Development of In-Hospital Outcomes in Patients undergoing Transcatheter Aortic Valve Implantation (TAVI) at an Interdisciplinary Heart Center: A Single-Center Experience of 489 Consecutive Cases

Background

Transcatheter Aortic Valve Implantation (TAVI) has emerged over time, reflected in appropriate adjustments in the European Society of Cardiology (ESC) guidelines in 2007, 2012 and 2017.

Objective

The aim of this study was to analyze in-hospital outcomes after TAVI in the development within a single heart center over a period of 10 years depending on adjustments in the guidelines, infrastructural and procedural determinants.

Methods

489 consecutive patients who underwent TAVI from 2010 and 2019 at our center were analyzed retrospectively. Patients were divided into 3 groups of different treatment circumstances depending on guidelines adjustments and local infrastructural progress (group 1: 2010-2015 (n = 132), group 2: 2016-2017 (n = 155), group 3: 2018-2019 (n = 202). The primary endpoint was defined as all-cause in-hospital mortality. Secondary endpoints were selected according to the Valve Academic Research Consortium (VARC)-2 definitions. Multivariate logistic regression analysis was performed to determine predictors of in-hospital mortality. Statistical significance was assumed for p < 0.05.

Results

489 patients (346 (70.8 %) transfemoral and 143 (29.2 %) transapical) underwent TAVI. Comparing periods (group 1 vs. 2 vs. 3) age (82.1 ± 6.2 vs. 82.5 ± 4.8 vs. 81.1 ± 5.1 years, p = 0.012) and EuroSCORE II (8.4 ± 6.0 vs. 5.8 ± 4.9 vs. 5.5 ± 5.0 %, p < 0.001) declined over time. Rates of in-hospital mortality decreased significantly (9.1 % vs. 5.8 % vs. 2.5 %, p = 0.029), especially with observed-to-expected mortality ratios indicating a disproportionate decline of in-hospital mortality (1.08 vs. 1.00 vs. 0.45). Furthermore, post-procedural complications, such as acute kidney injury stage 3 (10.6 % vs. 3.2 % vs. 4.5 %, p = 0.016) and bleeding complications (14.4 % vs. 11.6 % vs 7.9 %, p = 0.165) decreased from group 1 to 3. However, rates of permanent pacemaker implantations (7.6 % vs. 11.0 % vs. 22.8 %, p < 0.001) increased, associated with a switch towards self-expanding valves (0.0 % vs. 61.3 % vs. 76.7 %, p < 0.001). Length of hospitalization as well as stay at intensive care and intermediate care unit could be reduced significantly during the observation period. In multivariate analysis age (OR: 1.103; 95 % CI: 1.013 - 1.202; p = 0.025), creatinine level before TAVI (OR: 1.497; 95 % CI: 1.013 - 2.212; p = 0.043), atrial fibrillation (OR: 2.956; 95 % CI: 1.127 - 7.749; p = 0.028) and procedure duration (OR: 1.017; 95 % CI: 1.009 - 1.025; p < 0.001) could be identified as independent predictors of in-hospital mortality.

Conclusion

This study identified age, creatinine level before TAVI, the presence of atrial fibrillation and procedure duration as independent predictors for in-hospital mortality. Although these predictors decreased during the observation period, the decline in hospital-mortality was disproportionate, which was indicated by an observed-to-expected mortality ratio of 0.45 for the last observation period. However, it can be assumed that apart from patient-related factors, there were further institutional, technical and procedural developments, which ran in parallel and affected in-hospital mortality rates after TAVI.

Gerinnungsmanagement nach Transkatheter-Aortenklappenimplantation (TAVI)

In dieser Übersicht stellen wir die aktuelle Literatur zum Gerinnungsmanagement nach TAVI zusammen. Aus den publizierten Studien ergibt sich für die klinische Praxis, dass direkte orale Antikoagulanzien den Vitamin-K-Antagonisten nicht unterlegen sind, wenn aus anderen Gründen (z. B. Vorhofflimmern) eine Antikoagulation nach TAVI erforderlich ist. Die zusätzliche Gabe eines Thrombozytenaggregationshemmers bringt in dieser Konstellation keinen Vorteil. Bei Patienten, die keine Indikation für eine orale Antikoagulation haben, hat sich in vielen Zentren die duale Thrombozytenaggregationshemmung mit ASS und Clopidogrel für 3–6 Monate als Standard etabliert. Die randomisierte POPular TAVI-Studie hat allerdings gezeigt, dass die alleinige ASS-Gabe nach TAVI Blutungskomplikationen reduziert, bei gleicher Sicherheit in der Verhinderung thrombotischer Komplikationen.

P–195 The influence of hormones and initial cell number on the size of self-assembled embryo-like structures

Study question

Do hormonal treatments and initial cell number influence the formation of embryo-like structures (ELS) during their development in regard to size?

Summary answer

The chosen initial cell number for ELS-assembly seems to influence the ELS size only until day 4, while hormones affect embryo size throughout their development.

