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Biomedical subjects

W G Daniel

Publications and source records attributed to W G Daniel.

At least 55 records · Page 3Linked to original sources
PubMed2001

Transradial approach for renal artery stenting.

Percutaneous interventional procedures in the renal arteries are usually performed using a femoral or brachial vascular access. The transradial approach, which has been extensively investigated for coronary angiography and intervention, could be an attractive new technique for renal artery angioplasty and stenting. In 18 patients with hemodynamically relevant unilateral renal artery stenosis (mean diameter stenosis, 83% +/- 18%; right, n = 7; left, n = 11), interventional treatment with PTA and stenting was performed using a left (n = 16) or right (n = 2) radial artery access. Indications for the transradial approach were acute aorto-renal angles or severe peripheral arterial obstructions. After engagement of the renal artery ostium with a 6 Fr Multipurpose guiding catheter (length, 125 cm; Cordis) the stenosis was passed with a 0.014" guidewire followed by stent implantation (ACS Multi-Link RX Ultra, Guidant; length, 18 mm; diameter, 5 mm). Direct stenting was successfully performed in 16 cases. Predilatations were required in two cases. In five patients, optimal stent expansion was achieved by additional postdilatations. A primary technical success (residual stenosis < 30%) could be achieved in all cases. There were no periprocedural complications. According to color-coded doppler ultrasound, all access site arteries showed a normal perfusion. Clinically blood pressure control was improved in 11 patients with a significant reduction in systolic and diastolic blood pressure values. Serum creatinine values dropped from 1.81 +/- 0.3 mg/dl to 1.49 +/- 0.3 mg/dl (P < 0.001). Transradial renal artery angioplasty and stenting is technically feasible and safe. Particularly in patients with unfavorable vessel anatomy, this new cranio-caudal approach is an attractive alternative technique.

Aged↗
PubMed2001

Recommendations for standardization of EBT and MSCT scanning.

BACKGROUND: The detection and quantification of coronary calcifications by electron beam tomography (EBT) permits to diagnose coronary atherosclerosis in an early stage. Initial reports indicate that multislice spiral CT (MSCT) also permits the quantification of coronary calcium, while equivalency to EBT has not been definitely proven. Since image acquisition, reconstruction and evaluation parameters influence the results of calcium quantification with CT techniques, standardization of the investigation is mandatory to make results comparable. AIM: The article summarizes guidelines for image acquisition and evaluation by EBT and describes guidelines and consensus reports that were issued concerning the clinical use of the method.

Adult↗
PubMed2001

Changes in ocular blood flow velocities during external counterpulsation in healthy volunteers and patients with atherosclerosis.

BACKGROUND: External counterpulsation (ECP) is a new noninvasive means of augmenting organ perfusion by applying ECG-triggered diastolic pressure to the vascular bed of the lower limbs. In this study, effects of ECP on changes of ocular blood flow velocities were studied. METHOD: Mean, systolic and diastolic flow velocities of the ophthalmic artery were measured by Doppler sonography before and during ECP. Twelve healthy volunteers (age 31.3+/-4.3 years) and 12 patients with severe atherosclerosis (inclusion criteria: two atherosclerotic risk factors, at least one severe coronary stenosis, age 62.1+/-5.3 years) were included in the study. RESULTS: In healthy subjects, ECP changed diastolic flow velocity of the ophthalmic artery nonsignificantly from 21.6+/-7.7 to 23.7+/-10.5 cm/s. Systolic flow velocity decreased significantly from 36.1+/-13.6 to 28.9+/-10.2 cm/s (P<0.01). Mean flow velocity changed nonsignificantly from 28.1+/-9.4 to 26.5+/-9.9 cm/s. In atherosclerotic patients, mean flow velocity increased significantly from 26.3+/-11.4 to 29.3+/-11.2 cm/s (P<0.001), which was caused by significant diastolic flow augmentation from 19.7+/-9.1 to 23.9+/-9.7 cm/s (P<0.001). Systolic flow velocity was not changed significantly (from 34.2+/-12.8 to 32.6+/-11.8 cm/s). CONCLUSION: No significant change of mean blood flow velocity in the ophthalmic artery was found in young healthy subjects. In elderly patients with atherosclerosis, ECP significantly increased blood flow velocity in the ophthalmic artery by 11.4%. This may indicate an ocular perfusion benefit in these patients as a result of ECP and could also explain the increase of perfusion found in patients with retinal ischemia after ECP.

