surgical drainage of the infectious focus in the majority of affected individuals mortality was high (40%). Thus, coronary stent infection, although exceedingly rare, represents a life-threatening complication and should be considered in the differential diagnosis of patients presenting with fever during the first few weeks after PCI.

Angioplasty, Balloon, Coronary↗
PubMed2005

Limited diagnostic yield of non-invasive coronary angiography by 16-slice multi-detector spiral computed tomography in routine patients referred for evaluation of coronary artery disease.

AIMS: Multislice spiral computed tomography (MSCT) is a promising non-invasive method to diagnose coronary artery disease (CAD). As no detailed comparative evaluation in consecutive patients referred for evaluation of CAD has been reported, this prospective study evaluating 2384 coronary segments in 149 consecutive patients was performed. METHODS AND RESULTS: The coronary artery tree was analysed in 16 segments both for coronary angiography (CA) and MSCT; a luminal narrowing > or = 50% based on visual assessment was considered significant. By MSCT, 77% of 2110 angiographically assessable segments could be evaluated, 94% per patient in proximal and 70% in distal segments (P<0.001). Sensitivity of MSCT to detect significant stenoses was 30% in all, but only 10% in peripheral segments. The main limitations were calcifications in 34% of segments and motion artefacts in 24% of patients. Overall diagnostic sensitivity for the presence of significant CAD was 86% but specificity was only 49%. CONCLUSION: When compared with invasive CA, 16-slice MSCT is of limited diagnostic value for the diagnosis of CAD in consecutive patients. Despite a clinically useful sensitivity for the overall diagnosis of significant CAD, specificity is low. Thus, relevant decisions regarding the need of and suitability for possible revascularization procedures cannot be based on MSCT findings alone.

Coronary Angiography↗
PubMed2005

Right atrial pacing impairs cardiac function during resynchronization therapy: acute effects of DDD pacing compared to VDD pacing.

OBJECTIVES: We aimed to compare the hemodynamic effects of right-atrial-paced (DDD) and right-atrial-sensed (VDD) biventricular paced rhythm on cardiac resynchronization therapy (CRT). BACKGROUND: Cardiac resynchronization therapy improves hemodynamics in patients with severe heart failure and left ventricular (LV) dyssynchrony. However, the impact of active right atrial pacing on resynchronization therapy is unknown. METHODS: Seventeen CRT patients were studied 10 months (range: 1 to 46 months) after implantation. At baseline, the programmed atrioventricular delay was optimized by timing LV contraction properly at the end of atrial contraction. In both modes the acute hemodynamic effects were assessed by multiple Doppler echocardiographic parameters. RESULTS: Compared to DDD pacing, VDD pacing resulted in much better improvement of intraventricular dyssynchrony assessed by the septal-to-posterior wall motion delay (VDD 106 +/- 83 ms vs. DDD 145 +/- 95 ms; p = 0.001), whereas the interventricular mechanical delay (difference between onset of pulmonary and aortic outflow) did not differ (VDD 20 +/- 21 ms vs. DDD 18 +/- 17 ms; p = NS). Furthermore, VDD pacing significantly prolonged the rate-corrected LV filling period (VDD 458 +/- 123 ms vs. DDD 371 +/- 94 ms; p = 0.0001) and improved the myocardial performance index (VDD 0.60 +/- 0.18 vs. DDD 0.71 +/- 0.23; p < 0.01). CONCLUSIONS: Our findings suggest that avoidance of right atrial pacing results in a higher degree of LV resynchronization, in a substantial prolongation of the LV filling period, and in an improved myocardial performance. Thus, the VDD mode seems to be superior to the DDD mode in CRT patients.

Atrial Fibrillation↗
PubMed2005

How to prepare membrane proteins for solid-state NMR: A case study on the alpha-helical integral membrane protein diacylglycerol kinase from E. coli.

Several studies have demonstrated that it is viable to use microcrystalline preparations of water-soluble proteins as samples in solid-state NMR experiments [1-5]. Here, we investigate whether this approach holds any potential for studying water-insoluble systems, namely membrane proteins. For this case study, we have prepared proteoliposomes and small crystals of the alpha-helical membrane-protein diacylglycerol kinase (DGK). Preparations were characterised by 13C- and 15N-cross-polarization magic-angle spinning (CPMAS) NMR. It was found that crystalline samples produce better-resolved spectra than proteoliposomes. This makes them more suitable for structural NMR experiments. However, reconstitution is the method of choice for biophysical studies by solid-state NMR. In addition, we discuss the identification of lipids bound to membrane-protein crystals by 31P-MAS NMR.

Adenosine Triphosphate↗
PubMed2005

Long-term benefits and limitations of combined antianginal drug therapy in elderly patients with symptomatic chronic coronary artery disease.

