Tracking and motion analysis of the left ventricle with deformable superquadrics

We present a new approach to analyse the deformation of the left ventricle of the heart based on a parametric model that gives a compact representation of a set of points in a 3-D image. We present a strategy for tracking surfaces in a sequence of 3-D cardiac images. Following tracking, we then infer quantitative parameters which characterize: left ventricle motion, volume of left ventricle, ejection fraction, amplitude and twist component of cardiac motion. We explain the computation of these parameters using our model. Experimental results are shown in time sequences of two modalities of medical images, nuclear medicine and X-ray computed tomography (CT). Video sequences presenting these results are on the CD-ROM.     

Echocardiography in the evaluation of ventricular function

The ultrasonic beam used for quantitative assessment of left ventricular (LV) function traverses the heart in a projection similar to the familiar angiographic left anterior oblique projection. It crosses the anterior wall of the right ventricle, the right ventricular cavity, the interventricular septum, the LV cavity and the posterior wall of the left ventricle. Whereas the cyclic changes of the right ventricular diameter are rarely clearly determined by echocardiography, the easily assessed cyclic changes of the LV endocardial transverse diameter are useful measure of LV FUNCTION. Of practical importance are the percentage of systolic shortening of the LV diameter (%Sh) and the mean velocity of circumferential fiber shortening (VCF). There are several factors, such as placing of the ultrasonic transducer, the shape and size of the LV cavity and rotational movements of the heart as a whole, that influence echocardiographic determination of the transverse LV diameter. In patients with asynergic contraction, %Sh and VCF cannot be used as measures of overall LV performance, but localized contraction disturbances of the septum and the posterior wall may be detected from the reduced extent of wall motion in a given LV segment during a full sweep from the base to the apex. The most important indications for echocardiographic assessment of LV function are valvar diseases with chronic LV pressure or volume overload, and congestive cardiomyopathy. Echocardiography has proved useful in serial evaluation of LV function in patients undergoing valvar heart surgery. Assessment of LV volume by standard echocardiography using the cubic formula is not satisfactory. More accurate determination of volumes is provided by formulas that include the actual ratio of the LV long axis to the minor axis.     

Segmentation of 2-D and 3-D objects from MRI volume data using constrained elastic deformations of flexible Fourier contour and surface models

This paper describes a new model-based segmentation technique combining desirable properties of physical models (snakes), shape representation by Fourier parametrization, and modelling of natural shape variability. Flexible parametric shape models are represented by a parameter vector describing the mean contour and by a set of eigenmodes of the parameters characterizing the shape variation. Usually the segmentation process is divided into an initial placement of the mean model and an elastic deformation restricted to the model variability. This, however leads to a separation of biological variation due to a global similarity transform from small-scale shape changes originating from elastic deformations of the normalized model contours only. The performance can be considerably improved by building shape models normalized with respect to a small set of stable landmarks (AC-PC in our application) and by explaining the remaining variability among a series of images with the model flexibility. This way the image interpretation is solved by a new coarse-to-fine segmentation procedure based on the set of deformation eigenmodes, making a separate initialization step unnecessary. Although straightforward, the extension to 3-D is severely impeded by difficulties arising during the generation of a proper surface parametrization for arbitrary objects with spherical topology. We apply a newly developed surface parametrization which achieves a uniform mapping between object surface and parameter space. The 3-D procedure is demonstrated by segmenting deep structures of the human brain from MR volume data.     

State of the art: "diastology" research 1998

The performance of the left ventricle (LV) during diastole is defined by the pressure-volume relationship. Consequently, noninvasive techniques have been limited in the evaluation of diastolic function by their inability to evaluate intracardiac pressure, particularly LV filling pressure and end-diastolic pressure. Abnormalities of LV diastolic function play a major role in producing the clinical signs and symptoms of heart failure. Previous studies have demonstrated that the transmitral flow (TMF), pulmonary venous flow (PVF) and left atrial appendage flow (LAAF) velocity patterns determined by pulsed Doppler echocardiography are useful parameters for evaluating left atrial (LA) and LV hemodynamic events. However, these variables are influenced by loading conditions, particularly preload. Furthermore, it has become increasingly clear that abnormalities of LV diastolic function, such as relaxation and filling, can be assessed precisely using color Doppler M-mode echocardiography and pulsed tissue Doppler imaging irrespective of preload. This review presents a clinical approach to understanding the hemodynamic abnormalities of the LA and LV in a variety of cardiac diseases using these new modalities. In addition, the limitations of these techniques are discussed.     

