Heart Wall Motion Research Articles

Alterations in the local myocardial motion pattern in patients suffering from pressure overload due to aortic stenosis.

MR tissue tagging allows the noninvasive assessment of the locally and temporally resolved motion pattern of the left ventricle. Alterations in cardiac torsion and diastolic relaxation of the left ventricle were studied in patients with aortic stenosis and were compared with those of healthy control subjects and championship rowers with physiological volume-overload hypertrophy. Twelve aortic stenosis patients, 11 healthy control subjects with normal left ventricular function, and 11 world-championship rowers were investigated for systolic and diastolic heart wall motion on a basal and an apical level of the myocardium. Systolic torsion and untwisting during diastole were examined by use of a novel tagging technique (CSPAMM) that provides access to systolic and diastolic motion data. In the healthy heart, the left ventricle performs a systolic wringing motion, with a counterclockwise rotation at the apex and a clockwise rotation at the base. Apical untwisting precedes diastolic filling. In the athlete's heart, torsion and untwisting remain unchanged compared with those of the control subjects. In aortic stenosis patients, torsion is significantly increased and diastolic apical untwisting is prolonged compared with those of control subjects or athletes. Torsional behavior as observed in pressure- and volume-overloaded hearts is consistent with current theoretical findings. A delayed diastolic untwisting in the pressure-overloaded hearts of the patients may contribute to a tendency toward diastolic dysfunction.

In vivo magnetic resonance methods in pharmaceutical research: current status and perspectives.

In the last decade, in vivo MR methods have become established tools in the drug discovery and development process. In this review, several successful and potential applications of MRI and MRS in stroke, rheumatoid and osteo-arthritis, oncology and cardiovascular disorders are dealt with in detail. The versatility of the MR approach, allowing the study of various pathophysiological aspects in these disorders, is emphasized. New indication areas, for the characterization of which MR methods have hardly been used up to now, such as respiratory, gastro-intestinal and skin diseases, are outlined in a subsequent section. A strength of MRI, being a non-invasive imaging modality, is the ability to provide functional, i.e. physiological, readouts. Functional MRI examples discussed are the analysis of heart wall motion, perfusion MRI, tracer uptake and clearance studies, and neuronal activation studies. Functional information may also be derived from experiments using target-specific contrast agents, which will become important tools in future MRI applications. Finally the role of MRI and MRS for characterization of transgenic and knock-out animals, which have become a key technology in modern pharmaceutical research, is discussed. The advantages of MRI and MRS are versatility, allowing a comprehensive characterization of a diseased state and of the drug intervention, and non-invasiveness, which is of relevance from a statistical, economical and animal welfare point of view. Successful applications in drug discovery exploit one or several of these aspects. In addition, the link between preclinical and clinical studies makes in vivo MR methods highly attractive methods for pharmaceutical research.

REGIONAL MYOCARDIAL FUNCTION

Methods for noninvasive tissue tracking and quantification of myocardial shortening with magnetic resonance imaging have been developed using presaturation tagging and velocity encoded phase maps. The concurrent development of rapid scanning techniques, such that a complete cine loop of a slice can be obtained in a breath-hold, has made the measurement of myocardial wall motion in patients a simple and reproducible examination. These methods make it possible to quantify the severity and extent of regional heart wall motion abnormalities both at rest and during stress.

Quantification of the local heartwall motion by magnetic resonance myocardial tagging

Sophisticated magnetic resonance tagging techniques provide powerful tools for the non-invasive assessment of the local heartwall motion towards a deeper fundamental understanding of local heart function. For the extraction of motion data from the time series of magnetic resonance tagged images and for the visualization of the local heartwall motion a new image analysis procedure has been developed. New parameters have been derived which allows quantification of the motion patterns and are highly sensitive to any changes in these patterns. The new procedure has been applied for heart motion analysis in healthy volunteers and in patient collectives with different heart diseases. The achieved results are summarized and discussed.

Power Motion Imaging for Quantification of Heart Wall Motion: An Ultrasound Study in the Rabbit.

Power Motion Imaging for Quantification of Heart Wall Motion: An Ultrasound Study in the Rabbit.

Cardiokymograph system with a capacitance transducer and its preliminary application in the measurement of heart wall movement.

A novel cardiokymograph system is introduced. The new system features a capacitance transducer with increased sensitivity and can be used in multichannel measurements. The novelty of this technique is the injection of a current into the patient coupled with the use of a capacitive displacement transducer and the possibility of multichannel monitoring. It provides for the possibility of removing breath noise when some signal processing technique, such as adaptive filtering, is used. Further investigation is needed to demonstrate clinical significance and pathologies.

