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Biomedical subjects

A M Scheule

Publications and source records attributed to A M Scheule.

At least 19 recordsLinked to original sources
PubMed2006

Sixty-four-MSCT in the characterization of porcine acute and subacute myocardial infarction: determination of transmurality in comparison to magnetic resonance imaging and histopathology.

OBJECTIVE: The aim of this study was to assess the accuracy of MSCT in characterizing myocardial infarction (MI) and, thereby, determine the extent of early perfusion defect (ED), microvascular obstruction (MO) and transmural depth of late enhancement (LE) in comparison to MRI and histology. MATERIALS AND METHODS: Seven pigs were studied with MSCT (Somatom Sensation 64) and MRI (Magnetom Sonata) a median 1 and 21 days following temporary occlusion of a diagonal branch and creation of small reperfused infarction. For depiction of ED, CT images were acquired in the early arterial phase and following 35 s; LE and MO were evaluated on images obtained at 3, 5, 10 and 15 min. Thereby, a bolus/low-flow contrast injection protocol was used. Triphenyltetrazolium-chloride (TTC) stain and histology were obtained. Volumes of enhancement patterns were assessed as percentage of the ventricle and compared by Bland-Altman analysis. Segmental co-localization and graded transmurality was evaluated with weighted-kappa-test. RESULTS: Close spatial agreement was observed for MRI-MO and MSCT-MO (bias=0.55; CI=-1.49 to 2.60 at 5 min MSCT), TTC and MSCT-LE (bias=-1.28; CI=-3.76 to 1.19) or MRI-LE and MSCT-LE (bias=-0.79; CI=-4.19 to 2.60). There was good segmental co-localization for MO (weighted kappa=0.93) and high agreement for transmural extent of TTC, MRI-LE and MSCT-LE (weighted kappa=0.84 TTC versus MSCT; 0.86 MRI versus MSCT). Arterial and 35s ED significantly underestimated infarct size and showed poor segmental or transmural agreement (weighted kappa=0.33; 0.44). CONCLUSIONS: MSCT late-scans not only reliably depict size of MO and LE in acute or subacute infarct phases but, moreover, allow for accurate determination of LE transmurality.

Analysis of Variance↗
PubMed2006

Late myocardial enhancement assessed by 64-MSCT in reperfused porcine myocardial infarction: diagnostic accuracy of low-dose CT protocols in comparison with magnetic resonance imaging.

The purpose was to assess the practicability of low-dose CT imaging of late enhancement in acute infarction. Following temporary occlusion of the second diagonal branch, seven pigs were studied by multislice computed tomography (MSCT) and magnetic resonance imaging (MRI). Thus, 64-slice CT was performed at 3, 5, 10 and 15 min following the injection of contrast medium according to a bolus/low-flow protocol. Standard parameters of 120 kV and 800 mAs were compared with 80 kV and 400 mAs in various combinations. Infarct volumes were assessed as percentage of the ventricle for both MSCT and MR images. CT density values for viable and infarcted myocardium were obtained and image quality assessed. Mean infarct volume as measured by MRI was 12.33+/-7.06%. MSCT achieved best correlation of volumes at 5 and 10 min. Whilst lowering of tube current resulted in poor correlation, tube voltage did not affect accuracy of infarct measurement (r (2)=0.92 or 0.93 at 5 min, 800 mAs and 80 or 120 kV). In terms of image quality, greater image noise with 80 kV was compensated by significantly better contrast enhancement between viable and non-viable myocardium at lower voltage. Myocardial viability can accurately be assessed by MSCT at 80 kV, which ensures higher contrast for late enhancement and yields good correlation with MRI.

Analysis of Variance↗
PubMed2006

[Early systolic notched peripheral Doppler flow pattern as an indicator of functional obstruction of the common iliac artery after iatrogenic aortic dissection: a case report].