BACKGROUND: Chronic angina is a common and disabling disorder in the elderly. Combined antianginal drug treatment represents the mainstay of therapy in this population. However, there is a paucity of data regarding the effect of this strategy on long-term outcome in the elderly. METHODS: To assess the long-term effect of combined antianginal drug therapy in elderly individuals, we performed a long-term follow-up analysis of all 148 patients of the Trial of Invasive versus Medical therapy in Elderly (TIME) patients with chronic symptomatic coronary-artery disease assigned to an optimized medical therapy strategy. Angina severity, measures of quality of life (QOL), and survival were assessed after a median of 3.7 (0.1-6.9) years. RESULTS: At baseline, patients were 79.8 +/- 3.5 years old with Canadian Cardiovascular Society (CCS) class angina 3.0 +/- 0.7 despite the use of 2.4 +/- 0.6 antianginal drugs. Although antianginal drugs were increased to 2.8 +/- 0.9 (P < .01), 63 (43%) patients needed revascularization for refractory symptoms during the first year of observation (REVASC). At baseline, REVASC patients had more frequently CCS class 4 angina (37% vs 20%, P < 0.05) but reported less prior heart failure (5% vs 20%, P < 0.01), fewer prior cerebral events (3% vs 13%, P < .05) and a lower rate of two or more comorbidities (10% vs 33%, P < .01) than patients on continued drug therapy (DRUG). At long-term follow-up, angina severity was still higher in DRUG compared to REVASC patients (CCS class, 1.8 +/- 1.6 vs 1.0 +/- 1.4, P < .05) despite more antianginal drugs (2.1 +/- 1.1 vs 1.5 +/- 1.0, P < .01), whereas measures of QOL had improved similarly in both groups. In addition, long-term mortality was significantly higher in DRUG than in REVASC patients (38% vs 13%, P < .01). CONCLUSION: Combined antianginal drug therapy successfully relieved symptoms in most elderly patients with chronic angina but failed to do so in 43%. Patients who needed revascularization for refractory symptoms reported less angina, despite lower drug use during long-term follow-up and had a better long-term survival. Thus, the widely used strategy to increase antianginal drug therapy in elderly patients instead of evaluating them for revascularization should be reconsidered.

Aged↗
PubMed2004

Vascular responses at proximal and distal edges of paclitaxel-eluting stents: serial intravascular ultrasound analysis from the TAXUS II trial.

BACKGROUND: On the basis of brachytherapy experience, edge stenosis has been raised as a potential limitation for drug-eluting stents. We used serial intravascular ultrasound (IVUS) to prospectively analyze vessel responses in adjacent reference segments after implantation of polymer-controlled paclitaxel-eluting stents. METHODS AND RESULTS: TAXUS II was a randomized, double-blind trial with 2 consecutive patient cohorts that compared slow-release (SR) and moderate-release (MR) paclitaxel-eluting stents with control bare metal stents (BMS). By protocol, all patients had postprocedure and 6-month follow-up IVUS. Quantitative IVUS analysis was performed by an independent core laboratory, blinded to treatment allocation, in 5-mm vessel segments immediately proximal and distal to the stent. Serial IVUS was available for 106 SR, 107 MR, and 214 BMS patients. For all 3 groups, a significant decrease in proximal-edge lumen area was observed at 6 months. The decrease was comparable (by ANOVA, P=0.194) for patients in the SR (-0.54+/-2.1 mm2) and MR (-0.88+/-1.9 mm2) groups compared with the BMS (-1.02+/-1.9 mm2) group. For the distal edge, a significant decrease in lumen area was only observed with BMS (-0.91+/-2.0 mm2, P<0.0001); this decrease was significantly attenuated with SR (0.08+/-2.0 mm2) and MR (-0.19+/-1.7 mm2) stents (P<0.0001 by ANOVA). Negative vessel remodeling was observed at the proximal (-0.48+/-2.2 mm2, P=0.011) but not the distal edges of BMS and at neither edge of SR or MR stents. CONCLUSIONS: The marked reduction in in-stent restenosis with SR or MR stents is not associated with increased edge stenosis at 6-month follow-up IVUS. In fact, compared with BMS, there is instead a significant reduction in late lumen loss at the distal edge with TAXUS stents.

Coronary Restenosis↗
PubMed2004

Risks and benefits of optimised medical and revascularisation therapy in elderly patients with angina--on-treatment analysis of the TIME trial.