Clinical application of pulsed Doppler tissue imaging for assessing abnormal left ventricular relaxation

Conventional assessment of left ventricular (LV) relaxation by calculating the time constant of LV pressure decay during the isovolumic diastole requires an invasive approach. Conversely, noninvasive parameters obtained by measuring isovolumic relaxation time and transmitral flow velocity often give inaccurate information. Using LV pressure curve, pulsed Doppler echocardiography, and pulsed Doppler tissue imaging in 38 patients with heart disease and 12 control subjects, we calculated the time constant and recorded transmitral flow velocity and motion velocities at the endocardial portions of the ventricular septum and LV posterior wall. Compared with the controls, patients exhibited a prolonged time constant, a decreased peak early diastolic velocity of the LV posterior wall, and a prolonged time interval from the second heart sound to the peak of the early diastolic wave. The time constant correlated well with the isovolumic relaxation time and various parameters calculated from the transmitral flow velocity, except in patients with elevated LV end-diastolic pressure. In all subjects, the time constant correlated negatively with the peak early diastolic velocity of the posterior wall and positively with the time from the second heart sound to the peak of the early diastolic wave. Thus, early diastolic parameters derived from the motion velocity of the LV posterior wall by pulsed Doppler tissue imaging were closely related to the time constant. This technique may allow noninvasive evaluation of abnormal LV relaxation in patients with various heart diseases.     

Assessment of regional left ventricular wall stress after myocardial infarction by echocardiography-based structural analysis

OBJECTIVES: The objective of this study was to determine the distribution of regional left ventricular (LV) wall stress after myocardial infarction (MI). BACKGROUND: After a large MI, structural changes occur in the heart that ultimately may lead to alterations in LV size and shape, a process generally referred to as ventricular remodeling. Regional variation in myocardial wall stress may be responsible for initiation of physiologic and cellular changes that result in myocardial hypertrophy, dilatation, and remodeling after MI. Simplified geometric analytic methods of estimating global LV wall stress cannot determine regional variation such as that occurring after MI. METHODS AND RESULTS: To assess regional LV wall stress after MI, we applied the finite element method to patient-specific end-systolic LV models generated from echocardiographic imaging. After validation by comparison with analytic solutions of LV wall stress in idealized ventricles, LV models were constructed from rotated orthogonal apical images from 13 normal volunteers, 16 patients with recent (<4 days) anterior MI, and 7 patients with recent infero-posterior MI. The mean Von Mises stress was calculated for the entire LV and for 5 separate regions of the LV. Von Mises LV wall stress was increased globally in patients with anterior MI (211 +/- 46 kdyne/cm2; P < .002) or infero-posterior MI (175 +/- 23 kdyne/cm2; P = .04) compared with normal patients (144 +/- 57 kdyne/cm2). Global wall stress correlated directly with ejection fraction (P < .0001) and inversely with wall motion index (P < .004) in patients with anterior MI. Wall stress in the apical regions was increased by a factor of 2.3 in patients with anterior MI (P < .0001), whereas other regions did not differ from normal patients. There were no individual regions that were significantly different from normal in patients with infero-posterior MI. CONCLUSIONS: Anterior MI is associated with an increase in apical end-systolic wall stress compared with normal and infero-posterior MI. This may be an important stimulus for LV remodeling after anterior MI.     

