MRI of left ventricular function. J Nucl Cardiol
Departments of Radiology and Biomedical, University of Virginia Health System, Charlottesville, VA 22908, USA. Journal of Nuclear Cardiology
(Impact Factor: 2.94).
09/2007; 14(5):729-44. DOI: 10.1016/j.nuclcard.2007.07.006
Cardiac magnetic resonance imaging (CMR) is widely recognized as the most accurate noninvasive imaging modality for the assessment of left ventricular (LV) function. By use of state-of-the-art magnetic resonance imaging (MRI) scanners, electrocardiography (ECG)-gated cine images depicting LV function with high contrast and excellent spatial and temporal resolution are readily acquired in breath-holds of 5 to 10 heartbeats. For patients in whom breath-holding and ECG gating are difficult, real-time cine imaging without ECG gating and breath-holding can be performed. LV function can be qualitatively assessed from cine images, or alternatively, parameters such as LV volumes, ejection fraction, and mass may be quantified via computer-based analysis software. In addition, techniques such as myocardial tagging and newer variants can be used to qualitatively or quantitatively assess regional intramyocardial strain, twist, and torsion. Many of the CMR methods have undergone clinical evaluation in the settings of high-dose dobutamine stress testing and determination of myocardial viability. These methods are also very accurate for prognosis in coronary heart disease patients and may be quite useful for the detection of contractile dyssynchrony. When used together with other CMR techniques such as first-pass perfusion imaging or late gadolinium enhancement, CMR of LV function provides a wealth of information in a single imaging study.
Available from: Caroline Van de Heyning
- "An important finding of the present study is that LV volumes are significantly underestimated by 2D TTE in patients with moderate to severe primary MR in comparison with CMR, which is widely accepted as the most accurate non-invasive imaging tool to assess LV shape and sizes
. This finding might be of importance since adequate assessment of LV contractility and dimensions is crucial for clinical decision making in these patients. "
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ABSTRACT: Two-dimensional transthoracic echocardiography (2DTTE) remains the first-line diagnostic imaging tool to assess primary mitral regurgitation although cardiovascular magnetic resonance (CMR) has proven to establish left ventricular function more accurately and might evaluate mitral regurgitation severity more reliably. We sought to compare routine evaluation of left ventricular function and mitral regurgitation severity by 2DTTE with assessment by CMR in moderate to severe primary mitral regurgitation without overt left ventricular dysfunction.
We prospectively included 38 patients (79% of male, age 57 +/- 14 years) with at least moderate primary mitral regurgitation, a left ventricular ejection fraction >=60% and a left ventricular end-systolic diameter <=45 mm. Patients with evidence of coronary artery disease, arrhythmias or significant concomitant valvular disease were excluded. All patients were scheduled for 2DTTE and CMR.
Left ventricular end-diastolic and end-systolic volumes were significantly underestimated by 2DTTE in comparison with CMR, although there was a strong correlation (Pearson r = 0.81, p < 0.00001 and r = 0.7, p < 0.00001, respectively). Measurement of the regurgitant orifice was similar between 2DTTE PISA method and planimetry by CMR (47 +/- 24 vs. 42 +/- 16 mm2, p = 0.12) with a strong correlation between both imaging techniques (Pearson r = 0.76, p < 0.0001). By contrast, assessment of the regurgitant volume by 2DTTE and by phase contrast velocity mapping by CMR showed poor agreement.
In moderate to severe primary mitral regurgitation without overt left ventricular dysfunction, 2DTTE significantly underestimates left ventricular remodelling in comparison to CMR. Measurement of the regurgitant orifice with planimetry by CMR shows good agreement with the PISA method by 2DTTE and thus may be a valuable alternative to assess mitral regurgitation severity.
