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PubMed1996

Rod outer segment renewal in the retinae of deep-sea fish.

Outer segment renewal involves the synthesis of disc material in the photoreceptor inner segments, the shedding of the tips of the photoreceptor outer segments, and their phagocytosis by the retinal pigment epithelial cells. It has been suggested that in the retinae of deep-sea fish no renewal of outer segments may take place. In order to assess outer segment renewal in deep-sea fish retinae we counted (i) periciliary vesicles in rod inner segments as a parameter for disc-synthesis activity and (ii) phagosomes in retinal pigment epithelial cells as a parameter of shedding and phagocytosis in 12 species of deep-sea fish with multibank or single bank retinae. We also measured the lengths of rod outer segments in order to evaluate the balance between synthesis and phagocytotic activity. In four of these species (Synaphobranchus kaupi, Nematonurus armatus, Coryphaenoides guentheri and Halosauropsis macrochir) we further recorded size-related changes of these parameters and their relation to the position of a given rod within the banks in the retina. The number of periciliary vesicles was highest in inner segments of the most vitread bank and in the periphery of the retina. Phagosomes were most abundant in retinal pigment epithelial cells of the central retina. Long rod outer segments were most frequently recorded in the peripheral retina indicating that in this region new synthesis may outbalance shedding. Vitread rod outer segments were only slightly longer than sclerad ones. Larger animals had shorter rod outer segments than small ones. We present evidence that rod outer segment renewal takes place in the retina of all deep-sea fish. Vitread rods may be more active in this respect than sclerad ones.

Animals↗
PubMed1999

Capillary electrochromatography with segmented capillaries for controlling electroosmotic flow.

Capillaries consisting of two segments each packed with a different stationary phase were introduced for the control and manipulation of the electroosmotic flow (EOF) in capillary electrochromatography (CEC). This kind of column configuration was called segmented capillary where one segment was packed with octadecyl silica (ODS) and served as the separation segment while the other segment was packed with bare silica and functioned as the EOF accelerator segment. The average flow in the segmented capillary increased linearly with increasing fractional length of the EOF accelerator segment, and consequently the analysis time was reduced. Under a given set of conditions, the average flow can be varied over a certain range that extends from the EOF in the individual ODS capillary at the lower end to the EOF in the individual bare silica capillary at the higher end. The pore size of the bare silica in the EOF accelerator segment influenced the average flow in the segmented capillary. Because of the difference in the EOF of the individual segments, the average flow across the segmented capillary is partially degenerated from EOF to viscous flow. Furthermore, the retaining frits in CEC columns are restrictive points which slow down the average flow, thus furthering the degeneration of the flow from EOF to viscous flow. In other words, in CEC columns containing retaining frits, the flow of the mobile phase is not only based on electroosmosis but is contaminated by a viscous component.

Chromatography, Liquid↗
PubMedDate not supplied

Sequence comparisons of intermediate filament chains: evidence of a unique functional/structural role for coiled-coil segment 1A and linker L1.

A comprehensive analysis of the sequences of all types of intermediate filament chains has been undertaken with a particular emphasis on those of segment 1A and linker L1. This has been done to assess whether structural characteristics can be recognized in the sequences that would be consistent with the role of each region in the recently proposed "swinging head" hypothesis. The analyses show that linker L1 is the most flexible rod domain region, that it is the most elongated structure (on a per residue basis), and that it is the most variable region as regards sequence and length. Segment 1A has one of the two most highly conserved regions of sequence in the rod domain (the other being at the end of segment 2B), with seven particular residues conserved across all chain types. It also contains one of the very few potential interchain ionic interactions that could be conserved across all chain types. However, the aggregation of chains in segment 1A is specified less precisely overall by interchain ionic interactions than are the other coiled-coil segments. The apolar residue contents in positions a and d of the heptad substructure are the highest of any coiled-coil segment in the intermediate filament family. Segment 1A also displays an amino acid composition atypical of not only coiled-coil segments 1B and 2B, but indeed of two-stranded coiled coils in general. Nonetheless, molecular modeling based on the crystal structure of the monomeric 1A fragment from human vimentin shows that coiled-coil formation is plausible. The most extensive regions of apolar/aromatic residues lie at the C-terminal end of segment 2B in the helix termination motif and in segment 1A in and close to the helix initiation motif. The predicted stability of the individual alpha-helices in segment 1A is greater than in those comprising segments 1B and 2B, though potential intrachain ionic interactions are either lacking or are minimal in number. Analysis of the 1A sequence and those regions immediately N- and C-terminal to it has shown that the capping residues are near optimal close to the previously predicted ends, thus adding to the likely stability of the alpha-helical structure. However, a second terminating sequence is predicted in 1A (about 10 residues back from the C-terminus). This allows the possibility of some unwinding of the alpha-helical structure of 1A immediately adjacent to linker L1 when the head domains no longer stabilize the coiled-coil structure. All of these data are consistent with the concept of a flexible hinge at L1 and with the ability of the two alpha-helical coiled-coil strands to separate under appropriate conditions and partly unwind at their C-terminal ends to allow the head domains a greater degree of mobility, thus facilitating function.

