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PubMedDate not supplied

Local and remote ischemia-reperfusion injury is mitigated in mice overexpressing human C1 inhibitor.

Activation of the classical complement pathway is crucially involved in complement-mediated endothelial cell damage in ischemia-reperfusion injury. C1 inhibitor is the only known physiological inhibitor of classical complement pathway activation. Transgenic mice overexpressing human C1 inhibitor were used in a surgical lower torso and a liver ischemia-reperfusion model. Organ-specific endothelial disruption was determined by 125I-tagged albumin extravasation. In the lower torso ischemia-reperfusion model, transgenic mice overexpressing the C1 inhibitor were protected in the muscle and the lungs from endothelial cell damage. In the liver ischemia-reperfusion model, endothelial cell integrity was preserved in transgenic animals in the liver, the gut and the lungs. Our data indicate that inhibiting complement activation by a transgenic approach is effective in protection against ischemia-reperfusion injury.

Albumins↗
PubMed1978

An approach to inverse calculation of epicardial potentials from body surface maps.

The inverse problem of evaluating epicardial potentials from a knowledge of heart and torso geometry as well as body surface potentials is here formulated as a problem in control theory. As is well known, such an inverse problem is ill-posed and a regularization technique has been devised to overrun this difficulty. The resulting regularized problem is well-posed and requires the minimization of a cost function including, besides the square distance of any predicted surface potential distribution from the experimental one, a regularization term involving the second derivatives of the identified epicardial potentials. The results here presented were obtained on a model problem for a plane geometry. Surface potentials generated by multipoles and perturbated with a noise level reflecting both instrumentation and electrode placement uncertainties were fitted by the proposed method and 'epicardial potentials' were determined with a maximum sum square relative error of 15%. The results suggest that by introducing suited regularity constraints, the a priori difficulties inherent to the problem of computing epicardial potentials from torso potentials, can be overcome.

Action Potentials↗
PubMed2000

Noninvasive ECG imaging of electrophysiologically abnormal substrates in infarcted hearts : A model study.

BACKGROUND: Myocardial infarction and subsequent remodeling create substrates with altered electrophysiological (EP) properties that are highly arrhythmogenic. Existing ECG methods cannot always detect the existence of such substrates nor provide any detailed information about their EP characteristics. A noninvasive method with such capabilities is greatly needed for identifying patients at risk of arrhythmias and for guidance and evaluation of therapy. Recently, we developed a noninvasive ECG imaging modality that can reconstruct epicardial EP information from body surface potentials. We extended its application to hearts with structural disease and examined its ability to detect and characterize abnormal EP substrates. METHODS AND RESULTS: Epicardial potentials were recorded with a 490-electrode sock from an open-chest dog. Recordings were obtained from a normal heart and from the same heart 2 hours after left anterior descending coronary artery occlusion and ethanol injection to create an infarct. Body surface potentials were generated from these epicardial potentials in a human torso model. Realistic geometry errors and measurement noise were added to the torso data, which were then used to noninvasively reconstruct epicardial potentials and electrograms (EGMs), with excellent accuracy. EP characteristics associated with the infarct substrate were reconstructed, including (1) a negative region over the infarct, (2) EGMs with large predominant negative deflections (eg, Q-wave EGMs), (3) Q-wave EGMs with superimposed RS deflections reflecting local activation of surviving myocardium within the infarct border zone, (4) reduced magnitudes of EGM negative derivatives, and (5) negative QRS integrals of EGMs over the infarct. CONCLUSIONS: ECG imaging can noninvasively detect and map abnormal EP substrates associated with infarction and structural heart disease.

Animals↗
PubMed2000

A noninvasive imaging modality for cardiac arrhythmias.

