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J Garot

Publications and source records attributed to J Garot.

At least 19 recordsLinked to original sources
PubMed2005

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.

Algorithms↗
PubMed2004

[Localization of mitral valve prolapse zones with multiplane transesophageal echocardiography].

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.

Aged↗
PubMed2003

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.

Blood Volume↗
PubMed2003

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.

Hemodynamics↗
PubMed2002

[Changes in left ventricular torsion during ischemia-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.

Aged↗
PubMed2001

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.

Aged↗
PubMed2001

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.

Adult↗
PubMed2001

[Left ventricular functional imagery by magnetic resonance. Applications and developments].

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.

Heart Ventricles↗
PubMed2000

Fast determination of regional myocardial strain fields from tagged cardiac images using harmonic phase MRI.

BACKGROUND: Tagged MRI of the heart is difficult to implement clinically because of the lack of fast analytical techniques. We investigated the accuracy of harmonic phase (HARP) imaging for rapid quantification of myocardial strains and for detailed analysis of left ventricular (LV) function during dobutamine stimulation. METHODS AND RESULTS: Tagged MRI was performed in 10 volunteers at rest and during 5 to 20 microg(-1). kg(-1). min(-1) dobutamine and in 9 postinfarct patients at rest. We compared 2D myocardial strains (circumferential shortening, Ecc; maximal shortening, E(2); and E(2), direction) as assessed by a conventional technique and by HARP. Full quantitative analysis of the data was 10 times faster with HARP. For pooled data, the regression coefficient was r=0.93 for each strain (P<0.001). In volunteers, Ecc and E(2) were greater in the free wall than in the septum (P<0.01), but recruitable myocardial strain at peak dobutamine was greater in the LV septum (P<0.01). E(2) orientation shifted away from the circumferential direction at peak dobutamine (P<0.01). HARP accurately detected subtle changes in myocardial strain fields under increasing doses of dobutamine. In patients, HARP-determined Ecc and E(2) values were dramatically reduced in the asynergic segments as compared with remote (P<0.001), and E(2) direction shifted away from the circumferential direction (P<0.001). CONCLUSIONS: HARP MRI provides fast, accurate assessment of myocardial strains from tagged MR images in normal subjects and in patients with coronary artery disease with wall motion abnormalities. HARP correctly indexes dobutamine-induced changes in strains and has the potential for on-line quantitative monitoring of LV function during stress testing.

Adult↗
PubMed2000

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.

Animals↗
PubMed2000

Magnetic resonance imaging of myocardial infarct.

Magnetic resonance imaging offers the unique opportunity to directly visualize the size and location of myocardial infarcts (MIs) with excellent spatial resolution. Because infarct size is the most important determinant of postinfarct outcome, precise determination of infarct size may be valuable to risk stratify patients after acute MI. In addition, infarct imaging may provide direct information on the amount of irreversibly injured myocardium and thus can be used to identify myocardial viability in dysfunctional regions. Acute infarcts can be recognized as hyperintense signal on T2-weighted spin-echo images. This technique, however, does not identify chronic infarcts and may overestimate infarct size by including area at risk. Also, T2-weighted images often have a low signal-to-noise ratio. Contrast-enhanced perfusion imaging provides better-quality images. Extravascular contrast agents such as (Gd-DTPA) gadolinium diethyletriamine-pentaacetic acid identify infarcts as hyperenhanced regions on images acquired late after contrast injection. In addition, these tracers can examine the integrity and permeability of infarct microvasculature on first-pass perfusion images. Necrosis avid tracers and 23Na imaging are other new exciting approaches to identify infarcted myocardium acutely after MI. These techniques, are still investigational, and their value for clinical imaging remains to be established.

Contrast Media↗
PubMed2000

[The best of echocardiography in 1999].

As many techniques of medical investigation, echocardiography regularly benefits from technical innovations which, with application, prove to be extremely useful and, for some of them, even widen the field of investigation. The end of this decade has seen the introduction of major improvements. In daily practice, second harmonic imaging has been the most important technical advance with such improved quality of imaging that this mode has rapidly become the routine for transthoracic investigations in adults. All modern echocardiographs are, or can be, equipped at modest cost. Stress echocardiography, the diagnostic reliability of which is closely related to the quality of the imaging, has greatly benefited from this technique, to the point of obtaining equivalent results as nuclear medicine in the detection of myocardial ischaemia and cellular viability. The results are now sufficiently convincing for the technique to have a real prognostic value in myocardial ischaemia. Doppler tissue imaging is also a major advance but the clinical value is still under evaluation: the pulsed Doppler mode is quantifiable during the investigation, contrary to the calculation of transparietal velocity gradients which requires computerisation techniques not provided by all manufacturers. The regain in interest in contrast echocardiography is due to the development of agents which, injected intravenously, cross the pulmonary capillary barrier and opacify the left heart chambers. The reinforcement of the Doppler signal and improved detection of the endocardial echoes have justified the authorization of their commercialisation, but the essential point is their use in the investigation of myocardial perfusion which is under evaluation. Three-dimensional reconstruction has made great strides but its diffusion is still limited by the limited availability of the required powerful computers.

