Left ventricular chamber and wall mechanics in the presence of concentric geometry.

BACKGROUND: To test the hypothesis that in the presence of left ventricular concentric geometry the definition of 'normal' ejection fraction should be reconsidered, and normality should rather be considered to have a higher than usual lower limit METHODS: M-mode echocardiographic endocardial shortening (eS) was studied in 148 hypertensive patients with left ventricular concentric geometry (relative wall thickness > or = 0.42), 78 with normal (54 +/- 10 years, 27 women) and 70 with depressed midwall shortening (mS) (53 +/- 10 years, 26 women), based on normal distribution of stress-corrected mS, and compared to a reference adult population of 297 age-matched normal subjects (54 +/- 8 years, 121 women) with eS > or = 28%. RESULTS: Patients with low mS exhibited higher heart rates and body mass indices than control individuals (both P < 0.01); blood pressure, left ventricular mass, relative wall thickness and peripheral resistance were higher than in patients with normal mS, whereas cardiac index was reduced (all P< 0.01). Adjustment for body mass index and race attenuated but did not eliminate the differences between the two groups of patients (0.05 < P < 0.0001). In contrast, eS was higher than normal in patients with normal midwall shortening, whereas was 'normal' in patients with low left ventricular midwall function. More than 80% of patients in the lowest quartile of apparently normal eS exhibited clear-cut low left ventricular midwall function. CONCLUSIONS: 'Normal' left ventricular chamber function in the presence of concentric geometry is associated with depressed midwall performance, more severe left ventricular hypertrophy, lower cardiac output and higher peripheral resistance. 'Normal' eS is the hallmark of normal myocardial function when left ventricular geometry is normal, but should be considered as a marker of systolic dysfunction when associated with concentric left ventricular geometry. Normal limits for eS should be therefore reset to upper values.     

Left ventricular midwall mechanics in systemic arterial hypertension. Myocardial function is depressed in pressure-overload hypertrophy

BACKGROUND. Left ventricular (LV) midwall geometry has been described conventionally as the sum of the chamber radius and half of the wall thickness; this convention is based on the assumption of uniform transmural thickening during systole. However, theoretical considerations and experimental data indicate that the inner half (inner shell) of the LV wall thickens more than the outer half (outer shell). Thus, an end-diastolic circumferential midwall fiber exhibits a relative migration toward the epicardium during systole. As a result, the conventional method provides an overestimate of the extent of the midwall fiber shortening. METHODS AND RESULTS. We developed an ellipsoidal model with a concentric two-shell geometry (nonuniform thickening) to assess midwall fiber length transients throughout the cardiac cycle. This modified midwall method was used in the analysis of LV cineangiograms from 15 patients with systemic arterial hypertension and 14 normal subjects. Study groups were classified according to LV mass index (LVMI): 14 normal subjects (group I), eight hypertensive patients with a normal LVMI (group II), and seven hypertensive patients with an increased LVMI (group III). There were no significant differences in LV end-diastolic pressure or volume among the three groups; the ejection fraction was slightly greater in group II (70 +/- 5%) than in groups I (65 +/- 8%) and III (66 +/- 4%), but this trend did not achieve statistical significance. Values for endocardial and conventional midwall fractional shortening (FS) were also similar in the three groups. By contrast, FS by the concentric two-shell geometry (modified midwall method) in group III (16 +/- 2%) was significantly less than that seen in groups I and II (21 +/- 4% and 21 +/- 5%, respectively; both p less than 0.05). This difference achieves greater importance when it is recognized that mean systolic circumferential stress was lower in group III (151 +/- 22 g/cm2) than in groups I and II (244 +/- 37 g/cm2 and 213 +/- 38 g/cm2, respectively; both p less than 0.01). The midwall stress-shortening coordinates in six of the seven group III patients were outside the 95% confidence limits for the normal (group I) subjects. Thus, despite a normal ejection fraction, systolic function is subnormal in hypertensive patients with LV hypertrophy. CONCLUSIONS. Chamber dynamics provide an overestimate of myocardial function, especially when LV wall thickness is increased. This is due to a relatively greater contribution of inner shell thickening in pressure-overload hypertrophy.     