We report on a 57-year-old male patient with typical claudication localised in the right thigh, following aortic valve replacement. The ankle brachial index under resting conditions is within normal range on both sides. A conspicuous monomorphic double-humped peripheral Doppler flow pattern with an early systolic notch extending to the baseline can be registered in all the arteries of the right lower limb. The flow patterns of all other peripheral arteries are properly configured and of triphasic morphology. As the underlying cause of the pathologically altered Doppler flow morphology, aortic dissection Type A can be detected, extending from the former cannulation site of the ascending aorta into the right common iliac artery. Its dissection membrane functionally occludes the right common iliac artery in the early systole, the effect being brief and reversible. The pathogenesis of this morphologically altered Doppler flow pattern and potential differential diagnoses are discussed in this case report, also considering the current literature.

Aortic Dissection↗
PubMed2006

Incidental diagnosis of a left ventricular thrombus through novel magnetic resonance imaging technique in a patient undergoing coronary artery bypass grafting.

Stroke after cardiac surgery is a devastating complication. We report a case of incidental diagnosis of a left ventricular thrombus in a patient scheduled to undergo coronary artery bypass grafting. The preoperative diagnosis of an apical left ventricular thrombus was assessed by a novel, whole body MRI-angiography technique (TIMRA), which led to alteration of the operative approach as an additional thrombectomy was performed through an apical left ventriculotomy.

Coronary Artery Bypass↗
PubMed2005

Hypothermia-induced platelet aggregation: no effect of aprotinin (trasylol) but inhibition by eptifibatide (integrilin).

OBJECTIVES: The serine-protease inhibitor aprotinin protects platelet function during cardiopulmonary bypass. However, its safety and efficacy during deep hypothermic circulatory arrest (DHCA) is controversial, and aprotinin is suspected to cause thrombosis especially during hypothermia. The platelet GP IIb/IIIa inhibitor eptifibatide has been assumed to preserve platelet function during cardiopulmonary bypass without increasing bleeding complications. The aim of this study was to compare the effect of aprotinin and eptifibatide on platelet function under conditions of DHCA. METHODS: Heparinized blood from healthy volunteers (n = 10) was incubated in stasis for 30 minutes at 18 degrees C to simulate DHCA and compared to samples incubated at 37 degrees C. The effect of eptifibatide (2.5 microg/ml) and aprotinin (300 KIU/ml) on platelets under these conditions was analyzed by flow cytometry. Platelet aggregates were identified using CD41-antibody binding and size. GPIIb/IIIa function was evaluated with the activation-specific antibody PAC-1 after stimulation with 10 microM ADP. Aggregate numbers and antibody mean-fluorescence are reported as mean +/- standard deviation. RESULTS: Hypothermia induced a 2.5-fold increase of aggregates ( p < 0.001) and a 2.6-fold increase of GPIIb/IIIa activation ( p < 0.001). This effect was not influenced by aprotinin but almost completely inhibited by eptifibatide ( p < 0.001). CONCLUSIONS: Aprotinin has no procoagulatory effect on platelet function during hypothermia but is not protective either. Eptifibatide inhibits hypothermia-induced platelet aggregation in vitro and may prevent aggregate sequestration in the microvasculature and consecutive ischemic organ damage in vivo.

Aprotinin↗
PubMed2005

[MR angiography and determination of the flow reserve after minimal invasive direct coronary artery bypass (MIDCAB) surgery of the left internal mammary artery in comparison to multirow CT].

