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Stephen Schroeder

Publications and source records attributed to Stephen Schroeder.

At least 19 recordsLinked to original sources
PubMed2006

Non-invasive evaluation of coronary artery bypass grafts using 16-row multi-slice computed tomography with 188 ms temporal resolution.

BACKGROUND: Cardiac multi-slice computed tomography (MSCT) scanners permit visualization of the coronary arteries and coronary artery bypass grafts. The latest MSCT generation with true 16-detector slices (Sensation 16 Speed 4 D, Siemens, Forchheim, Germany) provides improved temporal and spatial resolution, as well as significantly reduced scan time. To assess, whether this technical improvement has also an impact on image quality and accuracy of MSCT diagnosis in patients with previous coronary artery bypass graft (CABG) surgery the following study was conducted. METHODS AND MATERIAL: Thirteen consecutive patients (pts) (10 male, 3 female, mean age 62 +/- 6.4 [55-73] years, heart rate 68 +/- 11 [52-88] bpm) and a total number of 43 coronary bypass grafts (11 arterial, 32 venous grafts) were examined by MSCT (gantry rotation time 375 ms). In addition to the analysis of coronary bypass grafts, 13 coronary segments (sgts) were evaluated in each patient (n = 169 sgts). MSCT results were compared with coronary angiography. RESULTS: Forty-one of 43 bypass grafts (95%) were analyzable by MSCT. In conventional angiography 16 of 43 (37%) grafts were occluded. Sixteen of them were correctly diagnosed by MSCT (sensitivity 100%). One graft showed a 50% anastomosis stenosis which was also detected. Twenty-five of 27 grafts without severe lesion showed no significant stenosis in MSCT (specificity 93%, positive predictive value (PPV) 89%, negative predictive value (NPV) 100%). Ninety of 108 (83%) high-grade stenosis (>70%) of the native coronary vessels were correctly detected (sensitivity 83%, PPV 78%). From the 61 sgts without high grade stenosis 36 were correctly classified (specificity 59%, NPV 67%). If sgts number 8, 9 and 10, which are normally not target for revascularization, are excluded sensitivity rises to 89%, specificity to 71%, PPV to 87% and NPV to 75%. The correct clinical diagnosis (absence or presence of a high grade stenosis of at least one bypass graft) was achieved in all patients. CONCLUSIONS: True 16-slice MSCT with faster gantry rotation time allows detection of lesions in coronary artery bypass grafts with high sensitivity and specificity. The evaluation of native vessels in pts with known CAD remains a diagnostic challenge. However, the correct clinical diagnosis was achieved in all pts. MSCT is a non-invasive tool to assess coronary artery bypass grafts.

Aged↗
PubMed2005

Assessment of left ventricular myocardial function using 16-slice multidetector-row computed tomography: comparison with magnetic resonance imaging and echocardiography.

OBJECTIVE: To assess functional parameters using multidetector-row computed tomography (MDCT) and echocardiography and to compare the results with magnetic resonance imaging (MRI). MATERIALS AND METHODS: End-diastolic-volume (EDV), end-systolic-volume (ESV), stroke-volume (SV), ejection-fraction (EF), and myocardial mass (MM) were calculated based on CT data sets from 52 patients. Echocardiography was performed in 24 of the 52 patients. The results from MDCT and echocardiography were compared with MRI. RESULTS: A strong correlation between MDCT and MRI (r=0.66-0.90) was found for all parameters. Echocardiography revealed a low or moderate correlation (0.05-0.59). Compared to MRI the average differences with MDCT were for EDV 15.1 ml, ESV 10.6 ml, SV 4.5 ml, EF 1.8%, and MM 8.2 g, for EDV determined by echocardiography 36.2 ml, ESV 6.8 ml, and EF 13.9%. Bland-Altman analysis revealed acceptable limits of agreement between MRI and MDCT. CONCLUSIONS: MDCT enables reliable quantification of left ventricular function. Echocardiography was found to have only a moderate agreement of functional parameters with MRI.

Coronary Angiography↗
PubMed2005

Usefulness of noninvasive MSCT coronary angiography as first-line imaging technique in patients with chest pain: initial clinical experience.