Amino Acid Motifs↗
PubMed1975

Natural history of S-T segment elevation after acute myocardial infarction.

Clinical, electrocardiographic and cineventriculographic data in two patient groups were analyzed to define the natural history of S-T segment elevation after myocardial infarction. In sixteen of 22 patients (73 percent) with acute inferior myocardial infarction, S-T segment elevation was present on hospital admission, persisting in 1 (5 percent) by the 2nd week. S-T segment elevation was present on admission in 18 of 23 patients (78 per cent) with acute anterior myocardial infarction and persisted in 13 after 1 week and in 9 of 14 (64 percent) during a follow-up period of 1 to 6 months. S-T segment elevation lasting more than 2 weeks after myocardial infarction did not resolve. Compared with patients with inferior myocardial infarction or anterior infarction without persistent S-T segment elevation, patients with anterior infarction and persistent S-T segment elevation had a higher level of mean maximal serum creatine phosphokinase (CPK), more severe left ventricular decompensation and a greater frequency of death in the early follow-up period. In a separate series of 95 patients with cineangiographically documented coronary artery disease, 40 of 65 patients (62 percent) with advanced anterior and apical asynergy had persistent S-T segment elevation. By contrast, only 1 of 30 (3 percent) with coronary disease and normal ventriculograms had persistent S-T segment elevation. We concluded that (1) the natural history of S-T segment elevation after myocardial infarction is resolution within 2 weeks in 95 percent of inferior but in only 40 percent of anterior infarctions; (2) S-T segment elevation persisting more than 2 weeks after myocardial infarction does not resolve; (3) persistent S-T segment elevation is associated with clinically more severe myocardial infarction; and (4) in patients with coronary artery disease, persistent S-T segment elevation after myocardial infarction is a specific but insensitive index of advanced asynergy.

Creatine Kinase↗
PubMed1975

Measurement of S-T segment elevation in acute myocardial infarction in man. Comparison of a precordial mapping technique and the Frank vector system.

Precordial S-T segment mapping has been used to evaluate the extent of ischemic injury in patients with acute myocardial infarction. Because precordial S-T segment mapping is time-consuming and is limited to patients with anterior wall myocardial infarction, we evaluated the possibility of using the magnitude (ST-VM) and direction (ST-VD) of the S-T vector, derived from X, Y and Z leads of the Frank vector system, as a substitute for the precordial S-T segment mapping technique. Precordial S-T segment mapping and Frank system vectorcardiograms were simultaneously obtained in three groups: (1) nine normal subjects; (2) nine patients with persistent S-T segment elevation 2 to 15 months after acute anterior myocardial infarction; and (3) nine patients with acute anterior myocardial infarction studied on 41 occasions. For both systems the S-T segments were analyzed 20 and 60 msec after completion of inscription of the QRS complex. The sum of the S-T segment elevations for the 35 sites (sigma ST) and the number of sites (NST) in which S-T segment elevations exceeded 0.1 mv were computed for the precordial S-T maps. The ST-VM and ST-VD were calculated by standard formulas from X, Y and Z lead tracings of the Frank vector system. Good correlations were observed between: ST-VM and sigma ST (r = +0.818 and +0.791 at 20 and 60 msec, respectively, P less than 0.001); and ST-VM and NST (r = +0.773 and +0.705 at 20 and 60 msec, respectively, P less than 0.001). Furthermore, changes in the location of S-T segment elevations in serial precordial S-T segment maps were reflected by changes in ST-VD. Observations in patients with inferior wall myocardial infarction suggest that ST-VM and ST-VD can be serially followed in such patients. Thus, estimation of the magnitude and direction of the S-T vector is a simple alternative to standard precordial S-T segment mapping that allows for continuous monitoring of S-T segment elevations in all patients with acute myocardial infarction.