BACKGROUND: The last decade witnessed an explosion of information regarding the genetic, molecular, and mechanistic basis of heart disease. Translating this information into clinical practice requires the development of novel functional imaging modalities for diagnosis, localization, and guided intervention. A noninvasive modality for imaging cardiac arrhythmias is not yet available. Present electrocardiographic methods cannot precisely localize a ventricular tachycardia (VT) or its key reentrant circuit components. Recently, we developed a noninvasive electrocardiographic imaging modality (ECGI) that can reconstruct epicardial electrophysiological information from body surface potentials. Here, we extend its application to image reentrant arrhythmias. METHODS AND RESULTS: Epicardial potentials were recorded during VT with a 490 electrode sock during an open chest procedure in 2 dogs with 4-day-old myocardial infarctions. Body surface potentials were generated from these epicardial potentials in a human torso model. Realistic geometry errors and measurement noise were added to the torso data, which were then used to noninvasively reconstruct epicardial isochrones, electrograms, and potentials with excellent accuracy. ECGI reconstructed the reentry pathway and its key components, including (1) the central common pathway, (2) the VT exit site, (3) lines of block, and (4) regions of slow and fast conduction. This allowed for detailed characterization of the reentrant circuit morphology. CONCLUSIONS: ECGI can noninvasively image arrhythmic activation on the epicardium during VT to identify and localize key components of the arrhythmogenic pathway that can be effective targets for antiarrhythmic intervention.

Animals↗
PubMed1983

Differential electrocardiographic effects of myocardial ischemia induced by atrial pacing in dogs with various locations of coronary stenosis.

The spatial distribution of abnormal repolarization potentials caused by regional myocardial ischemia was determined in 45 dogs. Ameroid constrictors were placed around the left circumflex artery in 10, the left anterior descending artery in 10, and the right coronary artery in 10. Ten dogs without constrictors served as controls. Electrocardiographic events were determined from body surface isopotential distributions, which were computed from potentials sensed by 84 torso electrodes. In control dogs, pacing to heart rates of 230 to 250 beats/min increased the intensity of positive and negative surface extrema during the ST segment without altering their spatial features. Two weeks after placement of the ameroid constrictors, tachycardia induced abnormal negative potentials during the ST segment. Localization of these ischemic forces varied with the placement of the constrictor in a manner consistent with the affected perfusion territories. However, much of the torso surface was involved by all lesions, and only small zones of ST segment depression unique to specific lesions could be identified. In five additional dogs a constrictor was placed on the right coronary artery 3 months after implantation of a device on the circumflex vessel. ST segment patterns during pacing in dogs with two lesions were consistent with the sum of the two individual lesions. Thus, the regional nature of myocardial ischemia is detectable in the body surface isopotential distributions, but the degree of spatial overlap may limit the value of such techniques in extending the usefulness of clinical exercise-stress electrocardiography.

Action Potentials↗
PubMed1993

Pace mapping using body surface potential maps to guide catheter ablation of accessory pathways in patients with Wolff-Parkinson-White syndrome.

BACKGROUND. A pace mapping technique using body surface potential maps (BSPMs) was developed to guide the positioning of an ablation catheter at the ventricular insertion point of accessory pathways (AP) in patients with the Wolff-Parkinson-White syndrome (WPW). METHODS AND RESULTS. The study was performed on 30 WPW patients. BSPMs were recorded with 63 leads distributed over the entire torso surface. The catheter used for radiofrequency ablation was first placed in the vicinity of the ventricular preexcitation site predicted by BSPMs recorded during the delta wave. BSPMs were then recorded during pacing with this catheter, the comparison between the preexcited and paced BSPMs indicated whether the pacing site was too anterior or posterior with respect to the preexcitation site, and the catheter was moved accordingly. This process was repeated until the preexcited and paced BSPMs were highly correlated (r > or = 0.8), and ablation then was attempted. It was possible to successfully ablate the AP in 28 patients after an investigation that lasted 54 +/- 44 minutes between the recording of the first paced BSPM and that of the BSPM paced at the successful ablation site. Patients with left free wall pathways needed less investigation time compared with patients with pathways of other locations (46 +/- 9 versus 100 +/- 25 minutes, p = 0.031). The sensitivity of BSPM pace mapping was assessed using pacing with a multipolar catheter, and significant changes were observed on the BSPMs for beats with pacing sites that were only 5 mm apart. CONCLUSIONS, BSPM pace mapping allowed us to achieve a 93% success rate with short investigation durations, provides significant information that cannot be obtained with the standard 12-lead ECG, is a self-correcting procedure that reduces the importance of BSPM alterations due to individual differences in the shape of the torso or heart, and is applicable only to patients with AP showing antegrade conduction.