Left ventricular mass and systolic dysfunction in essential hypertension

A relation between left ventricular (LV) hypertrophy and depressed midwall systolic function has been described in hypertensive subjects. However, a strong confounding factor in this relation is concentric geometry, which is both a powerful determinant of depressed midwall systolic function and a correlate of LV mass in hypertension. To evaluate the independent contribution of LV mass to depressed systolic function, 1827 patients with never-treated essential hypertension (age 48 +/- 12 years, men 58%) underwent M-mode echocardiography under two-dimensional guidance. Relative wall thickness was the strongest determinant of low midwall fractional shortening (r = -0.63, P < 0.0001). The significant inverse relation observed between LV mass and midwall fractional shortening (r = -0.43, P < 0.0001) persisted after taking into account the effect of relative wall thickness (partial r = -0.27, P < 0.0001). Within each sex-specific quintile of relative wall thickness, prevalence of subnormal afterload-corrected midwall systolic function was greater in subjects with, than in subjects without, LV hypertrophy (P < 0.05 for the first, third, fourth and fifth quintile). In a multiple linear regression analysis, both LV mass (P < 0.0001) and relative wall thickness (P < 0.0001) were independent predictors of a reduced midwall fractional shortening. In conclusion, the inverse association between LV mass and midwall systolic function is partly independent from the effect of relative wall thickness. LV hypertrophy is a determinant of subclinical LV dysfunction independently of the concomitant changes in chamber geometry.     

Left ventricular systolic and diastolic function after anthracycline chemotherapy in childhood

BACKGROUND: In childhood, late cardiotoxicity is characterized by inappropriately thin wall and consequent increased end-systolic wall stress, but the associations of impaired left ventricular geometry and function occurring under these circumstances need further investigation. HYPOTHESIS: The purpose of this study was to assess anthracycline late effects on the relationships occurring between increased end-systolic stress (ESS) and changes in both M-mode systolic measurements (i.e., endocardial and midwall fractional shortening) and Doppler diastolic indices in the pediatric age. METHODS: The population consisted of 101 children treated with anthracyclines for at least 12 months and 91 healthy children. Using M-mode echocardiography, end-systolic wall stress was calculated as index of afterload, and endocardial and midwall fractional shortening as systolic indices. Doppler transmitral measurements were made as diastolic indices. RESULTS: Patients treated with anthracyclines showed significantly lower relative wall thickness and left ventricular mass index, greater end-systolic wall stress, reduced endocardial and midwall fractional shortening and peak E/A ratio, prolonged deceleration, and isovolumic relaxation times. Direct relationships were found between end-systolic wall stress and both endocardial and midwall shortening. The use of midwall shortening in the relation showed a greater, but not significant increase (from 3 to 6%) in the proportion of patients with depressed systolic function than did endocardial shortening. In the anthracycline group, end-systolic wall stress was also inversely related to relative wall thickness and directly to isovolumic relaxation time. CONCLUSIONS: In childhood, reduced myocardial thickness and increased afterload explain much of systolic and diastolic dysfunction of late anthracycline toxicity. Midwall fractional shortening does not seem to add useful information for identifying subsets of children more prone to the development of heart failure.     

