Cardiovascular Magnetic Resonance Tagging Research Articles

Detection of apical hypertrophic cardiomyopathy; which is the appropriate imaging modality

Apical hypertrophic cardiomyopathy is a form of hypertrophic cardiomyopathy localized to the left ventricular apex. The disease is common in Japanese and other Asian populations but its presence has also been recognized, though less commonly, in non-Asian patients. Its prognosis is relatively benign in terms of cardiovascular mortality but morbid sequelae, such as diastolic dysfunction, left atrial enlargement, apical thrombi, ventricular aneurysms, and myocardial infarction, may occur. In patients with apical hypertrophic cardiomyopathy, the electrocardiographic changes and symptoms associated often mimic acute coronary syndromes. Invasive or noninvasive evaluation of the left ventricular cavity confirms the diagnosis of apical hypertrophic cardiomyopathy, with the “ace-of-spades” sign on left ventriculography being pathognomonic. It is therefore of utmost importance to use the appropriate imaging modalities to establish the correct diagnosis of apical hypertrophic cardiomyopathy. For instance, using doppler-echocardiography in 182 patients with apical hypertrophic cardiomyopathy, three morphologically distinct phenotypes i.e. (1) pure focal, (2) pure diffuse, and (3) a mixed type according to patterns of hypertrophy could be discerned [1]. Detailed subtyping turned out to be important in the prediction of development of atrial fibrillation, left atrial volume index and left ventricular longitudinal function. In the current edition of this issue, Duygu et al. [2] studied 17 patients with chest pain who had a pre-diagnosis of coronary artery disease but a final diagnosis of apical hypertrophic cardiomyopathy. Interestingly, all patients showed typical spade-like appearance of the left ventricle by contrast ventriculography and giant negative T-waves on the electrocardiogram. Transthoracic echocardiography showed a maximum wall thickness of 18 ± 4 mm and a mean gradient of 30 mmHg by Doppler echocardiography. None of the patients showed significant coronary artery disease; four patients showed myocardial bridging. The authors recommended that the diagnosis of apical hypertrophic cardiomyopathy should always be considered in certain patients with typical anginal symptoms and outspoken negative T waves on the electrocardiogram. As a result, physicians caring for patients with chest pain should consider apical hypertrophic cardiomyopathy in their differential diagnosis in case of a patient with chest pain and electrocardiographic changes suggestive of coronary artery disease. Stated by the authors, these patients should all undergo echocardiography to separate apical hypertrophic cardiomyopathy from acute myocardial ischemia. Although the authors mention that ischemic evaluation was not performed, they only refer to thallium myocardial scintigraphy as potential modality to identify ischemia in apical hypertrophic cardiomyopathy. Indeed, myocardial scintigraphy using perfusion tracers and metabolic markers have shown to be useful in the evaluation of cardiomyopathies [3–6]. It is, however, noteworthy that the authors did not refer to cardiac magnetic resonance imaging (CMR) as an accurate and reliable means of evaluating cardiac morphology, ventricular function, and myocardial perfusion, both for the left and the right ventricle therewith covering a whole spectrum of cardiac diseases [7–12]. In particular, CMR is very well suited for identifying and characterizing patients with hypertrophic cardiomyopathy [13, 14]. For instance, Tsukamoto et al. [15] showed systolic outward motion of the left ventricular apical wall in patients with apical hypertrophic cardiomyopathy using CMR tagging. In addition, CMR allows accurate evaluation of myocardial ischemia and infarction with the potential to establish the transmural extent of myocardial infarction with high spatial resolution [16–18]. Late gadolinium-enhanced CMR can clearly delineate subendocardial infarction and CMR appears to be more sensitive than other imaging methods in detecting small infarcts and ischemia [19–21]. In recent years, late gadolinium enhancement CMR has also been used to visualize myocardial interstitial abnormalities in patients with different forms of cardiomyopathies [22, 23]. In patients with apical hypertrophic cardiomyopathy, first-pass gadolinium delayed-enhanced CMR may show local delayed enhancement in the subendocardium in the hypertrophic lesion. The presence of perfusion defect and delayed enhancement may be a marker of a high-risk patient with apical hypertrophic cardiomyopathy [24]. On the other hand, patients with apical hypertrophic cardiomyopathy may show focal hyperenhancement of the non-hypertrophic basal lateral segment of the left ventricle, and absence of hyperenhancement of the hypertrophied apical segments [25]. It can be concluded that apical hypertrophic cardiomyopathy is a disease that may mimic coronary artery disease in a certain subset of patients. Hence, adequate diagnostic methods are needed to distinguish between these two entities. Although echocardiography remains the first line of investigation in these patients the final answer might be given by CMR.

