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PubMed1995

Noninvasive assessment of speed and stability of infarct-related artery reperfusion: results of the GUSTO ST segment monitoring study. Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded Coronary Arteries.

OBJECTIVES: The ST segment monitoring substudy of the Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded Coronary Arteries (GUSTO-I) trial compared the speed and stability of ST segment recovery among four thrombolytic strategies for acute myocardial infarction. BACKGROUND: Rapid resolution of ST segment elevation has been suggested as a noninvasive marker of infarct-related artery patency. We expected that patients treated with accelerated recombinant tissue-type plasminogen activator (rt-PA) would show a quicker recovery than that of other patients but that those treated with streptokinase would show greater stability of recovery. METHODS: ST segment monitoring was initiated in 1,067 patients within 30 min of the start of thrombolysis and continued for > 18 h with the use of a three-channel continuous vectorcardiographic monitor, a 12-lead continuous electrocardiographic (ECG) monitor or a three-channel (V2, V5, aVF) Holter ambulatory ECG monitor. RESULTS: Time to 50% recovery could be assessed in 618 patients and was similar in the four treatment groups: median 45 min with streptokinase/subcutaneous heparin, 45 min with streptokinse/intravenous heparin, 42 min with accelerated rt-PA and 47 min with combination therapy (p = 0.7). No significant difference among the thrombolytic regimens was shown with the three monitors used. Time to initiation of ST segment analysis was directly related to time to 50% recovery (p = 0.0001) and was its best predictor in a multiple regression model. ST segment elevation recurred equally in each treatment group (approximately 36%, p = 0.9) but was significantly more common in patients with a patent infarct-related artery (p = 0.033) or a low ejection fraction (p = 0.001). CONCLUSIONS: The greater 90-min patency seen with accelerated rt-PA in the angiographic substudy did not correlate with a shorter time to 50% ST segment recovery, possibly because of technical limitations and study design. The similar rates of recurrent ischemia (as assessed by ST elevation) among the regimens support the similar infarction and reocclusion rates seen in the main trial and angiographic substudy.

Drug Therapy, Combination↗
PubMed1995

Residual coronary reserve identifies segmental viability in patients with wall motion abnormalities.

OBJECTIVES: The aim of this study was to determine whether the presence of residual coronary reserve can in itself identify viable segments. BACKGROUND: Experimental data suggest that despite hypoperfusion at rest, viable myocardium may exhibit persistence of coronary reserve. Preliminary observations in patients show that in basally dyssynergic areas, a residual vasodilator capability is present despite hypoperfusion at rest and that a flow-mediated increase in regional wall motion identifies residual viability. METHODS: Fourteen patients with evidence of previous myocardial infarction, infarct-related single-vessel coronary artery disease and impaired regional ventricular function at rest underwent positron emission viability imaging by fluorine-18 deoxyglucose. In addition, blood flow at rest and vasodilator capability were regionally evaluated in all patients by means of nitrogen-13 ammonia. RESULTS: Of a total of 252 segments, 133 were dyssynergic at rest. Of these 133 segments, 60 (group 1) showed normal metabolic activity and only mild reduction in myocardial blood flow. The other 73 segments showed a marked reduction in flow; of these, 25 (group 2, viable) had persistent metabolic activity, whereas 48 (group 3, necrotic) did not. Despite similar levels of hypoperfusion at rest, group 2 segments showed a preserved coronary reserve that was virtually absent in necrotic segments (2.6 +/- 1.3 vs. 1.3 +/- 0.5, p < 0.01). This value was similar to that observed in viable group 1 segments (2.5 +/- 1.6, p = NS). CONCLUSIONS: In addition to characterizing myocardium at risk, imaging of coronary flow at baseline and after dipyridamole by positron emission tomography provides helpful information on myocardial viability that may integrate the "static" viability information obtained with the baseline flow/metabolic approach.

Aged↗
PubMedDate not supplied

The accuracy of ST segment deviation in prehospital cardiac monitoring.