Adolescent↗
PubMed1995

Body surface potential distributions during idiopathic ventricular tachycardia.

BACKGROUND: The purpose of this report is to describe the body surface potential maps (BSPMs) during idiopathic ventricular tachycardia (VT) and to determine what differences exist between different idiopathic VT morphologies. METHODS AND RESULTS: We performed BSPMs during VT on 12 consecutive patients (3 women and 9 men; mean age, 42 +/- 13 years) presenting symptomatic idiopathic VT referred to our institution for electrophysiological study. Basal ECG, chest radiograph, and echocardiogram were normal in all patients. Clinical tachycardia showed left bundle branch block pattern (LBBB) in 9 patients, with sustained VT in 5 and nonsustained VT in 4, and right bundle branch block pattern (RBBB) in 3 with sustained VT. We found a unique pattern of BSPMs in each of the 9 patients during idiopathic LBBB VT configuration, whether sustained or nonsustained VT. This pattern appeared at the onset of the QRS and remained stable during the whole QRS complex. The area of minimal potential located in the upper anterior part of the torso was compatible with an origin of VT in the right ventricular outflow tract, as confirmed in 5 patients by successful radiofrequency ablation. We found an evolving pattern with two phases in each of the three RBBB VTs. The electrical axis during the initial part of the QRS could correspond to an endocardial-epicardial vector. The second phase, with a high voltage and area of minimal potential located in the inferior and anterior part of the torso, was compatible with a left ventricular apical origin that was confirmed by epicardial and endocardial mapping during cryosurgery in 1 patient. For all the VTs, the QRS isoarea maps showed the same pattern as the second phase of the QRS. CONCLUSIONS: Two different BSPM patterns were found. All LBBB VTs had the same stable pattern corresponding to an infundibular origin. All RBBB VTs had an evolving pattern that stabilized in the second part of the QRS complex corresponding to an apical origin.

Adult↗
PubMed1975

Magnetic determination of the relationship between the S-T segment shift and the injury current produced by coronary artery occlusion.

Both the S-T segment shift and the injury current were measured using the direct-current magnetocardiogram (d-c MCG) in seven dogs undergoing coronary artery occlusion. The purpose of the measurements was to clarify the origin of the S-T shift in acute ischemia and infarction. Previous measurements, consisting of d-c electrograms recorded from the exposed epicardial surface in situ, are partially inconsistent; also, they are not necessarily representative of the surface electrocardiogram (ECG), which sums broadly over the myocardium. The d-c MCG allows steady myocardial currents in the intact torso to the measured externally; because the d-c MCG sums broadly over these currents, conclusions drawn from it are applicable to the ECG. Coronary artery occlusion was produced by inflating a tube which, about 1 week earlier, had been surgically installed around the artery and exteriorized. During occlusions carried out in the MIT magnetically shielded room, a sensitive magnetometer recorded the d-c MCG at various locations around the torso. Within 20 seconds after occlusion, equal and opposite S-T segment and base-line (d-c) shifts appeared on the d-c MCG; these shifts were maintained for at least 15 minutes, after which they slowly decreased. Therefore, during the acute ischemia produced by these occlusions, the S-T shift is a secondary result of a primary injury current that is interrupted during the S-T interval.

Animals↗
PubMed1978

Simulation studies of the electrocardiogram. II. Ischemia and infarction.