Power motion imaging for quantification of heart wall motion: an ultrasound study in the rabbit

Power motion imaging for quantification of heart wall motion: an ultrasound study in the rabbit

Tagasist: A post-processing and analysis tools package for tagged magnetic resonance imaging

The Magnetic Resonance Imaging technique myocardial tagging allows the tracking and measurement of local parameters of heart wall motion. Tagging provides detailed information about regional cardiac function never before available with non-invasive techniques. The growth of this technique has been limited in part by the availability of post-processing tools. We introduce the TAGged cine AnalySIS Tools package (TAGASIST) for the processing of images from this technique. TAGASIST includes a graphical user interface for image segmentation, kinematic analysis, plotting of regional averages as well as multiple subjects (or patient populations) simultaneously, statistical analysis, and a database of all studies processed.

Influence of age on the prognostic importance of left ventricular dysfunction and congestive heart failure on long-term survival after acute myocardial infarction

The aim of this study was to assess the importance of congestive heart failure and left ventricular (LV) systolic dysfunction after an acute myocardial infarction (AMI) on long-term mortality in different age groups. A total of 7,001 consecutive enzyme-confirmed AMIs (6,676 patients) were screened for entry into the TRAndolapril Cardiac Evaluation (TRACE) study. Medical history, echocardiographic estimation of LV systolic function determined as wall motion index, infarct complications, and survival were documented for all patients. To study the importance of congestive heart failure and wall motion index independent of age, we performed Cox proportional-hazard models in 4 different age strata (≤55 years, 56 to 65 years, 66 to 75 years, and >75 years). Patients in these strata had 1 -year mortality rates of 5%, 11%, 21%, and 32%, respectively. Three-year mortality rates were 11%, 20%, 34%, and 55%, respectively. The risk ratios (and 95% confidence limits) associated with congestive heart failure in the same 4 age strata were 1.9 (1.3 to 2.9), 2.8 (2.1 to 3.7), 1.8 (1.5 to 2.2) and 1.8 (1.5 to 2.2), respectively. The risk ratios associated with decreasing wall motion index were 6.5 (3.6 to 11.4), 3.3 (2.3 to 4.6), 2.7 (2.2 to 3.4), and 2.1 (1.7 to 2.6), respectively. In absolute percentages, there was an excess 3-year mortality associated with congestive heart failure in the 4 age strata of 14%, 24%, 25%, and 28%, respectively. The absolute excess in 3-year mortality associated with LV systolic dysfunction in the 4 age strata was 15%, 19%, 25%, and 21%, respectively. Thus, the relative importance of LV systolic dysfunction and congestive heart failure diminished with increasing age. However, the absolute excess mortality associated with congestive heart failure and LV systolic dysfunction was more pronounced in the elderly than in the young.

MRI of myocardial function: motion tracking techniques.

Methods for the noninvasive measurement of three-dimensional myocardial motion with MRI have recently been developed using presaturation tagging and velocity-encoded phase maps. The quality of clinical cardiac MRI studies has also recently improved with the advent of breath-hold scanning. The combination of breath-hold imaging with tagging and velocity-encoding sequences has made the measurement of myocardial wall motion in patients a simple and reproducible exam. These methods make it possible to quantify the severity and extent of regional heart wall motion abnormalities both at rest and during stress. This article reviews the MRI techniques developed for these applications.

Two-dimensional left ventricular deformation during systole using magnetic resonance imaging with spatial modulation of magnetization.

Myocardial tissue tagging with the use of magnetic resonance imaging allows noninvasive regional analysis of heart wall motion and deformation. However, any evaluation of the effect of disease or treatment requires a baseline reference of normal values and variation. We studied the two-dimensional motion of material points imaged within the left ventricular wall using spatial modulation of magnetization (SPAMM) in 12 normal human volunteers. Five parallel short-axis and five parallel long-axis slices were acquired at five times during systole. SPAMM tags were generated at end diastole using a 7-mm grid. Intersection point data were analyzed for displacement, rotation, and torsion, and triangles of points were analyzed for local rotation and principal strains. Short-axis displacement was the least in the septum for all longitudinal levels (P < .001). Torsion about the long axis was uniform circumferentially because of the motion of the centroids used to reference the rotation. In the long-axis images, the base displaced longitudinally toward the apex, with the posterior wall moving farther than the anterior wall (13.4 +/- 2.2 versus 9.7 +/- 1.8 mm, P < .001) in this direction. The largest principal strain (maximum lengthening) was approximately radially oriented in both views. In the short-axis images, the minimum principal strain (maximum shortening) increased in magnitude toward the apex (P < .001) with little circumferential variation, except at midventricle, where the anterior wall showed greater contraction than the posterior wall (-0.21 +/- 0.03 versus -0.19 +/- 0.02, P < .02). Consistent regional variations in deformation are seen in the normal human heart. Displacement and maximum shortening strains are well characterized with two-dimensional magnetic resonance tagging; however, higher-resolution images will be required to study transmural variations.