PURPOSE: Comparative studies with invasive coronary angiography (ICA) indicated a good sensitivity and specificity in the noninvasive detection of coronary artery disease (CAD) using Multi-slice spiral computed tomography coronary angiography (MS-CTA). The aim was to investigate the usefulness of MS-CTA as first-line imaging technique in patients (pts) with known or suspected CAD and low to intermediate probability of a severe coronary lesion. We report on our initial clinical experience using MS-CTA without compelled ICA. MATERIAL AND METHODS: One hundred thirty six patients with chest pain underwent MS-CTA on an outpatient basis (age 60+/-10, suspicion of CAD: n=95, suspicion of restenosis: n=24, after CABG: n=17). Based on the MS-CTA results, a recommendation concerning further diagnostics and therapy was given to each pt. A telephone interview was performed after 455+/-166 days to evaluate the further clinical course. RESULTS: Per pt, 8.2+/-2.7 coronary segments could be evaluated. Based on the MSCT results, the presence of flow-limiting stenoses was excluded in n=77 (57%) pts (group I). An additional ICA was recommended in n=59 (43%) pts (group II). An ICA had been performed in meantime in 27/136 (20%) pts, and could be avoided in the majority of pts. Nevertheless, 58/136 (42%) pts reported on improved clinical symptoms and 42/136 (31%) pts of improved quality of life. CONCLUSIONS: MS-CTA was found to be useful to evaluate the need and to reduce the total number of ICA in pts with unclear chest pain. It appears to be the first noninvasive modality, which might be used on a clinical routine basis in selected groups of pts.

Aged↗
PubMed2005

Visualization of pulmonary vein stenosis after radio frequency ablation using multi-slice computed tomography: initial clinical experience in 33 patients.

PURPOSE: Radio frequency ablation (RFA) of the pulmonary veins (PV) is an established technique for treatment of atrial fibrillation (AF). However, stenoses within the treated areas are well known complications. Thus, a reliable non-invasive diagnosis of PV stenosis would be an important step forward in the care of these patients (pts). Aim of the present study was the diagnostic accuracy of new multi-slice detected computed tomography (MSCT) in visualization of PV and in detecting PV stenosis. MATERIAL AND METHODS: A total of 33 pts (17 male, 16 female, mean age 57+/-10.2 years [40-71]) were included. Retrospectively ECG-gated CT angiography (CTA) was performed within 1 day to a maximum of 380 days after RFA with a MSCT scanner. Interpretation of the scan was performed on conventional contrast enhanced axial slices and on 3D volume rendering images (maximum intensity projection: MIP, multi-planar reconstruction: MPR). Lesion severity was determined on a semi-quantitative scale (mild: <20%, intermediate: 20-50%, severe >50%) and compared to conventional angiography which had been performed at the beginning and at the end of RFA. RESULTS: MSCTA was applied without any complications, and all treated pulmonary veins (n=73) could be visualized. Diagnostic image quality was obtained in all examinations. A significant stenosis was detected by conventional angiography in 26/73 (36%) PV (2/73 (3%) severe, 14/73 (19%) intermediate, 10/73 (14%) mild). Using MSCTA, only 13 stenosis in 73 treated PV could be visualized (1/73 (1%) severe, 6/73 (8%) intermediate, 6/73 (8%) mild). CONCLUSIONS: Multi-slice-detector CT is able to visualize PV and to detect PV stenoses. However, stenosis severity seems to be underestimated and not all lesions could be accurately detected. Larger studies have to be performed to further assess the diagnostic accuracy and clinical reliability of this new non-invasive method and to focus on the incidence of PV stenosis following RFA especially in long-time follow up.

Adult↗
PubMed2005

Influence of coenzyme Q(10) and cerivastatin on the flow-mediated vasodilation of the brachial artery: results of the ENDOTACT study.