PURPOSE: To evaluate graft patency, flow and flow reserve in patients with minimal invasive direct coronary artery bypass (MIDCAB) of internal mammary artery (IMA) grafts using a combined MR protocol with phase-contrast technique and MR angiography. MATERIAL AND METHODS: At a 1.5T Magnetom Sonata (SIEMENS), 19 symptomatic (angina CCS I-III, intermittent thoracic discomfort, scar disorders) patients (59.9 +/- 7.9 years old) with 19 left internal mammary artery (LIMA) grafts implanted in minimal invasive technique were examined 6.9 +/- 1.5 years post surgery. Contrast enhanced MR angiography (TR 2.5 ms, TE 1 ms, flip angle 20 (o), spatial resolution 1.4 x 0.9 x 1.0 mm(3), breath hold technique, no ECG-triggering, 25 ml Gd-DTPA) was performed to assess bypass patency. Phase-contrast flow measurements with retrospective gating (TR 41 msec, TE 3.2 msec, flip angle 30 degrees , spatial resolution 1.1 x 1.1 x 5 mm(3), temporal resolution 42 msec, venc 90 cm/sec) were applied in the IMA grafts at rest and after stress induction with dipyridamole (0.56 mg/kg/BW). For comparison, graft patency was evaluated by multidetector-row computed tomography (16-row CT). In 9 patients a selective catheter angiography was performed. RESULTS: MIDCAB grafts were occluded in 4/19 patients. In 4 patients the anastomosis to LAD was highly stenotic (> 70 %) at MDCT (2 experienced investigators in consensus reading). In MRA 9 grafts could be delineated completely including the distal anastomosis to LAD (47 %). In 9 patients the distal part could not be evaluated. In patients with patent grafts (MDCT), a significant improvement of graft flow (at rest 75.4 +/- 33.3 ml/min; after stress 202.7 +/- 49.6; P < 0.002) and flow reserve (patent grafts 3.0 +/- 1.1; stenotic grafts 1.5 +/- 0.2, P < 0.02; occluded grafts 0.9 +/- 0.2, P < 0.01) after stress induction was detected. Diastolic-to-systolic peak velocity ratios (D/S-PVR) at baseline were not significant between patent and stenotic grafts. Mean flow at baseline and after stress induction and flow reserve show a high sensitivity (91/92 /83 %) and specificity (86 /100/83 %) for detection of graft stenosis. MR angiography combined with flow reserve measurements could distinguish between occluded/stenotic and patent grafts in all MIDCAB grafts. CONCLUSION: MR imaging allows combined assessment of bypass patency and flow with flow reserve in patients after MIDCAB. The protocol of this study is applicable for the evaluation of graft patency in patients after revascularization.

Blood Flow Velocity↗
PubMed2005

Aortic root remodeling: functional MRI as an accurate tool for complete follow-up.

BACKGROUND: After aortic valve-sparing procedures patients should be evaluated regularly because of the risk for further disease progression in the remaining aorta as well as recurrent aortic insufficiency. The purpose of this study was to evaluate the potential of functional MRI as a single examination for complete follow-up of these patients. METHODS: Twenty-two patients with a mean age of 54 years (range 30 - 66) were prospectively examined at 1, 12, 24, 36, and 74 months postoperatively, following a Yacoub aortic root remodeling operation, using a 1.5 T MRI. The original disease was chronic aneurysm of the ascending aorta or root in 17, chronic dissection in 3, and acute dissection in 2 patients. Transverse graft diameters, regurgitant fraction, LVEDV, and cardiac index were measured using cine MRI. Results were compared to spiral computed tomography and transthoracic color Doppler echocardiography. Mean time of follow-up was 24.9 months and ranged from 1 to 74 months. RESULTS: There were 2 re-operations, 2 years after primary surgery, due to high aortic insufficiency. CT and MRI measurements of graft diameters correlated well (p = 0.4544). Mean graft diameter (mean +/- SD) was 30 +/- 3.7, 33 +/- 3.4, 36.5 +/- 1.5, 37 +/- 2.8, and 38.3 +/- 2.8 mm at 1, 12, 24, 36, and 74 months, respectively, indicating a significant increase of graft diameter (p < 0.0001). Mean regurgitant fraction as determined by MRI was 14 +/- 7, 12 +/- 9, 13 +/- 9, 15 +/- 7, and 14 +/- 9 % at 1, 12, 24, 36, and 74 months, respectively. Flow based grading of aortic insufficiency by MR imaging correlated well with color Doppler echocardiography (p < 0.0001). CONCLUSIONS: MRI provides an excellent, noninvasive, comprehensive tool for follow-up after valve-sparing aortic root reconstruction. The determination of regurgitant fraction, ventricular dimensions and functions, and graft diameters allows standardized imaging protocols with a high reproducibility, which may lead to this technique being favored for the follow-up of patients after aortic root remodeling.

Adult↗
PubMed2005

Perioperative monitoring of flow and patency in native and grafted internal mammary arteries using a combined MR protocol.