AIM: To assess treatment effects of optimised medical therapy and PCI or CABG surgery on one-year outcome in patients 75 years old with chronic angina. METHODS AND RESULTS: On-treatment analysis of the TIME data: all re-vascularised patients (REVASC n=174: 112 randomised to revascularisation and 62 to drugs with late revascularisation) were compared to all patients on continued drug therapy (MED n=127: 86 randomised to drugs and 41 to revascularisation only). Baseline characteristics of both groups were similar (age 80 +/- 4 years). Risk of death at one year (adjusted hazard ratio (HR)=1.31; 95%-CI: 0.58-2.99; P=0.52) and of death/infarction (adjusted hazard RATIO=1.77; 95%-CI 0.91-3.41; P=0.09) were comparable between REVASC and MED patients. Furthermore, the risk of death within 30 days was even slightly lower among REVASC patients (unadjusted hazard RATIO=0.73; 95%-CI: 0.21-2.53; P=0.98). Overall, REVASC patients had greater improvements in symptoms and well-being than MED patients (P<0.01). Surgical patients had similar mortality rates as angioplasty patients, but they also had greater symptomatic improvements (P<0.01). CONCLUSION: Treated medically, elderly patients with chronic angina have a similarly high 30-day and one-year mortality as patients of the same age being re-vascularised; however, they can expect lower improvements in symptoms and well being.

Aged↗
PubMed2004

Cost-effectiveness of invasive versus medical management of elderly patients with chronic symptomatic coronary artery disease. Findings of the randomized trial of invasive versus medical therapy in elderly patients with chronic angina (TIME).

AIM: To compare benefits and costs of invasive versus medical management in elderly patients with chronic angina. METHODS AND RESULTS: In a predefined subgroup of 188 patients of the Trial of Invasive versus Medical therapy in Elderly patients with chronic angina (TIME), one-year benefits were assessed as freedom from major events and improvements in symptoms and quality of live. Costs were determined as one-year costs of resource utilisation. Invasive patients had higher 30-day, but lower months 2-12 hospital and intervention costs than medical patients, resulting in somewhat higher one-year costs for invasive management (p=0.08). However, billing data available for a subgroup of patients showed higher practitioner's charges in the medical patients (adjusted p=0.0015). Incremental costs to prevent one major event by invasive management averaged CHF 10100 (95% CI: -800 to 28300) or 6965, ranging from average CHF 5100 (euro 3515) to CHF 11600 (euro 8000) in a best, compared to a worst, case scenario. CONCLUSIONS: Early increased costs of revascularization in invasive patients were balanced after one year by increased practitioners' charges and symptom-driven late revascularizations in medical patients. Therefore, the invasive strategy with improved clinical effectiveness at only marginally higher costs as medical management was cost-effective. Costs should not be an argument against invasive management of elderly patients with chronic angina.

Aged↗
PubMed2004

Prognostic value of stress testing in patients over 75 years of age with chronic angina.

STUDY OBJECTIVES: To define the prognostic value of stress testing (STRT) in patients >or= 75 years of age. DESIGN: Multicenter prospective randomized trial. SETTING: Tertiary care centers. PATIENTS: Two hundred ninety-two patients of the Trial of Invasive vs Medical Treatment of Elderly Patients aged >or= 75 years with chronic angina despite receiving two or more antianginal drugs were prospectively observed for 1 year. INTERVENTION: STRT (88% exercise ECG; 12% pharmacologic stress imaging) was performed if possible, and ischemia was diagnosed using current guidelines. Death for any reason and nonfatal myocardial infarction were outcome events. RESULTS: Patients who could perform STRT (148 patients) were younger, had a lower risk profile, received less medication, and had less severe angina than patients who could not perform STRT (144 patients). The 1-year mortality rate was only 1.4% in patients with negative STRT results (72 patients) compared to 5.3% in patients with positive STRT results (76 patients) and 13.7% in patients who had not undergone STRT due to unstable symptoms (95 patients). The corresponding 1-year rates of death/infarction were 2.8%, 15.8%, and 26.3%, respectively. After adjustment for baseline differences, mortality rates were no longer significantly different. However, compared to patients with negative STRT results, infarction and death/infarction rates remained higher in patients with provocable ischemia (hazard ratio [HR], 8.9 [p = 0.04]; HR, 6.1 [p = 0.02], respectively) and in patients without STRT due to unstable angina (HR, 11.8 [p = 0.02]; HR, 8.6 [p =.004], respectively). CONCLUSIONS: STRT in elderly patients is feasible and provides important prognostic information for their future management. Patients with negative STRT results after receiving therapy have a good prognosis, and their conditions may be managed conservatively.

Aged↗
PubMed2003

Long-term outcome of patients with silent versus symptomatic ischemia six months after percutaneous coronary intervention and stenting.