Abstract 2290: Assessment of Left Ventricular Torsion Using Two Dimensional Speckle Tracking Echocardiography: Comparison with Tagged Cardiac Magnetic Resonance.

Background. LV torsion from helically oriented myofibers is a key parameter of cardiac performance. Until now, LV torsion could only be assessed using tagged cardiac magnetic resonance (cMR). Because of its high spatial and temporal resolution, speckle tracking echocardiography (STE) could be an alternative to cMR. STE offers the opportunity to track myocardial motion independently of both cardiac translation and angle-dependency. The aim of this study was to evaluate the accuracy and reproducibility of STE for the estimation of LV torsion using cMR as the reference standard. Methods . Ten controls and 43 patients with a variety of cardiac disease underwent cMR and STE on the same day. STE datasets were analyzed using a prototype version of the 2DQ QLab software that allows to track speckles on a frame by frame basis in the endocardium and epicardium, and to derive LV torsion and twisting velocities. Care was taken to analyze cMR and STE data on similar short-axis slices, matched on basis of their end-diastolic internal dimensions. Inter- and intraobserver variabilities were estimated by two blinded observers for 20 patients. In 5 volunteers STE and cMR were repeated twice to assess test-retest reproducibility. Results . Measurements of endocardial, midwall and epicardial torsion by cMR and STE did not differ significantly from each other (12.6 ± 5.9° vs. 12.5 ± 5.6°, 10.7 ± 4.7° vs. 9.7 ± 4.1°, and 8.9 ± 4.1° vs. 8.5 ± 3.8°, all p=ns) and were highly correlated (r=0.96, 0.88 and 0.79), with only small intertechniques biases (0.11 ± 3.4°, 0.98 ± 4.7° and 0.4 ± 5.28°). Peak twisting velocities, obtained by deriving systolic torsion over time, were also similar between cMR and STE (54 ± 18°/s and 63 ± 23°/s, p=ns) and were highly correlated (r=0.74). The intra- and interobserver agreement for peak LV torsion measurements, assessed by the intraclass correlation coefficient, was equally good for cMR (ICC=0.98 and 0.96; bias 0.3 ± 2.9 and 0.65 ± 3.1°) and for STE (ICC=0.98 and 0.96; bias 0.05 ± 2.8 and 0.13 ± 4.7°). Test-retest reproducibility was also excellent. Conclusions . Our data show that, compared to cMR, STE allows LV torsion to be accurately and reproducibly measured. This should make LV torsion assessment more available in clinical and research cardiology.

High-Resolution Complementary Spatial Modulation of Magnetization (CSPAMM) Rat Heart Tagging on a 1.5 Tesla Clinical Magnetic Resonance System

The purpose of this study was to assess the feasibility of cardiac magnetic resonance (MR) tagging in rats on a standard clinical 1.5T MR system. Small animal models have been largely used as an experimental model in cardiovascular disease studies but mainly on high field systems (>4T) dedicated to research. Given the larger availability of routine clinical MR systems in centers with active cardiac research programs, it is of great interest to perform small animal imaging on whole-body MR systems of moderate field strength. The feasibility study was performed on 7 rats within 6 to 8 hours after myocardial infarction and 3 normal control rats. Myocardial strain was measured successfully in normal rats using the harmonic phase (ie, HARP) method, and a transmural gradient was demonstrated. In a rat model of acute occlusion/reperfusion, the myocardial circumferential strains were decreased, but the transmural strain gradient was preserved. This study demonstrated the feasibility of cardiac MR tagging in rats with a subendocardial resolution using a clinical 1.5T system.