Experimental studies of the myocardial action potentials following coronary artery occlusion have shown that the resulting regional ischemia is reflected by characteristics changes in the shapes of the action potentials in the ischemic region. The principal changes are decreases in the magnitude of the resting potential and in the action potential duration. Action potentials with prolonged durations have been observed in the infarcted regions of experimental animals after the development of inverted T waves in the surface electrocardiogram (ECG). We use such abnormal action potentials in our digital computer model to study the effects of acute myocardial ischemia and infarction on the surface ECG. The heart is represented in sufficient detail to allow variations in the location and size of the ischemic injury and in the distribution of the severity of injury within the injured region. The evolution of acute infarctions is simulated by progressively modifying the abnormal action potentials assigned to the injured region. Calculated standard 12 lead ECGs and torso isopotential surface maps for simulated acute ischemia and infarction are in good agreement with patient data reported in the literature. Typical simulations include anterior and inferior transmural ischemia and infarction and anterior subendocardial ischemia. The model is used to examine relationships between torso surface potentials during ventricular activation and recovery and the site and size of the ischemic injury.

Action Potentials↗
PubMed1979

The effects of variations in conductivity and geometrical parameters on the electrocardiogram, using an eccentric spheres model.

The effects of variations in the volume conductor properties of the torso on the electrocardiogram were studied by means of a theoretical eccentric spheres model. The model includes a blood cavity, cardiac muscle layer, pericardium, lung region, skeletal muscle layer, and subcutaneous fat. The source of the field is a double-layer spherical cap located within the myocardium. The following effects regarding the electrocardiogram (ECG) potentials were determined: (1) blood augments the potential, but less than predicted by simpler published models; (2) in anemia, high potentials are expected, whereas in polycythemia, voltages are reduced; (3) abnormally low lung conductivity (emphysema) causes low surface potentials whose magnitude is controlled by the low conductivity skeletal muscle layer; (4) low voltages result both from low and high pericardial conductivities; (5) the surface potential increases with increasing myocardial conductivity; (6) low skeletal muscle conductivity (Pompe's disease) causes high surface potentials; (7) obesity lowers the potential only slightly; (8) a thick myocardium, protruding into the lung region, slightly augments the potential; (9) an increase in the thickness of the myocardium at the expense of the blood cavity causes a decrease in potential; (10) the potential increases with increasing heart size; and (11) the location of the heart within the torso has a very significant effect on the surface potential distribution.

Action Potentials↗
PubMed2000

Objective measurement of functional upper-extremity movement using accelerometer recordings transformed with a threshold filter.

BACKGROUND AND PURPOSE: The consensus is that the most important outcome for rehabilitation is functional activity in the life situation. Constraint-Induced Movement Therapy, a new treatment that transfers in-clinic gains to the life situation, demands objective measurement of real-world movement. However, direct, objective, and accurate measures of arm use in the real world are not available. Previous attempts to use accelerometry to measure extremity movement have failed because of unacceptable variability. This problem has been addressed here by use of a threshold filter. METHODS: Nine stroke patients and 1 healthy individual wearing accelerometers were videotaped while they carried out their usual activities at home or in the clinic; the duration of their arm, torso, and ambulatory movements was judged by 2 observation teams. In addition, 11 college students performed 5 standardized activities of daily living for varying durations in the laboratory. The accelerometer data were transformed; the raw value recorded for a given epoch was set to a constant if it exceeded a low threshold. RESULTS: The threshold-filtered recordings measured the duration of movement accurately and with very little variability. Correlations between the threshold-filtered recordings and the observer ratings of the duration of arm, torso, and ambulatory movements were 0.93, 0.93 and 0.99, respectively; the corresponding correlations for the raw values were -0.17, 0.34, and 0.85. CONCLUSIONS: These results present initial evidence for the validity of threshold-filtered accelerometer recordings for objectively measuring the amount of real-world upper-extremity movement as an index of treatment outcome for rehabilitation patients.

Adult↗
PubMed2001

Imaging dispersion of myocardial repolarization, II: noninvasive reconstruction of epicardial measures.