5111820 System and method for magnetic resonance imaging of 3-dimensional heart wall motion with spatial modulation of magnetization

Spatial Modulation of Magnetization (SPAMM) with two sets of tagging planes orthogonal to the image plane is used in accordance with known techniques to image two-dimensional heart wall motion with MRI. However, such techniques are modified in accordance with the invention to permit direct assessment of three-dimensional heart wall motion from two-dimensional images using a three-dimensional SPAMM technique and a phase shift SPAMM technique. The three-dimensional SPAMM technique uses a third set of tagging planes oblique to the image plane to separate within-plane motion from through-plane motion. In accordance with the 3-dimensional SPAMM technique, the displacement of the oblique magnetization lines relative to the displacement of the spatial modulation pattern in the imaging plane during a preimaging time interval is indicative of the displacement of a body portion such as a patient's heart wall through the imaging plane during the preimaging time interval. Preferably, the oblique angle is 45° so that the amount of stripe displacement is equal to the amount of through-plane-motion. On the other hand, the phase-shift SPAMM technique encodes through-plane velocity as a corresponding phase shift. An integral may then be taken of the resulting phase-sensitized images in order to determine the through-plane displacement corresponding to the phase shift. Both techniques in accordance with the invention allow three-dimensional images of internal body tissues such as the heart wall to be imaged with minimal image acquisition and interpolation time.

Regional heart wall motion: two-dimensional analysis and functional imaging with MR imaging.

Analysis of the transmural distribution or nonradial components of myocardial motion has previously been possible only with use of invasive techniques such as implantation of radiopaque markers. Magnetic tagging of the heart wall in conjunction with magnetic resonance imaging allows noninvasive regional analysis of within-wall motion, including its separation into components of rigid body motion and deformation. The results of this analysis can be displayed as functional images. This provides a new tool for the study of heart wall motion that should be of use for both basic physiologic and clinical research applications.

Method for measuring three-dimensional motion with tagged MR imaging.

Recent methods of magnetic resonance imaging involve the placement of a grid of planes of saturation over the imaging plane; distortion of the grid corresponds to tissue displacement in two dimensions. An extension to this method that allows measurement of motion in the third dimension involves a second acquisition that tilts the grid, allowing analysis of motion normal to the imaging plane. A rotating phantom was used to verify the accuracy of the motion measurements, and the technique was applied to the heart wall and skeletal muscle. Phantom results show that the measure of z motion can be as accurate as that of x and y motion. Three-dimensional displacements of heart-wall and skeletal muscle are shown. With an accurate measure of three-dimensional motion, more complete analysis of heart-wall motion and contraction is possible.

Mitral valve replacement combined with coronary artery operation: Determinants of early and late results

Mitral valve replacement combined with coronary artery bypass grafting has been reported as being associated with a higher mortality than either mitral valve replacement or coronary artery bypass grafting alone. Cause of mitral valve disease and severity of mitral regurgitation have been reported as related to mortality. To study the correlation of the cause of mitral valve disease and severity of mitral regurgitation to hospital mortality and long-term survival, we analyzed the results of 135 patients undergoing mitral valve replacement and coronary artery bypass grafting between June 1974 and August 1989. The hospital mortality was 11.8% ( 16 / 135 ). Fifteen preoperative and operative variables were tested for correlation with hospital or late mortality using univariate tests and multivariate regression. Advanced age (>60 years), New York Heart Association functional class, and wall motion score were independently associated with hospital mortality ( p < 0.05). The cause of mitral valve disease and severity of mitral regurgitation were not related to hospital mortality or long-term survival ( p > 0.05). The follow-up rate was 96.6% for the hospital survivors ( 115 / 119 ). Mean follow-up was 52.6 ± 4.1 months. There were 35 late deaths. Survival was 91.9%, 89.9%, 78%, and 49.9% at 1, 2, 5, and 10 postoperative years, respectively. Preoperative New York Heart Association functional class and use of catecholamines during the postoperative intensive care period were independently related to late survival ( p < 0.05). In conclusion, this study suggested that operative mortality for mitral valve replacement combined with coronary artery bypass grafting was correlated with preoperative New York Heart Association functional class, advanced age (>60 years), and wall motion score, and that long-term survival was correlated with preoperative New York Heart Association functional class and use of catecholamines postoperatively. Neither cause of mitral valve disease nor severity of mitral regurgitation was correlated with hospital or long-term survival.

Myocardial tagging in polar coordinates with use of striped tags.