Adult↗
PubMed2001

Native tissue second harmonic imaging improves endocardial and epicardial border definition in dobutamine stress echocardiography.

AIMS: Native tissue second harmonic imaging (SHI) implemented in two-dimensional (2D) echocardiography was found to improve left ventricular (LV) endocardial border delineation. Dobutamine stress echocardiography (DSE) depends on the ability to adequately visualize these borders. We analysed whether SHI, compared to fundamental imaging (FI), can improve echogenicity qualitatively and quantitatively, as well as looking at the diagnostic accuracy of the stress test. METHODS AND RESULTS: Fifty consecutive patients with suspected or known coronary artery disease (history of myocardial infarction and/or coronary artery bypass grafting) underwent DSE sequentially by SHI as well as FI 3 days before or after quantitative coronary angiography. Regional mean echogenicity scores (0=uninterpretable; 4=excellent imaging) for SHI and FI at peak dobutamine titration were 1.8 +/- 0.8 and 1.0 +/- 0.6 (P=0.0020) for the anterior region, 2.3 +/- 0.8 and 1.5 +/- 0.7 (P=0.0002) laterally, 2.7 +/- 1.0 and 1.9 +/- 0.8 (P=0.0001) posteriorly, 2.9 +/- 0.8 and 2.2 +/- 0.7 (P<0.0006) inferiorly, 3.0 +/-0.7 and 2.2 +/- 0.7 (P=0.0001) septally, and 3.1 +/- 1.0 and 2.1 +/-0.8 (P=0.0001) anteroseptally, respectively. Medians [upper; lower quartiles] of a global endocardial visualization index (calculated analogously with the wall motion score index based on a 16-segment model recommended by the American Society of Echocardiography) for the harmonic and the fundamental techniques were 2.59 [2.91; 2.22] and 1.87 [2.19; 1.53] (P=0.0001) at rest, 2.62 [2.94; 2.13] and 1.84 [2.19; 1.50] (P=0.0001) at low dose dobutamine, 2.51 [3.00; 2.13] and 1.74 [2.00; 1.44] (P=0.0001) at peak dose dobutamine, and 2.52 [2.94; 2.19] and 1.76 [2.19; 1.38] (P=0.0001) at recovery, respectively. For repeated quantitative LV volumetry in the harmonic and fundamental modality by the same observer, coefficients of variation were 4.4 +/- 0.4 vs. 6.0 +/- 0.5 (P<0.0001) for end-diastolic volume, 7.4 +/- 0.8 vs. 9.2 +/- 1.1 (P<0.0001) for end-systolic volume, and 5.2 +/- 1.1 vs. 8.2 +/- 1.3 (P<0.0001) for ejection fraction, respectively. Sensitivity and specificity related to coronary angiography for both methods were 80% and 60% as well as 90% and 93%, respectively. CONCLUSION: Native tissue SHI enhances LV image quality in all stress stages of DSE in unselected patients. This translates into beneficial effects on not only qualitative but also quantitative testing and diagnostic accuracy. SHI should be recommended as a standard tool in DSE and extends its applicability to difficult-to-image patients previously deemed unsuitable.

Adult↗
PubMed2001

Patients with acute coronary syndromes express enhanced CD40 ligand/CD154 on platelets.

