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PubMed1985

Body surface distributions of ST segment changes after exercise in effort angina pectoris without myocardial infarction.

To investigate the sites of exercise-induced ST segment changes on the body surface in effort angina pectoris without myocardial infarction, we performed 87-lead ECG mapping in 61 patients before and 1.5 and 5 minutes after treadmill exercise. ST segment depression most often occurred in the left anterior chest leads and ST segment elevation developed mainly in the right upper chest leads. There was a good correlation between the number of lead points that showed ST segment depression (nSTd) and the number of those that showed ST segment elevation (nSTe) 1.5 minutes after exercise (r = 0.92). From 1.5 to 5 minutes after exercise, changes in nSTd for individual patients correlated well with changes in nSTe (r = 0.89). It was suggested that the ST segment elevation observed in this study directly reflected the subendocardial ischemia of the left ventricle. In patients with one-vessel disease (n = 32), there was wide overlap in the sites of ST segment changes among patients with left anterior descending artery disease (n = 19), those with left circumflex artery disease (n = 6), and those with right coronary artery disease (n = 7). These findings should lead to a better understanding of exercise-induced ST segment changes for the diagnosis of coronary artery disease.

Adult↗
PubMed1987

Differences in the frequency of ST segment depression during upright and supine exercise: assessment in normals and in patients with coronary artery disease.

Increased utilization of ambulatory ST segment monitoring mandates an appreciation of nonischemic variables that may influence the ST segment. While a greater frequency of ST segment depression has been reported with supine vs upright exercise, the relative false positive rate in both positions is not known. Thus, we compared the frequency of exercise ECG abnormalities during upright and supine bicycle exercise in two groups--17 normals and 46 patients with coronary artery disease. Exercise was performed in combination with radionuclide ventriculographic imaging. Peak exercise heart rate, peak systolic blood pressure, and exercise duration time were all slightly higher in the upright vs supine position (p less than 0.05). Nevertheless, the frequency of positive ST segment responses was more common in the supine position, both in the patients with coronary artery disease (54% vs 30%, p less than 0.05) and in the normal subjects (29% vs 6%, p = NS). The corresponding radionuclide ventriculographic responses, however, were normal during upright and supine exercise in 6 of the 11 CAD patients and in all five of the normal subjects with an abnormal ST segment response during supine exercise only. The frequency of exercise-induced chest pain was also similar in the two positions. Thus, we theorize that nonischemic factors may govern some positive ST segment responses in the supine position. This finding is of relevance for understanding the potential sources of physiologic false positive ST segment responses for ambulatory ST segment monitoring.

Adult↗
PubMed1991

Correlation between resting ST segment depression, exercise testing, coronary angiography, and long-term prognosis.

Resting ST segment depression has been identified as a marker for adverse cardiac events in patients with and without known coronary artery disease. To correlate this with exercise testing, coronary angiography, and how it impacts on long-term prognosis, a retrospective study was performed on 476 patients, of whom 223 had no clinical or electrocardiographic evidence of prior myocardial infarction while 253 were survivors of an infarction. All patients performed a standard exercise test and underwent diagnostic coronary angiography within an average of 32 days of their exercise test (range 0 to 90 days). Exclusions were women, those with left bundle branch block, left ventricular hypertrophy, use of digoxin, previous revascularization procedures, or significant valvular or congenital heart disease. Long-term follow-up was carried out for an average of 45 months (+/- 17). Of the patients without prior infarction, 23 (10%) had persistent resting ST segment depression, and of those with a prior history of infarction, 37 (15%) also had resting ST segment depression. Patients with resting ST segment depression and no prior myocardial infarction had a higher prevalence of severe coronary disease (three-vessel and/or left main) (30%) than those without resting ST segment depression (16%) (95% confidence interval [CI] for observed difference -5.0% to 33.9%, p = 0.12). The criterion of greater than or equal to 2 mm of additional exercise-induced ST segment depression was a particularly useful marker in these patients for the diagnosis of any coronary disease (likelihood ratio 3.35, 95% CI 0.56 to 19.93, p = 0.06). Patients with resting ST segment depression and a prior myocardial infarction had a 2.5 times higher prevalence of severe coronary artery disease compared with patients without resting ST segment depression (43% versus 17% prevalence, respectively, 95% CI for observed difference 9.38% to 42.8%, p less than 0.001) and also had larger left ventricles postinfarction (left ventricular end-diastolic volume index 102 ml/m2 compared with 96 ml/m2, p less than 0.001).(ABSTRACT TRUNCATED AT 400 WORDS)

Coronary Angiography↗
PubMed1992

Preservation of endothelium-dependent vasodilation in the spastic segment of the human epicardial coronary artery by substance P.