The effect of left bundle branch block on left ventricular remodeling, dyssynchrony and deformation of the mitral valve apparatus: an observational cardiovascular magnetic resonance imaging study

The effect of a left bundle branch block (LBBB) on cardiac function and remodeling in patients at different stages of heart failure (HF) is unknown. We used cardiac magnetic resonance imaging (CMR) to evaluate the effect of LBBB on left ventricular (LV) remodeling, mechanical dyssynchrony, functional mitral regurgitation (FMR) and deformation of the mitral valve apparatus (MVA) in LBBB patients at different stages of HF. In 12 LBBB patients with HF, 4 patients with isolated LBBB, and 4 controls, cine CMR was performed to measure LV remodeling, FMR grade and deformation of the MVA. CMR tagging was used to measure septal-to-lateral onset of shortening delay and coefficient of circumferential strain variation (CV) to quantify dyssynchrony. LV end-diastolic volume (LVEDV) and end-systolic volume (LVESV) were largest in LBBB patients with HF. Patients with isolated LBBB tended to have a larger LVESV and smaller LV ejection fraction compared to controls, (56 +/- 22 ml/m2 versus 45 +/- 9 ml/m2, P = ns, 42 +/- 9% versus 53 +/- 4 %, P = ns). QRS duration and septal-to-lateral-onset-of-shortening delay were comparable between LBBB patients with HF and isolated LBBB patients, CV was larger (98 +/- 45 versus 40 +/- 4, P < 0.05). MVA tenting and FMR were present both in LBBB patients with HF and patients with isolated LBBB and were not observed in controls. The presence of a LBBB in asymptomatic patients is related to mechanical dyssynchrony and deformation of the MVA and may be associated with LV remodeling. If confirmed, close monitoring or even timely initiation of therapy may be warranted in patients with isolated LBBB. This advocates to conduct a longitudinal CMR follow-up study on the clinical course in patients with isolated LBBB.

Effects of basic fibroblast growth factor microspheres on angiogenesis in ischemic myocardium and cardiac function: analysis with dobutamine cardiovascular magnetic resonance tagging

Therapeutic angiogenesis with angiogenic growth factors has described as one of the promising methods for collateral formation in the treatment of ischemic heart diseases. The purpose of this study is to assess the value of intramyocardial injection of slow-released basic fibroblast growth factor microspheres on angiogenesis and cardiac function in the early period of acute infarcted myocardium with dobutamine cardiovascular magnetic resonance tagging. Acute myocardial infarction was made by ligation of the left anterior descending coronary artery distal to its first diagonal branch. Immediately after coronary artery occlusion, 1 ml of saline containing 100 microg of basic fibroblast growth factor microspheres was injected into peri-infarct myocardial area in the basic fibroblast growth factor group, whereas only gelatin hydrogel microspheres with 1 ml of saline was given in control dogs. Cardiac function was evaluated by cine magnetic resonance imaging. Dobutamine cardiovascular magnetic resonance was performed at rest and during low doses of dobutamine to assess regional wall motion. Immunohistochemical study with von Willebrand factor was performed to observe angiogenesis. Left ventricular ejection fraction improved markedly 10 and 17 days after treatment in the basic fibroblast growth factor group. The basic fibroblast growth factor group had more viable myocardium. Microvessel density was higher in the basic fibroblast growth factor group than in the control group except the first day after treatment. Intramyocardial administration of basic fibroblast growth factor microspheres can promote the growth of microvessels and improve left ventricular function and myocardial viability in the early period of acute myocardial infarction.

Effect of Long-Term Cocaine Use on Regional Left Ventricular Function as Determined by Magnetic Resonance Imaging

This study examined left ventricular (LV) regional midwall circumferential strain by cardiac tagged magnetic resonance imaging in 32 long-term cocaine users and 14 nonusers. Most of the LV segmentations in the cocaine users had less average circumferential strain in the systolic and diastolic phases. The average diastolic strain in 5 ventricular segmentations was significantly less in the cocaine users (p<0.05). In conclusion, long-term cocaine use may be associated with regional LV dysfunction, especially diastolic dysfunction.