Ventricular and myocardial function following treatment of hypertension

This study assesses and evaluates left ventricular (LV) contractile function after treatment of hypertension, with an emphasis on LV midwall mechanics. Although prior studies have assessed cardiac function after hypertension treatment, none has performed an analysis of LV midwall mechanics. The Veterans Affairs Study of monotherapy in hypertension was a study large enough to permit analysis of midwall mechanics across a wide spectrum of mass changes accompanying hypertension treatment. LV chamber function was assessed by computing fractional shortening at the endocardial surface; LV midwall shortening was used to define myocardial function. Both shortening indexes were related to end-systolic circumferential stress in the entire population by partitioning values of mass and relative wall thickness changes. Two hundred sixty-eight patients were studied at baseline and again after a 1- or 2-year period. In the entire group, there was no significant change in circumferential shortening either at the endocardium (38 +/- 8% at baseline vs 37 +/- 7% at follow up, p = 0.29) or in shortening at the midwall (20 +/- 3% vs 20 +/- 3%, p = 0.53). However, 83 patients had a reduction in relative wall thickness and an increase in midwall shortening. The change in midwall shortening was significantly related to changes in relative wall thickness (r = -0.53, p = 0.0001). Thus, reductions in LV mass associated with antihypertensive therapy are generally not accompanied by a decrement in LV chamber or myocardial function. Improvement in midwall shortening is more closely related to normalization of LV geometry than to reduction in LV mass.     

Effect of electrocardiographic left ventricular hypertrophy on left ventricular systolic function in systemic hypertension (The LIFE Study). Losartan Intervention For Endpoint

Left ventricular (LV) ejection fraction is normal in most patients with uncomplicated hypertension, but the prevalence and correlates of decreased LV systolic chamber and myocardial function, as assessed by midwall mechanics, in hypertensive patients identified as being at high risk by the presence of LV hypertrophy on the electrocardiogram has not been established. Therefore echocardiograms were obtained in 913 patients with stage I to III hypertension and LV hypertrophy determined by electrocardiographic (Cornell voltage duration or Sokolow-Lyon voltage) criteria after 14 days' placebo treatment. The 913 patients' mean age was 66 years, and 42% were women. Fourteen percent had subnormal LV endocardial shortening, 24% had subnormal midwall shortening, and 13% had reduced stress-corrected midwall shortening. Nineteen percent had normal LV geometry, 11% had concentric remodeling, 47% had eccentric hypertrophy, and 23% had concentric hypertrophy. LV systolic performance evaluated by LV endocardial shortening and midwall shortening was impaired in 10% of patients with normal geometry, 20% with concentric remodeling, 27% with eccentric hypertrophy, and 42% with concentric hypertrophy. Relative wall thickness, an important independent correlate of LV chamber function, was related directly to endocardial shortening and negatively to midwall shortening and stress-corrected midwall shortening. LV mass was the strongest independent correlate of impaired endocardial shortening, midwall shortening, or both. In hypertensive patients with electrocardiographic LV hypertrophy, indexes of systolic performance are subnormal in 10% to 42% with different LV geometric patterns. Depressed endocardial shortening is most common in patients with eccentric LV hypertrophy, whereas impaired midwall shortening is most prevalent in patients with concentric remodeling or hypertrophy. Thus, in hypertensive patients with electrocardiographic LV hypertrophy, impaired LV performance occurs most often, and is associated with greater LV mass and relative wall thickness and may contribute to the high rate of cardiovascular events.     

Left ventricular hypertrophy in hypertension: stimuli, patterns, and consequences.

Left ventricular (LV) size in childhood closely parallels body size, whereas in adulthood LV mass is increasingly affected by effects of obesity, hypertension, the level of cardiac volume load, and the level of LV myocardial contractility. Recently, additional independent associations of diabetes, arterial structure and function and as yet unknown genes with higher LV mass have been defined; angiotensin II and insulin have also been suggested to be additive stimuli to LV hypertrophy. Consideration of the level of LV mass and of the LV wall thickness/chamber radius ratio (relative wall thickness) has identified four different geometric patterns of LV adaptation to hypertension, including concentric LV hypertrophy (increased mass and wall thickness), eccentric hypertrophy (increased mass, normal relative wall thickness), concentric remodeling (increased relative wall thickness with normal mass) and normal LV geometry. Concentric hypertrophy is associated with especially high arterial pressure while eccentric hypertrophy is associated with obesity and elevated volume load. Numerous studies show that increased LV mass predicts cardiovascular events and death independently of all conventional risk factors; initial studies have also identified adverse implications of low LV midwall function and high relative wall thickness. Pioneer studies strongly suggest that reversal of LV hypertrophy is associated with an improved prognosis.     