Acute Disease↗
PubMed1987

hunchback, a gene required for segmentation of an anterior and posterior region of the Drosophila embryo.

The locus hunchback (hb) is a member of the gap class of segmentation genes of Drosophila. A number of X-ray-induced deletions locate the hb locus at the chromosomal site 85A3-B1, to the right of the pink locus, which maps in the same interval. A total of 14 EMS and 3 X-ray-induced hb alleles have been studied. Homozygous mutant embryos show deletions of segments in two separate regions. In the six strong alleles, the labium and all three thoracic segments are deleted anteriorly while posteriorly the 8th abdominal segment and adjacent parts of the 7th abdominal segment are lacking. The eight weak alleles show smaller deletions both in the thoracic and posterior abdominal region. In the weakest allele only part of the mesothorax is deleted. Three hb alleles produce a homoeotic transformation: superimposed on a strong or weak deletion phenotype, head or thoracic segments are transformed into abdominal segments, respectively. This suggests that hb might also be involved in the regulation of genes in the Bithorax complex (BX-C). Fate mapping of the normal-appearing segments in strong mutant embryos using the UV-laser beam ablation technique (Lohs-Schardin et al., 1979) shows that these segments arise from the normal blastoderm regions. The mutant phenotype can be recognized soon after the onset of gastrulation in a failure to fully extend the germ band. In 6-hr-old mutant embryos, two clusters of dead cells are observed in the thoracic and posterior abdominal region. These observations indicate region specific requirement of hb gene function. The analysis of germ line chimeras by transplantation of homozygous mutant pole cells shows that hb is already expressed during oogenesis. Homozygous mutant embryos derived from a homozygous mutant germ line have a novel phenotype. The anterior affected region is enlarged, including all three gnathal segments and the anterior three abdominal segments. In addition three abdominal segments with reversed polarity are formed between the remaining head structures and the posterior abdomen. Heterozygous mutant embryos derived from a homozygous mutant germ line develop normally, indicating that maternal gene expression is not required for normal development.

Abdomen↗
PubMed1989

The sequences of the reovirus serotype 1, 2, and 3 L1 genome segments and analysis of the mode of divergence of the reovirus serotypes.

We report the sequence of the L1 genome segment of reovirus serotype 3 strain Dearing, which encodes the minor core component protein lambda 3. It is 3854 bp long, with a long open reading frame starting at position 19 that is 1267 codons long. Protein lambda 3 is not detectably related to any other protein, nor does it appear to possess motifs indicative of recognized specialized functions. We have also sequenced the L1 genome segments of reovirus serotypes 1 and 2. The serotype 1 and 3 L1 genome segments are extremely closely related; there are only 154 mismatches (4.1%), 80% of which are in third base codon positions, so that these two lambda 3 proteins are 98.3% related (only 22 mismatches out of 1267). The serotype 2 L1 genome segment is only 75% related to the serotype 1 and 3 genome segments, and the serotype 2 lambda 3 protein is 92% related to the serotype 1 and 3 lambda 3 proteins. We have also analyzed the divergence patterns by which the various reovirus genome segments evolved into the three serotype forms. It appears that serotype 2 separated from the serotype 1/3 precursor long before serotypes 1 and 3 themselves diverged. In all cases the third base codon positions in the various genome segments have diverged about 80% toward randomness. The first and second base codon positions have diverged much less and to varying degree, depending, presumably, on each protein's ability to accept changes without significant loss of function. For the separation into the serotype 1 and 3 forms, the extent of divergence of the various genome varies over a very wide range. The S1 genome segments have again diverged most extensively, the extent of divergence in the first, second, and third base codon positions being about 50, 35 and 75%, respectively. For seven other genome segments that we examined the extent of third base codon position divergence is 56, 53, 48, 29, 22, 13, and 6%, whereas first and second base codon position divergence ranges from no more than 6 to 2 and 3 to less than 1%, respectively. The most likely explanation of these patterns is that the separation of the various genome segments into the present-day serotype 1 and 3 associated forms occurred at different times during evolution, from progenitors that were genome segment reassortants with survival rates as high as or higher than those of homologous genome segment sets.