Occult Cardiac Contractile Dysfunction in Dystrophin-Deficient Children Revealed by Cardiac Magnetic Resonance Strain Imaging

Duchenne muscular dystrophy (DMD) is an inherited disease characterized by early onset of skeletal muscle degeneration and progressive weakness. Although dilated cardiomyopathy may occur during adolescence, it is often undetected early in its course because of physical inactivity and generalized debilitation. The purpose of this study was to apply the technique of cardiac magnetic resonance (CMR) tagging to detect occult cardiac dysfunction in young subjects with DMD by measuring myocardial strain and torsion. Thirteen DMD pediatric subjects without clinically apparent heart disease and 9 age-matched healthy males were recruited. Each was scanned on a 1.5-T clinical scanner to acquire contiguous short-axis planes from the apex to the mitral valve plane and then 3 tagged images at base, midventricle, and apex. Global and segmental myocardial net twist and circumferential strain were computed with the use of 2D homogeneous strain analysis. Ventricular torsion was computed by normalizing net twist by the distance from apex to mitral valve plane. DMD patients exhibited normal left ventricular volumes and ejection fractions but manifested reduced midventricular and basal cross-sectional global circumferential strain compared with the reference group (P<0.005). These alterations also appeared in segmental analyses in the septal, anterior, lateral, and inferior walls (P<0.05). In patients predisposed to cardiomyopathies because of dystrophinopathy, occult regional cardiac dysfunction can be diagnosed with CMR tagging. This method of strain imaging analysis may offer a sensitive approach for delineating the presence and progression of cardiovascular disease and for assessing therapies designed to modulate the onset and course of heart failure.

The Angiotensin II Type 2 Receptor and Improved Adjacent Region Function Post-MI

Angiotensin II type 2 receptor (AT2-R) overexpression in the mouse heart preserves left ventricular (LV) size and global LV function during post-MI remodeling. We hypothesized that CMR tagging would localize regional improvements in myocardial function during post-MI remodeling in AT2-R cardiac overexpressed transgenic mice (TG), which could explain the preservation of global LV function post-MI. Six male wild-type (WT) C57BL/6 mice and 10 TG mice were studied by CMR at baseline (day 0) and days 1, 7, and 28 post-MI. MI was induced by 1 hour occlusion of the LAD followed by reperfusion. On day 1 post-MI, gadolinium-DTPA was injected to assess infarct size. LV size and function was assessed by cine CMR. Mean % circumferential shortening (%CS) was calculated within infarcted, adjacent, and remote regions at each time point in WT and TG mice. Quantitative interstitial collagen and mean myocyte cross-sectional area was measured postmortem at day 28 post-MI. LV end-systolic volume was lower and ejection fraction higher at baseline in the TG group and these differences were maintained post-MI. Within infarcted and remote zones, although %CS was higher in TG mice at day 0, there was no difference by day 28 between groups. Within adjacent regions, while there was no difference at day 0 or 1 in TG vs. WT, %CS was significantly higher in TG mice by day 7, and these changes persisted out to day 28 post-MI. Regional interstitial collagen and myocyte size were similar between groups. Thus, myocardial tagging can detect regional differences in contractile function post-MI in TG mice, and AT2-R overexpression is associated with improved contractile function in adjacent noninfarcted myocardium.

Assessment of diastolic function by cardiovascular magnetic resonance

Background The assessment of diastolic heart function has been hampered by multiple difficulties. Cardiovascular magnetic resonance (CMR) is a new, noninvasive technique to study cardiac function. Methods The literature on CMR for the analysis of diastolic function and its clinical applications is extensively reviewed. Results Analysis of ventricular filling velocity and volume flow, volumetric assessment of ventricular chamber volume, analysis of 3-dimensional myocardial strains, and assessment of myocardial energy content are numerous validated applications of CMR. With the advent of real-time imaging and automated analysis of myocardial strains, CMR tagging is a promising method to assess regional diastolic function. Today, many CMR techniques are leaving the experimental or developmental stage rapidly and becoming clinically available for the evaluation of diastolic function in heart disease. Conclusions CMR is emerging as a highly accurate and reproducible noninvasive 3-dimensional technique for the assessment of diastolic function. (Am Heart J 2002;144:198-205.)