Regional deformation abnormalities in the heart wall provide a good indicator of ischemia. Myocardial tagging with magnetic resonance imaging is a new method of assessing heart wall motion during contraction. Current methods of myocardial tagging either do not provide two-dimensional information or lack a coordinate system well adapted to the morphology of the heart. In this article, the authors describe a new tagging method that provides a true polar coordinate system, with both radial and angular dimensions. This is accomplished with use of a section-selective version of spatially modulated magnetization resulting in striped tags (STAGs). These STAG planes are placed in the myocardium in a star pattern so that they intersect on the long axis of the heart and stripes appear through the width of the heart wall. In the short-axis view during contraction, rotation around the long axis yields angular information such as shear and twist, while separation of the stripes within the myocardium permits measurement of radial thickening. Therefore, this method provides a coordinate system for calculating two-dimensional strain that is adapted to the morphology of the left ventricle.

Heart wall motion: improved method of spatial modulation of magnetization for MR imaging.

A previously reported method of using magnetic resonance (MR) imaging to study heart wall motion involves a pair of nonselective radio-frequency (RF) pulses, separated by a magnetic field gradient pulse, prior to imaging; this produces images with a regular pattern of stripes that move with the heart wall and that have a sinusoidal intensity profile. It is demonstrated in this study that the substitution of more RF pulses, with their relative amplitudes distributed according to the binomial sequence, results in sharper stripes. This permits the use of a two-dimensional grid of stripes for more detailed studies of heart wall motion and provides a unique method of analyzing regional ventricular myocardial strain.

Three-dimensional left ventricular wall motion in man. Coordinate systems for representing wall movement direction.

We have studied the three-dimensional (3D) motion of left ventricular (LV) epicardial points by tracking one to three dozen coronary artery bifurcations in eleven human subjects. Wall motion was analyzed using several different coordinate systems: (1) cylindrical centered about the LV long axis, (2) spherical with origin at the LV center-of-gravity (COG), and (3) spherical with origin at the LV center-of-contraction (COC), the best-fit 3D point toward which the wall moves. The coordinate systems were studied both fixed and moving with time. Three-dimensional motions were decomposed into three directional components, with high radial (in and out) percentages being regarded as the figure-of-merit of a given coordinate system. Average percentage radial motions were fixed cylindrical 16%, fixed spherical COG 35%, fixed spherical COC 47%, moving cylindrical 17%, moving spherical COG 30%, moving spherical COC 91%. Spherical systems were generally better than cylindrical systems, with the COC representing a better origin than the COG. Moving systems were appreciably better than fixed only for the COC model, indicating that the COC, which traverses up and down the LV midline, moves significantly while the other systems are more stationary. At each instant in time, almost all (91%) of the 3D motion of the entire heart wall is directed toward a single moving 3D point, the COC. Thus, there exists in principle a near-perfect 3D heart wall motion model. Approximately 25% of 3D wall motion is unseen in conventional monoplane views. Also, any model that represents 3D wall motion only along fixed straight 3D lines (eg, end-diastole to end-systole) necessarily ignores 27% of the true 3D heart wall motion.

Methods for evaluating cardiac wall motion in three dimensions using bifurcation points of the coronary arterial tree.

An accurate three-dimensional (3D) representation of heart wall motion would be an important means of evaluating cardiac function. To accomplish this, we have developed an interactive computer graphics system designed to enter the time-dependent 3D positions of bifurcations of the coronary arterial tree. These bifurcations are precise markers of the epicardial surface, and their motions accurately represent the motion of the underlying heart wall. We demonstrate techniques for calculating local wall motion, including displacement and velocity, for determining a time-dependent center-of-contraction point towards which the epicardium tends to move and for tracking the mechanical contraction wave using cross-correlation methods. We have applied these techniques to study seven patients with normal left ventriculograms and coronary arteriograms. We have found these methods to be generally applicable and to provide information not obtainable without 3D analysis.

Graphics methods for tracking three-dimensional heart wall motion

An analysis of heart wall motion requires that specific points on the wall be identified and their movements tracked in three dimensions over several heart beats. A method to reconstruct time-dependent 3D coordinates from any two or more perspective views has been developed. We have used this method to determine accurately the 3D dynamics of bifurcation points of the coronary arteries or surgically implanted markers by tracking their projections in both views of a biplane coronary cineangiogram. The tracking operation is aided by a sophisticated interactive computer system which superimposes an animated graphics display onto the film image. This allows entries to be checked and corrected immediately. The most powerful tool provided by the graphics system is the ability to display the backprojections of positions from one view as auxiliary lines across the other view on which the projection of the point of interest must lie. We provide some examples of cardiac wall motion measures we have made using this system.