What is known already

The initial cell number is an important parameter for the development of ELS, which might help to better understand how embryos regulate their size. Previous studies on differently sized natural murine embryos revealed that an initial difference in size at the early stage is compensated until E6.75. Normal-size embryos experience an increased mitotic activity before E6.75, whereas larger sized embryos show an increased apoptotic activity, indicating an important control point of cell turnover by adapting mitotic activity and cell survival. Embryo development is strongly dependent on appropriate β-estradiol and progesterone levels.

Study design, size, duration

The first set of experiments interrogated the influence of initial cell number (two conditions) on the size of formed ELS during the first 3 days (D1–3). The second set included two different hormonal treatments and the two conditions of initial cell number (the same as in the first experiments) generating four different groups. For each day one Aggrewell (generating 1200 ELS/well) per condition was harvested. Experiments were repeated at least three times.

Participants/materials, setting, methods

ELS are generated by self-assembly in microwell-chamber plates combining embryonic stem cells, trophoblast stem cells and extraembryonic endoderm stem cells. Cells were cultured with and without addition of β-estradiol and progesterone, starting with different initial cell numbers (106 vs. 42 cells/ELS). ELS were harvested, stained, and at least 40 randomly picked ELS per condition were measured and statistically analyzed with Two-way ANOVA and Tukey’s multiple comparison test. Results show the average area ± SD.

Main results and the role of chance

The results show a continuous increase in the size of ELS during the first three days of cultivation, with significant lower values (on D1-D3) when ELS were assembled from 42 initial cells (D1: 224.1±87.7 μm²; D3: 674.0± 84.4 μm²) compared to ELS formed with 106 initial cells (D1: 467.1±224.1 μm²; D3: 1275.0±348.0 μm²). Onward on the course of self-assembly, ELS with 42 initial cells were still smaller on D4 (1465.7±657.6 μm²) compared to ELS formed with 106 initial cells (2028.6±522.4 μm²). However, these differences could not be measured on D5 (106 initial cells: 1892.2±603.7 μm²; 42 initial cells: 1855±448.5 μm²), D6 (106 initial cells: 2143.3±622.1 μm²; 42 initial cells: 1788.4±585.5 μm²) and D7 (106 initial cells: 2146.7±628.1 μm²; 42 initial cells: 2319.5±778.8 μm²). Differences between the conditions with and without hormonal treatments (HT) could also be detected especially when ELS were generated with 42 cells: on D4 ELS with HT (1730.4±852.4 μm²) were significantly larger than without hormones (1201.2±462.9 μm²). In contrast, on D7 HT influenced the size of ELS distinctly depending on the initial cell number (42 cells: 1989.2±558.3 μm² with HT vs. 2649.7±999.4 μm² without HT; 106 cells: 2334.9±770.2μm² with HT vs. 1958.6±486.1 μm² without HT).

Limitations, reasons for caution

An even cell distribution is crucial for reproducible ELS-formation. Unfortunately, the used techniques for cell seeding led to an uneven distribution within the microwells. Moreover, different orientation of ELS during the size assessment might be an additional reason for the high variance of ELS size within one condition.

Wider implications of the findings: Even if the results seem to be in accordance with the observations made with natural embryos regarding compensation of size until E6.75, additional experiments need to be conducted. Further investigations should be carried out by testing different culture formats to obtain a more even cell distribution during the cultivation.

Trial registration number

Not applicable

Comparative Methodological Assessment of the Randomized GLOBAL LEADERS Trial Using Total Ischemic and Bleeding Events

BACKGROUND

Time-to-first-event analysis considers only the first event irrespective of its severity. There are several methods to assess trial outcomes beyond time-to-first-event analysis, such as analyzing total events and ranking outcomes. In the GLOBAL LEADERS study, time-to-first-event analysis did not show superiority of ticagrelor monotherapy following one-month dual antiplatelet therapy (DAPT) after percutaneous coronary intervention to conventional 12-month DAPT followed by aspirin monotherapy in the reduction of the primary composite end point of all-cause mortality or new Q-wave myocardial infarction. This study sought to explore various analytical approaches in assessing total ischemic and bleeding events after percutaneous coronary intervention in the GLOBAL LEADERS study.

METHODS AND RESULTS

Total ischemic and bleeding events were defined as all-cause mortality, any stroke, any myocardial infarction, any revascularization, or Bleeding Academic Research Consortium grade 2 or 3 bleeding. We used various analytical approaches to analyze the benefit of ticagrelor monotherapy over conventional DAPT. For ischemic and bleeding events at 2 years after percutaneous coronary intervention, ticagrelor monotherapy demonstrated a 6% risk reduction, compared with conventional 12-month DAPT in time-to-first-event analysis (hazard ratio, 0.94 [95% CI, 0.88-1.01]; log-rank P=0.10). In win ratio analysis, win ratio was 1.05 (95% CI, 0.97-1.13; P=0.20). Negative binomial regression and Andersen-Gill analyses which include repeated events showed statistically significant advantage for ticagrelor monotherapy (rate ratio, 0.92 [95% CI, 0.85-0.99; P=0.020] and hazard ratio, 0.92 [95% CI, 0.85-0.99; P=0.028], respectively), although in weighted composite end point analysis, the hazard ratio was 0.93 (95% CI, 0.84-1.04; log-rank P=0.22).