OBJECTIVE: To investigate whether CD40L/CD154 on platelets and soluble CD40L/CD154 may play a role in the inflammatory process of acute coronary syndromes. DESIGN AND SETTING: Observational study in a university hospital. PATIENTS: 15 patients with acute myocardial infarction, 25 patients with unstable angina, 15 patients with stable angina, and 12 controls. MAIN OUTCOME MEASURES: CD40L/CD154 on platelets, P-selectin/CD62P on platelets, soluble CD40L/CD154 serum concentrations. RESULTS: Mean (SD) CD40L/CD154 expression on platelets was 6.2 (2.8) MFI (mean fluorescence intensity) in the infarct group, 11 (3.3) MFI in the unstable angina group (p < 0.001 v infarction), 3.6 (0.9) MFI in the stable angina group (p < 0.01 v infarction; p < 0.001 v unstable angina), and 3.2 (1.0) MFI in the controls (p < 0.01 v infarction; p < 0.001 v unstable angina; NS v stable angina). Soluble CD40L/CD154 concentration was 5.2 (1.1) ng/ml in the infarct group, 4.2 (0.7) ng/ml in the unstable angina group (p < 0.001 v infarction), 2.9 (1.0) ng/ml in stable angina group (p < 0.001 v infarction and unstable angina), and 3.0 (0.5) ng/ml in the controls (p < 0.001 v infarction and unstable angina; NS v stable angina). At a six months follow up, there was lower expression of CD40L/CD154 on platelets in patients with unstable angina (12.3 (3.6) v 3.8 (1.2) MFI, p < 0.0001) and acute myocardial infarction (6.2 (2.8) v 3.5 (0.8) MFI, p < 0.01) compared with their admission values six months earlier. Patients with unstable angina who needed redo coronary angioplasty (PTCA) or who had recurrence of angina were characterised by increased CD40L/CD154 expression on platelets compared with the remainder of the study group (recurrence of angina: 12.7 (3.2) v 9.7 (1.6) MFI, p < 0.05; re-do PTCA: 14.3 (4.2) v 10.3 (2.1) MFI, p < 0.05). CONCLUSIONS: Both CD40L/CD154 on platelets and soluble CD40L/CD154 are raised in patients with unstable angina and myocardial infarction. These findings suggest that CD40-CD40L/CD154 interactions may play a pathogenic role in triggering and propagation of acute coronary syndromes.

Aged↗
PubMed2000

Noninvasive coronary angiography by retrospectively ECG-gated multislice spiral CT.

BACKGROUND: We investigated the applicability and image quality of contrast-enhanced coronary artery visualization by multislice spiral CT using retrospective ECG gating. METHODS AND RESULTS: Twenty-five patients in sinus rhythm (significant coronary artery stenoses ruled out by invasive angiography) were studied with a multislice spiral CT (Siemens SOMATOM Volume Zoom). In inspiration (mean breath-hold, 37 seconds), a volume data set of the heart was acquired (intravenous contrast agent; 4 x 1-mm slice thickness; 500-ms rotation; table feed, 1.5 mm/360 degrees ). Simultaneous recording of the ECG permitted retrospective reconstruction of contiguous cross sections in intervals of 1 mm at any desired interval of the cardiac cycle. The mean duration of the image reconstruction window was 185 ms. Next to 3-dimensional reconstructions of the heart and coronary arteries, multiplanar reconstructions were rendered to determine the visualized length of the coronary arteries, the contrast-to-noise ratio, and the correlation of coronary artery diameters to quantitative coronary angiography. CONCLUSIONS: The coronary arteries could be visualized over long segments (left main, 9+/-4 mm; left anterior descending, 112+/-34 mm; left circumflex, 80+/-29 mm; right coronary artery, 116+/-33 mm). On average, 78+/-16% of these distances were visualized free of motion artifacts. The mean contrast-to-noise ratio was 9.3+/-3.3. Coronary artery diameters in multislice spiral CT showed close correlation to quantitative coronary angiography (CT, 3.3+/-1.0 mm; angiography, 3. 2+/-0.9 mm; mean difference, 0.38 mm; r=0.86). Contrast-enhanced multislice spiral CT permits visualization of the coronary artery lumen. Further studies are necessary to determine whether image quality is sufficient to reliably detect coronary artery stenoses.