The objective of this study was to determine if endothelium-dependent vasodilation is preserved in the spastic segment of the epicardial coronary artery. Segmental responses of the coronary artery to substance P were examined by the use of a quantitative angiographic technique in 21 patients with variant angina. Coronary diameter at the basal state did not differ between the spastic and the nonspastic segments (2.3 +/- 0.2 mm, 2.3 +/- 0.4 mm, p greater than 0.05). Changes in coronary diameter in response to substance P did not differ between segments with ergonovine-induced spasm and nonspastic segments. Maximal dilation averaged 27.1 +/- 9.5% in the spastic segment and 24.4 +/- 9.6% in the nonspastic segment (expressed as a percent increase over the value before drug administration). It appears that both the potential of the endothelium to release endothelium-dependent relaxing factor and the dilating response of the smooth muscle to endothelium-dependent relaxing factor are preserved, even in the spastic segment.

Angina Pectoris, Variant↗
PubMed1976

Experimental myocardial infarction: XII. Dynamic changes in segmental mechanical behavior of infarcted and non-infarcted myocardium.

The mechanical behavior of ischemic myocardium was studied in anesthetized open chest dogs. In each animal, a small well localized myocardial infarction was produced by ligation of a single ventricular branch of the left circumflex coronary artery. Serial in situ measurements of segment length were made by mercury-in-Silastic gauges sutured directly to the left ventricular surface. After coronary ligation, systolic aneurysmal bulging of the ischemic segment was uniformly noted. This was quantified as follows: normalized segment length change in this region, expressed in muscle lengths (where muscle lengths = phasic segment length amplitude/end-diastolic segment length), immediately increased from 0.06 +/- 0.01 (standard error of the mean) to 0.10 +/- 0.02 muscle lengths (+67 percent, P less than 0.02). Over a 6 hour period, muscle lengths progressively declined to near control values, but retained an aneurysmal contour. End-diastolic segment length increased 5 percent above control values after coronary occlusion and remained fixed at this level for 6 hours. In contrast, noninfarcted myocardium exhibited no significant changes in muscle length or end-diastolic segment length. These studies demonstrate that the degree of systolic aneurysmal bulging in infarcted myocardium, although initially great, resolves within 6 hours but retains an aneurysmal contour. These findings are consistent with either partial return of contractility or diminished local compliance, but persistence of an aneurysmal shape favors the latter mechanism. The fixed increase in end-diastolic segment length suggests that "stress-relaxation" takes place in the infarcted region. It is possible that diminished compliance in zones of infarction, previously noted after several days, begins within a few hours after the onset of ischemia.

Animals↗
PubMed1979

Effects of digitalis on normal and abnormal left ventricular segmental dynamics.

To study the effects of digoxin on regional left ventricular performance, continuous ventricular dynamics were assessed in nine patients with stable coronary disease. Computer-assisted analysis of the fluoroscopic motion of surgically implanted mid wall myocardial markers was used. The markers define six minor ventricular radii and outline the left ventricle. One and one-half hours after administration of 1 mg of intravenous digoxin, mean velocity of circumferential fiber shortening for all segments increased 19 percent, from 0.67 +/- 0.06 to 0.78 +/- 0.06 circumference/sec (P less than 0.01) and ejection fraction increased 4.5 percent, from 0.50 +/- 0.03 to 0.53 +/- 0.03 (P less than 0.05). Segmental velocity of circumferential fiber shortening, total segmental shortening and early segmental systolic shrtening increased in 83 percent to 91 percent of normal segments, depending on which index was used. Only 45 to 55 percent of initially abnormal segments benefited from digoxin. In general, segmental dyssynergy increased even when net ventricular function was enhanced. These results suggest that in pateints with chronic left ventricular contraction abnormalities due to coronary disease, deterioration of performance in abnormal regions after administration of digoxin may result from increased stress imposed by increased afterload and by improved segmental dynamics in more normal areas.