AIM: Endothelial dysfunction (ED) is the functional prestep in atherosclerosis. Aim of the present study was to evaluate the effects of a potent antioxidant (coenzyme Q(10), CoQ(10)) and of cerivastatin on ED of the brachial artery. METHODS AND RESULTS: Twenty-five male patients with manifest ED (flow-mediated vasodilation [FMD%]<4.5%) were included in this prospective, randomized, cross-over study. ED of the brachial artery was assessed by the use of high-resolution ultrasound. Each patient had to pass through three treatment phases ((1) single therapy with cerivastatin (C), (2) single therapy with CoQ(10), (3) combination therapy). FMD% significantly improved throughout all treatment phases ((1) 3.50+/-4.05% vs. 8.80+/-6.39%, p=0.009; (2) -0.25+/-4.0% vs. 7.06%+/-4.39%, p=0.004; (3) 3.14+/-3.54% vs. 8.82+/-5.78%, p=0.011). C led to a significant decrease of CoQ(10) plasma levels (1.23+/-0.34 vs. 0.87+/-0.39 microg/ml, p=0.004). CONCLUSION: Our results indicate a positive influence of CoQ(10) supplementation on human ED, which appears to be independent of lipid lowering. Although large-scale studies evaluating other antioxidants failed to demonstrate a positive prognostic effect, Q(10) has never been evaluated in larger trials. Experimental as well as clinical results indicate that CoQ(10) warrants further attention in atherosclerosis research.

Adult↗
PubMed2005

Diagnostic accuracy of noninvasive coronary imaging using 16-detector slice spiral computed tomography with 188 ms temporal resolution.

OBJECTIVES: The aim of our study was to evaluate the diagnostic accuracy of 16-multi-detector spiral computed tomography (MDCT) with 188 ms temporal resolution. BACKGROUND: Because of rapid technical innovations, MDCT coronary imaging has significantly improved in the last five years. Recent results indicate a high diagnostic accuracy, especially in patients with clinical suspicion of coronary artery disease (CAD). METHODS: A total of 72 consecutive patients (30 women, 42 men, age 64 +/- 10 years) scheduled for invasive coronary angiography (ICA) because of suspected CAD were additionally studied by MDCT (Sensation 16 Speed 4D, Siemens, Forchheim, Germany). Thirty-seven of 72 patients (51%) received an additional beta-blockade before MDCT because of heart rates >65 beats/min. The MDCT scans were analyzed regarding the presence of coronary artery lesions. Results were compared with ICA. RESULTS: All 72 scans showed diagnostic image quality (heart rate: 64.1 +/- 9.2 beats/min, calcium mass: 86 +/- 156 mg). Thirteen coronary segments were evaluated in each patient. Sixty-two of 936 (6.6%) segments showed a nondiagnostic image quality. All segments were included in the analysis. A total of 117 relevant lesions (diameter stenosis >50%) were detected using ICA, and 96 of 117 (82%) were detected by MDCT. Sensitivity, specificity, and positive and negative predictive values for the whole study group were as follows: 82%, 98%, 87%, and 97%, respectively. The correct clinical diagnosis of presence or absence of significant CAD was obtained in 65 of 72 (90%) patients. All stenoses were detected by MDCT in 52 of 72 (72%) patients. CONCLUSIONS: Our results indicate a high diagnostic accuracy of 16-slice MDCT with improved temporal resolution.

Adult↗
PubMed2005

Evaluation of cardiac function and myocardial viability with 16- and 64-slice multidetector computed tomography.

Retrospectively ECG-gated MDCT shows a high correlation and acceptable agreement of left-ventricular functional parameters compared to MR imaging. Thus, in addition to the non-invasive evaluation of coronary arteries, further important additional information of left-ventricular functional parameters with clinical and prognostic relevance can be achieved by one single MDCT examination. For assessment of myocardial viability, low-dose CT late enhancement scanning is feasible, and preliminary results look promising. CT late enhancement adds valuable diagnostic information on the haemodynamical significance of coronary stenoses or prior to interventional procedures.

Animals↗
PubMed2005

Technology insight: possible applications of multislice computed tomography in clinical cardiology.

With the introduction of four-slice scanners in 1999, multislice CT (MSCT) technology became available for investigative examination of the heart. Since then, MSCT technology has undergone rapid technical progress; temporal and spatial resolutions have been especially improved. The improved diagnostic image quality has led to more possible uses of MSCT being defined. At present, issues such as visualization of coronary artery bypass grafts, detection of stenoses of native coronary arteries, description of coronary anomalies, and calcium scoring, can be investigated reasonably well. Other features, such as plaque imaging and visualization of intracoronary stents, need further evaluation. A large number of factors, however, such as heart rate, atrial fibrillation, breathing artefacts and severe calcification, still influence image quality and reduce validity. In this article we provide a summary of current fields of application of cardiac MSCT. The word 'indication' is consciously avoided because official guidelines for the use of MSCT in heart examination have not yet been issued. Hopefully, prospective multicenter trials will be performed soon, providing more data with which to establish guidelines for both cardiologist and radiologist.