Hypothesis of the compression of morbidity: an example of theoretical development in epidemiology]

To assess the usefulness of the tissue Doppler imaging variables for the evaluation of left ventricular (LV) systolic function, we compared variables obtained by the pulsed Doppler method with the LV ejection fraction (%EF) and the maximum value for the first derivative of LV pressure (peak dP/dt). We examined 65 patients, including 15 patients with noncardiac chest pain, 15 with ischemic heart disease, 15 with dilated cardiomyopathy, 10 with hypertensive heart disease, and 10 with asymmetric septal hypertrophic cardiomyopathy. The subendocardial systolic wall motion velocity patterns were recorded for LV posterior wall and ventricular septum in the parasternal LV long-axis view. The peak dP/dt was significantly lower in the hypertensive heart disease, hypertrophic cardiomyopathy, and dilated cardiomyopathy groups. The peak systolic velocity was lower and the time from the electrocardiographic Q wave to the peak of the systolic wave for the posterior wall was longer in the hypertensive heart disease (5.9 +/- 0.5 cm/sec and 215 +/- 21 msec, respectively), hypertrophic cardiomyopathy (6.2 +/- 0.9 cm/sec and 217 +/- 17 msec, respectively), and dilated cardiomyopathy (5.2 +/- 0.8 cm/sec and 235 +/- 26 msec, respectively) groups than in the noncardiac chest pain (7.7 +/- 0.9 cm/sec and 187 +/- 24 msec, respectively) and the ischemic heart disease (7.6 +/- 0.8 cm/sec and 184 +/- 22 msec, respectively) groups. In all groups, the peak systolic velocity and the time from the electrocardiographic Q wave to the peak of the systolic wave for the posterior wall correlated directly and inversely, respectively, with the %EF (r = 0.59, p < 0.0001; r = -0.59, p < 0.0001) and the peak dP/dt (r = 0.75, p < 0.0001; r = -0.68, p < 0.0001). Both tissue Doppler variables for the ventricular septum did not correlate with the %EF but roughly correlated with peak dP/dt. We conclude that the systolic LV wall motion velocity parameters obtained by pulsed tissue Doppler imaging may be useful for noninvasive evaluation of global LV systolic function in patients with no regional asynergy.     

Targeting the minor groove of DNA

Congenital nystagmus is an oculomotor disorder in which fixation is disrupted by rhythmical, bilateral involuntary oscillations. Clinically these eye movements have been described with some degree of success in terms of their peak-to-peak amplitude, frequency, mean velocity and waveform shape. However, it has not proved possible to diagnose any underlying pathology from the nystagmus characteristics. Here, we propose a new approach to understanding the nystagmus using dynamical systems theory. Our approach is based on the use of delay embedding techniques, which allow one to relate a time series of scalar observations to the state space dynamics of the underlying dynamical system. Using this approach we quantify the dynamics of the nystagmus in the region of foveation and present evidence to suggest that it is low-dimensional and deterministic. Our results put new constraints on acceptable models of nystagmus and suggest a way to make a closer link between data analysis and model development. This approach raises the hope that techniques originally developed to stabilise chaotic systems, by using small perturbations, may prove useful in the control of nystagmus.     

Fast numerical algorithms for fitting multiresolution hybrid shape models to brain MRI

In this paper, we present new and fast numerical algorithms for shape recovery from brain MRI using multiresolution hybrid shape models. In this modeling framework, shapes are represented by a core rigid shape characterized by a superquadric function and a superimposed displacement function which is characterized by a membrane spline discretized using the finite-element method. Fitting the model to brain MRI data is cast as an energy minimization problem which is solved numerically. We present three new computational methods for model fitting to data. These methods involve novel mathematical derivations that lead to efficient numerical solutions of the model fitting problem. The first method involves using the nonlinear conjugate gradient technique with a diagonal Hessian preconditioner. The second method involves the nonlinear conjugate gradient in the outer loop for solving global parameters of the model and a preconditioned conjugate gradient scheme for solving the local parameters of the model. The third method involves the nonlinear conjugate gradient in the outer loop for solving the global parameters and a combination of the Schur complement formula and the alternating direction-implicit method for solving the local parameters of the model. We demonstrate the efficiency of our model fitting methods via experiments on several MR brain scans.     