Adult↗
PubMed2000

[Noninvasive imaging of coronary arteries with electron beam tomography (EBCT)].

Coronary angiography remains the diagnostic standard for establishing the presence, site, and severity of coronary artery disease. Electron beam computed tomography (EBCT), a non-invasive imaging method with very high spatial and temporal resolution, is well suited for cardiac imaging. Using a standard protocol, EBCT permits the visualization of the coronary arteries. Stenoses and occlusions of the native arteries and of coronary artery bypass grafts can be reliably diagnosed. Extremely calcified segments have to be excluded from evaluation. Reduced image quality, mainly due to fast vessel motion and superposition of large veins, impairs the results obtained for the right and left circumflex coronary artery. Possible clinical applications are the follow-up after angioplasty (PTCA without stent) and bypass surgery, the exclusion of coronary artery disease in patients with low likelihood of disease, and the evaluation of coronary anomalies.

Angioplasty, Balloon, Coronary↗
PubMed2000

Imaging of the coronary arteries using magnetic resonance angiography.

Magnetic resonance imaging of the coronary arteries is difficult due to the tortuous course of these vessels, their small diameter, and their rapid movement caused by respiration and cardiac contraction. Initial investigations could demonstrate the feasibility of non-invasive magnetic resonance coronary angiography using 2-dimensional turbo-FLASH gradient-echo sequences in repeated breathholds of approximately 16 heart beats duration. Further developments, especially the design of navigator-echo-based respiratory gated 3-dimensional imaging sequences, permitted the acquisition of contiguous volume data sets of the heart which eliminated many limitations of 2-dimensional repeated breathhold sequences. With a spatial resolution of approximately 1.2 x 1.2 x 2 mm and a temporal resolution of approximately 126 ms, several authors reported sensitivities of 70-80% and specificities of approximately 90% for the detection of coronary artery stenoses. Further improvements can be expected from new, intravascular contrast agents and from ultrafast sequences which permit acquisition of a sufficiently large imaging volume within one single breathold.

Coronary Angiography↗
PubMed2000

[New techniques for the quantification of myocardial function: acoustic quantification, color kinesis, tissue Doppler and "strain rate imaging"].

In this article, the authors discuss different semi-quantitative methods for the analysis of global and regional myocardial function. Analysis of endocardial motion and direct measurements of myocardial velocities are the basic principles. The former is a two-dimensional technique which, however, requires good image quality and which is influenced by motion artefacts. The latter technique has a better signal to noise ratio and offers the opportunity to sufficiently quantify diastole. Strain rate imaging is a new and interesting way to display and evaluate regional myocardial deformation.

Echocardiography, Doppler↗
PubMed2000

Aortic dissection.

Aortic dissection is a life-threatening cardiovascular emergency requiring immediate diagnosis and treatment. It is mainly associated with hypertension and the Marfan syndrome. Diagnosis has been revolutionized by the use of transesophageal echocardiography (TEE), which allows for rapid and safe assessment of this condition. Echocardiographic hallmarks of aortic dissection ar the presence of a dissection membrane separating a true from a false lumen, rupture sites in the membrane with to-and-from flow, aortic regurgitation, and pericardial effusion. Dissection of the ascending aorta, which has an extremely high mortality and necessitates emergency surgery, is diagnosed quickly and accurately by TEE.

Aortic Dissection↗
PubMed2000

Noninvasive detection of coronary artery stenosis using contrast-enhanced three-dimensional breath-hold magnetic resonance coronary angiography.