The objective of this study was to evaluate graft flow (f) and patency (p) in patients with internal mammary artery (f,p) and venous (p only) grafts using a combined MR protocol with phase-contrast technique and MR angiography. 42 patients with 42 left internal mammary artery (LIMA) and 63 venous grafts were examined pre and 6 months post coronary artery bypass graft (CABG) surgery. Phase-contrast flow measurements were applied to the IMA. Post-operatively, a contrast enhanced MR angiogram was performed to assess bypass patency. LIMA/venous grafts were occluded in 3/42 and 13/63, respectively. Flow in LIMA decreased from 19.4+/-10.4 ml min(-1) m(-2) pre-operatively to 13.4+/-9.7 ml min(-1) m(-2) post-operatively (p<0.002). In contrast, flow in the native right IMA increased from 17.6+/-8.7 ml min(-1) m(-2) pre-operatively to 24.8+/-9.0 ml min(-1) m(-2) post-operatively (p<0.001). MRI allows a combined assessment of bypass patency and flow. This study protocol may be applicable to perioperative follow-up studies in patients after CABG surgery.

Aged↗
PubMed2001

[2D-phase contrast flow evaluation and contrast-enhanced MR angiography for perioperative assessment of internal mammary artery grafts].

PURPOSE: To evaluate LV functional parameters, graft flow and patency in patients with IMA grafts using a combined MR protocol with phase-contrast technique and contrast enhanced MR angiography. MATERIAL AND METHODS: Using a 1.5 T MR system 27 patients with 27 left internal mammary artery (LIMA) and 41 venous grafts were examined before and 6 months after CABG surgery. A T(1)w-TSE sequence (slice thickness 5 mm) was applied for morphological imaging. LV function (EF, CO) was evaluated on cine images (segmented FLASH 2D, TR(eff) 11 ms, TE 4.8 ms, flip angle 25 degrees ). A phase-contrast FLASH 2D (TR 24 ms, TE 5 ms, flip angle 20 degrees ) sequence was applied for aortic and IMA flow measurements. Postoperatively, a contrast enhanced FLASH 3D MR angiography (TR 3.8 ms, TE 1.4 ms, flip angle 30 degrees ) with 25 ml Gd-DTPA was performed to assess bypass patency. RESULTS: In patients with reduced LV function (ejection fraction < 50 %) an improvement of the ejection fraction from 38.4 +/- 10.3 % to 49.8 +/- 15.3 % (p < 0.05) was found postoperatively. LIMA grafts were occluded in 1/27 patients, while 6/41 venous grafts were occluded. Distal LIMA anastomoses were demonstrated in 33 % by MRA. Flow of LIMA decreased from 21.2 +/- 11 ml/min/m(2) preoperatively to 14.4 +/- 9.6 ml/min/m(2) postoperatively (p < 0.01). CONCLUSION: MR imaging allows accurate combined assessment of LV function, bypass patency and flow. The protocol of this study may be applicable for perioperative follow-up studies in patients after CABG surgery.

Aged↗
PubMed2001

Long-term results after early primary repair of tetralogy of Fallot.

OBJECTIVE: Early primary repair of tetralogy of Fallot has been routinely performed at Children's Hospital, Boston, since 1972. We evaluated the long-term outcome of this treatment strategy including the influence of a transannular patch. METHODS: Fifty-seven patients less than 24 months of age (median 8 months) underwent primary repair of tetralogy of Fallot between January 1972 and December 1977. Thirty-one patients had a transannular patch. Survival and freedom from reintervention were determined by the Kaplan-Meier method with 95% confidence intervals. RESULTS: There were 8 early deaths, and 1 patient died 24 years after initial repair. Recent follow-up was obtained for 45 of the 49 long-term survivors (92%). Median follow-up was 23.5 years. Ten patients underwent reintervention, 8 of whom underwent relief of right ventricular outflow tract obstruction. Right ventricular outflow tract obstruction occurred in 6 patients without a transannular patch and 2 with a transannular patch (33% vs 6%, P =.04). One pulmonary valve replacement was performed at another institution 20 years after the repair. Forty-one long-term survivors were in New York Heart Association class I and 4 were in class II. Actuarial survival was 86% at 20 years (95% confidence intervals = 80%-92%). Freedom from reintervention was 93% at 5 years (95% confidence intervals = 87%-99%) and 79% at 20 years (95% confidence intervals = 70%-86%). No significant differences were found between patients with and without a transannular patch (survival, P =.34; freedom from reintervention, P =.09, log-rank tests). CONCLUSIONS: Long-term survival is excellent and the freedom from reintervention is satisfactory after early primary repair of tetralogy of Fallot in the 1970s. Use of a transannular patch does not reduce late survival and is associated with a lower incidence of right ventricular outflow tract obstruction.