Adult↗
PubMed2000

[Chronic ischemic left ventricular dysfunction: myocardial hibernation?].

Hibernating myocardium is a term which covers chronic ischaemic left ventricular dysfunction which is potentially reversible after revascularisation. Hibernating myocardium is classically associated with chronic hypoperfusion responsible for hypocontraction and cellular degeneration. This "classical" conception has been questioned as some workers emphasise that the reduction in coronary reserve responsible for repeated episodes of ischaemia and stunning could be the main causes of myocardial dysfunction. Position emission tomography (PET), and, most of all, myocardial scintigraphy and dobutamine echocardiography are the most commonly used techniques for detecting hibernating myocardium. Their sensitivity is good but the specificity and positive predictive value of dobutamine echocardiography seems to be better than the isotopic techniques. Structural abnormalities of hibernating myocardium and the delay, which is often long, between revascularisation and improvement, may explain some of the discordances between these techniques. Irrespective of the term used, hibernation or chronic ischaemic left ventricular dysfunction with myocardial viability, the reported data is in favour of coronary revascularisation with improved long-term quality of life and reduced mortality in patients with positive viability tests.

Cardiotonic Agents↗
PubMed2000

[Alterations of left ventricular mechanics after anterior myocardial infarction. Quantitative analysis by tissue doppler echocardiography].

Myocardial ischemia is usually responsible for alterations of regional left ventricular function which are not quantified by routine echocardiography. We used tissue Doppler echocardiography to quantitate the three main components (radial, longitudinal and angular) of left ventricular function, and their alterations after acute anterior myocardial infarction. Radial function was assessed by the myocardial velocity gradient derived from M-mode color tissue Doppler echocardiography, and longitudinal function by the pulsed wave tissue Doppler echocardiography, in 26 patients who experienced a first acute anterior myocardial infarction and in 11 matched healthy subjects. We describe a new tissue Doppler method for the measurement of septal angular deformation during cardiac contraction. In healthy subjects, our results showed heterogeneous regional myocardial contraction. Septal angular deformation occurred in the same direction and was of the same order as predicted by previous MRI studies. After anterior infarction, systolic and diastolic myocardial velocity gradients were dramatically decreased in the anterior wall when compared with controls (p < 0.01), whereas the systolic velocity gradient was significantly higher in the opposite wall (p < 0.05). Pulsed wave tissue Doppler echocardiography revealed significant alterations of longitudinal left ventricular function. Septal angular deformation was decreased after anterior infarct, and a good correlation was found between the angle of rotation and the left ventricular ejection fraction by cineangiography. These results indicate that tissue Doppler echocardiography has the potential for measuring the three main components of regional left ventricular function, and for quantitatively assessing their functional alterations induced by acute myocardial ischemia.

Diastole↗
PubMed1999

Prediction of functional recovery of viable myocardium after delayed revascularization in postinfarction patients: accuracy of dobutamine stress echocardiography and influence of long-term vessel patency.