Cardiovascular Ultrasound 12/2013; 11(1):46. DOI:10.1186/1476-7120-11-46 · 1.34 Impact Factor
Available from: Bruce S Spottiswoode
- "A number of different CMR tissue tracking methods may be used to assess cardiac mechanics, including myocardial tagging [10,11], harmonic phase analysis (HARP) , velocity encoded phase contrast (PC) [13,14], and displacement encoding with stimulated echoes (DENSE) [15,16]. Furthermore, all of these methods are applicable to both humans [10-17] and mice [18-33]. Among these techniques, tagging is the most widely used, but has the significant disadvantage that image analysis is cumbersome and time consuming. "
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ABSTRACT: Quantitative noninvasive imaging of myocardial mechanics in mice enables studies of the roles of individual genes in cardiac function. We sought to develop comprehensive three-dimensional methods for imaging myocardial mechanics in mice.
A 3D cine DENSE pulse sequence was implemented on a 7T small-bore scanner. The sequence used three-point phase cycling for artifact suppression and a stack-of-spirals k-space trajectory for efficient data acquisition. A semi-automatic 2D method was adapted for 3D image segmentation, and automated 3D methods to calculate strain, twist, and torsion were employed. A scan protocol that covered the majority of the left ventricle in a scan time of less than 25 minutes was developed, and seven healthy C57Bl/6 mice were studied.
Using these methods, multiphase normal and shear strains were measured, as were myocardial twist and torsion. Peak end-systolic values for the normal strains at the mid-ventricular level were 0.29 ± 0.17, -0.13 ± 0.03, and -0.18 ± 0.14 for E(rr), E(cc), and E(ll), respectively. Peak end-systolic values for the shear strains were 0.00 ± 0.08, 0.04 ± 0.12, and 0.03 ± 0.07 for E(rc), E(rl), and E(cl), respectively. The peak end-systolic normalized torsion was 5.6 ± 0.9°.
Using a 3D cine DENSE sequence tailored for cardiac imaging in mice at 7 T, a comprehensive assessment of 3D myocardial mechanics can be achieved with a scan time of less than 25 minutes and an image analysis time of approximately 1 hour.
Journal of Cardiovascular Magnetic Resonance 12/2011; 13(1):83. DOI:10.1186/1532-429X-13-83 · 4.56 Impact Factor
Available from: Kieran Clarke
- "Scaling down imaging techniques to study the ever increasing number of small animal disease models has been a formidable challenge . The rat model of myocardial infarction, induced by occlusion of the left anterior descending coronary artery, is widely used and has provided data essential for the development of surgical and pharmacological therapy . "
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ABSTRACT: In humans, dynamic contrast CMR of the first pass of a bolus infusion of Gadolinium-based contrast agent has become a standard technique to identify under-perfused regions of the heart and can accurately demonstrate the severity of myocardial infarction. Despite the clinical importance of this method, it has rarely been applied in small animal models of cardiac disease. In order to identify perfusion delays in the infarcted rat heart, here we present a method in which a T1 weighted MR image has been acquired during each cardiac cycle.
In isolated perfused rat hearts, contrast agent infusion gave uniform signal enhancement throughout the myocardium. Occlusion of the left anterior descending coronary artery significantly reduced the rate of signal enhancement in anterior regions of the heart, demonstrating that the first-pass method was sensitive to perfusion deficits. In vivo measurements of myocardial morphology, function, perfusion and viability were made at 2 and 8 days after infarction. Morphology and function were further assessed using cine-MRI at 42 days. The perfusion delay was larger in rat hearts that went on to develop greater functional impairment, demonstrating that first-pass CMR can be used as an early indicator of infarct severity. First-pass CMR at 2 and 8 days following infarction better predicted outcome than cardiac ejection fraction, end diastolic volume or end systolic volume.
First-pass CMR provides a predictive measure of the severity of myocardial impairment caused by infarction in a rodent model of heart failure.
Journal of Cardiovascular Magnetic Resonance 08/2011; 13(1):38. DOI:10.1186/1532-429X-13-38 · 4.56 Impact Factor
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