CONCLUSIONS

Statistical analyses considering repeated events or event severity showed that ticagrelor monotherapy consistently reduced ischemic and bleeding events by 5% to 8%, compared with conventional 1-year DAPT. Applying multiple statistical methods could emphasize the multiple facets of a trial and result in accurate and more appropriate analyses. Considering the recurrence of ischemic and bleeding events, ticagrelor monotherapy appeared to be beneficial after percutaneous coronary intervention. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT01813435.

Quantitative and qualitative assessment of left ventricular volume with ECG-gated multislice spiral CT: value of different image reconstruction algorithms in comparison to MRI

Purpose: To assess the value of different image reconstruction algorithms for assessment of the left ventricular function using retrospectively ECG-gated multislice spiral computed tomography (MSCT) of the heart.

Material and Methods: MSCT and cine magnetic resonance (MR) imaging of the heart were performed in 15 patients. For MSCT, standard and multisegmental image reconstruction with improved temporal resolution were used. Standardized multiplanar reformats in the short axis and long axis views were reconstructed from MSCT data. End-systolic (ESV) and end-diastolic volume (EDV), stroke volume (SV), ejection fraction (EF) and myocardial mass (MM) were calculated. Left ventricular wall motion was assessed qualitatively.

Results: MSCT was in acceptable agreement with MR imaging for quantification of the ventricular function. According to the Bland–Altman approach the mean differences for the left ventricular volumes (ESV, EDV, SV) ranged from −9.6 ml to 3.1 ml with standard image reconstruction and from −0.6 ml to 1.9 ml utilizing multisegmental image reconstruction with limits of agreement ranging from −26.6 ml to 12.5 ml and −15.6 ml to 15.0 ml, respectively. Applying the multisegmental image reconstruction algorithm, a significantly improved agreement with the MR data was found for EDV, SV and EF. For wall motion analysis, standard image reconstruction showed a significant difference to MR imaging with a correspondence in 83.75% of the 240 assessed segments, while multisegmental image reconstruction agreed with MR imaging in 92.5% of the segments.

Conclusion: Multisegmental image reconstruction improves the quantitative assessment of left ventricular function when compared to standard image reconstruction. Multisegmental image reconstruction allows qualitative wall motion analysis.

ULTRASOUND SPECTROSCOPY

We introduce the concept of "Ultrasound Spectroscopy". The premise of ultrasound spectroscopy is that by acquiring ultrasound RF data at multiple power and frequency settings, a rich set of features can be extracted from that RF data and used to characterize the underlying tissues. This is beneficial for a variety of problems, such as accurate tissue classification, application-specific image generation, and numerous other quantitative tasks. These capabilities are particularly relevant to point-of-care ultrasound (POCUS) applications, where operator experience with ultrasound may be limited. Instead of displaying B-mode images, a POCUS application using ultrasound spectroscopy can, for example, automatically detect internal abdominal bleeding. In this paper, we present ex vivo tissue phantom studies to demonstrate the accuracy of ultrasound spectroscopy over previous approaches. Our studies suggest that ultrasound spectroscopy provides exceptional accuracy and informative features for classifying blood versus other tissues across image locations and body habitus.

Pretreatment with prasugrel in non-ST-segment elevation acute coronary syndromes

BACKGROUND

Although P2Y12 antagonists are effective in patients with non-ST-segment elevation (NSTE) acute coronary syndromes, the effect of the timing of administration--before or after coronary angiography--is not known. We evaluated the effect of administering the P2Y12 antagonist prasugrel at the time of diagnosis versus administering it after the coronary angiography if percutaneous coronary intervention (PCI) was indicated.

METHODS

We enrolled 4033 patients with NSTE acute coronary syndromes and a positive troponin level who were scheduled to undergo coronary angiography within 2 to 48 hours after randomization. Patients were randomly assigned to receive prasugrel (a 30-mg loading dose) before the angiography (pretreatment group) or placebo (control group). When PCI was indicated, an additional 30 mg of prasugrel was given in the pretreatment group at the time of PCI and 60 mg of prasugrel was given in the control group.

RESULTS

The rate of the primary efficacy end point, a composite of death from cardiovascular causes, myocardial infarction, stroke, urgent revascularization, or glycoprotein IIb/IIIa inhibitor rescue therapy (glycoprotein IIb/IIIa bailout) through day 7, did not differ significantly between the two groups (hazard ratio with pretreatment, 1.02; 95% confidence interval [CI], 0.84 to 1.25; P=0.81). The rate of the key safety end point of all Thrombolysis in Myocardial Infarction (TIMI) major bleeding episodes, whether related or not related to coronary-artery bypass grafting (CABG), through day 7 was increased with pretreatment (hazard ratio, 1.90; 95% CI, 1.19 to 3.02; P=0.006). The rates of TIMI major bleeding and life-threatening bleeding not related to CABG were increased by a factor of 3 and 6, respectively. Pretreatment did not reduce the rate of the primary outcome among patients undergoing PCI (69% of the patients) but increased the rate of TIMI major bleeding at 7 days. All the results were confirmed at 30 days and in prespecified subgroups.