Obesity is associated with altered apical left ventricular rotation: A cardiac magnetic resonance tagging study Peter G. Danias, Nicholas A. Tritos, Matthias Stuber, Carol J. Salton, Kraig V. Kissinger, Warren J. Manning. Beth Israel Deaconess Medical Center, Boston, MA, Joslin Diabetes Center, Boston, MA

Obesity is associated with altered apical left ventricular rotation: A cardiac magnetic resonance tagging study Peter G. Danias, Nicholas A. Tritos, Matthias Stuber, Carol J. Salton, Kraig V. Kissinger, Warren J. Manning. Beth Israel Deaconess Medical Center, Boston, MA, Joslin Diabetes Center, Boston, MA

Two-dimensional spatial and temporal displacement and deformation field fitting from cardiac magnetic resonance tagging

Tagged magnetic resonance imaging is a specially developed technique to noninvasively assess contractile function of the heart. Several methods have been developed to estimate myocardial deformation from tagged image data. Most of these methods do not explicitly impose a continuity constraint through time although myocardial motion is a continuous physical phenomenon. In this paper, we propose to model the spatio-temporal myocardial displacement field by a cosine series model fitted to the entire tagged dataset. The method has been implemented in two dimensions (2D)+time. Its accuracy was successively evaluated on actual tagged data and on a simulated two-dimensional (2D) moving heart model. The simulations show that an overall theoretical mean accuracy of 0.1 mm can be attained with adequate model orders. The influence of the tagging pattern was evaluated and computing time is provided as a function of the model complexity and data size. This method provides an analytical and hierarchical model of the 2D+time deformation inside the myocardium. It was applied to actual tagged data from a healthy subject and from a patient with ischemia. The results demonstrate the adequacy of the proposed model for this evaluation.

Imaging heart motion using harmonic phase MRI

This paper describes a new image processing technique for rapid analysis and visualization of tagged cardiac magnetic resonance (MR) images. The method is based on the use of isolated spectral peaks in spatial modulation of magnetization (SPAMM)-tagged magnetic resonance images. We call the calculated angle of the complex image corresponding to one of these peaks a harmonic phase (HARP) image and show that HARP images can be used to synthesize conventional tag lines, reconstruct displacement fields for small motions, and calculate two-dimensional (2-D) strain. The performance of this new approach is demonstrated using both real and simulated tagged MR images. Potential for use of HARP images in fast imaging techniques and three-dimensional (3-D) analyses are discussed.

Cardiac motion tracking using CINE harmonic phase (HARP) magnetic resonance imaging.

This article introduces a new image processing technique for rapid analysis of tagged cardiac magnetic resonance image sequences. The method uses isolated spectral peaks in SPAMM-tagged magnetic resonance images, which contain information about cardiac motion. The inverse Fourier transform of a spectral peak is a complex image whose calculated angle is called a harmonic phase (HARP) image. It is shown how two HARP image sequences can be used to automatically and accurately track material points through time. A rapid, semiautomated procedure to calculate circumferential and radial Lagrangian strain from tracked points is described. This new computational approach permits rapid analysis and visualization of myocardial strain within 5-10 min after the scan is complete. Its performance is demonstrated on MR image sequences reflecting both normal and abnormal cardiac motion. Results from the new method are shown to compare very well with a previously validated tracking algorithm. Magn Reson Med 42:1048-1060, 1999.

Cardiac motion tracking using CINE harmonic phase (HARP) magnetic resonance imaging

This article introduces a new image processing technique for rapid analysis of tagged cardiac magnetic resonance image sequences. The method uses isolated spectral peaks in SPAMM-tagged magnetic resonance images, which contain information about cardiac motion. The inverse Fourier transform of a spectral peak is a complex image whose calculated angle is called a harmonic phase (HARP) image. It is shown how two HARP image sequences can be used to automatically and accurately track material points through time. A rapid, semiautomated procedure to calculate circumferential and radial Lagrangian strain from tracked points is described. This new computational approach permits rapid analysis and visualization of myocardial strain within 5–10 min after the scan is complete. Its performance is demonstrated on MR image sequences reflecting both normal and abnormal cardiac motion. Results from the new method are shown to compare very well with a previously validated tracking algorithm. Magn Reson Med 42:1048–1060, 1999. © 1999 Wiley-Liss, Inc.