Background— The extent of the peri-infarct zone by magnetic resonance imaging (MRI) has been related to all-cause mortality in patients with coronary artery disease. This relationship may result from arrhythmogenesis in the infarct border. However, the relationship between tissue heterogeneity in the infarct periphery and arrhythmic substrate has not been investigated. In the present study, we quantify myocardial infarct heterogeneity by contrast-enhanced MRI and relate it to an electrophysiological marker of arrhythmic substrate in patients with left ventricular (LV) systolic dysfunction undergoing prophylactic implantable cardioverter defibrillator placement. Methods and Results— Before implantable cardioverter defibrillator implantation for primary prevention of sudden cardiac death, 47 patients underwent cine and contrast-enhanced MRI to measure LV function, volumes, mass, and infarct size. A method for quantifying the heterogeneous infarct periphery and the denser infarct core is described. MRI indic...

Infarct tissue heterogeneity by magnetic resonance imaging identifies enhanced cardiac arrhythmia susceptibility in patients with left ventricular dysfunction.

Objectives The goal of this study was to assess the association between left atrial (LA) volume and function measured with feature-tracking cardiac magnetic resonance (CMR) and development of heart failure (HF) in asymptomatic individuals. Background Whether alterations of LA structure and function precede or follow HF development remains incompletely understood. We hypothesized that significant alterations of LA deformation and architecture precede the development of HF in the general population. Methods In a case-control study nested in MESA (Multi-Ethnic Study of Atherosclerosis), baseline LA volume and function assessed using CMR feature-tracking were compared between 112 participants with incident HF (mean age 68.4 ± 8.2 years; 66% men) and 224 age- and sex-matched controls (mean age 67.7 ± 8.9 years; 66% men). Participants were followed up for 8 years. All individuals were in normal sinus rhythm at the time of imaging, without any significant valvular abnormalities and free of clinical cardiovascular diseases. Results Individuals with incident HF had greater maximal and minimal LA volume indexes (LAVImin) than control subjects (40 ± 13 mm3/m2 vs. 33 ± 10 mm3/m2 [p Conclusions Deteriorations in LA structure and function preceded development of HF. Lower global PLAS and higher LAVImin, measured using CMR feature-tracking, were independent markers of incident HF in a multiethnic population of asymptomatic individuals.

Association of CMR-Measured LA Function With Heart Failure Development: Results From the MESA Study

Late enhancement imaging is used to diagnose and characterize a wide range of ischemic and non-ischemic cardiomyopathies, and its use has become ubiquitous in the cardiac MR exam. As the use of late enhancement imaging has matured and the span of applications has widened, the demands on image quality have grown. The characterization of sub-endocardial MI now includes the accurate quantification of scar size, shape, and characterization of borders which have been shown to have prognostic significance. More diverse patterns of late enhancement including patchy, mid-wall, sub-epicardial, or diffuse enhancement are of interest in diagnosing non-ischemic cardiomyopathies. As clinicians are examining late enhancement images for more subtle indication of fibrosis, the demand for lower artifacts has increased. A range of new techniques have emerged to improve the speed and quality of late enhancement imaging including: methods for acquisition during free breathing, and fat water separated imaging for characterizing fibro-fatty infiltration and reduction of artifacts related to the presence of fat. Methods for quantification of T1 and extracellular volume fraction are emerging to tackle the issue of discriminating globally diffuse fibrosis from normal healthy tissue which is challenging using conventional late enhancement methods. The aim of this review will be to describe the current state of the art and to provide a guide to various clinical protocols that are commonly used.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/jmri.23605

Cardiac imaging techniques for physicians: Late enhancement †

From the first measurements of the distribution of pulmonary blood flow using radioactive tracers by West and colleagues (J Clin Invest 40: 1–12, 1961) allowing gravitational differences in pulmona...

https://www.physiology.org/doi/pdf/10.1152/japplphysiol.00320.2012

Imaging lung perfusion.

Contour Tracking in Echocardiographic Sequences via Sparse Representation and Dictionary Learning

Background
Left atrial volume (LAV) and emptying fraction (LAEF) are phasic during cardiac cycle. Their relationships to left ventricular end diastolic pressure (LVEDP) have not been fully defined.

/pdf/relationship-of-phasic-left-atrial-volume-and-emptying-4ii9hsecr4.pdf

Relationship of phasic left atrial volume and emptying function to left ventricular filling pressure: a cardiovascular magnetic resonance study

Purpose:

To evaluate the performance of lung perfusion imaging using two-dimensional (2D) first pass perfusion MRI and a quantitation program based on model-independent deconvolution algorithm.