Adult↗
PubMed1981

S-T segment elevation and coronary spasm in response to exercise.

The prevalence rate of exercise- S-T segment elevation of 0.1 mV or greater in symptomatic patients is 3.0 to 6.5 percent in most studies. S-T segment elevation is associated with a more severe degree of myocardial ischemia than depression and frequently implies a high grade coronary stenosis in the vessel that supplies the site of ischemia. Leads V4 to V6 and bipolar lead CM5 have been found to be relatively insensitive in detecting exercise-induced S-T segment elevation. The pathogenesis of S-T segment elevation is different in three clinical patient subsets reviewed. In patients afer infarction, the largest of the three subgroups, exercise-induced S-T segment elevation usually appears in leads with Q waves, is more common after anterior myocardial infarction and implies underlying akinetic of dyskinetic wall motion. Of patients with variant angina, 10 to 30 percent have during exercise S-T segment elevation that is most likely provoked by coronary arterial spasm. The natural history of variant angina is cyclic, and clinical observations and laboratory findings are dependent on particular phases in the disease process and treatment. Finally, 0.2 to 1.7 percent of symptomatic patients without infarction or variant angina have exercise-induced S-T segment elevation. Although most of the latter have fixed high grade coronary arterial stenoses at angiography, the exact pathogenetic mechanism of S-T segment shift in this patient group is not yet fully understood.

Angina Pectoris↗
PubMed1984

Persistent ST-segment elevation and left ventricular wall abnormalities: a 2-dimensional echocardiographic study.

Twenty-three patients with an anterior wall myocardial infarction (MI) and persistent ST-segment elevations (Group I) were examined for wall motion abnormalities using 2-dimensional (2-D) echocardiography. Twenty-two (96%) had dyskinetic wall motion of the infarcted area and 10 (43%) had a left ventricular aneurysm. Among 15 patients who had a chronic anterior wall MI without ST-segment elevation (Group II), 13 (86%) had akinesia of the infarcted segment. To document that dyskinetic wall motion caused the persistent electrocardiographic ST-segment elevations, 15 patients with an acute anterior wall MI (Group III) were followed by serial 2-D echocardiography for 2 to 24 months (mean 8). Of the 10 patients who had dyskinetic wall motion abnormalities on their initial 2-D echocardiogram, persistent ST-segment elevation developed in 9. All 5 patients with akinetic or severely hypokinetic wall motion abnormalities on their first 2-D echocardiogram did not show ST-segment elevation on late follow-up surface electrocardiograms. Infarct size as determined by peak creatine kinase levels for the former subgroup was greater than that for the latter subgroup (2243 +/- 429 vs 899 +/- 320 IU, respectively, p less than 0.01). In conclusion, persistent ST-segment elevation after an acute anterior wall MI is indicative of dyskinetic wall motion rather than aneurysm formation. Dyskinesia precedes the appearance of ST-segment elevation and is probably responsible for these changes on the surface electrocardiogram. Infarct size is larger in persons in whom dyskinetic wall motion abnormalities are likely to develop.

Adult↗
PubMed1991

Reactivity of proximal and distal angiographically normal and stenotic coronary segments in chronic stable angina pectoris.