Relative wall thickness is an independent predictor of left ventricular systolic and diastolic dysfunctions in essential hypertension.

The objective of this study was to elucidate the relationship between left ventricular geometry and left ventricular (LV) function in patients with untreated essential hypertension. We evaluated LV systolic and diastolic functions by M-mode echocardiography in 24 normotensive control subjects (NC) and 129 patients with essential hypertension. Patients were divided into four groups according to the relative wall thickness and LV mass index: a normal left ventricle (n=57), a concentric remodeling (n=7), a concentric hypertrophy (n=31), and an eccentric hypertrophy (n=34) group. LV systolic function as measured by midwall fractional shortening (FS) was significantly decreased in both the concentric remodeling and concentric hypertrophy groups; no differences were observed for endocardial FS. LV diastolic function as measured by isovolumic relaxation time (IRT) was also decreased in both the concentric remodeling and concentric hypertrophy groups. In multivariate analysis, relative wall thickness (p<0.0001), end-systolic wall stress (p<0.0001), and systolic blood pressure (p=0.002) were independently associated (r2=0.72) with midwall FS in a model including age, LV mass index, body mass index, diastolic blood pressure and IRT. In addition, relative wall thickness (p=0.0008) and age (p<0.0001) were independently associated (r2=0.31) with IRT in a model including LV mass index, end-systolic wall stress, body mass index, systolic and diastolic blood pressures and midwall FS. We conclude that LV geometry as evaluated by relative wall thickness may provide a further independent stratification of LV systolic and diastolic functions in essential hypertension.     

Physiological left ventricular hypertrophy.

Echocardiograms were recorded in 154 active athletes (from various sports) and 21 ex-athletes and compared with those in 40 normal control subjects (non-athletes). Diastolic cavity dimension and posterior wall and septal thickness were measured and left ventricular mass and the ratio of posterior wall thickness to cavity radius and of septum to posterior wall thickness calculated. As a group athletes had a significantly increased diastolic cavity dimension, posterior wall and septal thickness, and left ventricular mass. The ratio of posterior wall thickness to cavity radius was distributed as a single continuous variable with a significantly increased mean, and there was no separate subgroup of shot putters or weight lifters with inappropriate hypertrophy. The mean ratio of septum to posterior wall thickness was normal, but there was a wide range of values up to 2.1:1. Ex-athletes had entirely normal left ventricular dimensions and wall thickness. When athletes are categorised by their standard of competition national standard competitors had a significantly increased posterior wall and septal thickness and left ventricular mass compared with university and non-competitive sportsmen. In conclusion, strenuous activity results in left ventricular hypertrophy which is appropriate to the body size of the athlete and the degree of activity but not to its type.     

Independent association of coronary flow reserve with left ventricular relaxation and filling pressure in arterial hypertension

BackgroundIt has been recognized that "cross-talk" occurs between coronary flow and left ventricular (LV) function. This study tested the hypothesis that impairment of coronary flow reserve (CFR) in arterial hypertension is associated with LV systolic and diastolic dysfunction, independent of abnormalities in LV geometry.MethodsWe studied 59 newly diagnosed, never-treated hypertensive patients, using transthoracic Doppler echocardiography including pulsed Tissue Doppler of mitral annulus and CFR on left anterior descending artery (low-dose dipyridamole). The study population was divided into two groups on the basis of age-normalized relative wall thickness (RWTn): 36 patients with normal LV geometry (RWTn 0.41).ResultsPatients with LV concentric geometry (RWTn > 0.41) had significantly lower values of midwall shortening (but not of endocardial shortening), longer isovolumic relaxation time (IVRT), lower Tissue Doppler-derived early diastolic velocity (E(m)), higher ratio of transmitral E velocity to E(m), and lower CFR as compared to patients with normal LV geometry (RWTn 相似文献   

A mathematical model of the dynamic geometry of the intact left ventricle and its application to clinical data.

