Fluid- and Biomechanical Analysis of Ascending Thoracic Aorta Aneurysm with Concomitant Aortic Insufficiency.

We present a comprehensive and original framework for the biomechanical analysis of patients affected by ascending thoracic aorta aneurysm and aortic insufficiency. Our aim is to obtain crucial indications about the role played by deranged hemodynamics on the ATAAs risk of rupture. Computational fluid dynamics analysis was performed using patient-specific geometries and boundary conditions derived from 4D MRI. Blood flow helicity and wall shear stress descriptors were assessed. A bulge inflation test was carried out in vitro on the 4 ATAAs after surgical repair. The healthy volunteers showed no eccentric blood flow, a mean TAWSS of 1.5 ± 0.3 Pa and mean OSI of 0.325 ± 0.025. In 3 aneurismal patients, jet flow impingement on the aortic wall resulted in large TAWSS values and low OSI which were amplified by the AI degree. However, the tissue strength did not appear to be significantly reduced. The fourth patient, which showed the lowest TAWSS due to the absence of jet flow, had the smallest strength in vitro. Interestingly this patient presented a bovine arch abnormality. Jet flow impingement with high WSS values is frequent in ATAAs and our methodology seems to be appropriate for determining whether it may increase the risk of rupture or not.

Effects of glycaemic variability on cardiac remodelling after reperfused myocardial infarction: Evaluation of streptozotocin-induced diabetic Wistar rats using cardiac magnetic resonance imaging.

AIMS: In addition to hyperglycaemia, glycaemic variability seems to be associated with poor outcomes after acute myocardial infarction. This study explored the impact of glycaemic variability in diabetic Wistar rats subjected to myocardial ischaemia/reperfusion. METHODS: Animals with streptozotocin-induced diabetes received insulin either to maintain stable hyperglycaemia (Dh group) or to generate glycaemic variability (Dv). After experimental myocardial ischaemia/reperfusion was surgically induced, 7T cardiac magnetic resonance imaging (CMR) was performed at weeks 1 (w1) and 3 (w3). RESULTS: Twenty-six rats were randomized [sham group (S): n=5; control group (C): n=7; Dh group: n=6; and Dv group: n=8]. The mean amplitude of glucose reflecting glycaemic variability was higher in the Dv than in the Dh group (9.1±2.7mmol/L vs 5.9±1.9mmol/L; P<0.05). CMR assessment at w3 revealed ventricular enlargement in both Dh and Dv groups compared with the C and S groups (end-diastolic volume: 1.60±0.22 and 1.36±0.30mL/kg compared with 1.11±0.13 and 0.87±0.11mL/kg, respectively; P<0.05). Circumferential strain was altered between w1 and w3 in the remote area only in the Dv group, resulting in a lower value in this group than in the S, C and Dh groups (-0.11±0.01 vs -0.17±0.05, -0.15±0.03 and -0.16±0.03, respectively; P<0.05). In addition, at w3, oedema was also higher in the remote area in the Dv than in the C group (18.3±4.9ms vs 14.5±1.7ms, respectively; P<0.05). CONCLUSION: In the context of experimental myocardial ischaemia/reperfusion, our results suggest that glycaemic variability might have a potentially deleterious impact on myocardial outcomes beyond the classical glucose metrics.

[Atypical MRI image of Tako-Tsubo syndrome: a case report]. / Aspect IRM atypique du syndrome de tako-Tsubo : à propos d'un cas.

Since the 1990s, a new entity cardiomyopathy is described: the Tako-Tsubo syndrome. The Mayo Clinics' criteria have been defined by to help diagnose: LV dysfunction, electrical modifications, and complete recovery. It is a Caucasian woman aged 66 hospitalized for chest pain syndrome occurred during the funeral. In support, we note the presence of STEMI. The patient received the conventional treatment of acute coronary syndrome. Cardiac ultrasound, angiography is in favor of Tako-Tsubo syndrome. MRI shows an unusual location: a delayed enhancement in epicardial associated pericardial effusion mimicking myopericarditis.

No post-conditioning in the human heart with thrombolysis in myocardial infarction flow 2-3 on admission.