Amino Acid Sequence↗
PubMed1993

Histologic studies in percutaneous transluminal coronary angioplasty for chronic total occlusion: comparison of tapering and abrupt types of occlusion and short and long occluded segments.

OBJECTIVES: The purpose of this study was to examine the histologic-angiographic correlates of chronic total coronary occlusion and to explain why a tapering type of occlusion and short occluded segments are favorable for percutaneous transluminal coronary angioplasty. BACKGROUND: Coronary angioplasty is less successful for vessels with chronic total occlusion than for highly stenotic but patent vessels. Several clinical and angiographic factors determining the rate of initial success have been investigated, but the underlying histologic features are not clear. METHODS: Ten autopsy hearts that showed chronic total coronary occlusion on cineangiography performed < or = 3 months before death were selected. In all, the estimated duration of occlusion was > 1 year. At autopsy, postmortem angiography was performed and hearts were fixed with 10% buffered formalin. Occluded segments were sectioned transversely and serially into slices 10 microns thick. Every five slices were stained in hematoxylin-eosin and elastic van-Gieson. RESULTS: Ten hearts with chronic total coronary occlusion were angiographically classified into five with a tapering and five with an abrupt type of occlusion and seven with a short (< or = 15 mm) and three with a long (> 15 mm) occluded segment. Histologically, the occluded segment was composed of loose or dense fibrous tissue, atheroma, small vascular channels and calcified tissue. Reconstruction of the serial preparations showed that small lumen recanalized areas (diameter 160 to 230 microns) with surrounding loose fibrous tissue penetrated the occluded segment in four hearts with occlusion of the tapering type and a short occluded segment. In these four cases, the lack of anterograde flow on cineangiography could be explained by the presence of rich collateral flow. In three cases of the abrupt type of occlusion with a short occluded segment, a mass of loose fibrous tissue penetrated the occluded segment. In hearts with a long occluded segment (one with a tapering type of occlusion and two with an abrupt type), there was no recanalization and loose fibrous tissue was dispersed in the occluded segment. CONCLUSIONS: Chronic total coronary occlusion of the tapering type or with a short occluded segment, or both, is possibly favorable for angioplasty, because small lumen recanalized areas or loose fibrous tissue penetrates the occluded segment and may form a route for successful angioplasty.

Aged↗
PubMed1996

Prognostic significance of precordial ST segment depression during inferior myocardial infarction in the thrombolytic era: results in 16,521 patients.

OBJECTIVES: We examined the prognostic significance of precordial ST segment depression among patients with an acute inferior myocardial infarction. BACKGROUND: Although precordial ST segment depression has been associated with a poor prognosis, this correlation has not been adequately quantified, partly because of small sample sizes and methodologic limitations in previous studies. METHODS: We examined the clinical and angiographic outcomes of 16,521 patients with an acute inferior myocardial infarction who underwent thrombolysis in the Global Utilization of Streptokinase and t-PA for Occluded Coronary Arteries (GUSTO-I) study. Patients were classified into those without precordial ST segment depression (n = 6,422 [38.9%]), those with ST segment depression in leads V1 to V3 only (n = 5,850 [35.4%]), those with ST segment depression in leads V4 to V6 only (n = 876 [5.3%]) and those with ST segment depression in both leads V1 to V3 and leads V4 to V6 (n = 3,373 [20.4%]) on initial electrocardiography. Outcome measures included postinfarction complications (second- or third-degree heart block, congestive heart failure or shock) and 30-day and 1-year mortality. RESULTS: Patients with precordial ST segment depression had larger infarctions, more postinfarction complications and a higher mortality rate than those without precordial ST segment depression (4.7% vs. 3.2% at 30 days; 5.0% vs. 3.4% at 1 year; both p < 0.001), regardless of whether ST segment depression was noted in leads V1 to V6 or in leads V4 to V6. The magnitude of precordial ST segment depression (sum of leads V1 to V6) added significant independent prognostic information after adjustment for clinical risk factors; the risk of 30-day mortality increased by 36% for every 0.5 mV of precordial ST segment depression. CONCLUSIONS: Assessment of the magnitude of precordial ST segment depression is useful for acute risk stratification in patients with an inferior myocardial infarction.