CONCLUSIONS

Among patients with NSTE acute coronary syndromes who were scheduled to undergo catheterization, pretreatment with prasugrel did not reduce the rate of major ischemic events up to 30 days but increased the rate of major bleeding complications. (Funded by Daiichi Sankyo and Eli Lilly; ACCOAST ClinicalTrials.gov number, NCT01015287.).

Elevated TNFalpha production in whole blood in patients with severe COPD: the potential link to disease severity

OBJECTIVE

The relationship between tumour necrosis factor-alpha (TNFalpha), severity of pulmonary disease and nutritional depletion in chronic obstructive pulmonary disease (COPD) remains unclear. We aimed to clarify the role of lipopolysaccharide (LPS) as a potential stimulus of cytokine production and the role of these cytokines in the alteration of body composition in patients with different degrees of COPD.

PATIENTS AND METHODS

We studied 29 weight-stable out-patients with different severites of COPD who had no evidence of recent infection or significant co-morbidity. Baseline serum TNFalpha levels and TNFalpha response to LPS in whole blood were measured in patients and 20 aged matched controls.

RESULTS

Serum TNFalpha was significantly elevated in patients versus controls (2.1 +/- 0.3 vs. 1.1 +/- 0.1 pg/ml, mean +/- SEM, P = 0.007). In patients with COPD, we found a significant correlation between serum TNFalpha levels and disease severity, assessed as FEV(1) %predicted (r = 0.49, P = 0.02). Response to lipopolysaccharide did not differ significantly between patients and controls. However, within the patient group those with more severe disease (FEV(1) < or = 30% predicted, n = 12) had an enhanced response compared to patients with mild-to-moderate disease (all P < 0.05 for LPS > 1 ng/ml). Spontaneous TNFalpha production was 5.0 times higher in patients with severe COPD compared to mild-to-moderate COPD (P = 0.02). There was no relation between body composition and serum TNFalpha or TNFalpha response to LPS.

CONCLUSION

Increasing airflow obstruction and hypercapnia are associated with an enhanced TNFalpha response in COPD.

Abnormal striatal and thalamic dopamine neurotransmission: Genotype-related features of dystonia

OBJECTIVE

To determine whether changes in D(2) receptor availability are present in carriers of genetic mutations for primary dystonia.

METHODS

Manifesting and nonmanifesting carriers of the DYT1 and DYT6 dystonia mutations were scanned with [(11)C] raclopride (RAC) and PET. Measures of D(2) receptor availability in the caudate nucleus and putamen were determined using an automated region-of-interest approach. Values from mutation carriers and healthy controls were compared using analysis of variance to assess the effects of genotype and phenotype. Additionally, voxel-based whole brain searches were conducted to detect group differences in extrastriatal regions.

RESULTS

Significant reductions in caudate and putamen D(2) receptor availability were evident in both groups of mutation carriers relative to healthy controls (p < 0.001). The changes were greater in DYT6 relative to DYT1 carriers (-38.0 +/- 3.0% vs -15.0 +/- 3.0%, p < 0.001). By contrast, there was no significant difference between manifesting and nonmanifesting carriers of either genotype. Voxel-based analysis confirmed these findings and additionally revealed reduced RAC binding in the ventrolateral thalamus of both groups of mutation carriers. As in the striatum, the thalamic binding reductions were more pronounced in DYT6 carriers and were not influenced by the presence of clinical manifestations.

CONCLUSIONS

Reduced D(2) receptor availability in carriers of dystonia genes is compatible with dysfunction or loss of D(2)-bearing neurons, increased synaptic dopamine levels, or both. These changes, which may be present to different degrees in the DYT1 and DYT6 genotypes, are likely to represent susceptibility factors for the development of clinical manifestations in mutation carriers.

Inflammatory pathways in patients with heart failure and preserved ejection fraction

Immune activation is well established in patients with chronic heart failure and reduced ejection fraction (HF and reduced EF) and is associated with an impaired prognosis. Patients with heart failure and preserved ejection fraction (HF and preserved EF) have an impaired prognosis as well. It is not known whether they have signs of immune activation.

METHODS

We studied patients with HF and preserved EF (n=17, NYHA II [n=7]/III [n=10]) and patients with HF and reduced EF (n=17 NYHA II [n=1]/III [n=16]) and 20 controls. Echocardiography demonstrated preserved ejection fraction (LVEF 59+/-9%), but LV hypertrophy in patients with preserved EF as compared with patients with reduced EF (LVEF 23+/-5%). We evaluated levels of TNFalpha, its receptors (sTNFR-1 and 2), IL-6, IL-10 and NT-proBNP.