Doppler analysis of pulmonary venous flow profiles in orthotopic heart transplant recipients: a comparison with mitral flow profiles and atrial function

Previous Doppler studies of transmitral flow profiles in heart transplant recipients suggested left ventricular (LV) diastolic dysfunction. The influence of left atrial filling and emptying on mitral Doppler profiles in heart transplant recipients has not been studied systematically. In the present study, pulmonary venous flow profiles, mitral flow profiles, left atrial area change and mitral annulus motion were analyzed in 20 orthotopic heart transplant recipient and 20 control subjects by transthoracic and transesophageal echocardiography and Doppler. Mitral flow profiles revealed a "restrictive" pattern with a high early-to-late diastolic flow velocity ratio in transplant patients (2.16 +/- 0.52 vs. 1.30 +/- 0.25, p < 0.0001), which was mainly due to a reduced late diastolic maximum mitral flow velocity (32.6 +/- 8.3 vs. 51.6 +/- 12.4 cm/s, p < 0.0001). Left atrial area change (35.9 +/- 13.9 vs. 58.1 +/- 17.0%, p < 0.0006) and mitral annulus motion (9.2 +/- 3.3 vs. 12.2 +/- 2.0%, p < 0.05) were reduced in transplant recipients, compared to controls. Pulmonary venous flow parameters in transplant recipients were markedly altered during systole, when pulmonary venous flow parameters are influenced primarily by atrial function rather than by diastolic LV properties: peak systolic flow velocity (45.5 +/- 8.2 vs. 62.3 +/- 14.0 cm/s, p < 0.001), maximum flow velocity ratio (0.87 +/- 0.19 vs. 1.45 +/- 0.33), time velocity integral of pulmonary venous flow during systole (9.3 +/- 2.3 vs. 17.1 +/- 4.0 cm, p < 0.001) and the systolic fraction of the time velocity integral (52.6 +/- 10.8 vs. 68.5 +/- 6.8%, p < 0.001) were lower in heart transplant recipients than in controls. These findings are compatible with atrial dysfunction and reduced mitral annulus motion. The results of this study indicate that LV diastolic dysfunction is not the only possible cause of altered transmitral Doppler profiles in heart transplant recipients. Atrial abnormalities represent a major contributing factor to altered mitral and pulmonary venous flow patterns. Analysis of transmitral Doppler profiles alone are therefore not adequate for analysis of diastolic LV function in heart transplant recipients.     

Biases in three-dimensional structure-from-motion arise from noise in the early visual system

The projected pattern of retinal-image motion supplies the human visual system with valuable information about properties of the three-dimensional environment. How well three-dimensional properties can be recovered depends both on the accuracy with which the early motion system estimates retinal motion, and on the way later processes interpret this retinal motion. Here we combine both early and late stages of the computational process to account for the hitherto puzzling phenomenon of systematic biases in three-dimensional shape perception. We present data showing how the perceived depth of a hinged plane ('an open book') can be systematically biased by the extent over which it rotates. We then present a Bayesian model that combines early measurement noise with geometric reconstruction of the three-dimensional scene. Although this model has no in-built bias towards particular three-dimensional shapes, it accounts for the data well. Our analysis suggests that the biases stem largely from the geometric constraints imposed on what three-dimensional scenes are compatible with the (noisy) early motion measurements. Given these findings, we suggest that the visual system may act as an optimal estimator of three-dimensional structure-from-motion.     