AIMS: Proof-of-concept evidence suggests that mechanical ischaemic post-conditioning (PostC) reduces infarct size when applied immediately after culprit coronary artery re-opening in ST-elevation myocardial infarction (STEMI) patients with thrombolysis in myocardial infarction 0-1 (TIMI 0-1) flow grade at admission. Whether PostC might also be protective in patients with a TIMI 2-3 flow grade on admission (corresponding to a delayed application of the post-conditioning algorithm) remains undetermined. METHODS AND RESULTS: In this multi-centre, randomized, single-blinded, controlled study, STEMI patients with a 2-3 TIMI coronary flow grade at admission underwent direct stenting of the culprit lesion, followed (PostC group) or not (control group) by four cycles of (1 min inflation/1 min deflation) of the angioplasty balloon to trigger post-conditioning. Infarct size was assessed both by cardiac magnetic resonance at Day 5 (primary endpoint) and cardiac enzymes release (secondary endpoint). Ninety-nine patients were prospectively enrolled. Baseline characteristics were comparable between control and PostC groups. Despite comparable size of area at risk (AAR) (38 ± 12 vs. 38 ± 13% of the LV circumference, respectively, P = 0.89) and similar time from onset to intervention (249 ± 148 vs. 263 ± 209 min, respectively, P = 0.93) in the two groups, PostC did not significantly reduce cardiac magnetic resonance infarct size (23 ± 17 and 21 ± 18 g in the treated vs. control group, respectively, P = 0.64). Similar results were found when using creatine kinase and troponin I release, even after adjustment for the size of the AAR. CONCLUSION: This study shows that infarct size reduction by mechanical ischaemic PostC is lost when applied to patients with a TIMI 2-3 flow grade at admission. This indicates that the timing of the protective intervention with respect to the onset of reperfusion is a key factor for preventing lethal reperfusion injury in STEMI patients. CLINICAL TRIAL NUMBER: NCT01483755.

Type 2 diabetes mellitus and obesity in young adults: the extreme phenotype with early cardiovascular dysfunction.

AIM: A pilot study to phenotype young adults (< 40 years) with Type 2 diabetes mellitus. METHODS: Twenty people with Type 2 diabetes (aged 18-40 years), 10 lean and 10 obese control subjects underwent detailed assessment, including tagged cardiac magnetic resonance imaging, inflammatory proteins, lipids, vitamin D and maximal oxygen uptake. Outcomes were compared between the group with Type 2 diabetes and the control group. RESULTS: Mean (standard deviation) age, Type 2 diabetes duration and BMI in the group with Type 2 diabetes were 31.8 (6.6) years, 4.7 (4.0) years and 33.9 (5.8) kg/m(2) respectively. Compared with lean control subjects, those with Type 2 diabetes had more deleterious profiles of hyperlipidaemia, vitamin D deficiency, inflammation and maximal oxygen uptake relative to body mass. However, there was no difference between the group with Type 2 diabetes and the obese control group. The group with Type 2 diabetes had a higher left ventricular mass and a trend towards concentric remodelling compared with the lean control group (P = 0.002, P = 0.052) but not the obese control group (P > 0.05). Peak early diastolic strain rate was reduced in the group with Type 2 diabetes [1.51 (0.24)/s] compared with the lean control [1.97 (0.34)/s, P = 0.001] and obese control [1.78 (0.39)/s, P = 0.042] group. CONCLUSIONS: Young adults with Type 2 diabetes and those with obesity have similar adverse cardiovascular risk profiles, higher left ventricular mass and a trend towards left ventricular concentric remodelling. In addition, those with Type 2 diabetes demonstrate diastolic dysfunction, a known risk marker for future heart failure and mortality.

[Contribution of magnetic resonance imaging in diagnosis of pericardial mesothelioma: a case report]. / Apport de l'imagerie par résonance magnétique au diagnostic du mésothéliome péricardique: à propos d'un cas.

Pericardial mesothelioma is a rare form of pericardial tumor. The invasive investigations such as biopsy make the diagnosis. Non-invasive imaging techniques provide valuable information about its diagnosis and its clinical impact. We report here the results of magnetic resonance imaging of pericardial mesothelioma in a 65-year-old woman. The originality and purpose of this case is to illustrate the additional value of magnetic resonance imaging that should be systematically performed when assessing this pathology.