RESULTS

TNFalpha, was highest in HF with reduced EF (2.87+/-0.65 vs 1.67+/-0.58 pg/mL, p<0.001) compared to preserved EF and similar between HF with preserved EF and controls. However, sTNFR1 (1618+/-384 vs 1017+/-302 pg/mL, p<0.001) and sTNFR2 levels (3554+/-916 vs 2041+/-586 pg/mL, p<0.001) in HF with preserved EF were significantly higher compared with controls. The same was true for IL-6, IL-10 and NT-proBNP. The highest cytokine and NT-proBNP levels were present in HF with reduced EF. There was a negative correlation between TNFalpha, and LVEF (r=- 0.700; p<0.0001) and positive correlations between sTNFR1 and 2 with NT-proBNP.

CONCLUSION

Patients with HF and preserved EF already show signs of systemic-immune activation which may contribute to the impaired prognosis and the progression to HF with reduced EF.

QUANTITATIVE EXAMINATION OF A NOVEL CLUSTERING METHOD USING MAGNETIC RESONANCE DIFFUSION TENSOR TRACTOGRAPHY

Introduction: MR diffusion tensor imaging (DTI) is the most powerful and currentlythe only way to visualize the organization of white matter fiber tracts in vivo. As this is a relatively newimaging technique, new tools are developed for quantifying fiber tracts, andrequire evaluation. We examined scalar indices of the diffusion tensor with two different tractography methods. We compared a novel clustering approach with a multiple region of interest (MROI) approach in a healthy and disease (schizophrenia) population. Methods: DTI images were acquired in 12 participants (n=6 patients withschizophrenia: 58 ± 12 years; n=6 controls: 57 ± 21 years) on a 1.5 Tesla GE system with diffusion gradients applied in 23 non-collinear directions, repeated three times. Tractography andfiber tract creation was performed using 3D Slicer software. Interraterreliability of the clustering approach and its similarity to the MROI methodwere evaluated. Results: The clustering approach was reliable both quantitatively and spatially (k > 0.8 for all tracts). There was high spatial(voxel-based) agreement between the clustering and MROI methods. Fractionalan isotropy and trace values were highly correlated between the clustering and MROI methods (p < 0.001 for all tracts). Discussion: Our clustering method has excellent interrater reliability and thereis a high level of agreement between our clustering method and the MROI method, both quantitatively and spatially. The clustering method is less susceptible touser bias. Moreover, not limited by a priori predictions, our clustering method may be a more robust and efficient way to identify and measure fiber tracts of interest. (colour figure available in PDF version)

STATISTICAL SHAPE ANALYSIS OF BRAIN STRUCTURES USING SPHERICAL WAVELETS

We present a novel method of statistical surface-based morphometry based on the use of non-parametric permutation tests and a spherical wavelet (SWC) shape representation. As an application, we analyze two brain structures, the caudate nucleus and the hippocampus, and compare the results obtained to shape analysis using a sampled point representation. Our results show that the SWC representation indicates new areas of significance preserved under the FDR correction for both the left caudate nucleus and left hippocampus. Additionally, the spherical wavelet representation provides a natural way to interpret the significance results in terms of scale in addition to knowing the spatial location of the regions.

Calcium scoring of aortic valve calcification in aortic valve stenosis with a multislice computed tomography scanner: non-enhanced versus contrast-enhanced studies

PURPOSE

Previous studies have shown a positive correlation between amount of aortic valve calcification (AVC) and degree of aortic valve stenosis (AVS). We have investigated whether calcium scoring of AVC from contrast-enhanced images is reliable.

MATERIAL AND METHODS

Nineteen patients with suspected AVS underwent retrospectively ECG-gated multislice computed tomography (MSCT). Standardized scan protocols were applied prior to (120 KV, 133 mAseff) and after (120 KV, 500 mAseff) the administration of non-ionic contrast material. Image reconstruction was performed at 60% of the RR interval (slice thickness 3 mm, reconstruction increment 2 mm). AVC was quantified using Agatston score and calcium mass. The number of lesions was calculated. All nonenhanced images were scored using thresholds of 130 HU and 350 HU. Contrast-enhanced images were assessed with a threshold of 350 HU exclusively.

RESULTS

Fifteen patients with AVCs were included in the statistical analysis. The mean Agatston score (calcium mass) in non-enhanced images was 2888.4 +/- 2844.4 (694.2 mg +/- 869.3 mg). Altering the threshold from 130 HU to 350 HU led to a 58.2% (30.5%) decrease in the AVC score (P values < 0.001). Contrast-enhanced images showed an increased Agatston score (calcium mass) of 56.2% (33.5%) compared to non-enhanced images (P values <0.05) with the same threshold of 350 HU.

CONCLUSION

Quantification of AVC from contrast-enhanced images is not reliable, as contrast material simulates calcification.

Quantitative and qualitative assessment of left ventricular volume with ECG-gated multislice spiral CT: value of different image reconstruction algorithms in comparison to MRI

PURPOSE

To assess the value of different image reconstruction algorithms for assessment of the left ventricular function using retrospectively ECG-gated multislice spiral computed tomography (MSCT) of the heart.