Exercise Tolerance↗
PubMed2001

MRI diagnosis of a previously undiagnosed large trabecular ventricular septal defect in an adult after multiple catheterizations and angiocardiograms.

Ventricular septal defect (VSD) is the most frequent congenital heart disease (25-30%). The diagnosis of VSD is usually made echocardiographically by means of colour Doppler ultrasound, and is confirmed by angiocardiography in most cases. We describe a case in which an additional large trabecular VSD was demonstrated by MRI after previous cardiac catheterizations and angiocardiography in various hospitals. MRI allows an exact presentation of the anatomy, including areas that are difficult to assess, for instance the apical septum. Determination of cardiac output, regurgitation volume and the Qp/Qs quotient in patients with shunt volume in heart defects is also possible with one examination.

Adult↗
PubMed2001

Management of transposition of the great arteries with single coronary artery.

Approximately 5% of patients with transposition of the great arteries have a single coronary artery. In the early years of the arterial switch procedure a single coronary artery was associated with an increased risk of mortality. This was particularly true for the most common type of single coronary artery in which there is a right posterior ostium giving rise to a right coronary artery that passes to the right atrioventricular groove and a left coronary artery that passes posterior to the pulmonary artery. An understanding of the mechanisms by which this coronary pattern increases the risk of mortality has led to neutralization of this risk factor. The risk of late reintervention after an arterial switch with single coronary artery is increased with a single left posterior ostium with the right coronary passing anterior to the aorta. The mechanism remains unclear.

Coronary Vessels↗
PubMed2000

Conventional high resolution versus fast T(2)-weighted MR imaging of the heart: assessment of reperfusion induced myocardial injury in an animal model.

Cardiac image quality in terms of spatial resolution and signal contrast was assessed for conventional and newly developed T(2)-weighted fast spin-echo imaging with high k-space segmentation. The capability in revealing regional myocardial edema and cellular damage was examined by a porcine model using histopathologic correlation. Twelve porcine hearts were excised from slaughtered animals and instantly perfused with 1000 mL cold cardioplegic solution. After 4 h of cold ischemia the hearts were reperfused for one hour using a "Langendorff" perfusion model followed by MR imaging at 1.5 Tesla. Three additional pig hearts served as controls and were studied by MR directly after harvesting. Histopathological analysis of regional tissue changes was performed macro- and microscopically. Short axis T(2)-weighted (3000/45 and 90) high quality fast spin-echo (FSE) images were recorded without cardiac action and signal intensity was correlated with histology. These images also served as gold standard for evaluation of newly developed faster sequences allowing measuring times shorter than 20 s. Fast T(2)-weighted imaging comprised single-slice fast spin echo (moderate echo train length of 23 echoes, FSE(m)), and multi-slice single-shot half-Fourier fast spin-echo (71 echoes, FSE(HASTE)) sequences, supplemented by versions with inversion recovery preparation (FSE(m)IR and FSE(HASTE)IR). Systolic function after reperfusion was restored in 10 porcine hearts. Tissue alterations included myocardial edema and contraction band necrosis which was found to be most severe in myocardium with maximum T(2) SI. Especially FSE(m) and FSE(m)IR sequences allowed differentiation of all categories of tissue damage on a high level of significance. In contrast, single-shot FSE(HASTE) and FSE(HASTE)IR sequences did not provide sufficient image quality to discriminate moderate and severe myocardial damage (p > 0.05). Different degrees of myocardial injury after ischemia and reperfusion can be staged by MR imaging, especially using conventional high resolution T(2)-weighted FSE sequences. The animal study indicates that fast T(2)-weighted FSE(m) and FSE(m)IR sequences lead to superior image quality and diagnostic accuracy compared to FSE(HASTE) and FSE(HASTE)IR imaging.

Analysis of Variance↗
PubMed2000

An immediate, allergic skin reaction to aprotinin after reexposure to fibrin sealant.