PCATMIP: enhancing signal intensity in diffusion-weighted magnetic resonance imaging.

Diffusion-weighted MRI studies generally lose signal intensity to physiological motion, which can adversely affect quantification/diagnosis. Averaging over multiple repetitions, often used to improve image quality, does not eliminate the signal loss. In this article, PCATMIP, a combined principal component analysis and temporal maximum intensity projection approach, is developed to address this problem. Data are first acquired for a fixed number of repetitions. Assuming that physiological fluctuations of image intensities locally are likely temporally correlated unlike random noise, a local moving boxcar in the spatial domain is used to reconstruct low-noise images by considering the most relevant principal components in the temporal domain. Subsequently, a temporal maximum intensity projection yields a high signal-intensity image. Numerical and experimental studies were performed for validation and to determine optimal parameters for increasing signal intensity and minimizing noise. Subsequently, a combined principal component analysis and temporal maximum intensity projection approach was used to analyze diffusion-weighted porcine liver MRI scans. In these scans, the variability of apparent diffusion coefficient values among repeated measurements was reduced by 59% relative to averaging, and there was an increase in the signal intensity with higher intensity differences observed at higher b-values. In summary, a combined principal component analysis and temporal maximum intensity projection approach is a postprocessing approach that corrects for bulk motion-induced signal loss and improves apparent diffusion coefficient measurement reproducibility.

Interpolation of vector fields from human cardiac DT-MRI.

There has recently been increased interest in developing tensor data processing methods for the new medical imaging modality referred to as diffusion tensor magnetic resonance imaging (DT-MRI). This paper proposes a method for interpolating the primary vector fields from human cardiac DT-MRI, with the particularity of achieving interpolation and denoising simultaneously. The method consists of localizing the noise-corrupted vectors using the local statistical properties of vector fields, removing the noise-corrupted vectors and reconstructing them by using the thin plate spline (TPS) model, and finally applying global TPS interpolation to increase the resolution in the spatial domain. Experiments on 17 human hearts show that the proposed method allows us to obtain higher resolution while reducing noise, preserving details and improving direction coherence (DC) of vector fields as well as fiber tracking. Moreover, the proposed method perfectly reconstructs azimuth and elevation angle maps.

The role of imaging and molecular imaging in the early detection of metabolic and cardiovascular dysfunctions.

Despite intense effort, obesity is still rising throughout the world. Links between obesity and cardiovascular diseases are now well established. Most of the cardiovascular changes related to obesity can be followed by magnetic resonance imaging (MRI) or by magnetic resonance spectroscopy (MRS). In particular, we will see in this review that MRI/MRS is extremely well suited to depict (1) changes in cardiac mass and function, (2) changes in stroke volume, (3) accumulation of fat inside the mediastinum or even inside the cardiomyocytes, (4) cell viability and (5) molecular changes during early cardiovascular diseases.

[Mechanisms of delayed myocardial enhancement and value of MR and CT contrast materials in the evaluation of myocardial viability]. / Mécanismes du rehaussement tardif myocardique et apport des produits de contraste en IRM et scanner dans le diagnostic de viabilité myocardique.

The purpose of this article is to present a brief theoretical review of the models characterizing delayed myocardial enhancement applicable to both MR and CT imaging, review the different characteristics of commercially available gadolinium-based and iodinated contrast materials, and summarize the literature on the potential value of dedicated MR imaging contrast currently in development for the diagnosis of myocardial viability. The intensity of myocardial enhancement following infarction is related to two factors: expansion of the interstitial volume (15+/-2% in normal myocardium and 80+/-3% within necrosis) secondary to cell necrosis and perfusion abnormalities due to the absence of revascularization or lesions to the microcirculation. A kinetic model of contrast material properties within myocardium could be constructed from Kety's equation with regards to enhancement within the different myocardial tissues (viable myocardium, necrotic myocardium, fibrosis, no-reflow zones, stunned or hibernating myocardium). This model can be applied to both CT and MR since clinically available contrast agents are extracellular, inert and kinetically comparable. The development of dedicated contrast agents for viability and necrosis or molecular contrast agents open new horizons for preclinical research.