Elevation or depression of the ST segment of the 12-lead electrocardiogram is an important and established marker of myocardial ischemia or injury. The ST segment deviation in normal individuals using standard cardiac monitoring equipment in the clinical setting of prehospital transport has not been studied. The hypothesis that we tested is that ST segment changes do not occur in normal subjects on standard prehospital cardiac monitors during transport. During a simulated transport, we monitored healthy volunteers of both sexes between the ages of 20 and 30 who had a normal cardiovascular history, physical examination, and 12-lead electrocardiogram. Fourteen of 34 subjects (41%) who qualified as normal exhibited ST segment deviation on the monitor. Of these 14, 11 exhibited ST segment depression, and 3 exhibited ST segment elevation. We conclude that normal individuals can exhibit ST segment deviation on standard prehospital cardiac monitoring equipment during routine transport.

Adult↗
PubMed1995

Spatial regulation of segment polarity gene expression in the anterior terminal region of the Drosophila blastoderm embryo.

The effects of mutations in five anterior gap genes (hkb, tll, otd, ems and btd) on the spatial expression of the segment polarity genes, wg and hh, were analyzed at the late blastoderm stage and during subsequent development. Both wg and hh are normally expressed at blastoderm stage in two broad domains anterior to the segmental stripes of the trunk region. At the blastoderm stage, each gap gene acts specifically to regulate the expression of either wg or hh in the anterior cephalic region: hkb, otd and btd regulate the anterior blastoderm expression of wg, while tll and ems regulate hh blastoderm expression. Additionally, btd is required for the first segmental stripe (mandibular segment) of both hh and wg at blastoderm stages. The subsequent segmentation of the cephalic segments (preantennal, antennal and intercalary) appears to be dependent on the overlap of the wg and hh cephalic domains as defined by these gap genes at the blastoderm stage. None of these five known gap genes are required for the activation of the labral segment domains of hh and wg, which are presumably either activated directly by maternal pathways or by an unidentified gap gene.

Animals↗
PubMed2005

Intraoperative tumor segmentation and volume measurement in MRI-guided glioma surgery for tumor resection rate control.

RATIONALE AND OBJECTIVES: Gross-total surgery under intraoperative magnetic resonance imaging (MRI) is a promising method of glioma removal. The purpose of this article is intraoperative measurement of resected tumor volume in MRI-guided glioma surgery using semiautomatic image segmentation to unbiased resection rate control. MATERIALS AND METHODS: A newly developed software program based on a fuzzy connectedness (FC) segmentation algorithm was used to achieve fast and semiautomatic tumor segmentation and tumor volume measurement. The program was validated by retrospective study of eight glioma cases and then applied to seven glioma cases. All clinical cases underwent actual MRI-guided surgery using 0.3-T open magnets. RESULTS: The volume of the tumor before resection ranged from 10.1 to 206.7 mL. A comparison of the results of manual segmentation with those of the semiautomatic FC-based segmentation gave an average dice similarity coefficient of 0.80 and an average match of 76%. Volume measurement combined with a developed software program enabled quantitative monitoring of tumor removal, which was critical in the near-total resection of glioma in MRI-guided surgery. CONCLUSION: The FC-based tumor segmentation method can be used for intraoperative tumor segmentation and volume measurement in MRI-guided glioma surgery using 0.3-T open magnets. This method is useful for objective resection rate monitoring, which may ultimately minimize the amount of residual tumor in glioma surgery.

Adolescent↗
PubMed2004

Quantitative relation of ST-segment depression during exercise to the magnitude of myocardial ischemia as assessed by single-photon emission computed tomographic myocardial perfusion imaging.

The mechanism of ST-segment depression during exercise electrocardiographic treadmill testing (ETT) is unknown. The relatively good correlation between the results of ETT and myocardial perfusion imaging suggests that ST-segment depression may be related to the magnitude of ischemia. Previous studies that investigated this relation have produced conflicting results. We evaluated 1,006 patients who underwent symptom-limited ETT and technetium-99m single-photon emission computed tomographic myocardial perfusion imaging at rest and during stress at a single institution. The magnitude, extent, and duration of ST-segment depression were each strongly associated with the magnitude of myocardial ischemia (p <0.001 for all). The magnitude, extent, and duration of ST-segment depression were highly correlated with each other and had similar relations to the magnitude of ischemia. After adjustment for significant clinical and ETT parameters, these relations remained highly significant. The location of myocardial ischemia was unrelated to ST-segment depression. This large study found that ST-segment depression during ETT is strongly associated with the magnitude of ischemia. These data support a causative role for the magnitude of ischemia in the generation of ST-segment depression.