Quantitative two-dimensional echocardiographic assessment of regional wall motion during transient ischemia and reperfusion in the rat

Nonlethal myocardial ischemia produces profound and long-lasting effects on regional ventricular function and metabolism (myocardial stunning) and protects against myocardial infarction from subsequent prolonged ischemia (ischemic preconditioning). Two-dimensional echocardiography (2DE) is an essential tool for quantitative analysis of regional and global left ventricular (LV) function during myocardial ischemia and reperfusion and the study of these phenomena. However, the inability to perform 2DE in the open-chest rat heart has seriously limited the use of this model. To investigate the effect of transient coronary occlusion on segmental wall motion and LV geometry, we employed a 20 MHz intravascular ultrasound catheter placed on the epicardial surface of the rat heart (n = 15) to yield 2DE images suitable for quantitative analysis. Three 2-minute left coronary occlusions were made, separated by 5 minutes of reperfusion, with imaging during occlusion and at 5 and 60 minutes of reperfusion. Ischemic and nonischemic wall thicknesses, LV cross-sectional area, estimated LV volume, and the fractional changes of these parameters were measured. In eight animals these values were also compared with necropsy measurements of wall thickness, LV cross-sectional area, and volume. LV and right ventricular structures were well visualized in short-axis cross-sectional images in all animals, and images suitable for quantitative analysis were obtained in 92% of the periods. Coronary occlusion caused immediate, marked LV cavitary expansion, which rapidly returned to normal by 5 minutes of reperfusion. Active systolic thickening of the anterior wall at baseline (47% +/- 3%) became passive thinning during occlusion (-6% +/- 2%) and recovered partially, to 30% +/- 3% at 5 minutes of reperfusion and 42% +/- 4% at 60 minutes (p < 0.0005 at 5 minutes of reperfusion vs baseline; p not significant at 60 minutes). Recovery of thickening after 5 minutes of reperfusion was not different after the first versus third occlusion (23% +/- 4% vs 30% +/- 3%; p = 0.19). Measurements made by 2DE correlated well with those made by necropsy, although wall thickness was slightly thicker by 2DE. We conclude that epicardial echocardiography with an intravascular ultrasound catheter provides quantifiable 2DE images in this model and yields accurate information on segmental wall thickening and ventricular geometry not available by other techniques. Left coronary occlusion in the rat is associated with marked global and segmental LV expansion, which rapidly reverses with reperfusion. Postischemic regional wall motion abnormalities are present after coronary occlusion as brief as 2 minutes and can be measured accurately. The effect of multiple brief occlusions is not cumulative.(ABSTRACT TRUNCATED AT 400 WORDS)     

Simulation of Airfoil Icing with a Novel Morphogenetic Model

In this paper, we describe a new modeling approach to tackle the challenging problem of in-flight icing prediction. In this approach, termed morphogenetic modeling, we predict the structural details of aircraft ice accretion by emulating the behavior of individual fluid elements. A two-dimensional morphogenetic model is used here to predict the ice accretion shape forming on a National Advisory Committee For Aeronautics 0012 airfoil under various atmospheric conditions. The influence of the surface heat transfer formulation on the ice accretion shape is examined. We complement the numerical simulation with an analytical model for airfoil icing that is based on a simple form of the mass and heat conservation equations. This analytical investigation allows us to identify a significant new dimensionless ratio, the runback factor, defined as the ratio of the impinging water mass flux to the freezing mass flux at the stagnation line. An increasing runback factor leads to a quantifiable downstream displacement of the accretion mass. We also use the analytical model to verify the morphogenetic model during the early stages of icing, and find that there is reasonable agreement between the two models in terms of ice accretion shape. A comparison with experimental data and other models shows that even simple morphogenetic modeling is competitive with existing models. Further improvements will take advantage of the model’s unique ability to simulate discontinuous ice accretions in complex geometries, leading to a considerable advancement in the simulation of in-flight icing.     