OBJECTIVES: We sought to evaluate dobutamine stress echocardiography (DSE) for predicting recovery of viable myocardium after revascularization with cineangiography as a gold standard for left ventricular (LV) function. We studied the influence of late vessel reocclusion on regional LV function. BACKGROUND: Dobutamine stress echocardiography is a well established evaluation method for myocardial viability assessment. In previous studies the reference method for assessing LV recovery was echocardiography, long-term vessel patency has not been systematically addressed. METHODS: Sixty-eight patients with a first acute myocardial infarction (AMI) and residual stenosis of the infarct related artery (IRA) underwent DSE (mean +/- standard deviation) 21 +/- 12 days after AMI to evaluate myocardial viability. Revascularization of the IRA was performed in 54 patients by angioplasty (n = 43) or bypass grafting (n = 11). Coronary angiography and LV cineangiography were repeated at four months to assess LV function and IRA patency. RESULTS: Sensitivity and specificity of DSE for predicting myocardial recovery after revascularization were 83% and 82%. In the case of late IRA patency, specificity increased to 95%, whereas sensitivity remained unchanged. In the 16 patients with myocardial viability and late IRA patency, echocardiographic wall motion score index decreased after revascularization from 1.83 +/- 0.15 to 1.36 +/- 0.17 (p = 0.0001), and left ventricular ejection fraction (LVEF) increased from 0.52 +/- 0.06 to 0.57 +/- 0.06 (p = 0.0004), whereas in five patients, reocclusion of the IRA prevented improvement of segmental or global LV function despite initially viable myocardium. CONCLUSIONS: Dobutamine stress echocardiography is reliable to predict recovery of viable myocardium after revascularization in postinfarction patients. Late reocclusion of the IRA may prevent LV recovery and influence the accuracy of DSE.

Adult↗
PubMed1999

Coronary blood flow reserve and wall motion recovery in patients undergoing angioplasty for myocardial infarction.

AIMS: The aim of this study was to evaluate the relationship between coronary flow reserve and the recovery of wall motion contractility in patients with recent myocardial infarction. METHODS AND RESULTS: Nineteen patients (55 +/- 8 years) undergoing balloon angioplasty for recent myocardial infarction were studied. After angioplasty, coronary flow reserve was lower in the infarct-related artery than in a reference artery, 2.2 +/- 0.6 and 2.8 +/- 0.7, respectively, P < 0.05. There was no immediate correlation between coronary blood flow reserve measured after angioplasty and wall motion index. There was a negative correlation between coronary flow reserve and the number of necrotic segments (r = -0.43; P0.006). At the 4 month control angiogram, there was a significant increase in both left ventricular ejection fraction (59 +/- 14% vs 51 +/- 13%; P < 0.05) and wall motion index (-0.63 +/- 1.2 vs -1.94 +/- 0.9 units SD, P = 0.005). In patients in whom wall motion improved (> 1 unit SD), the immediate coronary flow reserve was higher (P < 0.05) than in patients without improved wall motion. In this group, the increase in wall motion index was correlated to the coronary blood flow reserve (r = 0.55; P < 0.02). CONCLUSION: These data show that after myocardial infarction, coronary flow reserve is associated with myocardial viability.

Aged↗
PubMed1999

Quantitative systolic and diastolic transmyocardial velocity gradients assessed by M-mode colour Doppler tissue imaging as reliable indicators of regional left ventricular function after acute myocardial infarction.

AIMS: The aim of this study was to determine whether myocardial velocity gradients assessed by M-mode colour Doppler tissue imaging could be of clinical relevance and represent reliable indicators of regional left ventricular function after acute myocardial infarction. METHODS AND RESULTS: Among 64 consecutive patients with a first acute myocardial infarction, in 50 who had a marked asynergy in the parasternal short-axis view at the mid-papillary muscle level, myocardial velocities and velocity gradients were assessed in the anteroseptum and posterior wall by M-mode Doppler tissue imaging. Similar measurements were obtained in 11 matched healthy volunteers who served as a control group. In patients with anterior myocardial infarction, the peak myocardial velocity gradient in the anteroseptum was significantly lower when compared with controls (mean +/- [SD] 0.0 +/- 0.5 vs 1.1 +/- 0.7 s-1 during systole, P < 0.01; and 0.3 +/- 0.6 vs 2.0 +/- 0.5 s-1 during diastole, P < 0.01). Conversely, the peak systolic myocardial velocity gradient in the posterior wall was significantly higher than in controls (2.6 +/- 1.2 vs 1.8 +/- 1.2 s-1, P < 0.05). In patients with inferior myocardial infarction, the peak velocity gradient in the posterior wall was significantly lower when compared with healthy subjects (0.9 +/- 0.6 vs 1.8 +/- 1.2 s-1 during systole and 1.4 +/- 1.4 vs 4.9 +/- 1.2 s-1 during diastole, both P < 0.01). The peak systolic tissue velocity gradient in the anteroseptum was significantly higher than in controls (2.1 +/- 1.0 vs 1.1 +/- 0.7 s-1, P < 0.01). CONCLUSION: The present study indicates that myocardial velocity gradients assessed by M-mode Doppler tissue imaging are of clinical relevance for the characterization of ischaemic myocardial dysfunction after infarction and may provide quantitative assessment of segmental left ventricular function in this clinical setting.

Aged↗