BACKGROUND: The safety of fibrin tissue adhesives has been a concern since they entered wide clinical application. Most commercially available kits contain the proteolytic inhibitor, aprotinin, to stabilize the fibrin clot. A bovine protein, this substance has an allergenic potency. CASE REPORT: This case report presents a patient who had a generalized allergic skin reaction, probably triggered by aprotinin upon reexposure to fibrin sealant injected subgaleally to achieve closure of a liquor fistula after neurosurgical treatment. The serologic investigation revealed aprotinin-specific IgE and IgG. From 1990 through 1998, reports of five allergic reactions following 1 million exposures to fibrin sealant were made to the manufacturer. The clinical relevance of allergic reactions to aprotinin contained in fibrin sealants and measures to avoid them are discussed. CONCLUSION: These hypersensitivity reactions are extremely rare (incidence, 0.5/100,000 for all reactions and 0.3/100,000 for serious reactions), but they must be kept in mind as possible adverse events after repeated applications of fibrin sealants within a few weeks.

Antibodies, Anti-Idiotypic↗
PubMed2000

[The MR signal behavior of a 4-week-old occlusive myocardial infarct in an animal experiment].

PURPOSE: To correlate signal behaviour in T1- and T2-weighted images after Gd-DTPA with regional histopathology in occlusive myocardial infarction (MI). METHODS: Ligation of a diagonal branch of the LAD was performed in seven sheep. Four weeks later 0.1 mmol Gd-DTPA/kg were injected in five sheep 15 min before cardiac arrest and the sheep were slaughtered. In vitro imaging was performed at 1.5 T included T1- and T2-weighted spin echo sequences in long and short axis views. Signal intensities (SI) were determined in 36 myocardial segments per slice and compared to macro- and microscopy. RESULTS: In all animals an antero-lateral infarct region was evident histologically. This region presented with increased T2 SI and T1 SI after Gd-DTPA. The number of segments with increased SI in T1-weighted images was higher (n = 195 segments) compared to segments with increased T2 SI (n = 122 segments). Granulation tissue could be differentiated from rarely vascularized connective tissue at a high level of significance (p < 0.001) by T1 and T2 SI analysis. Wall thickness was significantly decreased in necrotic myocardium (3.8 +/- 1.2 mm) compared to normal tissue (9.8 +/- 1.1 mm, p < 0.001). CONCLUSION: In four-week-old occlusive MI the extent of necrosis can be accurately assessed by analysis of post contrast T1-weighted images. Considering regional T2 SI, granulation tissue can be differentiated from regions with predominant fibrous organisation.

Animals↗
PubMed2000

The significance of preformed aprotinin-specific antibodies in cardiosurgical patients.

UNLABELLED: Acute hypersensitivity reactions are serious complications of reexposure to aprotinin. Previous contact via infusions or fibrin tissue adhesives can induce specific antibodies. In this study, we aimed to elucidate the preoperative prevalence of aprotinin-specific antibodies in patients scheduled for cardiac operations. Sera of 520 consecutive cardiosurgical patients were collected preoperatively and screened retrospectively for aprotinin-specific IgG using a standard enzyme-linked immunosorbent assay (ELISA). Positive sera were analyzed also for aprotinin-specific IgA (ELISA) and IgE (fluorescence enzyme immunoassay). The histories of all patients were reviewed with focus on aprotinin preexposure. Of 520 patients, 22 (4%) had specific IgG. Only three of these had a documented aprotinin preexposure. Of 448 patients exposed to aprotinin intraoperatively, 15 had preformed specific antibodies. The only patient presenting with severe anaphylaxis was positive for both IgG and IgE, and had a recent IV preexposure in cardiovascular surgery. The presence of aprotinin-specific IgG alone seems not to induce adverse reactions on exposure. Exposure history alone is not sensitive enough to identify patients with aprotinin-specific antibodies. IMPLICATIONS: Anaphylaxis on IV reexposure to aprotinin is a medical emergency. The clinical significance of preformed aprotinin-specific IgG remains questionable, whereas preformed IgE was present in the only patient who suffered from severe anaphylaxis on reexposure to aprotinin. Preformed antibodies are not reliably predicted by exposure history.

Aged↗