In this paper we examine the relations that may exist between the geometric variables most frequently used to describe left ventricular contraction. The left ventricle is represented by a thick-walled cylinder contracting both radially and longitudinally. For this model, wall thickening, mid-wall radius shortening and longitudinal axis shorteining can be shown to be uniquely related during contraction, whereas it can be demonstrated that internal radius shortening is not uniquely related to these variables, but is also determined by the specific geometry of the cylinder, expressed in terms of the mid-wall radius-to-wall thickness (R/h) ratio of the cylinder. Detailed analysis of the same variables in 44 normal subjects, 32 patients with aortic stenosis and 54 patients with valvular regurgitation (33 aortic and 21 mitral), strongly suggests that the same relations are also clinically applicable. For instance, ventricular longitudinal axis shortening can be estimated with some accuracy from the standard M-mode echocardiogram. Also, wall thickening can be viewed as the direct reflection of the shortening that occurs in the circumferential and longitudinal directions, whereas internal radius shortening is significantly influenced by the R/h ratio of the ventricle, a consideration which becomes important when analyzing results in patients with left ventricular hypertrophy.     

Relations of ambulatory blood pressure level and variability to left ventricular and arterial function and to left ventricular mass in normotensive and hypertensive adults

OBJECTIVE: To assess the relationships between the level and variability of ambulatory blood pressure and left ventricular and arterial function. METHOD: We related 24 h ambulatory systolic blood pressure (SBP) and diastolic blood pressure (DBP), measures of their variability and clinic blood pressures to echocardiographic measures of left ventricle geometry and systolic function, total peripheral resistance, and the pulse pressure: stroke volume ratio as a measure of arterial stiffness in 58 normotensive and 222 unmedicated hypertensive adults. RESULTS: For hypertensive patients and for the entire population, awake and home ambulatory as well as technician-measured DBP were negatively related to left ventricle midwall fractional shortening (MWS) and to MWS as a percentage of the value predicted for end-systolic stress (afterload-corrected MWS), with inconsistent relations with SBP. Similarly, the SD and coefficient of variation of awake ambulatory DBP, but not SBP, were negatively related to both measures of left ventricle midwall function. Hypertensive patients in the lowest quintile of afterload-corrected MWS had similar physician-measured but higher ambulatory awake and home as well as technician-measured DBP, but not SBP, and higher SD of awake SBP and DBP than did those with higher afterload-corrected MWS. Ambulatory awake, home, and sleep as well as technician-measured DBP, but not SBP, were positively related to total peripheral resistance at rest whereas all components of ambulatory SBP, but not DBP, were positively related to the resting p;ulse pressure: stroke index ratio, a measure of arterial stiffness. We detected no relation between the nocturnal dip in blood pressure and any measure of left ventricular or arterial function or left ventricle geometry. Finally, left ventricle mass and relative wall thickness were related most strongly to awake and home ambulatory SBP whereas left ventricular relative wall thickness was also related to the SD of awake DBP. CONCLUSION: For this population of predominantly hypertensive unmedicated adults, ambulatory blood pressures during waking hours and at home were related to left ventricular and arterial function, the strongest relations being negative ones of DBP with left ventricular midwall function and positive ones of ambulatory DBP with peripheral resistance and ambulatory SBP with a measure of arterial stiffness. For this population the nocturnal dip of blood pressure was not related to measures either of cardiovascular function or of left ventricular structure.     