MATERIAL AND METHODS

MSCT and cine magnetic resonance (MR) imaging of the heart were performed in 15 patients. For MSCT, standard and multisegmental image reconstruction with improved temporal resolution were used. Standardized multiplanar reformats in the short axis and long axis views were reconstructed from MSCT data. End-systolic (ESV) and end-diastolic volume (EDV), stroke volume (SV), ejection fraction (EF) and myocardial mass (MM) were calculated. Left ventricular wall motion was assessed qualitatively.

RESULTS

MSCT was in acceptable agreement with MR imaging for quantification of the ventricular function. According to the Bland-Altman approach the mean differences for the left ventricular volumes (ESV, EDV, SV) ranged from -9.6 ml to 3.1 ml with standard image reconstruction and from -0.6 ml to 1.9 ml utilizing multisegmental image reconstruction with limits of agreement ranging from -26.6 ml to 12.5 ml and -15.6 ml to 15.0 ml, respectively. Applying the multisegmental image reconstruction algorithm, a significantly improved agreement with the MR data was found for EDV, SV and EF. For wall motion analysis, standard image reconstruction showed a significant difference to MR imaging with a correspondence in 83.75% of the 240 assessed segments, while multisegmental image reconstruction agreed with MR imaging in 92.5% of the segments.

CONCLUSION

Multisegmental image reconstruction improves the quantitative assessment of left ventricular function when compared to standard image reconstruction. Multisegmental image reconstruction allows qualitative wall motion analysis.

Bestimmung linksventrikulärer Funktionsparameter mittels EKG-gesteuerter Mehrschicht-Computertomographie im Vergleich mit der invasiven Ventrikulographie

PURPOSE

To evaluate the accuracy of left ventricular function using a multidetector CT (MDCT) with retrospective ECG-gating and to compare the results with conventional ventriculography.

MATERIALS AND METHODS

In 26 patients, retrospectively ECG-gated MDCT of the heart (Volume Zoom, Siemens, Germany) as well as conventional coronary angiography including ventriculography was performed to exclude or follow coronary artery disease. CT examination (120 KV, 400 mAs) was carried out with 4 x 1 mm collimation (500 ms gantry rotation time). For CT angiography, 150 ml of contrast media was injected intravenously at a flow rate of 4 ml/s. All data sets of the functional cardiac parameters were reconstructed in end-systolic and end-diastolic phase. End-systolic volume (ESV), end-diastolic volume (EDV) and ejection fraction (EF) were determined from multiplanar reformations orthogonally through the cardiac short axis and analyzed using special evaluation software (ARGUS, Siemens). The results were compared with ESV, EDV and EF obtained from invasive ventriculography.

RESULTS

In all cases, a sufficient quality of the MDCT images was achieved. EDV (150.1 +/- 16.2 ml MDCT vs. 138.7 +/- 16.9 ml ventriculography; mean difference 11.4 +/- 12.7 ml; r = 0.51) had an acceptable correlation to conventional ventriculography, and ESV (58.1 +/- 14.6 ml vs. 50.2 +/- 13.4 ml; mean difference 7.9 +/- 8.8 ml; r = 0.81) and EF (60.9 +/- 13.6 % vs. 64.9 +/- 12.7 %; mean difference 4.0 +/- 6.2 %; r = 0.79) showed a good correlation. In comparison with invasive ventriculography, MDCT tended to overestimate significantly EDV (p = 0.008) and ESV (p = 0.003) and to underestimate EF (p = 0.001).

CONCLUSION

MDCT of the heart with retrospective ECG-gating enables efficient estimation of left ventricular function, providing important additional information of non-invasive cardiac imaging using MDCT. However, EDV and EVS were significantly overestimated and EF was underestimated in MDCT compared to ventriculography.

[Quantification of cardiac function with multislice spiral CT using retrospective EKG-gating: comparison with MRI]

PURPOSE

To quantify left ventricular function derived from retrospectively ECG-gated multislice spiral CT (MSCT) data sets in comparison to MRI.

MATERIALS AND METHODS

In 16 patients (14 males, 2 females, mean age 56.8 +/- 11.5 years), retrospectively ECG-gated MSCT angiography of the coronary arteries and breath-hold steady state free precession cine MRI were performed. From MSCT data-sets, 20 axial image series were reconstructed every 5 % of the RR interval. Multiplanar images were reformatted in the short axis orientation from axial images. End-systolic and end-diastolic images were selected. From these images end-systolic volume (ESV), end-diastolic volume (EDV) and stroke volume (SV) as well as the ejection fraction (EF) and myocardial mass (MM) were determined using the Simpson's method and compared with MRI. Furthermore, image quality was assessed for both imaging modalities using a four point grading scale.

RESULTS

All parameters were found to have an excellent correlation between MSCT and MRI data (Pearson's correlation coefficient 0.95 - 0.99), without clinically relevant differences between both modalities. On average, the difference between both methods was 0.5 ml for ESV, 0.8 ml for EDV, 1.3 ml for SV, 0.9 % for EF and 2.3 g for MM. Image quality was slightly better for MRI (1.5 +/- 0.65) than for MSCT (1.64 +/- 0.74).

CONCLUSION

Retrospectively ECG-gated MSCT angiography can not only visualize the coronary arteries but also enables precise quantification of the left ventricular function from the same MSCT data set.

