[IRM et myocardite infectieuse]. / IRM et myocardite infectieuse.

Over the past ten years, cardiac MRI has become an indispensable tool for acute myocarditis diagnosis. Under appropriate conditions, cardiac MRI may allow postponement of initial coronary angiography in many instances. The 2020 ESC guidelines give a class I recommendation to its use in the setting of MINOCA for differential diagnosis between acute myocardial infarction, myocarditis, Tako-Tsubo and other cardiac pathologies, in order to improve therapeutic management and follow-up. This article describes the technical characteristics of MRI in myocarditis (Lake Louise diagnostic criteria and criteria based on myocardial tissue mapping), the main differential diagnoses, the prognostic value and addresses the issue of myocarditis in the setting of COVID-19.

[Cardiac MRI: technical considerations]. / Les conditions techniques d'utilisation de l'IRM cardiaque.

Establishing a clinical cardiovascular magnetic resonance imaging (MRI) program needs a dedicated technical surroundings as well as a specific and expert staff. These guidelines based either on proofs or on expert consensus are stated in order to help the physicians to reach or maintain the competence required for clinical use of cardiovascular MRI. After the general safety statements, the guidelines are focused on hardware and software requirements, the MRI sequences and views, the post-acquisition analysis, and the staff. Specific safety concerns are then approached, more particularly stress testing MRI.

[Cardiovascular magnetic resonance and multislice coronary CT in ischemic cardiomyopathy]. / IRM et scanner cardiaque dans la cardiopathie ischémique.

Cardiovascular magnetic resonance imaging and multislice coronary CT are frequently used in patients with suspected or known coronary artery disease. However, clinical indications of such noninvasive imaging techniques remain debated. This manuscript points out the advantages and limitations of each technique while clarifying their potential clinical indications.

Assessment of myocardial deformations from untagged cardiac cine MRI.

This paper presents a method for the assessment of left ventricular myocardial deformations from untagged cardiac cine MRI. Firstly, a level set segmentation process is applied on the dataset to detect both endocardial and epicardial boundaries. Then the successive contours are matched using an original procedure that consists in an alignment followed by a morphing process. From the matched contours, we deduced an initial velocity of the contour points that will be used in a Thin-Plate Splines approximation method for estimating of the velocity flow on the complete myocardial structure. Finally, local measurements of ventricular deformations are derived from the velocity flow. The validation of the method is performed both mathematically and by comparing the measurements to those obtained on the same patients with the HARmonic Phase reference (HARP) method applied on matched tagged MR images.

[Assessment of myocardial function and perfusion by MRI two days and four months after acute myocardial infarction revascularised by primary angioplasty]. / Evaluation par IRM de la fonction et de la perfusion myocardique à deux jours et quatre mois de l'infarctus aigu du myocarde revascularisé par angioplastie primaire.

The extent of gadolinium enhancement assessed by cardiac MRI is an accepted marker of myocardial necrosis. The correlation between late enhancement and other parameters of infarct size after myocardial infarction have previously been described. However, the prognostic value of the extent of late enhancement in terms of myocardial recovery remains controversial especially in revascularised infarcts analysed by early MRI. In order to clarify this question the authors compared the results of MRI at two days and four months after myocardial infarction benefiting from early revascularisation. Between July 2002 and November 2004, the authors included patients with myocardial infarction treated by primary angioplasty and examined by MRI (Siemens Symphony 1.5 T) at two days and three to five months after myocardial infarction. The left ventricular ejection fraction, volume, mass and wall thickness were measured. Perfusion at first passage (PP) and late enhancement were analysed after injection of 20 cc of gadolinium. An eight segment short axis model was used for PP and analysis of late enhancement. Each segment was assessed for transmural or subendocardial hypoperfusion for PP assessment and the wall thickness with late enhancement (1-25%, 26-50%, 51-75%, and 76-100%) was measured to calculate the percentage of myocardial mass showing late enhancement. Thirty-nine patients (thirty three men) were included. The average age was 59 +/- 10 years. TIMI III flow was obtained in all but one (TIMI II) patient. Cardiac MRI was performed 2.1 +/- 1.5 days and 4.6 +/- 1.7 months after myocardial infarction. The ejection fraction increased from 48.7 +/- 12.6% to 54.2 +/- 11.1%, p<0.05, and was related to infarct size (p<0.01). Forty-eight per cent of dysfunctional segments at the initial MRI improved their contractility and the extent of transmural late enhancement was inversely correlated with wall thickening at initial (p<0.01) and four month MRI (p<0.01). The PP improved significantly (regression from 9.5 +/- 8.2% to 2.8 +/- 4.1% of segments with abnormal myocardial perfusion, p<0.01). The late enhancement with respect to total myocardial mass decreased from 20.0 +/- 10.7% to 13.0 +/- 8.1%, p<0.01). Despite restoring TIMI III flow, early myocardial reperfusion is incomplete and improves in the medium term. The authors also observed a reduction in late enhancement at four months, indicating that the results immediately after myocardial infarction may overestimate the infarct size and that this sign does not represent necrotic tissue alone but also viable myocardium with a potential for recovery.