OBJECTIVES: The purpose of this study was to evaluate a contrast-enhanced three-dimensional (3D) breath-hold magnetic resonance (MR) technique for detection of coronary artery stenoses. BACKGROUND: The accuracy of previously published MR coronary angiography protocols varies widely. Recently, coronary artery imaging using T1-shortening contrast agent has become possible, but so far there are no data concerning its clinical application. METHODS: Magnetic resonance coronary angiography was performed in 50 patients with suspected coronary artery disease. Magnetic resonance data acquisition using an ultrafast 3D gradient-echo sequence lasted over 32 heartbeats within one single breath-hold. Twenty milliliters of gadopentetate dimeglumine was injected at a flow rate of 1 ml/s for two successive studies covering the main coronary arteries in single-oblique planes. Stenosis assessment by MR was compared with significant (diameter stenosis > 50%) stenoses on X-ray angiography. Evaluation was limited to the proximal and mid-coronary artery segments. RESULTS: Two hundred sixty-eight of 350 artery segments (76.6%) could be evaluated. Left circumflex coronary artery was only evaluable in 50% of cases by MR. In the evaluable segments, 48 of 56 stenoses and 193 of 212 nonstenotic segments were correctly classified by MR. On a patient basis, MR correctly identified 34 of 36 patients with and 8 of 14 patients without significant coronary stenoses as demonstrated by X-ray angiography (sensitivity 94.4%, specificity 57.1%). CONCLUSIONS: Oblique projection contrast-enhanced MR coronary angiograms obtained within one single breath-hold permit identification of patients with coronary stenoses in the proximal and mid segments of the major coronary arteries with satisfactory accuracy.

Adult↗
PubMed2000

[Pneumatic external counterpulsation (PECP): a new treatment option in therapy refractory inner ear disorders?].

BACKGROUND: The established therapeutic principle for sudden deafness and tinnitus is based on the stimulation of the inner ear perfusion by infusion therapy using vaso-active or hemodilutive agents. Concerning a mechanically induced increase of the inner ear's blood supply, the new technique of Pneumatic External Counterpulsation (PECP) was performed. This technique had already been used successfully in patients suffering from coronary heart disease. Due to an ECG-guided pneumatic compression of the lower extremities during diastole an increase of arterial perfusion of the extracranial supplying brain vessels can be obtained by PECP-treatment. PATIENTS AND METHODS: PECP was used in 33 patients (22 males, 11 females) between 19 and 76 years of age suffering from persisting acute hearing disorders and/or tinnitus after adequate infusion therapy. 3 patients revealed mild complications during PECP-treatment (e.g. thoracic pain) which seemed to be related to the therapeutic regime and disappeared completely after cessation of PECP. 30 patients underwent PECP-treatment on 5 following days for 1 hour. This standardized hourly treatment regime was extended to 10 days in 12 patients. Therapeutic effects were determined by color-coded duplexsonography and pure tone audiometry eventually masking the audiogram. RESULTS: During treatment an increase of 19% flow volume in the internal carotid arteries and of 11% in the vertebral arteries was evaluated using color-coded duplexsonography. In 47% of cases (n = 14) decrease of tinnitus intensity and/or tinnitus appearance with an average of 16 dB was perceived after the end of the treatment series. Hearing threshold increased in 28% of cases (n = 7) with an average threshold shift of 19 dB after PECP-treatment. All patients were examined by pure tone audiometry during the follow-up after 4, 8 and 12 weeks as well as after 6 and 12 months. In all cases the audiometric benefit lasted throughout the follow-up 1 year, after treatment. CONCLUSIONS: The determination of a positive correlation between vascular flow increase in the extracranial brain-supplying vessels during PECP-treatment and the encouraging therapeutic results obtained by audiometry seem to make this new and promising therapeutic option effective, practicable and easy to handle. These preliminary results of the PECP technique should be validated in further studies featuring larger numbers of patients suffering from therapy-resistant inner ear disorders.

Adult↗