Chi-Square Distribution↗
PubMed2004

Comparison of eight- versus 16-slice multidetector-row computed tomography for visibility and image quality of coronary segments.

Ten patients who underwent conventional coronary angiography (CA) were examined with both 8- and 16-slice multidetector-row computed tomography (MDCT) angiography within 6 months, and visibility and image quality of 16-slice MDCT-CA were compared with those of 8-slice MDCT-CA directly. In 136 segments determined by conventional CA, 101 (74.3%) and 126 (92.6%) segments were judged assessable by 8- and 16-slice MDCT-CA, respectively. Segment visibility in the right coronary and left circumflex arteries, as well as distal segments and small segments with diameters of <3.0 mm, was higher using 16-slice MDCT-CA than that of 8-slice MDCT-CA. As causes for invisibility in segments considered to be invisible, adjacent structures, as well as small diameters, were reduced by 16-slice MDCT-CA, suggesting that high spatial resolution contributes to higher visibility; however, nonassessable segments due to extensive calcium by 8-slice MDCT-CA were also judged nonassessable by 16-slice MDCT-CA.

Coronary Angiography↗
PubMed2005

ST-segment analysis to predict infarct size and functional outcome in acute myocardial infarction treated with primary coronary intervention and adjunctive abciximab therapy.

ST-segment resolution is used to classify the response to reperfusion therapy in acute myocardial infarction, but the possibility to predict outcome in individual patients is unclear, particularly in the setting of primary percutaneous coronary intervention (PCI) and abciximab therapy. We studied 213 patients who underwent successful revascularization with PCI. Maximal ST-segment elevation was measured before and 30 minutes after PCI. Patient outcome was defined on the basis of infarct size and left ventricular ejection fraction (EF) as derived from gated single-photon emission computed tomography that was acquired 1 month after infarction. Patients who had > or =50% ST resolution showed a smaller infarct (15.1 +/- 13.6% vs 19.9 +/- 15.7%, p < 0.05) but not a higher left ventricular EF (48.7 +/- 12.3% vs 45.2 +/- 11.8%) than did patients who had <50% resolution. According to cluster analysis of infarct size and left ventricular EF, 132 patients had favorable outcome (central values: infarct size 7.5%, left ventricular EF 55%) and 81 did not (central values: infarct size 30%, left ventricular EF 36%). Using receiver-operating characteristic curve analysis, the optimal ST-resolution cutoff was >60%, with 77% sensitivity and 51% specificity for predicting favorable outcome. ST-segment elevation < or =4.5 mV before PCI was 80% sensitive and 48% specific, and ST-segment elevation < or =1 mV after PCI was 74% sensitive and 60% specific for predicting favorable outcome. In conclusion, in the setting of primary PCI and abciximab therapy, ST-segment elevation resolution requires a high threshold (>60%) to effectively classify patients; the capability of ST-segment analysis to predict patient outcome is limited, with ST-segment elevation after PCI showing the best compromise between sensitivity and specificity.

Abciximab↗
PubMed2006

Detection of coronary artery stenosis using 40-channel computed tomography with multi-segment reconstruction.

Coronary angiographic studies performed with 16-channel multidetector computer tomographic scanners have demonstrated accurate detection of coronary vessel stenosis but are limited by a significant number of non-evaluable segments. To date, only single-center experience with multidetector computer tomography has been reported. We performed a prospective, blinded study at 2 institutions to determine the feasibility and diagnostic accuracy of coronary angiography using 40-channel multidetector computer tomography with multi-segment reconstruction for the detection of obstructive coronary artery disease (CAD). Multidetector computer tomographic studies were performed in 85 patients who were referred for invasive coronary angiography with clinically suspected CAD. Datasets were analyzed by blinded, independent review. Of 1,145 segments that were suitable for analysis as determined by angiography, 1,045 (91.3%) were evaluable on multidetector computer tomography. Segment-based sensitivity, specificity, and positive and negative predictive values for detecting > or =50% luminal stenoses were 86%, 97%, 75%, and 97%, respectively. The area under the receiver-operating characteristic curves for the detection of > or =50% angiographic stenosis by multidetector computer tomography was 0.94. In a patient-based analysis, the sensitivity, specificity, and positive and negative predictive values for detecting subjects with > or =1 segment with > or =50% stenosis were 98%, 93%, 94% and 93%, respectively. In conclusion, coronary angiography using 40-channel multidetector computer tomography with multi-segment reconstruction accurately detects coronary segments and patients with obstructive CAD, with a small number of non-evaluable cases.