To assess whether vasoreactivity of significant coronary stenosis (greater than 50% intraluminal diameter reduction) and that of angiographically normal coronary segments differs in proximal and distal locations, 53 patients (40 men, 13 women, mean +/- standard deviation age 55 +/- 11 years) with chronic stable angina and angiographically documented coronary artery disease were studied. While abstaining from antianginal therapy, all 53 patients underwent coronary arteriography before and after 1 mg of intracoronary isosorbide dinitrate and 21 of the 53 also before and after 20 to 30 micrograms intracoronary ergonovine. Computerized quantitative angiography was used to assess changes in the intraluminal diameter of 126 normal coronary segments (63 proximal, 63 distal) and 43 significant coronary stenoses. Nitrates dilated proximal normal coronary segments by 7.4 +/- 1.2% and distal normal coronary segments by 15 +/- 1.7% (p less than 0.01). Significant proximal coronary stenoses dilated by 11 +/- 2.5% and distal stenoses by 23 +/- 2.8% (p less than 0.01) after nitrates. Ergonovine reduced the diameter of proximal normal coronary segments by 9.3 +/- 1.7% and that of normal distal segments by 15.5 +/- 1.4% (p less than 0.01). Proximal stenoses constricted by 11 +/- 2.2% and distal stenoses by 18.4 +/- 2.8% (p = 0.06). Analysis of segments showed that nitrates dilated 19 of 63 (30%) proximal normal segments by (greater than or equal to 10%), 31 of 63 (49%) distal (p less than 0.05) and 21 of 43 (49%) stenoses.(ABSTRACT TRUNCATED AT 250 WORDS)

Angina Pectoris↗
PubMed1982

Relation of serum total cholesterol and triglyceride levels to the amount and extent of coronary arterial narrowing by atherosclerotic plaque in coronary heart disease. Quantitative analysis of 2,037 five mm segments of 160 major epicardial coronary arteries in 40 necropsy patients.

The amount of cross-sectional area narrowing by atherosclerotic plaques was determined histologically in each 5 mm segment of the entire lengths of the right, left main, left anterior descending, and left circumflex coronary arteries in 40 patients with fatal coronary heart disease and known fasting serum total cholesterol and triglyceride levels. The patients were divided into four groups based upon the serum total cholesterol and triglyceride levels: group I, total cholesterol of 250 mg/dl or less, triglyceride of 170 mg/dl or less; group II, total cholesterol of 250 or less, triglyceride of more than 170; group III, total cholesterol of more than 250, triglyceride of 170 or less; group IV, total cholesterol of more than 250, triglyceride of more than 170. The number of 5 mm segments of coronary artery narrowed severely (76 to 100 percent in cross-sectional area) by atherosclerotic plaques in each group was as follows: 172 of 505 (34 percent) 5 mm segments from group I; 242 of 353 (69 percent) segments from group II; 120 of 295 (41 percent) from group III and 425 of 884 (48 percent) segments from group IV. The mean percentage of 5 mm segments narrowed severely was significantly greater in group II than in group I (p less than 0.005) or group III (p less than 0.01). Additionally, the mean number of four coronary arteries per subject severely narrowed and the number of subjects with severe narrowing of the left main coronary artery were significantly greater in groups II and III than in group I. The percentages of 5 mm segments narrowed severely correlated significantly with the serum triglyceride level (p less than 0.03). Although it correlated with the number of severely narrowed coronary arteries per subject, the serum total cholesterol level did not correlate with the percentage of 5 mm segments of coronary artery with severe narrowing.

Adult↗
PubMed1992

The monolingual nature of speech segmentation by bilinguals.

Monolingual French speakers employ a syllable-based procedure in speech segmentation; monolingual English speakers use a stress-based segmentation procedure and do not use the syllable-based procedure. In the present study French-English bilinguals participated in segmentation experiments with English and French materials. Their results as a group did not simply mimic the performance of English monolinguals with English language materials and of French monolinguals with French language materials. Instead, the bilinguals formed two groups, defined by forced choice of a dominant language. Only the French-dominant groups showed syllabic segmentation and only with French language materials. The English-dominant group showed no syllabic segmentation in either language. However, the English-dominant group showed stress-based segmentation with English language materials; the French-dominant group did not. We argue that rhythmically based segmentation procedures are mutually exclusive, as a consequence of which speech segmentation by bilinguals is, in one respect at least, functionally monolingual.

Adult↗
PubMed1985

Computerized EEG pattern classification by adaptive segmentation and probability density function classification. Clinical evaluation.