BACKGROUND: Dispersion of myocardial repolarization supports the development and maintenance of life-threatening arrhythmias. Current noninvasive approaches for detecting substrates with increased dispersion based on ECG measures (eg, QT dispersion) have shown limited success and inconsistencies. The companion article shows that, in contrast, epicardial potentials and derived measures reflect local dispersion of repolarization. Here, using a recently developed ECG imaging method, we evaluate the feasibility of noninvasive reconstruction of such epicardial measures from body-surface ECG data. METHODS AND RESULTS: Epicardial potentials were recorded with a 224-electrode sock from an open-chest dog during control, regional warming, cooling, and simultaneous adjacent warming and cooling to induce localized changes in myocardial repolarization and regions of increased dispersion. Body-surface potentials were generated from these epicardial potentials in a human torso model. Realistic geometric errors and measurement noise were added to the torso data, which were then used to noninvasively reconstruct epicardial measures of repolarization dispersion (activation recovery intervals [ARIs] and QRST integrals). Repolarization properties were accurately depicted by ECG imaging, including (1) shortened ARIs and increased QRST integrals over the warmed region, (2) prolonged ARIs and decreased QRST integrals over the cooled region, and (3) high gradients of ARIs and QRST integrals over the adjacent warmed and cooled regions. CONCLUSIONS: ECG imaging can reconstruct repolarization properties accurately and localize areas of increased dispersion of repolarization in the heart noninvasively. Its clinical significance lies in the possibility of noninvasive risk stratification and in guidance and evaluation of therapy.

Animals↗
PubMed1996

Software upgrading in a CT scanner. Influence on quantitative CT.

PURPOSE: In an attempt to improve field uniformity and CT number stability, the software in a CT scanner was replaced with a new version. The purpose of the present study was to investigate the influence of the software upgrading on density measurements. MATERIAL AND METHODS: The upgrading influence was investigated by means of a torso phantom (European spinal). The phantom simulates a torso which contains 3 vertebrae of different densities. RESULTS: Despite the use of a reference standard under the phantom, the software change resulted in: a) improved short-term precision; b) increased density values at 80 and 100 kVp, decreased at 130 kVp; and c) increased influence of the kVp on the values. CONCLUSION: The results of the present study suggest that conversion factors have to be used in density values for reference populations as well as in the values of patients undergoing follow-up studies.

Absorptiometry, Photon↗
PubMedDate not supplied

Retinal vein occlusion in lymphomatoid papulosis.

PURPOSE: To describe an unusual patient who presented with hemi-retinal vein occlusion and lymphomatoid papulosis (LyP). METHODS: Clinicopathological case study. RESULTS: A 42 year old female patient presented with blurring of vision in her left eye and a nodular eruption of the skin involving arms, face and torso. She also complained of a non-itchy, blotchy rash on the arms, face and torso lasting for period of three months. Ocular examination showed a left superior hemi-retinal vein occlusion. The nodules resolved spontaneously over a period of two-three weeks leaving a faint scar. Hematological and systemic evaluation for auto-immune disorders, hypercoagulability, systemic malignancy and lymphoma were negative. A biopsy of the skin nodule was performed which showed infiltration of lymphoid blast cells which were CD30 positive. Based on the clinicopathological features a diagnosis of lymphomatoid papulosis (LyP) was made. CONCLUSIONS: Clinical and pathological features of this patient may suggest the retinal vein occlusion may be secondary to LyP.

Adult↗
PubMed2000

Sex differences in the anatomical distribution of melanocytic nevi in Canadian Hutterite children.

BACKGROUND: Studies of the distribution of melanocytic nevi (MN) and/or cutaneous malignant melanoma (CMM) in white populations have commonly observed greater numbers of MN and CMM on the torsos of males and on the limbs of females. The most commonly cited explanation for this sex difference is differential sunlight exposure of body subsites due to gender differences in clothing styles and recreational activities. Less common, but more speculative, explanations suggest hormonal differences or regional differences in melanocytes across body subsites. OBJECTIVE: The purpose of the present study was to evaluate these explanations in light of sex differences in the anatomical distribution of nevi in Canadian Hutterite children whose traditional religious costume protects them from sun exposure. METHODS: Nevi counts from 178 male and 154 female children, aged 5 to 15 years, from 23 Central Alberta Hutterite colonies were broken down by age and body subsite. RESULTS: At age levels from 6 to 15 years, males had greater nevus counts on the torso, whereas females had greater counts on the upper and lower limbs. CONCLUSION: The appearance of this distribution of nevi in sun-protected children as early as age 6 is problematic for explanations based on differential sunlight exposure and hormonal changes at puberty.