Coronary Angiography↗
PubMed2006

Intrahepatic Glissonian access for segmental liver resection in cirrhotic patients.

The main goal of segmental technique is to preserve the maximum amount of liver parenchyma. Liver-preserving techniques are especially important for patients with hepatocellular carcinoma and cirrhosis. We report the technique for segmental liver resection in cirrhotic patients and detail technical difficulties and immediate surgical outcome. For right segmental liver resections the intrahepatic access is performed through small incisions around the hilar plate. Left segmental resection technique also consists of small incisions following specific anatomic landmarks. Nineteen cirrhotic patients underwent segmental liver resections. A blood transfusion was required in 2 patients. No patient experienced major bleeding from the liver incisions made for intrahepatic access. The median hospital stay was 5 days. No surgical mortality occurred. The intrahepatic access technique allows individual resections of liver segments and is feasible even in cirrhotic patients. Knowledge of segmental liver resection techniques is an essential armamentarium in the modern era of liver surgery.

Adult↗
PubMed2004

Psychological distance to reward: equating the number of stimulus and response segments.

Psychological distance to reward, or the segmentation effect, refers to the preference for a terminal link of a concurrent-chains schedule consisting of a simple reinforcement schedule (e.g. fixed interval [FI] 30s) relative to its chained-schedule counterpart (e.g. chained FI 15s FI 15s). This experiment was conducted to examine whether the segmentation effect is due to the number of terminal-link stimulus and response segments per se. Three pigeons pecked under a concurrent-chains schedule in which identical variable-interval (VI) schedules operated in the initial links. In each session, half the terminal-link entries followed one initial-link key and the other half followed the other initial-link key. The initial-link keys correlated with the different terminal links were manipulated across conditions. In the first three conditions, each terminal link contained a chained fixed-time (FT) FT schedule, and in the final three conditions, each terminal link contained a chained FI FI schedule. In each condition, in one terminal link (alternating), the order of two key colors correlated with the different schedule segments alternated across terminal-link entries, whereas in the other terminal link (constant), the order of two other key colors was identical for each entry. With the chained FT FT schedule terminal links, there was indifference between the alternating and constant terminal links within and across pigeons, as indexed by initial-link choice proportions. In addition, terminal-link response rates were relatively low. With the chained FI FI schedule terminal links, for each pigeon, there was relatively more preference for the alternating terminal link and terminal-link response rates increased relative to conditions with the chained FT FT schedule terminal links. These data suggest that the segmentation effect is not due simply to the number of terminal-link stimulus or response segments per se, but rather to a required period of responding during a stimulus segment that never is paired with reinforcement.

Adaptation, Psychological↗
PubMed2006

An identification technique for evaluating body segment parameters in the upper extremity from manipulator-hand contact forces and arm kinematics.

OBJECTIVE: To show that it is possible to determine segment masses and segment centers of mass by measuring manipulator-hand contact forces and joint angles during upper extremity movement. BACKGROUND: The method serves as a quick subject specific body segment parameter evaluation technique. Clinically we see this method as an alternative upper extremity body segment parameter evaluation study especially useful in rehabilitation treatment activities. METHODS: The experiment is based on coupling the human arm with a robotic manipulator which is then used for imposing a specified sagittal plane trajectory. Joint angles and forces in the contact point serve as input to the identification procedure. For verification purposes the proposed identification procedure was first performed on a mechanical arm. Afterwards a low velocity trajectory was imposed into all joints of the human upper extremity, with very small angular deviations. Within this small angular region the arm was assumed to be represented as a linear system. FINDINGS: The outcome of the identification procedure is an estimate of masses and center of mass coordinates for the lower arm and palm segments, their products for the upper arm and the passive moments around the measured angle of all joints in the sagittal plane. The results obtained for three particular human arms are eventually compared to the average population based literature. CONCLUSION: From the clinical point of view the study can become useful for biomechanical evaluation and for evaluating biomechanical properties of lower extremities or other body segments. This method may also provide a foundation to measuring body segment moments of inertia and joint viscoelastic parameters.