Development of a Robot‐Based Sheet Metal Forming Process

This paper describes a new sheet metal forming process for the production of sheet components for prototypes and small lot sizes. The generation of the shape is based on kinematics and is implemented by means of a new forming machine consisting of two industrial robots. Compared to conventional sheet metal forming machines, this newly developed forming process offers a high geometrical form flexibility, and comparatively small deformation forces enable high deformation degrees. The principle of the procedure is based on flexible shaping by means of a freely programmable path‐synchronous movement of the two robots. The final shape is produced by the incremental infeed of the forming tool in depth direction and its movement along the contour in lateral direction at each level of the depth direction. The supporting tool with its simple geometry is used to support the sheet metal and follows the forming tool at the rear side of the sheet metal. The sheet metal components manufactured in first attempts are of simple geometry like frustum and frustum of pyramids as well as spherical cups. Among other things the forming results are improved by an adjustment of the movement strategy, a variation of individual process parameters and geometric modifications of the tools. In addition to a measurement of the form deviations of the sheet with a Coordinate Measurement Machine, screened and deformed sheets are used for deformation analyses. Furthermore, the incremental forming process is analysed with assistance of the finite element method. In total the results show that a robot‐based sheet metal forming with kinematic shape generation is possible and leads to acceptable forming results. In order to be able to use the potential of this process, a goal‐oriented process design is as necessary as specific process knowledge. In order to achieve process stability and safety, the essential process parameters and the process boundaries have to be determined.     

Dynamic stiffness and implications for assisting the operation of the left ventricle

The distribution of bending strain and stiffness in the wall of the left ventricle (LV) is relevant to the augmentation of its function by a modified skeletal-muscle wrap in the new surgical procedure of cardiomyoplasty. A novel approach to ventricular mechanics is presented which blends some finite-element results in engineering with new data available on ventricular geometry. Two simplified axisymmetric strip-element models of the LV are used to illustrate aspects of myocardial stiffness in the bending-strain-energy distribution and the effect on wrap synchronization of a change in cross-fibre stiffness when the heart has nonuniform or ectopic beats. The nonlinear and time-dependent nature of both camping and wall stiffness is derived from differential equations governing the dynamic paths from systole to diastole of finite wall elements around the periphery of an oblique LV slice using magnetic resonance imaging (MRI) data. This leads to a geometric method for determining these parameters. Results for time-dependent stiffnesses of elements in their trajectories are presented for a normal heart.     

G1 accumulation caused by iron deprivation with deferoxamine does not accompany change of pRB status in ML-1 cells

In hypertension, several factors disturb coronary circulation and the metabolic reserve of the heart. This study was undertaken to test whether in hypertensive patients global and regional left ventricular (LV) function is related during exercise to the presence of significant coronary stenosis and whether lowering of coronary perfusion pressure through rapid normalization of the diastolic pressure may modify the dynamics of the left ventricle. Thirty-five patients with mild to moderate hypertension undergoing coronary angiography for the evaluation of chest pain were included in the study; upright bicycle exercise echocardiography tests were performed without therapy and 1 day later 1 h after sublingual administration of nifedipine. LV ejection fraction and regional wall motion scores were evaluated and compared at baseline, peak exercise, immediate postexercise, and recovery phases in each test through digital on-line storing of echocardiographic images. Twenty-one patients had normal coronary arteries (group 1) and 14 significant coronary stenoses (group 2); age, gender, heart rate, blood pressure, left ventricular diameter and mass index, and ejection fraction were similar in the two groups. At peak exercise LV ejection fraction slightly increased in group 1, whereas it slightly decreased in group 2 (both during the test without therapy and after nifedipine administration). All patients in group 1 had normal left ventricular wall motion during exercise; 13 of 14 patients in group 2 had LV wall motion abnormalities at peak exercise. Nifedipine did not produce any effect on LV regional wall motion in group 1, but it induced significant changes in LV regional wall motion in seven patients in group 2. Changes in LV wall motion between the two test groups were related to the number of the stenotic coronary vessels: the normal exercise test before and after therapy and the two normalized tests after nifedipine administration were in fact observed in patients with one-vessel disease, whereas worsening or changes in the site of ischemia were observed only in patients with multivessel disease. Regional and global left ventricular dynamics during exercise is mainly dependent on the existence of significant coronary artery disease. Rapid decrease of blood pressure does not alter the regional dynamics of the left ventricle during exercise in patients without coronary artery disease, but it may induce normalization, worsening, or changes in the site of wall motion abnormalities in hypertensives with significant coronary stenoses.     