Electrocardiography↗
PubMed2006

Bone width is correlated positively with the upper to the lower segment ratio in elderly men--the MINOS study.

Before puberty, limbs grow more rapidly than the spine. During puberty, lengthening of the spine and increase in bone width accelerate. Correlation of parameters with lengths of the upper and lower segments and with the upper/lower segment ratio may indicate the period of growth critical for their determination. We assessed the association of bone mineral and width with the upper/lower segment ratio in 542 elderly men from the MINOS cohort. Areal bone mineral density (aBMD) was measured at the lumbar spine and right hip using pencil-beam dual-energy X-ray absorptiometry and at the distal forearm using single energy X-ray absorptiometry. Upper/lower segment ratio correlated positively with bone mineral content (BMC), aBMD and width of third lumbar vertebra (L3), femoral neck and distal radius. Men in the highest quartile of the upper/lower segment ratio had larger bones by 2.5 to 5.0% (0.3-0.4 SD, p<0.02-0.002) compared with the lowest quartile. Bone width correlated more strongly with the upper segment length than with that of the lower one. Volumetric BMD (vBMD) did not correlate with the upper/lower segment ratio nor with the lengths of the body segments. At the femoral neck and distal radius, men in the highest quartile of the upper/lower segment ratio had higher estimated cortical thickness (5.3%, 0.41 SD, p<0.01 and 4.0%, 0.31 SD, p<0.03), bigger cortical area (8.0%, 0.54 SD and 6.8%, 0.52 SD, p<0.0001) and higher estimated bending strength (9.3 to 13.3%, 0.46 to 0.54 SD, p<0.0001). Elderly men with the higher upper/lower segment ratio had higher BMC and bending strength because they had wider bones, not higher vBMD. The bone size correlated positively with the length of the upper segment, not negatively with that of the lower segment. Our data may suggest an important role of pubertal growth for both bone width and strength in men but do not establish the determinants of this association. Given methodological limitations, these results need to be confirmed in a younger and more representative group of men.

Absorptiometry, Photon↗
PubMed2005

Effect of soft segment length on properties of fluorinated polyurethanes.

The effects of soft segment length on the variations in morphology, surface composition, and hydrophilicity have been studied in fluorinated polyurethanes (FPUs) and correlated with their preliminary blood compatibility as evidenced by in vitro platelet adhesion experiments. The fluorinated polyurethanes were obtained using hexamethylene diisocyanate (HDI) and chain extender of 2,2,3,3-tetrafluoro-1,4-butanediol (TF) as the hard segment as well as various soft segments-polytetramethyl oxides (PTMO) with molecular weights of 650, 1000, 1400, and 2000. The increased phase separation in hard-segment domains with lengthening soft segment was observed by FT-IR, which is believed to result in enhanced strength of hydrogen bonds and good hard-segment order arrangement. Thin-film XRD results indicate at least three lateral distances existing between adjacent hard segments in the crystallized hard segment. Their distribution depends strongly on the length of soft segment. Lengthening soft segment promotes the formation of dense arrangement of crystallized hard segments. Compared with the effect of phase separation, surface composition was found to exert a major influence on the preliminary blood compatibility of fluorinated polyurethanes. Increasing fluorine content by decreasing soft segment length promotes reduction in platelet adhesion and activation on polyurethane surfaces.

Adsorption↗
PubMed2006

An automatic variational level set segmentation framework for computer aided dental X-rays analysis in clinical environments.

An automatic variational level set segmentation framework for Computer Aided Dental X-rays Analysis (CADXA) in clinical environments is proposed. Designed for clinical environments, the segmentation contains two stages: a training stage and a segmentation stage. During the training stage, first, manually chosen representative images are segmented using hierarchical level set region detection. Then the window based feature extraction followed by principal component analysis (PCA) is applied and results are used to train a support vector machine (SVM) classifier. During the segmentation stage, dental X-rays are classified first by the trained SVM. The classifier provides initial contours which are close to correct boundaries for three coupled level sets driven by a proposed pathologically variational modeling which greatly accelerates the level set segmentation. Based on the segmentation results and uncertainty maps that are built based on a proposed uncertainty measurement, a computer aided analysis scheme is applied. The experimental results show that the proposed method is able to provide an automatic pathological segmentation which naturally segments those problem areas. Based on the segmentation results, the analysis scheme is able to provide indications of possible problem areas of bone loss and decay to the dentists. As well, the experimental results show that the proposed segmentation framework is able to speed up the level set segmentation in clinical environments.