Cardiology↗
PubMed2005

Use of an antecedent analysis and a force sensitive platform to compare stereotyped movements and motor tics.

Stereotyped movements displayed by 6 participants and tics displayed by 6 children were evaluated using an antecedent behavioral analysis and a force sensitive platform. We found that tics occurred more often in an alone condition when compared to high preference toy and play conditions, whereas stereotyped movements were more variable across conditions. Using temporal measures and spectral analysis data from the force sensitive platform, we found that stereotyped movements tended to be longer in duration and displayed more rhythmic qualities when compared to tics. Results indicate that stereotyped movements and tics differ both quantitatively and qualitatively and support the use of new technologies, such as force plate technology, to more accurately evaluate these differences.

Antipsychotic Agents↗
PubMed2005

ECG-gated 16-MDCT of the coronary arteries: assessment of image quality and accuracy in detecting stenoses.

OBJECTIVE: The aim of this study was to investigate image quality and diagnostic accuracy in detecting coronary artery lesions using a 16-MDCT scanner. MATERIALS AND METHODS: Thirty-seven patients (28 men, nine women) underwent unenhanced helical CT and MDCT angiography of the coronary arteries. After patients received oral beta-blocker medication, CT scans were obtained during a single breath-hold with a 16-MDCT scanner using ECG-gating (0.75-mm collimation, 2.8-mm table feed/rotation, 0.42-sec rotation time). The image quality was assessed in terms of artifacts and segment visibility by two reviewers. Stenosis severity was compared with the results of conventional invasive coronary angiography. RESULTS: The data evaluation of the image quality was based on a total of 488 segments, of which 380 segments were considered to have diagnostic image quality. One hundred eight segments (22.1%) could not be sufficiently evaluated because of severe calcifications (35 segments) and motion artifacts (73 segments). The mean calcium score (Agatston score equivalent [ASE]) was 524.3 +/- 807.6. Twenty-eight (75.7%) of the 37 patients had an ASE of less than 1,000 (mean ASE, 90.8 +/- 152.3 [SD]), and nine (24.3%) patients had an ASE of 1,000 or greater (mean ASE, 1,761.0 +/- 637.6). For detecting lesions 50% or greater (without any exclusion criteria), the overall sensitivity, specificity, positive predictive value, and negative predictive value were 59%, 87%, 61%, and 87%, respectively. When limiting the number of patients to those with a calcium score of less than 1,000 ASE, the threshold-corrected sensitivity for lesions 50% or greater was 93%; specificity, 94%; positive predictive value, 68%; and negative predictive value, 99%. CONCLUSION: In patients with no or moderate coronary calcification, MDCT of coronary arteries using 16-MDCT technology allows the reliable detection of coronary artery stenoses with high diagnostic accuracy. Obtaining an initial unenhanced scan was found to be mandatory to avoid performing useless examinations in patients with severe calcifications.

Adrenergic beta-Antagonists↗
PubMed2004

[Noninvasive detection of coronary stenosis using 16-slice detector computed tomography in carefully selected patients].