Characteristics of medical care related to autopsy authorization in a pediatric hospital

Patients with atypical chest pain frequently lack significant coronary artery disease (CAD) and are, therefore, at low risk for future adverse cardiovascular events. We hypothesized that in this group of patients, stress echocardiography could identify those at risk for cardiac events. We retrospectively reviewed (mean follow-up 23.0 +/- 7.2 months) the prognostic value of stress echocardiography for major (cardiac death, myocardial infarction, congestive heart failure, and unstable angina) and total (major events plus coronary revascularization) cardiac events in 661 patients with atypical chest pain, normal global left ventricular (LV) systolic function, and no history of CAD. A positive stress echocardiogram was defined as the development of new or worsening wall motion abnormalities with exercise stress (80%) or dobutamine (20%). A total of 41 cardiac and 16 major events were noted. The event-free survival for total cardiac events was 97% for a normal stress echocardiogram and 93% for a normal stress electrocardiogram (ECG) at 30 months. A positive stress ECG predicted an event-free rate of 86% compared with 74% for stress-induced wall motion abnormalities and 42% if stress-induced LV dysfunction accompanied the wall motion abnormalities. A strategy recommending invasive studies based on positive stress echocardiogram results increased the per-patient cost, but led to greater savings per cardiac event predicted and provided incremental prognostic value for future cardiac events beyond clinical and stress electrocardiographic data. Thus, stress echocardiography in low-risk patients for CAD appears to be more cost effective than a stress ECG.     

Size estimation method for patch used in reconstruction of LV cavity

The reconstruction of LV cavity is accomplished by suturing a patch to the viable myocardium to exclude the infarcted area from the high LV pressures. However, there is no clear guideline to estimate the size of patch used for LV reconstruction. We have designed a new method to determine the correct patch size, and applied it in 5 cases. The suture line of the patch is at the junction of contractile (functional) and infarcted portions of LV. The patch size is determined by the length of AB, termed "a", as the base, where "point A" represents the junction on the LV anterior wall side, and "point B" the junction of the LV posterior wall side, from RAO 30 degrees projection of the left ventriculogram obtained by cardiac catheterization. In LV aneurysm, we designed the patch in the range of a/2 < l < or = pi a/2, where patch length on RAO 30 degrees is considered "l". An effort was made to reconstruct to normalize LV volume and contour by designing the patch size to be a/2 < l < a, particularly when the contractile portion was enlarged by aneurysm. On the other hand, in post AMI VSD, LV contractile portion is not enlarged in early stage. Therefore, the patch was designed in the range of a < l < or = pi a/2 to maintain LV volume. Postoperative LV volume can be calculated prior to surgery, by using the lengths of the designed patch. Postoperative analysis indicated that the actual LV volume and contour were almost identical to our estimation. This method is very useful in planning the patch size for LV reconstruction.     

Left ventricular geometry in presenting untreated hypertension

In order to investigate the spectrum of geometry in our patient population, 63 untreated hypertensives underwent two-dimensional echocardiography. Left ventricular (LV) mass index and relative wall thickness, a measure of wall thickness in relation to cavity size, were calculated from the M-mode strip. In addition, to assess the sphericity of the left ventricle the ratio of LV minor to major hemiaxis was calculated. The subjects comprised 41 men (17 Caucasian, 22 Afro-Caribbean and two Oriental), and 21 women (five Caucasian, 12 Afro-Caribbean and two Oriental). Concentric hypertrophy was present in 46% of subjects, concentric remodelling in 32% of subjects, eccentric hypertrophy in only 6% of subjects and a normal left ventricular shape in 16% of subjects. The degree of sphericity of the left ventricle was similar among the four groups, suggesting that it does not change in uncomplicated hypertension. In contrast to the previously published combined series from Sassari and New York we had a low proportion of patients with either eccentric hypertrophy or normal left ventricular geometry. This is probably due to the high proportion of Afro-Caribbean subjects in our clinic population who are more likely to have left ventricular hypertrophy.