MR/CT multimodal registration of short-axis slices in CT volumes.

This paper deals with the registration of Magnetic Resonance (MR) and Computerized Tomography (CT) cardiac images. We use a multimodal iconic algorithm based on the maximisation of the mutual information of the joint histogram of two images. We apply it to the registration of MR and CT cardiac images. The purpose is to determine in a (3D+t) CT data volume, short-axis slices that correspond to the (2D+t) short-axis MR slices, acquired on the same patient. The couples of images should be similar according to their spatial position, orientation and cardiac cycle phase. We used the Powell's direction set optimization method for the maximisation of the mutual information, which gives good results with an appropriate initialization.

[Evaluation of left ventricular function: echocardiography, MRI or CT?]. / Evaluation de la fonction ventriculaire gauche: échocardiographie, IRM ou scanner?

The objective of this article is to clarify the advantages and limits of echocardiography, MRI, and CT for the determination of left ventricular (LV) function, emphasising the importance of evaluating global ventricular function. MRI is the reference technique, owing to its precision, reproducibility, and innocuous nature. However, echography is performed much more frequently because it is more widely available and easier to carry out. It is our reference technique in everyday practice. More recently, synchronised multi-slice tomodensitometry has provided dynamic reconstructed images of the left ventricle throughout the cardiac cycle, offering a succession of short axis views covering the entire volume of the ventricle. These acquisitions, in addition to non-invasive coronary angiography, allow the LV ejection fraction to be determined. With MRI, study of the LV function does not require any contrast medium to be injected and makes use of effective semi-automatic segmentation programs.

Segmentation of cardiac cine-MR images and myocardial deformation assessment using level set methods.

In this paper, we present an original method to assess the deformations of the left ventricular myocardium on cardiac cine-MRI. First, a segmentation process, based on a level set method is directly applied on a 2D + t dataset to detect endocardial contours. Second, the successive segmented contours are matched using a procedure of global alignment, followed by a morphing process based on a level set approach. Finally, local measurements of myocardial deformations are derived from the previously determined matched contours. The validation step is realized by comparing our results to the measurements achieved on the same patients by an expert using the semi-automated HARP reference method on tagged MR images.

[Localization of mitral valve prolapse zones with multiplane transesophageal echocardiography]. / Localisation des zones de prolapsus valvulaire mitral en échographie transoesophagienne multiplan.

CONTEXT: There are few literature data on the localization and extent of mitral valve prolapse zones with transesophageal echocardiography (TEE). AIM OF THE STUDY: To assess a standardized imaging technique for the localization and extent determination of prolapse zones, based on 3 easily reproducible views with multiplane TEE. METHODS: Seventy patients with severe mitral regurgitation due to valve prolapse requiring a multiplane TEE prior to surgery (valve repair or replacement) have been retrospectively assessed. Data of TEE on the localization and extent of prolapse zones have been confronted to per-operative anatomical observations (gold standard). RESULTS: The sensitivity of TEE for the identification of isolated P2 prolapse, prolapse with commisural extension, isolated rupture of the posterior commisure and bi-valvular prolapses were respectively at 96%, 88%, 86% and 80%. The corresponding specificities were from 98% to 100%. CONCLUSIONS: The use of a standardized technique with the use of 3 easily reproducible incidences with multiplane TEE allows a precise definition of the localization and extent of mitral valve prolapse zones, in order to potentially indicate valve repair.

Impact of microvascular integrity and local viability on left ventricular remodelling after reperfused acute myocardial infarction.