Algorithms↗
PubMed2005

Patients with prolonged ischemic chest pain and presumed-new left bundle branch block have heterogeneous outcomes depending on the presence of ST-segment changes.

OBJECTIVES: The purpose of this research was to examine the prognostic value of ST-segment changes (concordant ST-segment elevation and/or precordial V1 to V3 ST-segment depression) during presumed-new left bundle branch block (LBBB) in patients receiving fibrinolytic therapy. BACKGROUND: These patients are often considered high-risk, but their outcome is not well-defined. METHODS: The Hirulog and Early Reperfusion or Occlusion (HERO)-2 trial compared bivalirudin with heparin in patients receiving streptokinase for ST-segment elevation or presumed-new LBBB. Each patient with LBBB was matched with a control (with normal intraventricular conduction) for age, gender, pulse rate, systolic blood pressure, Killip class, and region. RESULTS: A total of 300 patients had LBBB (92 with and 208 without ST-segment changes) and 15,340 had normal conduction. Acute myocardial infarction (AMI) occurred in 80.7% of LBBB patients and 88.7% of controls (p = 0.006). ST-segment changes were specific (96.6%) but not sensitive (37.8%) for enzymatic diagnosis of AMI. Mortality at 30 days was similar in LBBB patients with ST-segment changes (21.7%) and controls (25.0%, p = 0.563), but lower in LBBB patients without ST-segment changes than in controls (13.5% vs. 21.6%, p = 0.022). In the whole HERO-2 cohort, the LBBB patients with ST-segment changes had higher mortality than patients with normal conduction (odds ratio [OR] 1.37, 95% confidence interval [CI] 0.78 to 2.42). The LBBB patients without ST-segment changes had lower mortality than patients with normal conduction (OR 0.52, 95% CI 0.33 to 0.80). CONCLUSIONS: ST-segment changes during LBBB are specific for the diagnosis of AMI and predict 30-day mortality; LBBB patients without ST-segment changes have lower adjusted 30-day mortality than those with normal conduction. Trials are required to determine the best treatment for high-risk and low-risk patients with LBBB.

Aged↗
PubMed2006

Microplitis demolitor bracovirus genome segments vary in abundance and are individually packaged in virions.

Polydnaviruses (PDVs) are distinguished by their unique association with parasitoid wasps and their segmented, double-stranded (ds) DNA genomes that are non-equimolar in abundance. Relatively little is actually known, however, about genome packaging or segment abundance of these viruses. Here, we conducted electron microscopy (EM) and real-time polymerase chain reaction (PCR) studies to characterize packaging and segment abundance of Microplitis demolitor bracovirus (MdBV). Like other PDVs, MdBV replicates in the ovaries of females where virions accumulate to form a suspension called calyx fluid. Wasps then inject a quantity of calyx fluid when ovipositing into hosts. The MdBV genome consists of 15 segments that range from 3.6 (segment A) to 34.3 kb (segment O). EM analysis indicated that MdBV virions contain a single nucleocapsid that encapsidates one circular DNA of variable size. We developed a semi-quantitative real-time PCR assay using SYBR Green I. This assay indicated that five (J, O, H, N and B) segments of the MdBV genome accounted for more than 60% of the viral DNAs in calyx fluid. Estimates of relative segment abundance using our real-time PCR assay were also very similar to DNA size distributions determined from micrographs. Analysis of parasitized Pseudoplusia includens larvae indicated that copy number of MdBV segments C, B and J varied between hosts but their relative abundance within a host was virtually identical to their abundance in calyx fluid. Among-tissue assays indicated that each viral segment was most abundant in hemocytes and least abundant in salivary glands. However, the relative abundance of each segment to one another was similar in all tissues. We also found no clear relationship between MdBV segment and transcript abundance in hemocytes and fat body.

Animals↗
PubMed1999

ST-segment elevation during dobutamine stress testing predicts functional recovery after acute myocardial infarction.