BACKGROUND AND PURPOSE: Due to technical improvements, multislice spiral computed tomography (MSCT) has become available for the noninvasive visualization of human coronary arteries. The current scanner generation provides 16 detector slices. The aim of the present study was to evaluate the influence of a careful patient selection on the diagnostic accuracy of noninvasive angiography. PATIENTS AND METHODS: Out of a study population of 60 patients, 36 with mild coronary calcifications (Agatston score < 500) were selected for the present retrospective analysis. In addition to conventional coronary angiography (CCA), all patients underwent a noninvasive MSCT examination of the coronary arteries. All coronary segments were assessed with respect to image quality and presence of severe lesions with a diameter stenosis >or = 50%. The MSCT examinations were performed using a Sensation 16 scanner (Siemens Medical Systems, Forchheim, Germany). RESULTS: The Agatston score of the study population was 83.3 +/- 125.4 (0-491.3), calcium mass 14.7 +/- 21.4 (0-83) mg CaHA (calcium hydroxyapatite). Diagnostic image quality could be obtained in 391/455 coronary segments (86%). 26 lesions > or = 50% could be detected by MSCT, CCA confirmed the presence of 21 lesions. No false-negative results were obtained (sensitivity: 100%, specificity: 99%, positive predictive value: 0.81, negative predictive value: 1.0). CONCLUSION: The new MSCT generation with 16 detector slices permits a noninvasive visualization of the coronary arteries with good image quality. It could be shown that a careful patient selection is of major importance for the diagnostic accuracy of MSCT imaging. It appears to be useful to perform a stepwise imaging, starting with a native scan to rule out severe calcifications. Prospective multicenter trials with larger patient numbers are required to confirm these initial results.

Calcinosis↗
PubMed2004

Noninvasive detection of coronary lesions using 16-detector multislice spiral computed tomography technology: initial clinical results.

OBJECTIVES: The aim of our study was to evaluate the feasibility of detecting coronary artery lesions using a new computed tomography (CT) scanner with 16 detectors and faster gantry rotation. BACKGROUND: Computed tomography angiography of the coronaries permits assessment of the coronaries; however, image quality is still impaired by motion artifacts and calcifications. METHODS: Sixty patients scheduled for conventional coronary angiography (CCA) were additionally studied by multislice spiral computed tomography (MSCT). Calcium scores and a contrast-enhanced visualization of the coronaries were performed and analyzed regarding evaluability, presence of coronary artery lesions, and correct clinical diagnosis. RESULTS: Calcium scoring was successful in all patients; 58 of 60 patients had a diagnostic contrast-enhanced scan. Mean calcium score was 506 +/- 743 Agatston score equivalent (ASE); 13 of 58 (22%) patients had an ASE >or=1,000, 46 of 58 (78%) patients <1,000. In 763 coronary segments, CCA detected a total of 75 lesions >or=50%. The MSCT correctly assessed 54 of these. Twenty-one lesions were missed or incorrectly underestimated. Sensitivity was 72%, specificity 97%. When restricting analysis to patients with an ASE <1,000, 40 significant lesions >or=50% were seen on CCA, and MSCT correctly detected 39 lesions (sensitivity 98%, specificity 98%). Regardless of any threshold, the correct clinical diagnosis could be obtained in 58 of 60 (97%) of all patients. CONCLUSIONS: In individuals with low-to-moderate amounts of coronary artery calcium, 16-detector CT coronary angiography has high sensitivity and specificity for the diagnosis of significant coronary artery stenosis.

Adult↗
PubMed2004

Diagnostic accuracy of multidetector computed tomography coronary angiography in patients with angiographically proven coronary artery disease.

OBJECTIVES: The aim of the present study was to evaluate the diagnostic accuracy in detecting high-grade coronary stenoses in patients with known coronary artery disease (CAD) using multidetector computed tomography (MDCT). BACKGROUND: The MDCT systems with electrocardiographic (ECG)-gating permit visualization of the coronary arteries. However, severe calcifications and higher heart rates are known to degrade image quality and limit correct diagnosis. METHODS: Sixty-six patients with proven CAD as assessed by conventional coronary angiography (CCA) were studied by MDCT (mean time 24 months postangiography). Total calcium score and all coronary arteries, including distal segments and side branches, were assessed with respect to evaluability, presence of high-grade coronary artery stenoses (>70%), and correct diagnosis. Results were compared to CCA. RESULTS: A total of 105 lesions were detected by CCA. The MDCT correctly detected 39 lesions (sensitivity 37%, specificity 99%). The correct clinical diagnosis could be obtained in 24 patients (36%). Artifacts due to elevated heart rates or severe coronary artery calcification were the main cause of degraded image quality inhibiting correct diagnosis. In 21/66 patients (32%) all four major coronary vessel segments could be visualized. A threshold for maximum heart rate and a maximum calcification level were established (65 beats/min and an Agatston Score Equivalent of 335, respectively). A second analysis was made using these thresholds. Of all patients studied, 10/11 (91%) were correctly diagnosed when adhering to these thresholds. CONCLUSIONS: When using MDCT as a noninvasive diagnostic modality to assess advanced CAD, it appears to be mandatory to preselect patients in order to achieve reliable results.