OBJECTIVES: We sought to evaluate the incidence of silent ischemia versus symptomatic ischemia six months after percutaneous coronary intervention (PCI) and its impact on prognosis and to test the utility of myocardial perfusion single-photon emission computed tomography (SPECT), or MPS, for risk stratification in these patients. BACKGROUND: Silent ischemia is frequent after PCI. However, little is known about silent ischemia and long-term outcome after PCI and stenting. METHODS: In 356 consecutive patients with successful PCI and stenting and follow-up MPS after six months, long-term follow-up (4.1 +/- 0.3 years) was performed. The MPS images were interpreted by defining summed stress, rest, and difference scores (summed difference score [SDS] = extent of ischemia) and related to symptoms and outcome. Critical events included cardiac death, myocardial infarction, and target vessel revascularization. RESULTS: Eighty-one patients (23%) had evidence of target vessel ischemia, which was silent in 62%. The only independent predictor of silent ischemia was SDS (odds ratio 0.64, p = 0.001). During follow-up, 67 critical events occurred. For patients with an SDS of 0, 1-4, and >4, the critical event rates were 17%, 29%, and 69%, respectively. Similarly, patients without ischemia, silent ischemia, and symptomatic ischemia had 17%, 32%, and 52% of critical events, respectively. Diabetes (relative risk 1.98, p = 0.03) and SDS (relative risk 1.2, p < 0.001) were independent predictors of critical events. The MPS image added incremental information for the prediction of critical events. CONCLUSIONS: Six months after PCI and stenting, 23% of patients had target vessel ischemia, which was silent in 62%. Silent ischemia predicted a worse outcome than did no ischemia and tended to have a better outcome than symptomatic ischemia. This was closely related to the extent of ischemia. The SDS added incremental value to pre-scan findings with respect to diagnosis and prognosis, indicating the utility of MPS for risk stratification after PCI and stenting.

Adult↗
PubMed2002

Systematic use of a collagen-based vascular closure device immediately after cardiac catheterization procedures in 1,317 consecutive patients.

Despite recent advances in interventional cardiology, vascular access complications continue to be a significant problem. Conventional manual compression of the femoral access site is associated with prolonged immobilization and significant patient discomfort. We investigated the performance of a collagen-based closure device applied immediately after catheterization and its complication rate in 1,317 consecutive patients undergoing cardiac catheterization or coronary angioplasty. Patients undergoing coronary angioplasty (n = 644) received more heparin than patients with diagnostic cardiac catheterization (n = 673; 9,675 +/- 1,144 IU vs. 6,419 +/- 2,211 IU; P < 0.0001). Deployment success rates of the closure device were comparable for patients undergoing diagnostic vs. interventional procedures (95.8% vs. 96.7%; P = 0.46). Complete hemostasis immediately after deployment of the device was achieved in > 90% of all patients, but was lower in the interventional group (93.7% vs. 90.6%; P = 0.05). Major complications including any vascular surgery, major bleeding requiring transfusion, retroperitoneal hematoma, thrombosis or loss of distal pulses, groin infections, significant groin hematoma, and death were observed in 0.53% of all patients, with no differences between diagnostic or interventional patients (0.62% vs. 0.45%; P = 0.953). Subgroup analysis revealed female gender as a predictor of access site complications. Systematic sealing of femoral access sites after both diagnostic and interventional procedures allows for immediate sheath removal with reliable hemostasis. The use of a collagen-based closure device is associated with a low rate of clinically significant complications.

Aged↗
PubMedDate not supplied

Incremental cost-effectiveness of drug-eluting stents compared with a third-generation bare-metal stent in a real-world setting: randomised Basel Stent Kosten Effektivitäts Trial (BASKET).

BACKGROUND: No prospective trial-based data are available for incremental cost-effectiveness of drug-eluting stents (DES) compared with bare-metal stents (BMS) in unselected patients, as treated in everyday practice. METHODS: The Basel stent cost-effectiveness trial (BASKET) included 826 consecutive patients treated with angioplasty and stenting for 1281 de-novo lesions, irrespective of indication for angioplasty. Patients were randomised to one of two DES (Cypher, n=264; Taxus, n=281) or to a cobalt-chromium-based BMS (Vision, n=281) and followed up for 6 months for occurrence of major adverse cardiac events and costs. Analysis was by intention-to-treat. The primary endpoint was cost-effectiveness after 6 months, with effectiveness defined as reduction of major adverse cardiac events. FINDINGS: Cardiac death, myocardial infarction, or target vessel revascularisation occurred in 39 of 544 (7.2%) patients with DES and 34 of 280 (12.1%) with BMS (odds ratio 0.56, 95% CI 0.35-0.91; p=0.02), without significant differences between the two DES. Total costs at 6 months were higher with DES (mean 10,544, SD 6849) than with BMS (9639, 9067; p<0.0001); higher stent costs of DES were not compensated for by lower follow-up costs. Incremental cost-effectiveness ratio of DES compared with BMS to avoid one major event was 18,311, and costs per quality-adjusted life-year gained were more than 50 000. Subgroup analyses showed that DES were more cost-effective for elderly patients in specific high-risk groups. INTERPRETATION: In a real-world setting, use of DES in all patients is less cost effective than in studies with selected patients. Use of these stents could be restricted to patients in high-risk groups.

Adult↗