[Restrictive cardiomyopathy versus constrictive pericarditis in patients with diastolic dysfunction: MR imaging features]. / Comment je fais la différence en IRM entre une cardiomyopathie restrictive et une péricardite constrictive en présence d'une adiastolie?

Restrictive cardiomyopathies are characterized by diastolic dysfunction while systolic function is usually preserved. MRI is helpful by its ability to characterize tissues, especially the demonstration of interstitial or nodular fibrosis based on the underlying etiology. In the presence of constrictive pericarditis from pericardial inflammation, fibrosis or calcifications, diastolic expansion is impaired resulting in poor diastolic ventricular filling, resulting in a characteristic type of diastolic impairment, adiastole. MRI can demonstrate the underlying anatomical lesion: pericardial thickening, though the presence of a pericardium or normal thickness does not entirely exclude the possibility of constriction. As such, the presence of additional imaging features such as abnormal right ventricular shape, vena cava dilatation, and paradoxical movement of the intraventricular septum, during operator-guided deep respiration.

Comparison of the angiographic myocardial blush grade with delayed-enhanced cardiac magnetic resonance for the assessment of microvascular obstruction in acute myocardial infarctions.

BACKGROUND: Both myocardial blush grade (MBG) and cardiac magnetic resonance (CMR) are imaging tools that can assess myocardial reperfusion after primary percutaneous coronary intervention (PCI) for acute myocardial infarction (AMI). OBJECTIVES: We studied the relation between MBG and gadolinium-enhanced CMR for the assessment of microvascular obstruction (MVO) in patients with acute ST-elevated myocardial infarction (STEMI) treated by primary PCI. MATERIAL AND METHODS: MBG was assessed in 39 patients with initial TIMI 0 STEMI successfully treated by PCI, resulting in TIMI 3 flow grade and complete ST-segment resolution. These MBG values were related to MVO determined by CMR, performed between 2 and 7 days after PCI. Left ventricular (LV) volumes were determined at baseline and at 6-month follow-up. RESULTS: No statistical relation was found between MBG and MVO extent at CMR (P = 0.63). Regarding MBG 0 and 1 as a sign of MVO, the sensitivity and specificity of these scores were 53.8 and 75%, respectively. In this study, CMR determined MVO was the only significant LV remodeling predicting factor (beta = 31.8; P = 0.002), whatever the MBG status was. CONCLUSION: MBG underestimates MVO after an optimal revascularization in AMI compared with CMR. This study suggests the superior accuracy of delayed-enhanced magnetic resonance over MBG for the assessment of myocardial reperfusion injury that is needed in clinical trials, where the principal endpoint is the reduction of infarct size and MVO.

Denoising human cardiac diffusion tensor magnetic resonance images using sparse representation combined with segmentation.

Cardiac diffusion tensor magnetic resonance imaging (DT-MRI) is noise sensitive, and the noise can induce numerous systematic errors in subsequent parameter calculations. This paper proposes a sparse representation-based method for denoising cardiac DT-MRI images. The method first generates a dictionary of multiple bases according to the features of the observed image. A segmentation algorithm based on nonstationary degree detector is then introduced to make the selection of atoms in the dictionary adapted to the image's features. The denoising is achieved by gradually approximating the underlying image using the atoms selected from the generated dictionary. The results on both simulated image and real cardiac DT-MRI images from ex vivo human hearts show that the proposed denoising method performs better than conventional denoising techniques by preserving image contrast and fine structures.

Presence and extent of cardiac magnetic resonance microvascular obstruction in reperfused non-ST-elevated myocardial infarction and correlation with infarct size and myocardial enzyme release.