Changes in midwall systolic performance and cardiac hypertrophy reduction in hypertensive patients

OBJECTIVE: To investigate changes in left ventricular (LV) performance, as evaluated by measurement of midwall LV fractional shortening (FS), after reduction of cardiac hypertrophy. DESIGN AND METHODS: Echocardiographic evaluation of LV anatomy and function was performed by M-mode echocardiography at baseline, after long-term antihypertensive therapy, and after treatment withdrawal in 68 asymptomatic hypertensive patients (50 males, 18 females, age range 22-62 years). Patients were divided according to the presence of LV hypertrophy (LVH) at baseline (LV mass index, LVMI, > or = 51 g/m(2.7)). RESULTS: At baseline patients with concentric (relative wall thickness > 0.44) LV hypertrophy (n = 38) or remodelling (n = 7) had reduced midwall shortening with respect to patients with normal LV geometry (n = 4) or eccentric LVH (n = 19); no differences were observed for endocardial FS. After long-term treatment (average 15 months), in 11 patients LV mass remained within normal limits, in 45 patients LVH reduction was obtained, while in 12 patients LV mass remained persistently elevated. Midwall FS was significantly increased in patients with reduction of LVH both during treatment and after withdrawal of treatment, while it remained significantly lower in patients with persistently elevated LV mass. Changes in midwall fractional shortening were independently associated with modifications in relative wall thickness (P < 0.00001), with changes in end-diastolic dimensions (P < 0.0001) and those of LVMI (P< 0.02) as shown by multivariate analysis. CONCLUSION: LV midwall systolic performance significantly improved after reduction of LVH, even in the presence of high blood pressure values. Modifications in relative wall thickness are more independently associated with changes, in LV diastolic dimensions and mass, to midwall improvement     

Effect of Tool Geometry Parameters on the Formability of a Camera Cover in the Deep Drawing Process

The formability of the drawn part in the deep drawing process depends not only on the material properties, but also on the equipment used, metal flow control and tool parameters. The most common defects can be the thickening, stretching and splitting. However, the optimization of tools including the die and punch parameters leads to a reduction of the defects and improves the quality of the products. In this paper, the formability of the camera cover by aluminum alloy A1050 in the deep drawing process was examined relating to the tool geometry parameters based on numerical and experimental analyses. The results showed that the thickness was the smallest and the stress was the highest at one of the bottom corners where the biaxial stretching was the predominant mode of deformation. The problems of the thickening at the flange area, the stretching at the side wall and the splitting at the bottom corners could be prevented when the tool parameters were optimized that related to the thickness and stress. It was clear that the optimal thickness distribution of the camera cover was obtained by the design of tools with the best values—with the die edge radius 10 times, the pocket radius on the bottom of the die 5 times, and the punch nose radius 2.5 times the sheet thickness. Additionally, the quality of the camera cover was improved with a maximum thinning of 25% experimentally, and it was within the suggested maximum allowable thickness reduction of 45% for various industrial applications after optimizing the tool geometry parameters in the deep drawing process.     

Relation between left ventricular midwall function and coronary vasodilator capacity in arterial hypertension

In systemic hypertension, depressed left ventricular midwall shortening predicts an adverse outcome and is associated with increased left ventricular relative wall thickness, which has been proposed as an independent predictor of cardiovascular risk and reduced coronary reserve. This study was designed to investigate whether depressed midwall shortening is associated with more critical impairment of coronary function and with exercise-induced myocardial ischemia. Sixty untreated hypertensive patients without coronary artery stenosis and 20 normotensive volunteers underwent exercise ECG testing, standard and transesophageal echocardiography to assess the occurrence of exercise-induced myocardial ischemia, left ventricular mass, geometry, and midwall shortening, and coronary vasodilator capacity. Compared with hypertensive patients with normal midwall shortening, those with depressed function (n=15) had higher minimum coronary resistance (1.19+/-0.27 versus 1.39+/-0.20 mm Hg/cm per second, P<0.01) and prevalence of exercise-induced myocardial ischemia (36 versus 67%, P<0.05). Within the hypertensive group, midwall shortening was inversely related to minimum coronary resistance (r=-0.42, P<0.01). Compared with patients with an exercise ECG test negative for myocardial ischemia, those with a positive test result (n=26) had higher minimum coronary resistance (1.13+/-0.21 versus 1.38+/-0.27 mm Hg/cm per second, P<0.01) and lower midwall shortening (104+/-16 versus 93+/-14%, P<0.01). We conclude that hypertensive patients with depressed midwall shortening have more severe impairment of coronary function and a higher prevalence of exercise-induced myocardial ischemia as compared with hypertensive patients with normal midwall shortening. These findings suggest that a decrease in myocardial performance may be related, at least in part, to chronic intermittent myocardial ischemia caused by a critical impairment of coronary vasodilator capacity.     