Materials and Methods:

In eight healthy volunteers 2D first pass lung perfusion was imaged in coronal planes using a partial Fourier saturation recovery stead state free precession (SSFP) technique with a temporal resolution of 160 ms per slice acquisition. The dynamic signal in the lung was measured over time and absolute perfusion calculated based on a model-independent deconvolution program.



Results:

In the supine position mean pulmonary perfusion was 287 ± 106 mL/min/100 mL during held expiration. It was significantly reduced to 129 ± 68 mL/min/100 mL during held inspiration. Similar differences due to respiration were observed in prone position with lung perfusion much greater during expiration than during inspiration (271 ± 101 versus 99 ± 38 mL/min/100 mL (P < 0.01)). There was a linear increase in pulmonary perfusion from anterior to posterior lung fields in supine position. The perfusion gradient reversed in the prone position with the highest perfusion in anterior lung and the lowest in posterior lung fields.



Conclusion:

Lung perfusion imaging using a 2D saturation recovery SSFP perfusion MRI coupled with a model-independent deconvolution algorithm demonstrated physiologically consistent dynamic heterogeneity of lung perfusion distribution. J. Magn. Reson. Imaging 2011;. © 2011 Wiley-Liss, Inc.

https://www.onlinelibrary.wiley.com/doi/pdf/10.1002/jmri.22527

Effects of respiratory cycle and body position on quantitative pulmonary perfusion by MRI

A large gel phantom was used to assess phase offset in through-plane phase contrast images in x (left to right), y (anterior to posterior) and z directions at the isocenter and in positions ±40 mm and ±80 mm away from the isocenter. Repeated measures were averaged and fit to linear regressions. Phase correction was validated in human study for the assessment of aorta and pulmonary artery (PA) flow which was followed immediately by a phantom scan using the same settings. The aorta and PA flow corrected by the regression calculated background phase was compared to that corrected by the measured background phase in the phantom study. Results The gel phantom experiments showed a linear phase descent in z direction through the isocenter with an average slope of -0.019±0.001 cm/s/mm (R2=0.998), demonstrating a velocity descent per millimeter away from the isocenter. The change in z direction was consistent in anterior, posterior, left and right sides of the phantom. There was also a linear phase descent (slope 0.009±0.0005 cm/s/mm, R2 =0.999) in the y direction but phase shift was limited in the x direction (slope 0.0005±0.0008 cm/s/mm, R2 =0.241). In human studies (N=30), average background phase velocity measured by phantom was 0.85± 0.56 cm/s in aortic position and 1.0 ±0.74 cm/s in PA, resulting in 8.9% and 7.5% flow errors in aorta and PA, respectively. The calculated aortic background phase velocity using linear regression was 0.81±0.47 cm/s which was not significantly different from phantom measured phase (p=NS). Calculated phase in the aortic position was applied to correct background phase in both aorta and PA flow given their proximity. Compared to phantom corrected measurements, the flow corrected using calculated phase yielded a very small residual error, mean 0.9±4.0 ml/beat in aorta and 0.9±5.1 ml/beat in PA. Conclusions Phantom experiments demonstrated linear phase variations in the y and z directions but to a less extent in the x direction. Findings in human studies indicate that the linear phase shift is a significant source of phase error and can be removed using linear regression calculated phase from the image itself. Image based background phase correction is a promising alternative to phantom calibration in clinical practice. Funding None.

/pdf/image-based-magnetic-field-background-correction-for-aortic-1e1rsbj4yo.pdf

Image based magnetic field background correction for aortic and pulmonary artery flow measurement using phase contrast

Using inversion recovery steady-state free precession segmented k-space imaging for the detection of myocardial infarction, we noticed that some structures appeared in the wrong locations of the image. In this work, the spatial displacement is demonstrated and explained from both theoretical and experimental points of view. The effect is due to a change in phase from segment to segment of the detected magnetization from species with long T1's such as cysts, fluid collections, and cerebrospinal fluid. Depending on the number of k-space segments and view ordering, structures can be replicated throughout the image or displaced by half of the phase-encoding field of view. Magn Reson Med 54:481–485, 2005. © 2005 Wiley-Liss, Inc.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/mrm.20566

William Schapiro

Papers

Relationship of phasic left atrial volume and emptying function to left ventricular filling pressure: a cardiovascular magnetic resonance study

Effects of respiratory cycle and body position on quantitative pulmonary perfusion by MRI

Image based magnetic field background correction for aortic and pulmonary artery flow measurement using phase contrast

On the cause of spatial displacement of long T1 species in segmented inversion recovery prepared imaging.

Abstract 2609: Coronary Vasomotion in Normal Subjects with Risk Factors for Atherosclerosis: Noninvasive Assessment