OBJECTIVE: Microvascular obstruction (MO) is a factor of adverse outcome in patients with ST-elevated myocardial infarction (STEMI). We assessed the presence and extent of MO and its relationship with infarct size and left ventricular (LV) functional parameters after acute non-ST-elevated myocardial infarction (NSTEMI). METHODS: Twenty-five patients with first acute NSTEMI underwent a cine and first-pass perfusion cardiac magnetic resonance (CMR) study, with late gadolinium enhancement imaging 72 h after myocardial infarction. RESULTS: MO was detected in 32% of patients, and its extent comprised 0.5-3.1% of the total LV mass (mean 1.9 +/- 1.2%). Patients with MO had a significantly larger infarct size than patients without (14.1 +/- 5.9 vs. 5.3 +/- 4.1% LV mass; p < 0.001). There was no significant difference between both groups for the LV functional parameters and LV ejection fraction (58.5 +/- 6.8 vs. 62.6 +/- 9.6%; p = 0.29). Patients with MO showed a higher troponin I release (570 +/- 364 vs. 148 +/- 103 IU; p = 0.003) and a higher creatine kinase release (29,887 +/- 18,263 vs. 10,287 +/- 5,283 IU; p = 0.007). CONCLUSIONS: In patients with acute NSTEMI, MO has a frequency similar to that observed in patients with STEMI and also correlates with the infarct extent. The prognostic significance on clinical outcome remains to be shown in this specific population.

[Ischemic heart disease (myocardial perfusion and viability): techniques and results]. / Cardiopathies ischémiques (perfusion myocardique et viabilité): techniques et résultats.

Over the last two decades, the understanding, diagnosis and treatment of patients with suspected or known coronary artery disease have made tremendous progress, in particular with the help of the development of non-invasive methodologies for assessing myocardial perfusion and viability. Clinically, nuclear medicine techniques (particularly SPECT imaging) have predominated. With the recent technical developments allowing for a combined assessment of perfusion and irreversible damage with late enhancement imaging, MRI will now play a major role in the assessment of ischemic heart disease.

[Right atrial angiosarcoma and MRI: a case report]. / Angiosarcome de l'oreillette droite et IRM: à propos d'un cas.

The authors report a case of right atrial angiosarcoma in a 29 year old man presenting with massive pericardial effusion. This case illustrates the value of MRI in the preoperative evaluation, providing accurate information about the site and extension of the tumor, and even about the malignant nature of the lesion. Multiplanar transesophageal echocardiography did not provide any additional information in this case.

Airway narrowing in healthy humans inhaling methacholine without deep inspirations demonstrated by HRCT.

Normal subjects prevented from taking a deep breath show changes in airflow similar to those of asthmatics when challenged with methacholine (MCh). To confirm airway narrowing by MCh in this setting and to determine its location, we concurrently measured changes in airway lumenal area using high resolution computed tomography (HRCT) and airflow using partial spirometry in five normal subjects challenged with increasing doses of MCh under prohibition of deep breaths. In an attempt to improve imaging accuracy, we corrected for the changes in lung volume during bronchoprovocation. At every step of the provocation, scanning was performed at approximately the same lung volume. On the HRCT images, airway area decreased in response to the increasing doses of MCh to 91 +/- 2%, 88 +/- 2%, and 80 +/- 2% of baseline at the doses of MCh 0.25, 0.75, and 2.5 mg/ml, respectively (p < 0.001). Airway narrowing showed no predilection for particular airway sizes and occurred in a heterogeneous pattern. The changes in the mean airway lumenal area as measured by HRCT and the mean partial spirometric outcomes were highly correlated: FEV(1)p (r(2) = 0.46, p = 0.001), FVCp (r(2) = 0.20, p = 0.05), FEV(1)/FVCp (r(2) = 0.55, p = 0.002), MMEFp (r(2) = 0.31, p = 0.01), and taup (r(2) = 0.51, p = 0.0004). We conclude that in normal subjects who are prevented from taking a deep breath, the spirometric changes occurring with aerosol MCh challenge are associated with conducting airway narrowing.

MR imaging of the heart: functional imaging.

To date, most applications of cardiovascular MRI relate to the evaluation of major vessels rather than the heart itself. However, MRI plays a major role in the evaluation of specific types of cardiovascular pathology, namely intracardiac and paracardiac masses, pericardial disease, and congenital heart disease. In addition, because the visualization of cardiovascular anatomy with MR is non-invasive and permits three-dimensional analysis but also allows functional assessment of the cardiac pump, it is clear that MRI will have a growing and significant impact over the next years. We review some of the technical aspect of cardiac MRI and describe the current and potential clinical and investigative applications of this new methodology.