A series of 63 clinical EEGs showing a variety of normal and abnormal patterns was analysed by computer with particular reference to the different types of pattern within the same EEG. Boundaries between different patterns were established by means of adaptive segmentation, so that the duration of the resulting segments was determined by the particular EEG itself (thus the term 'adaptive'). Four channels from each EEG were analysed, paired (left and right) channels were simultaneously segmented and analysed interactively. Similar segments were then clustered without supervision by estimating a probability density function in a 2-dimensional 'feature space' having dimensions of mean frequency and mean power. Individual clusters emerged as well-defined peaks of the surface, individual segments or small groups of duration insufficient to constitute a separate cluster, being identified as 'singular events' (e.g., rare sharp waves, artifacts). The autocorrelation function was used to characterize the EEG both for the segmentation and for the subsequent clustering of the resulting segments. In confirmation of our previous work, adaptive segmentation based on the autocorrelation function of the EEG was found to be quite satisfactory. Unsupervised clustering by estimation of the probability density function in feature space was found to give the correct number of clusters (usually less than 5) in a majority of the records (65%), but in the remaining minority of cases (35%), either overclustering or underclustering occurred. Further, the 'singular events' were occasionally partly included in a formal cluster. Comparison of these results of EEG clustering by unsupervised probability density function estimation with earlier results obtained by supervised hierarchical clustering suggests that there may be subtle cues used by the electroencephalographer in the classification of EEG patterns which have not been adequately approximated by the computer algorithms thus far used in this work. Hence at least some minimal degree of supervision in the clustering process may be necessary, at least for the present. On the other hand, the method recommends itself for the representation of illustrative EEG summaries which, in conjunction with a short written report, would provide the clinical neurologist with a sufficient picture of the real EEG without, in most cases, the need to inspect the original record.

Action Potentials↗
PubMed1986

Differential sensitivities of morphine and motilin to initiate migrating motor complex in isolated intestinal segments. Regeneration of intrinsic nerves.

The effect of morphine and motilin on surgically isolated segments of small intestine was studied in 8 dogs. In 4 dogs, the small intestine was divided into four segments by simple transection and reanastomosis (group 1); in 4 others, a 2-4-cm colonic segment was interposed at each of the transection sites (group 2). The migrating motor complex initially cycled independently in each segment in group 1 dogs; after that the migration of the migrating motor complex across transection and reanastomosis began to recover and the recovery was complete 100 days after surgery. In contrast, in group 2 dogs the migration of the migrating motor complex from one segment to the next did not recover even 180 days after surgery. Morphine bolus or infusion initiated premature phase III activity in all segments but the sensitivity to morphine decreased distally. Motilin bolus or infusion initiated premature phase III activity only in the first three segments. The sensitivity to motilin also decreased distally. We concluded that (a) the interposition of a foreign segment severely impedes or prevents the regeneration of enteric nerves; (b) the sensitivity of morphine and motilin in initiating premature phase III activity decreases distally in small intestine; and (c) motilin does not initiate premature phase III activity in the ileum, but morphine may initiate premature phase III activity at all sites in the small intestine.

Animals↗
PubMed1988

Load-displacement properties of lower cervical spine motion segments.

The load-displacement behavior of 35 fresh adult cervical spine motion segments was measured in compression, shear, flexion, extension, lateral bending and axial torsion tests. Motion segments were tested both intact and with posterior elements removed. Applied forces ranged to 73.6 N in compression and to 39 N in shear, while applied moments ranged to 2.16 Nm. For each mode of loading, principal and coupled motions were measured and stiffnesses were calculated. The effect of disc degeneration on motion segment stiffnesses and the moments required for motion segment failure were also measured. In compression, the stiffnesses of the cervical motion segments were similar to those of thoracic and lumbar motion segments. In other modes of loading, cervical stiffnesses were considerably smaller than thoracic or lumbar stiffnesses. Removal of the posterior elements decreased cervical motion segment stiffnesses by as much as 50%. Degenerated cervical discs were less stiff in compression and stiffer in shear than less degenerated discs, but in bending or axial torsion, no statistically significant differences were evident. Bending moments causing failure were an order of magnitude lower than those for lumbar segments.

Cervical Vertebrae↗
PubMed1989

The use of magnetic resonance imaging for measuring segment inertial properties.