OBJECTIVES: The aims of this study were (1) to assess the relation between ST-segment elevation and wall motion response occurring during dobutamine testing and (2) to evaluate the usefulness of stress-induced ST-segment elevation for predicting functional recovery after acute myocardial infarction. BACKGROUND: Clinical significance of stress-induced ST-segment elevation after acute myocardial infarction remains controversial. According to previous studies, it may reflect a larger infarcted area, depressed left ventricular function, left ventricular aneurysm, stress-induced dyskinesia, residual myocardial ischemia, or viability in the affected region. Whether transient ST-segment elevation occurring during dobutamine testing may predict functional recovery is unknown. METHODS AND RESULTS: We studied 38 patients who underwent dobutamine stress testing early (5 +/- 2 days) after a first acute myocardial infarction. Dobutamine was infused at increasing doses from 5 to a maximum of 40 microg/kg per minute, with the addition of up to 1 mg of atropine if the target rate could not be reached by dobutamine alone. Twelve-lead electrocardiography and cross-sectional echocardiography were continuously monitored throughout the test. Dobutamine-induced ST-segment elevation was defined as a new or worsening >/=1 mm elevation, 80 ms after J point, in >/=2 infarct-related leads. Quantitative angiography was available in all patients before hospital discharge. Follow-up resting echocardiography was recorded in all patients 12 to 18 months after the acute event. ST-segment elevation was observed in 20 of the 38 patients. There were no significant differences between patients with and those without dobutamine-induced ST-segment elevation in age, site of infarction, peak level of total creatine kinase enzyme, and use of thrombolytic therapy, angioplasty, or both. Persistent akinesis without change during dobutamine stress testing was more frequently observed in patients without ST elevation (P <. 05). A biphasic response during dobutamine testing was more frequently observed in patients with ST-segment elevation (P =.01). Multivariate analysis selected 2 independent variables associated with ST-segment elevation: a biphasic response during dobutamine stress (chi-square = 7.3; P =.007) and the minimal lumen diameter of the infarct-related vessel at quantitative angiography (chi-square = 5.5; P <.02). Functional recovery was demonstrated in 26 patients. Sensitivity of ST-segment elevation for the prediction of functional recovery was 69%, specificity 83%, positive predictive value 90%, and accuracy 74%. Two independent variables predicting functional recovery were selected: dobutamine-induced ST-segment elevation (chi-square = 9.1; P =.003) and a biphasic response during stress (chi-square = 6.15; P =.013). CONCLUSIONS: Dobutamine-induced ST-segment elevation in the infarct-related leads is an ancillary sign of viable myocardium in jeopardy. It has a high specificity and an acceptable sensitivity for the prediction of functional recovery after acute myocardial infarction.

Adrenergic beta-Agonists↗
PubMed2000

Effects of inotropic stimulation on segmental left ventricular relaxation quantified by color kinesis.

Although myocardial ischemia impairs left ventricular (LV) relaxation before contractile function, regional LV diastolic dysfunction is difficult to evaluate by conventional echocardiography. Because beta-adrenergic stimulation enhances myocardial relaxation, we sought to characterize segmental LV diastolic function (by color kinesis) during dobutamine stress echocardiography and compare it with independently assessed segmental systolic function. We studied 22 patients with suspected coronary artery disease with color kinesis by acquiring digital images with endocardial motion display throughout diastole. Quantification of LV segmental diastolic peak filling rate (SPFR, normalized to segmental end-diastolic area/s) was obtained at rest, low-dose, and peak dobutamine infusion in myocardial segments visualized from the short-axis and/or apical 4-chamber views. In patients with resting normal LV systolic function and a dobutamine-induced hypercontractile response (group I, n = 13 patients; 102 segments), progressive increases in SPFR (p <0.001) were seen in all segments. However, in LV segments with resting systolic wall motion abnormalities (group II, n = 9 patients; 74 segments) SPFR measured at rest was significantly lower than that in group I (p <0.005) and did not increase significantly in response to dobutamine. In both groups of patients, LV myocardial segments (n = 528; rest and after dobutamine)-systolic and quantitative diastolic function-were concordant in 84% and 77% as viewed from short-axis and apical views, respectively. Thus, segmental LV diastolic function can be measured with color kinesis at rest and after inotropic stimulation, allowing comparison with segmental systolic function during pharmacologic stress testing.

Aged↗
PubMed1999

Observer variation in measured ST-segment elevation.