Adolescent↗
PubMed2005

Initial development and testing of a novel foam-based pressure sensor for wearable sensing.

BACKGROUND: This paper provides an overview of initial research conducted in the development of pressure-sensitive foam and its application in wearable sensing. The foam sensor is composed of polypyrrole-coated polyurethane foam, which exhibits a piezo-resistive reaction when exposed to electrical current. The use of this polymer-coated foam is attractive for wearable sensing due to the sensor's retention of desirable mechanical properties similar to those exhibited by textile structures. METHODS: The development of the foam sensor is described, as well as the development of a prototype sensing garment with sensors in several areas on the torso to measure breathing, shoulder movement, neck movement, and scapula pressure. Sensor properties were characterized, and data from pilot tests was examined visually. RESULTS: The foam exhibits a positive linear conductance response to increased pressure. Torso tests show that it responds in a predictable and measurable manner to breathing, shoulder movement, neck movement, and scapula pressure. CONCLUSION: The polypyrrole foam shows considerable promise as a sensor for medical, wearable, and ubiquitous computing applications. Further investigation of the foam's consistency of response, durability over time, and specificity of response is necessary.

Journal Article↗
PubMed2005

The feasibility of laryngoscope-guided tracheal intubation in microgravity during parabolic flight: a comparison of two techniques.

We determined the feasibility of laryngoscope-guided tracheal intubation (LG-TI) in microgravity obtained during parabolic flight and tested the hypothesis that LG-TI is similarly successful in the free-floating condition, with the patient's head gripped between the anesthesiologist's knees, as in the restrained condition, with the torso strapped to the surface. Three personnel with no experience in airway management or microgravity participated in the study. LG-TI of a sophisticated full-size manikin was attempted on seven occasions in each condition by each investigator after ground-based training. The parabolic flights, which took place in an Airbus 300 over the Atlantic Ocean, provided 23 s of microgravity. During this time, the investigator opened a box with airway equipment, performed LG-TI, and attached and held onto a self-inflating bag. The efficacy of ventilation was assessed during level flight by squeezing the bag and noting whether the manikin sensors indicated a tidal volume > or =300 mL. There were no differences in ventilation success (41% versus 33%) or time to successful insertion (both 18 s) between the free-floating and the restrained conditions. More than 90% of failures were caused by the inability to insert the tracheal tube within 23 s. There were no differences in performance among investigators. We conclude that LG-TI is feasible in microgravity obtained during parabolic flight, but the success rate is infrequent because of severe time restrictions. There were no differences in success rate between the free-floating condition, with the head gripped between the knees, and the restrained condition, with the torso strapped to the surface.

Adult↗
PubMed1990

Pattern formation under the control of the terminal system in the Drosophila embryo.

The specification of the most anterior and posterior domains of the Drosophila embryo depends on the activity of the torso protein, a putative tyrosine kinase receptor. Localized torso activity at the poles of the embryo generates graded information that specifies distinct portions of the body. The primary response to the terminal signal in the posterior end of the embryo is likely to be the activation of the gap genes huckebein and tailless. Here I address the question of how the graded maternal signal generates different elements of the pattern at the posterior end of the embryo and what role huckebein and tailless activities may play in this process. These experiments show that distinctly localized activities of huckebein and tailless are responsible for the appropriate expression of other genes known to be under the control of the terminal system. Moreover, they suggest that different elements of the terminal pattern can be specified in response to distinct levels of graded tailless activity.

Animals↗