Adult↗
PubMed2005

A new strategy to obtain robust markers for blood vessels segmentation by using the watersheds method.

The watersheds method is a powerful segmentation tool developed in mathematical morphology. In order to prevent its over-segmentation, in this paper, we present a new strategy to obtain robust markers for segmentation of blood vessels from malignant tumors. For this purpose, we introduced a new algorithm. We propose a two-stage segmentation strategy which involves: (1) extracting an approximate region containing the blood vessel and part of the background near the blood vessel, and (2) segmenting the blood vessel from the background within this region. The approach effectively reduces the influence of peripheral background intensities on the extraction of a blood vessel region. In this application the important information to be extracted from images is only the number of blood vessels present in the images. The proposed strategy was tested on manual segmentation, where segmentation errors less than 10% for false positives and 0% for false negatives are observed. It is demonstrated by extensive experimentation, by using real images, that the proposed strategy was suitable for our application in the environment of a personal computer.

Algorithms↗
PubMed2004

Specially adapted interactive tools for an improved 3D-segmentation of the spine.

For imaging purposes of the spine, segmented image data provides the basis for a variety of modern clinical applications. However, the anatomical complex structure of the spine as well as the extensive degenerative bony deformations apparent in the clinical situation, generally complicate the application of a fully automated segmentation. To serve the special needs for image segmentation of the spine anatomy a newly developed software system is presented, that implements specially adapted interactive tools, taking its 'axis'-skeletal structure into account. A standardized protocol combines the newly developed interactive tools (rotation transformation, warped dissection plane) with standard segmentation tools to provide both a fast and accurate segmentation procedure. The introduced software environment has been valuable for the segmentation of cervical, thoracic and lumbar spines segments based on clinical routine and research images.

Computers↗
PubMed2004

Admission Troponin T and measurement of ST-segment resolution at 60 min improve early risk stratification in ST-elevation myocardial infarction.

AIMS: The prognostic value of admission troponin T (tnT) levels and the resolution of the ST-segment elevation in ST-elevation myocardial infarction (STEMI) is well established. However, the combination of these two early available markers for predicting risk has not been evaluated. METHODS AND RESULTS: We evaluated 516 patients with fibrinolytic treated STEMI from the ASSENT-2 and ASSENT-PLUS studies, which had both admission tnT and ST-monitoring available. We used a prospectively defined cut-off value of tnT of 0.1microg/l. For ST-segment resolution, a cut-off of 50% measured after 60min was used. Both a tnT >/=0.1microg/l (n=116) and ST-segment resolution <50% (n=301) were related to higher one-year mortality, 13% vs 4% (P<0.001) and 8.4% vs 2.8% (P=0.009), respectively. In a multivariate analysis ST-segment resolution was and tnT showed a strong trend to be independently related to mortality. The combination of both further improved risk stratification. The one-year mortality in the group with elevation of tnT and without ST-segment resolution compared to the group without tnT elevation and with ST-segment resolution was 18.2% vs 2.8% (P<0.001). CONCLUSIONS: Both tnT on admission and ST-segment resolution after 60min are strong predictors of one-year mortality. The combination of both gives additive early information about prognosis and further improves risk stratification.

Arrhythmias, Cardiac↗
PubMed2004

Segmental hypoplasia of the great saphenous vein and varicose disease.