STUDY OBJECTIVE: ST-segment elevation is used to make early decisions about using thrombolytic therapy in patients with suspected myocardial infarction. This study was performed to assess interobserver and intraobserver variation in subjects' measurements of ST-segment elevation in isolated ECG complexes. METHODS: We performed a masked, paired-sample experiment. Emergency physicians, emergency medicine residents, and senior medical students were asked to measure ST-segment elevations in a packet of 40 isolated single ECG complexes from patients with proven myocardial infarction. Each packet consisted of 20 pairs of randomly ordered ECG complexes. Subjects were masked to the duplicate nature of the pairs of complexes. Estimates of each ST-segment measurement pair were subtracted; summary statistics were calculated for these differences. Agreement between first and second ST-segment estimates was analyzed by using weighted kappa values. Tests for differences in the paired ST-segment estimations among groups were carried out with 1-factor analysis of variance. RESULTS: Fifty-two subjects completed the study and measured a total of 2,070 ST segments (1,035 pairs). The mean difference in segment height among all groups was 0.28 mm (95% confidence interval [CI], 0.27 to 0.30). The median was 0.2 mm, the 80th percentile was 0.5 mm, and the 95th percentile was 0.9 mm. Statistical agreement between paired ST-segment measurements was very good (kappa=0.85; 95% CI, 0.83 to 0.87). However, by using a threshold of at least 2.0 mm for ST-segment elevation, 143 (14%) of 1,035 paired estimations (95% CI, 12% to 16%) produced inconsistent classifications. Physicians, residents, and students had similar median differences (P =.77). Some subjects exhibited more intraobserver variation than did others, and some complexes were associated with greater intraobserver variation than others (P <.001). CONCLUSION: One fifth of the time, intraobserver measurements of paired ST-segment elevations differed by more than half a millimeter. Independent interpretations of the same ST segment by the same reader as greater than or equal to 2.0 mm or not were different 14% of the time. This could result in misclassification of candidates for thrombolytic therapy.

Electrocardiography↗
PubMed1998

Intravenous electron-beam computed tomographic coronary angiography for segmental analysis of coronary artery stenoses.

OBJECTIVES: We sought to identify and localize significant coronary stenoses on a segmental basis by electron-beam computed tomography (EBCT) and intravenous administration of a contrast agent. BACKGROUND: The clinical applicability and limitations of intravenous EBCT coronary angiography have not been defined. METHODS: EBCT was performed within 24 h of selective coronary angiography (SCA) in 28 patients (19 men and 9 women, mean [+/-SD] age 60 +/- 10 years). After examination for coronary calcium, EBCT coronary angiography was performed using overlapping slices (in-plane resolution 0.34 to 0.41 mm) with a nominal slice thickness of 1 mm. Based on quantitative analysis of SCA, lumen diameter narrowing > or = 50% (i.e., significant stenoses) was evaluated in 8 (major) or 12 (including side branches) coronary artery segments, using both two-dimensional (tomographic) and three-dimensional (volume) data sets. RESULTS: Of the 330 segments assessable by SCA, 237 (72%) were visualized by EBCT. The sensitivity (+/-SE) for detection of significant stenoses was 82 +/- 6%; specificity was 88 +/- 2%; positive and negative predictive values were 57 +/- 7% and 96 +/- 2%, respectively; and overall accuracy was 87 +/- 2%. If only eight (major) coronary artery segments were considered, 194 (88%) of 221 segments were visualized, and the overall accuracy was 90 +/- 2%. Seven (18%) of 38 significantly stenotic segments were classified as having < 50% stenoses by EBCT. Six of these segments (86%), but only 9 (29%) of the 31 correctly classified stenotic segments, were severely calcified (area > 20 mm2, p = 0.02). In 23 (12%) of 199 nonstenotic segments falsely classified as having > or = 50% stenosis by EBCT, the lumen diameter was significantly smaller than that of the segments correctly classified as negative (mean [+/-SD] 1.5 +/- 0.8 vs. 2.9 +/- 1.1 mm, p < 0.001). CONCLUSIONS: Intravenous EBCT coronary angiography allows for accurate segmental evaluation of significant disease in the major coronary arteries and may be of value for ruling out significant disease. The main determinant of false negative results is substantial segmental calcification, whereas the main determinant of false positive results is small vessel size.

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