OBJECTIVE: To assess left ventricular remodelling in patients with reperfused acute myocardial infarction and to study its relation to microvascular damage. PATIENTS: 25 patients successfully treated by primary percutaneous coronary angioplasty for acute myocardial infarction. SETTING: University hospital METHODS: Indexed end diastolic (EDVi) and end systolic (ESVi) volumes were assessed on admission and repeated at days 1 and 8. Coronary flow reserve (CFR) was assessed in the infarct related artery on day 1. Myocardial blood volume was assessed on admission and at day 8 by myocardial contrast echocardiography. In patients who manifested persistent myocardial dysfunction at hospital discharge (n = 21), local inotropic reserve was assessed by dobutamine echocardiography at day 7. RESULTS: On admission, patients with and without local viability had similar EDVi and ESVi (EDVi 67 (9) and 73 (14) ml/m(2), respectively; ESVi 34 (8) and 40 (11) ml/m(2), respectively; NS). EDVi increased to 97 (22) ml/m(2) in patients without local viability (p < 0.01 v admission) but remained unchanged at 70 (11) ml/m(2) in patients with viable myocardium (NS v admission). For pooled patient data, the percentage change in EDVi correlated with CFR (r = 0.76, p < 0.0001) and myocardial blood volume in the infarct territory (r = 0.80, p < 0.0001). CONCLUSION: Left ventricular dilatation may preferably occur in patients without local viability and is correlated with early CFR and extent of myocardial blood volume in the infarct territory.

Magnetic resonance imaging of acute myocardial ischaemia and infarction.

Recent developments in cardiac magnetic resonance imaging (MRI) have led to tremendous breakthroughs in the imaging of acute myocardial ischaemia and infarction. Hardware and acquisition sequences have improved image quality while simplifying cardiac examinations. Cine-MRI allows for accurate time-resolved imaging of global and segmental left ventricular (LV) function with high spatial resolution. Dynamic multislice MRI of myocardial perfusion is now widely available allowing for the detection of microvascular obstruction after myocardial infarction (MI) or adding significant diagnostic value over usual clinical and biological markers after non ST elevation coronary syndromes. Direct high-resolution MRI of MI is well standardized with important clinical implications for the diagnosis of myocardial viability. In addition, stress cardiac MRI enables time-resolved analysis of myocardial perfusion under pharmacological stress, or accurate assessment of regional LV function during dobutamine cine-MRI for detection of myocardial ischaemia and/or viability. Non-invasive MR coronary angiography is beyond the scope of this article.

[Changes in left ventricular torsion during ischemia-reperfusion]. / Altérations de la rotation systolique du ventricule gauche au cours de l'ischémie-reperfusion.

We aimed to characterise the alterations of left ventricular twist during ischaemia-reperfusion and to study their relationship to global left ventricular function. Systolic left ventricular twist was measured at the mid-papillary muscle level by colour tissue Doppler echocardiography in 7 anaesthetised open-chest dogs at baseline, 90 min-occlusion of the left anterior descending, and 180 min after reflow. Tissue Doppler was also performed in 34 patients after anterior infarct and in 20 controls. In controls, rotation occurred counterclockwise when viewed from the base. In a random subset of subjects, the assessment of ventricular twist by tissue Doppler was validated against magnetic resonance myocardial tagging. Myocardial ischaemia led to a decrease in ventricular twist in dogs and infarct patients (p < 0.01). This decrease was correlated with the extent of the asynergic area and global left ventricular function (p < 0.001). In dogs, cardiac twist was higher after reflow relative to ischaemia (p < 0.01). Thus, acute myocardial ischaemia is responsible for a decrease in left ventricular twist that is related to global ventricular function. Colour tissue Doppler echocardiography provides straightforward assessment of left ventricular twist in humans.

Stratification of single-vessel coronary stenosis by ischemic threshold at the onset of wall motion abnormality during continuous monitoring of left ventricular function by semisupine exercise echocardiography.

We studied the relation between the ischemic threshold at the onset of wall motion abnormality on exercise echocardiography (EE) and the severity of coronary stenosis in patients with 1-vessel coronary artery disease (CAD). We screened 216 consecutive patients who underwent coronary angiography and EE for suspected CAD. Ninety-five (74 men; age, 56 +/- 12 years) satisfied the study criteria, that is, the presence of 1-vessel disease or no evidence of CAD on angiography and a normal baseline echocardiogram. Eighty-seven patients had 1-vessel CAD on angiography, and exercise-induced wall motion abnormality occurred in 73 (77%). Optimal cutoff values of percent diameter stenosis and minimal lumen diameter for predicting a positive EE were 61% (sensitivity and specificity of 76%) and 1.12 mm (sensitivity and specificity of 74%). Among patients with positive EE, heart rate-blood pressure product at ischemic threshold was correlated with quantitative coronary stenosis (r = -0.72, P <.001). The ischemic threshold from continuous monitoring of left ventricular function during semisupine EE is correlated with the severity of coronary stenosis among patients with 1-vessel disease and a normal resting echocardiogram.