Adult↗
PubMed2003

Effects of local all-trans-retinoic acid delivery on experimental atherosclerosis in the rabbit carotid artery.

BACKGROUND: Retinoids regulate a variety of biological processes and play an important role in cell differentiation and proliferation. All-trans retinoid acid (atRA) is known to inhibit smooth muscle cell growth and thus is supposed to have favorable effects on the incidence of restenosis after percutaneous coronary interventions. The broad biological spectrum, however, leads to numerous severe side effects which limit the clinical use of a systemic application of atRA. In order to avoid systemic side effects, local delivery of atRA is preferable. The aim of this study was to evaluate the effects of atRA on the response to injury in a second-injury model of experimental balloon angioplasty. METHODS: After induction of a fibromuscular plaque in the right carotid artery of 40 New Zealand rabbits, 35 animals underwent balloon angioplasty of the preformed plaque formation. Subsequent local atRA delivery (10 ml, 10 microM) with the double-balloon catheter was performed in 15 animals. Five animals received vehicle only as sham controls, and five animals were solely electrostimulated, 15 animals served as control group with balloon angioplasty only. Vessels were excised 7 days (n=15) and 28 days (n=30) after intervention. Immunocytochemistry with antibodies against smooth muscle alpha-actin and myosin, bromodeoxyuridine, macrophages, collagen I and III and von Willebrand factor was performed. Quantitative analysis was done by computerized morphometry. RESULTS: After local atRA delivery in vivo, the extent of stenosis was markedly reduced with 21.7+/-8.3% (mean+/-S.D.) 4 weeks after intervention compared to 31.8+/-13.4% in balloon-dilated animals (P=0.0937). Both a reduced early neointimal proliferation (P=0.0002) and an increase in overall vessel diameter (4 weeks after intervention, P=0.0264) contributed to a limitation of restenosis in atRA-treated animals. Immunocytochemistry revealed a more intense alpha-actin staining pattern after local atRA therapy indicating redifferentiating effects of atRA on vascular smooth muscle cells. CONCLUSIONS: Local delivery of atRA led to limitation of restenosis formation in this animal model. The concept of a local atRA therapy might be a promising way to exploit the potential of atRA for vascular indications while minimizing the severe side effects of systemic retinoid therapy.

Actins↗
PubMed2003

Non-invasive evaluation of coronary artery bypass grafts using multi-slice computed tomography: initial clinical experience.

Recurrence of angina pectoris in patients with previous coronary artery bypass graft (CABG) surgery due to severe coronary artery disease (CAD) is a common problem. Non-invasive imaging of coronary artery bypass grafts by computed tomography was first described in the early 1980s. Meanwhile, multi-slice computed tomography (MSCT) is now available. This new technique allows detection of coronary lesions with good sensitivity and specificity due to continuous improvement and modification of this method. The aim of this study was to investigate whether stenosis or occlusion of CABG can be detected by MSCT. Ten consecutive male patients (mean age 61+/-9.1 years) with previous CABG surgery and 21 bypass grafts (14 venous grafts, seven arterial grafts) were included in this study. Conventional coronary angiography and MSCT angiography (MSCTA) were performed in all patients. MSCTA results were compared with coronary angiography in regard of visualization and lesion detection in CABG. The analysis of MSCTA was performed blinded to the angiographic results. It was found that 18 of 21 bypass grafts (86%) were analyzable by MSCTA: seven of 21 (33%) grafts showed a significant stenosis (>75%), while six of them were detected by MSCTA (sensitivity: 86%, positive predictive value: 0.75). Dissection of one arterial graft could not be evaluated by MSCTA. Twelve of 13 grafts without severe lesion showed no significant stenosis in MSCTA (negative predictive value: 0.86). All grafts without severe lesions by MSCT showed no significant lesion in X-ray angiography (specificity: 100%). MSCTA is a promising new method for the detection of lesions in coronary artery bypass grafts. However, these data based on a small number has to be reevaluated by larger studies.

Aged↗