Crack characterization using guided circumferential waves

This paper examines the propagation of guided circumferential waves in a hollow isotropic cylinder that contains a crack, with the goal of using these guided waves to both locate and size the crack. The crack is sized using a modified Auld's formula, which relates the crack's length to a reflected energy coefficient. The crack is then located by operating on the backscattered signal with a time-frequency digital signal processing (DSP) technique, and then comparing these results to those obtained if the cylinder is perfect. The guided circumferential waves are generated with a commercial finite element method (FEM) code. One objective of this work is to demonstrate the effectiveness of using sophisticated DSP techniques to describe the effect of scattering on dispersive waves, showing it is possible to characterize cracks systematically and accurately by quantifying this scattering effect. The results show that the need for high frequency signals to detect small cracks is significantly decreased by using these techniques.

Time-frequency representations of Lamb waves

The objective of this study is to establish the effectiveness of four different time-frequency representations (TFRs)--the reassigned spectrogram, the reassigned scalogram, the smoothed Wigner-Ville distribution, and the Hilbert spectrum--by comparing their ability to resolve the dispersion relationships for Lamb waves generated and detected with optical techniques. This paper illustrates the utility of using TFRs to quantitatively resolve changes in the frequency content of these nonstationary signals, as a function of time. While each technique has certain strengths and weaknesses, the reassigned spectrogram appears to be the best choice to characterize multimode Lamb waves.

[Diagnosis of lung embolism with multislice spiral CT]

In recent years CT has been established as the method of choice for the diagnosis of central pulmonary embolism to the level of the segmental arteries. The key advantage of CT over competing modalities is the reliable detection of relevant alternative or additional disease causing the patient's symptoms. Although the clinical relevance of isolated peripheral emboli remains unclear, the alleged poor sensitivity of CT for the detection of such small clots has to date prevented the acceptance of CT as the gold standard for diagnosing pulmonary embolism. With the advent of multislice CT we can now cover the entire chest of a patient with 1-mm slices within one breath-hold. In comparison with thicker sections the detection rate of subsegmental emboli can be significantly increased with 1-mm sections. In addition the interobserver correlation which can be achieved with 1-mm sections by far exceeds the reproducibility of competing modalities. Meanwhile use of multislice CT for a combined diagnosis of pulmonary embolism and deep venous thrombosis with the same modality appears to be clinically accepted. In the vast majority of patients who receive a combined thoracic and venous multislice CT examination the scan either confirms the suspected diagnosis or reveals relevant alternative or additional disease. The therapeutic regimen is usually chosen based on the functional effect of embolic vascular occlusion. With the advent of fast CT scanning techniques, also functional parameters of lung perfusion can be non-invasively assessed by CT imaging. These advantages let multislice CT appear as an attractive modality for a non-invasive, fast, accurate and comprehensive diagnosis of pulmonary embolism, its causes, effects and differential diagnoses.

NUDEL is a novel Cdk5 substrate that associates with LIS1 and cytoplasmic dynein

Disruption of one allele of the LIS1 gene causes a severe developmental brain abnormality, type I lissencephaly. In Aspergillus nidulans, the LIS1 homolog, NUDF, and cytoplasmic dynein are genetically linked and regulate nuclear movements during hyphal growth. Recently, we demonstrated that mammalian LIS1 regulates dynein functions. Here we characterize NUDEL, a novel LIS1-interacting protein with sequence homology to gene products also implicated in nuclear distribution in fungi. Like LIS1, NUDEL is robustly expressed in brain, enriched at centrosomes and neuronal growth cones, and interacts with cytoplasmic dynein. Furthermore, NUDEL is a substrate of Cdk5, a kinase known to be critical during neuronal migration. Inhibition of Cdk5 modifies NUDEL distribution in neurons and affects neuritic morphology. Our findings point to cross-talk between two prominent pathways that regulate neuronal migration.

Regulation of cytoplasmic dynein behaviour and microtubule organization by mammalian Lis1

Whereas total loss of Lis1 is lethal, disruption of one allele of the Lis1 gene results in brain abnormalities, indicating that developing neurons are particularly sensitive to a reduction in Lis1 dosage. Here we show that Lis1 is enriched in neurons relative to levels in other cell types, and that Lis1 interacts with the microtubule motor cytoplasmic dynein. Production of more Lis1 in non-neuronal cells increases retrograde movement of cytoplasmic dynein and leads to peripheral accumulation of microtubules. These changes may reflect neuron-like dynein behaviours induced by abundant Lis1. Lis1 deficiency produces the opposite phenotype. Our results indicate that abundance of Lis1 in neurons may stimulate specific dynein functions that function in neuronal migration and axon growth.