Left ventricular midwall mechanics in subjects with aortic stenosis and normal systolic chamber function

BACKGROUND AND AIM OF THE STUDY: Endocardial indices of left ventricular (LV) systolic function overestimate myocardial performance in hypertrophic left ventricles. Midwall fractional shortening (mFS) is a more reliable index of systolic performance. Aortic stenosis (AS) is a common cause of LV hypertrophy (LVH), but midwall mechanics in this condition have not been analyzed. Also, a tendency towards hyperdynamic LV chamber function has been reported in women with AS in comparison with men, but whether there exist gender-related discrepancies in midwall performance is not known. METHODS: The study group included 147 patients with AS and normal chamber systolic function. LV diameters and thicknesses, LV mass, relative wall thickness (RWT), endocardial fractional shortening, stroke volume, ejection fraction (EF), mFS and stress-corrected mFS were determined. RESULTS: Patients with AS showed depressed mFS (16.2 +/- 2.5% versus 18.8 +/- 2.4%, p <0.0001) and stress-corrected mFS (84.3 +/- 13.8% versus 100.0 +/- 12.6%, p <0.0001) when compared to controls. The subset with moderate AS had lower mFS (15.9 +/- 2.0%) than those with mild AS (16.9 +/- 2.4%), and further depression was present in subjects with severe AS (13.8 +/- 2.2%, p <0.0001). A similar trend was observed for stress-corrected mFS (mild AS, 88.5 +/- 13.3%; moderate AS, 82.0 +/- 11.5%; severe AS, 71.2 +/- 12.0%, p <0.0001). Multivariate analysis identified RWT as the best predictor of mFS and stress-corrected mFS. Logistic regression showed that depressed stress-corrected mFS was independently associated with the presence of symptoms. Endocardial fractional shortening and EF were increased in women compared to men, but there were no gender-related differences in mFS (16.2 +/- 2.5% versus 16.1 +/- 2.4%, p = 0.84) and stress-corrected mFS (84.0 +/- 14.1% versus 84.5 +/- 13.5%, p 0.82). CONCLUSION: Aortic stenosis is associated with depression in LV midwall mechanics. Systolic midwall performance reduces as the severity of valve disease increases, and this relationship is mediated by parallel changes in LV geometry.     

Relation of midwall circumferential systolic stress to equatorial midwall fibre shortening in chronic aortic regurgitation. Value as a predictor of postoperative outcome.

Nineteen patients with chronic aortic regurgitation and a large increase in heart size were studied before aortic valve replacement. By relating midwall circumferential systolic stress to midwall circumferential fibre shortening (Cs/Cd) before operation the patients could be divided into two well defined groups. Twelve patients (group 1) had a pronounced decrease in heart size as measured by the cardiothoracic ratio and an excellent clinical outcome six months after operation. Seven patients (group 2) had no significant decrease in heart size and a less good clinical outcome. The ratio of midwall circumferential systolic stress to end systolic volume index was significantly higher in group 1 than in group 2. Group 2 had more severe left ventricular hypertrophy determined by the ratio of the wall thickness to the minor internal radius of the left ventricle (h:r ratio), total left ventricular mass, and left ventricular mass to end diastolic volume ratio. There were no significant differences in any other haemodynamic or angiographic indices between the two groups. Thus the relation of midwall circumferential systolic stress to fibre shortening is useful in determining the prognosis in individual patients with chronic aortic regurgitation undergoing aortic valve replacement.     