The purpose of the study was to determine whether valid measures of segment inertial properties can be generated from a series of cross-sectional tissue scans using magnetic resonance imaging (MRI). The cross-sectional images for eight baboon cadaver segments (four forearms, two upper arms, and two lower legs) were digitized to yield areas of muscle, bone, and fat tissues. These data, along with tissue density values, were used for calculations of segment volume (V), density (D), mass (M), center of mass location (CM), and moment of inertia (Icm) about a transverse axis through the segment center of mass. Criterion measures of these properties were obtained using standard experimental techniques. Close agreement was found between criterion and MRI values for mean segment CM (44.67 vs. 43.36% from proximal end, respectively) while mean segment D was the same (1.124 g.cm-3) for both methods. MRI procedures tended to overestimate segment V(595.3 vs. 633.4 cm3), M(720.0 vs. 769.9 g), and Icm (3.208 vs. 3.332 x 10(-3) kg.m2). It was concluded that MRI represents a promising technique for generating valid measures of segment inertial characteristics as well as other anatomical features.

Animals↗
PubMed1994

Body segment growth during infancy.

In order to better understand relationships between physical growth and motor development during infancy, changes in segment inertias were examined. A rationale based on dynamic systems theory and intersegmental moments was used to select the variables: the segment mass and principal moments of nine segments. The hypothesis was that there are differences in growth velocity between segments and these are consistent with the principles of cephalocaudal development and distal to proximal growth. A mathematical model of the segments was used to examine changes of the inertia parameters. Twenty-seven normal infants carried to full term and aged between 2 and 9 months at the beginning of the study were photographed once a month for 6 months. Outlines of segments from front and side 35 mm images were digitized and mass and principal moments of inertia estimates obtained. Polynomial regression was used to give the development curves regression coefficients for the 155 data points. Also, linear regressions were fitted to the six growth data points of each subject. Most of the relationships between chronological age and segment mass and principal moments were significant and linear. The differences in growth velocity between segments were significant and partially consistent with the growth principles. However, there were considerable differences, in particular for the lower trunk and the shank, where it appears that growth may be irregular until after the age of 15 months.

Anthropometry↗
PubMed1996

Precise determination of anthropometric dimensions by means of image processing methods for estimating human body segment parameter values.

A method has been developed for the precise determination of anthropometric dimensions from the video images of four different body configurations. High precision is achieved by incorporating techniques for finding the location of object boundaries with sub-pixel accuracy, the implementation of calibration algorithms, and by taking into account the varying distances of the body segments from the recording camera. The system allows automatic segment boundary identification from the video image, if the boundaries are marked on the subject by black ribbons. In connection with the mathematical finite-mass-element segment model of Hatze, body segment parameters (volumes, masses, the three principal moments of inertia, the three local coordinates of the segmental mass centers etc.) can be computed by using the anthropometric data determined videometrically as input data. Compared to other, recently published video-based systems for the estimation of the inertial properties of body segments, the present algorithms reduce errors originating from optical distortions, inaccurate edge-detection procedures, and user-specified upper and lower segment boundaries or threshold levels for the edge-detection. The video-based estimation of human body segment parameters is especially useful in situations where ease of application and rapid availability of comparatively precise parameter values are of importance.

Adult↗
PubMed1996

Changes in segment mass and mass distribution during pregnancy.

The purpose of the study was to evaluate the rates of change in the estimated masses and principal moments of inertia of the body segments during the second and third trimesters of pregnancy. Fifteen subjects, on average 15.1 weeks pregnant, were tested monthly until term. The body was modelled as 16 segments consisting of 2 cm stacked elliptical cylinders sectioned in the transverse plane. Linear regressions were fitted to the segment inertias and regression coefficients determined for the individual growth curves. The mean rate of increase for the lower trunk mass was 0.29 kg per week and 0.0069 kg m2 per week for the transverse axis principal moment. Differences between the means of the segments for rates of change of mass and the three principal moments were then tested. All four ANOVAs used to test the differences were significant. The post hoc analysis established that over the second and third trimesters the lower trunk inertias increased at a greater rate than all other segments and there were no significant differences between the remaining segments. The effect of such changes in the trunk segment masses and principal moments was illustrated by an analysis of intersegmental dynamics during a sit to stand of one pregnant subject whose lower trunk mass increased from 21.6 kg to 28.4 kg. A knowledge of the differences in an individual's segment inertias should lead to a better understanding of how movements are affected during pregnancy.

Abdomen↗