Microtubule binding by CRIPT and its potential role in the synaptic clustering of PSD-95

CRIPT is a postsynaptic protein that binds selectively to the third PDZ domain (PDZ3) of PSD-95. Here we show that CRIPT also binds directly to microtubules, thereby linking PSD-95 to the microtubule cytoskeleton. Disrupting the CRIPT-PSD-95 interaction in cultured hippocampal neurons with a PDZ3-specific peptide prevented the association of PSD-95 with microtubules and inhibited the synaptic clustering of PSD-95, chapsyn-110/PSD-93 and GKAP (a PSD-95-binding protein). However, the number of synapses and the synaptic clustering of NMDA receptors were unaffected, suggesting that PSD-95-family proteins are not essential for the maintenance of synapses and the synaptic localization of NMDA receptors.

[Computed tomography of the abdomen with multidetector-array CT]

BACKGROUND

The advent of multidetector CT (MDCT) constitutes a quantum leap creating a wealth of new opportunities in medical imaging. However, while the basic principles of spiral CT still apply, we are now challenged to rethink our strategies in planning a CT study to take full advantage of the increased capabilities of MDCT.

MATERIALS AND METHODS

We report here our preliminary experiences with MDCT for abdominal CT imaging within a 5-month period. During this time, suitable protocols for investigation of the abdomen using MDCT were developed. The capabilities of MDCT allow for tailoring dedicated CT protocols for routine applications as well as for biphasic liver studies and CT angiography of the aorta and abdominal vessels.

RESULTS

The speed of MDCT can either be used to reduce the time needed to cover a given volume, or to use narrower beam collimations to increase the resolution of detail along the z-axis and reduce volume averaging. Higher scan speed allows reduction of the amount of contrast material in vascular applications and suppression of motion artifacts. Higher spatial resolution with thinner collimations reduces volume averaging and improves the detection of small hepatic and pancreatic lesions. Detailed analysis of vascular structures and high-quality three-dimensional reformations become feasible. New problems arise from the large amount of data generated by MDCT.

CONCLUSIONS

MDCT offers a wealth of new opportunities that help us to come to a fast and accurate diagnosis in suspected abdominal disease. Traditional indications for performing CT are reemphasized and new clinical applications can be exploited.

CRIPT, a novel postsynaptic protein that binds to the third PDZ domain of PSD-95/SAP90

The synaptic protein PSD-95/SAP90 binds to and clusters a variety of membrane proteins via its two N-terminal PDZ domains. We report a novel protein, CRIPT, which is highly conserved from mammals to plants and binds selectively to the third PDZ domain (PDZ3) of PSD-95 via its C terminus. While conforming to the consensus PDZ-binding C-terminal sequence (X-S/T-X-V-COOH), residues at the -1 position and upstream of the last four amino acids of CRIPT determine its specificity for PDZ3. In heterologous cells, CRIPT causes a redistribution of PSD-95 to microtubules. In brain, CRIPT colocalizes with PSD-95 in the postsynaptic density and can be coimmunoprecipitated with PSD-95 and tubulin. These findings suggest that CRIPT may regulate PSD-95 interaction with a tubulin-based cytoskeleton in excitatory synapses.

Interaction between the C terminus of NMDA receptor subunits and multiple members of the PSD-95 family of membrane-associated guanylate kinases

Selective concentration and anchoring of ionotropic receptors at the synapse is essential for neuronal signaling. Little is known about the molecules that mediate receptor clustering in the CNS. With use of the yeast two-hybrid system to screen a rat brain cDNA library and by in vitro binding assays, we have identified an interaction between NMDA receptor subunits 2A and 2B (NR2A and NR2B) and three distinct members of the PSD-95/SAP90 family of membrane-associated putative guanylate kinases. The interaction is mediated by binding of the C terminus of the NMDA receptor subunits to the first two PDZ (also known as GLGF or DHR) domains of PSD-95/SAP90, an abundant synaptic protein associated with the membrane cytoskeleton. PSD-95 is also known to bind and cluster Shaker-type voltage-gated K+ channels. Similarities between the C-termini of NR2 subunits and K+ channels suggest a common C-terminal binding motif for PDZ domains. These data suggest that PDZ domains can function as modules for protein-protein interactions. Members of the PSD-95 family might serve to anchor NMDA receptors to the submembrane cytoskeleton and aid in the assembly of signal transduction complexes at postsynaptic sites.

Clustering of Shaker-type K+ channels by interaction with a family of membrane-associated guanylate kinases

ANCHORING of ion channels at specific subcellular sites is critical for neuronal signalling, but the mechanisms underlying channel localization and clustering are largely unknown (reviewed in ref. 1). Voltage-gated K+ channels are concentrated in various neuronal domains, including presynaptic terminals, nodes of Ranvier and dendrites, where they regulate local membrane excitability. Here we present functional and biochemical evidence that cell-surface clustering of Shaker-subfamily K+ channels is mediated by the PSD-95 family of membrane-associated putative guanylate kinases, as a result of direct binding of the carboxy-terminal cytoplasmic tails to the K+ channel subunits to two PDZ (also known as GLGF or DHR) domains in the PSD-95 protein. The ability of PDZ domains to function as independent modules for protein-protein interaction, and their presence in other junction-associated molecules (such as ZO-1 (ref. 3) and syntrophin), suggest that PDZ-domain-containing polypeptides may be widely involved in the organization of proteins at sites of membrane specialization.