OBJECTIVES: Primitive narrowing of great saphenous vein segments (saphenous hypoplasia) has been described in healthy limbs. The aim of the present study was to detect great saphenous vein segmental hypoplasia in limbs with varicose veins and to evaluate the local anatomical and haemodynamic patterns. MATERIALS AND METHODS: The incidence of saphenous hypoplasia and the local haemodynamic rearrangement were evaluated by duplex ultrasonography in 676 normal limbs and in 320 limbs with varicose veins. RESULTS: Segmental hypoplasia was demonstrated in 84 normal limbs and in 79 limbs with saphenous reflux. In the latter, the retrograde flow leaves the GSV at the proximal end of the hypoplastic segment to feed tributary veins. CONCLUSIONS: Saphenous hypoplasia occurs in varicose limbs more frequently than in healthy ones (p= >0.001). It greatly influences the path of the reflux and the anatomy of the varicose veins. GSV segmental hypoplasia can be detected preoperatively by duplex ultrasonography. Its occurrence may influence surgical management for two main reasons: in about 68% of varicose limbs with segmental hypoplasia, the distal GSV is competent. If the distal GSV is varicose, its size and flow direction is normalised by treating the accessory vein that bypasses the hypoplastic segment.

Adolescent↗
PubMed2004

Mechanisms of recurrent atrial fibrillation after pulmonary vein isolation by segmental ostial ablation.

OBJECTIVES: The aim of this study was to determine the mechanisms responsible for recurrent atrial fibrillation (AF) after pulmonary vein isolation (PV) by segmental ostial ablation. BACKGROUND: Recovery of conduction into a previously isolated PV is a common observation when there is recurrent AF soon after segmental ostial ablation. However, the mechanisms of recurrent AF have been unclear. METHODS: A repeat ablation procedure was performed in 50 patients who had recurrent paroxysmal AF at a mean of 7 +/- 6 months after segmental ostial ablation to isolate the PVs. During the repeat procedure, a ring catheter was inserted into each PV during sinus rhythm and AF to determine whether the veins were still isolated and, if not, whether there were PV tachycardias with a cycle length shorter than in the adjacent left atrium during AF. RESULTS: There was recovery of conduction over a previously ablated muscle fascicle in >/=1 PV in 49 patients (98%). There were 10 +/- 2 episodes of PV tachycardia per minute in 36 (72%) of the 50 patients during AF. Repeat ablation was performed by segmental ostial ablation (23 patients) or by left atrial catheter ablation to encircle the left- and right-sided PVs 1 to 2 cm from the ostia, with additional ablation lines in the posterior left atrium and mitral isthmus (27 patients). At 6-month follow-up, among 23 patients who underwent repeat ablation by segmental ostial ablation, AF recurred in 4 (21%) of the 19 patients who had PV tachycardias and in 3 (75%) of the 4 patients who did not (P = .03). Among the 27 patients who underwent left atrial ablation, AF recurred in 2 (12%) of the 17 patients who had PV tachycardias and in 1 (10%) of the 10 patients who did not (P = 0.7). CONCLUSIONS: Recovery of conduction in previously ablated muscle fascicles is a common finding in patients with recurrent AF after segmental ostial ablation. The efficacy of repeat segmental ostial ablation depends on the presence of PV tachycardias, whereas left atrial ablation is effective regardless of whether PV tachycardias are present or not during AF.

Atrial Fibrillation↗
PubMed2006

Automatic segmentation as a tool for examining the handwriting process of children with dysgraphic and proficient handwriting.

The purpose of this study was to use an x-y digitizer to collect handwriting samples typical of those written by the child in his or her natural environment, to analyze these samples with novel segmentation algorithms, and to present them visually in ways that illuminate spatial and temporal dynamic features amongst children with dysgraphic and proficient handwriting. While using the POET software (Penmanship Objective Evaluation Tool), a paragraph was copied onto paper affixed to an x-y digitizer by third-grade students, 14 with proficient and 14 with poor handwriting. A segmentation algorithm was developed to automatically isolate writing segments. Results yielded significant differences between the groups in various measures, including the number of the raw segments (i.e., the number of segments before combined with letters), the number of reverse segments (i.e., when the participant returned to correct or complete a previously written segment), the number of letters per minute, and the mean "In-Air" time between letters. Variability in both the spatial and temporal domains of instances of the same letter throughout the text was greater among the dysgraphic handwriters in comparison to the variability among the proficient. These results demonstrated the potential of using automated analytic techniques and visual display to achieve a more comprehensive understanding of handwriting difficulties.

Agraphia↗