Simulation and Experimental Study on Roll-Forming Limit of Cup

Roll forming can improve the material utilization rate and production efficiency of cups with a curved rotary profile, but there is no basis for the determination of forming limit. The DEFORM-3D software was used to simulate the roll forming of cups. The influence of the billet wall thickness and bottom thickness, coefficient of friction, radius of roller, and the fillet radius of the punch on the forming limit was studied, and the damage value and velocity vector were analyzed. The results showed that the forming limit of the billet’s wall thickness in roll forming for a cup is about 62%. With the increase of the ratio of the formed cup’s wall thickness to the billet’s bottom thickness, the forming limit of wall thickness will be slightly reduced. A larger radius of roller, fillet radius of punch, and friction coefficient between punch and billet and a smaller friction coefficient between roller and billet are good for decreasing the damage value and improving the roll-forming limit. According to the numerical simulation results, the roll-forming limit diagram of cups is established, and the accuracy of the forming limit diagram is verified by experiments.     

Myocardial function and geometry in hypertensive subjects with low levels of afterload

Background It has been hypothesized that the level of end-systolic wall stress (σ_m) is a feedback signal that regulates the level of hypertrophy. Thus, low levels of σ_m may signify inappropriate hypertrophy. Methods To characterize left ventricular (LV) structure and systolic function in hypertensive subjects with low levels of σ_m, we studied 763 patients. LV function was studied by midwall stress-shortening analysis. Partition values for σ_m were derived from a separate group of normal subjects, and the study population was divided into low stress (group I, n = 136), high stress (group III, n = 157), and intermediate stress group II (n = 470). LV chamber and myocardial function were characterized by relating shortening at the endocardium and at the midwall, respectively, to stress. Results As expected, group III patients had the highest values for systolic blood pressure and LV cavity size but the lowest values for wall thickness and relative wall thickness. Surprisingly, however, there were no significant differences among stress groups with regard to age or body mass index. Contrary to the hypothesis that low levels of stress are indicative of excessive hypertrophy, there were no significant differences among the 3 groups with regard to LV mass or any form of LV mass index. Furthermore, despite lower mean values for afterload, group I patients had significantly lower values for midwall shortening, and this finding was indicative of reduced myocardial function; stress-shortening plots demonstrated that 28% of group I patients fell below 95% CI compared with 10% of group II and only 5% of group III patients. Conclusions Hypertensive subjects with low values for σ_m have more concentric LV geometry (higher relative wall thickness) and, on average, reduced myocardial function. (Am Heart J 2002;143:546-51.)     

Relation of midwall circumferential systolic stress to equatorial midwall fibre shortening in chronic aortic regurgitation. Value as a predictor of postoperative outcome

Nineteen patients with chronic aortic regurgitation and a large increase in heart size were studied before aortic valve replacement. By relating midwall circumferential systolic stress to midwall circumferential fibre shortening (Cs/Cd) before operation the patients could be divided into two well defined groups. Twelve patients (group 1) had a pronounced decrease in heart size as measured by the cardiothoracic ratio and an excellent clinical outcome six months after operation. Seven patients (group 2) had no significant decrease in heart size and a less good clinical outcome. The ratio of midwall circumferential systolic stress to end systolic volume index was significantly higher in group 1 than in group 2. Group 2 had more severe left ventricular hypertrophy determined by the ratio of the wall thickness to the minor internal radius of the left ventricle (h:r ratio), total left ventricular mass, and left ventricular mass to end diastolic volume ratio. There were no significant differences in any other haemodynamic or angiographic indices between the two groups. Thus the relation of midwall circumferential systolic stress to fibre shortening is useful in determining the prognosis in individual patients with chronic aortic regurgitation undergoing aortic valve replacement.