Transesophageal magnetic resonance imaging of the aortic arch and descending thoracic aorta in patients with aortic atherosclerosis.

OBJECTIVES: We sought to determine the feasibility and potential of transesophageal magnetic resonance imaging (TEMRI) for quantifying atherosclerotic plaque burden in the aortic arch and descending thoracic aorta in comparison with transesophageal echocardiography (TEE). BACKGROUND: Improved morphologic assessment of atherosclerotic plaque features in vivo is of interest because of the potential for improved understanding of the pathophysiology of plaque vulnerability to rupture and progression to clinical events. Magnetic resonance imaging (MRI) is well suited for atherosclerotic plaque imaging. Performing MRI using a radio frequency (RF) receiver probe placed near the region of interest improves the signal-to-noise ratio (SNR). METHODS: High-resolution images of the thoracic aortic wall were obtained by TEMRI in 22 subjects (8 normals, 14 with aortic atherosclerosis). In nine subjects, we compared aortic wall thickness and circumferential extent of atherosclerotic plaque measured by TEMRI versus TEE using a Bland-Altman analysis. Additional studies were performed in a human cadaver with pathology as an independent gold standard for assessment of atherosclerosis. RESULTS: In clinical and experimental studies, we found similar measurements for aortic plaque thickness but a relative underestimation of circumferential extent of atherosclerosis by TEE (p = 0.001), due in large part to the lower SNR in the near field. CONCLUSIONS: Using TEMRI allows for quantitative assessment of thoracic aortic atherosclerotic plaque burden. This technique provides good SNR in the near field, which makes it a promising approach for detailed characterization of aortic plaque burden.

[Left ventricular functional imagery by magnetic resonance. Applications and developments]. / Imagerie fonctionnelle du ventricule gauche par résonance magnétique. Applications et développements.

Technical developments have considerably reduced the acquisition time and have improved the quality of magnetic resonance imaging. The recent recommendations of the European Society of Cardiology place MRI in the front line of investigations for the diagnosis and evaluation of congenital heart disease, cardiac tumours and pathology of the pericardium and great vessels. With the possibility of obtaining oblique planes in all 3 dimensions, MRI is the reference for the measurement of left ventricular mass, volumes, and ejection fraction, with the major advantage of not depending on hypotheses of left ventricular geometry. In addition to these known applications, the development of functional cardiac MRI has led to significant advances in the study of regional myocardial function and perfusion. The aim of this article is to discuss present indications and the potential developments of functional cardiac MRI, focusing on the quantitative evaluation of myocardial function and perfusion.

Transmural contractile reserve after reperfused myocardial infarction in dogs.

OBJECTIVES: The goal of this study was to characterize detailed transmural left ventricular (LV) function at rest and during dobutamine stimulation in subendocardial and transmural experimental infarcts. BACKGROUND: The relation between segmental LV function and the transmural extent of myocardial necrosis is complex. However, its detailed understanding is crucial for the diagnosis of myocardial viability as assessed by inotropic stimulation. METHODS: Short-axis tagged magnetic resonance images were acquired at five to seven levels encompassing the LV from base to apex in seven dogs 2 days after a 90-min closed-chest left anterior descending coronary occlusion, followed by reflow. Myocardial strains were measured transmurally in the entire LV by harmonic phase imaging at rest and 5 ig x kg(-1) x min(-1) dobutamine. Risk regions were assessed by radioactive microspheres, and the transmural extent of the infarct was assessed by 2,3,5 triphenyltetrazolium chloride staining. RESULTS: Circumferential shortening (Ecc), radial thickening (Err) and maximal shortening at rest were greater in segments with subendocardial versus transmural infarcts, both in subepicardium (-1.1+/-1.0 vs. 2.5+/-0.6% for Ecc, -0.5+/-1.9 vs. -1.8+/-1.0% for Err, p < 0.05) and subendocardium (-2.0+/-1.4 vs. 2.8+/-0.8%, 2.4+/-1.7 vs. 0.0+/-0.9%, respectively, p < 0.05). Under inotropic stimulation, risk regions retained maximal contractile reserve. Recruitable deformation was found in outer layers of subendocardial infarcts (p < 0.01 for Ecc and Err) but also in inner layers (p < 0.01). Conversely, no contractile reserve was observed in segments with transmural infarcts. CONCLUSIONS: Under dobutamine challenge, recruitment of myofiber shortening and thickening was observed in inner layers of segments with subendocardial infarcts. These results may have important clinical implications for the detection of myocardial viability.