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Ocular inoculation of monkeys with simian varicella virus: clinical and histopathologic observations.

PURPOSE: To explore the possibility that inoculation of the eyes of African green monkeys with simian varicella virus (SVV) induces the symptoms of herpes zoster ophthalmicus (HZO), as seen in humans, and to develop a realistic and reproducible animal model of herpes zoster ophthalmicus for experimental studies. METHODS: In the first experiment, the right eyes of three African green monkeys were inoculated by intrastromal and subconjunctival injections with a suspension of SVV-infected Vero cells. In the second experiment, three additional monkeys were pretreated with intramuscular injections of methylprednisolone (41 mg/kg) for 7 days before ocular inoculation with SVV and for 3 weeks at 14 mg/kg after virus inoculation. The eyes were examined by slit-lamp biomicroscopy. Histologic, immunohistochemical, and electron microscopic studies were performed. RESULTS: In the first experiment, all three animals developed high titers of anti-SVV antibodies (IgG). Diffuse stromal opacity, with keratitic precipitates, stromal edema, and mild vascularization of the cornea, appeared 12 to 14 days after inoculation. The onset of ocular disease was correlated with the rise in serum antibody levels. There was no clinical evidence of a systemic viral infection resulting from the corneal inoculations in these monkeys. In the second experiment, all three animals treated with methylprednisolone developed severe ocular pathology within 1 week of inoculation. The clinical appearance of the diseased eyes strongly indicated that local viral infection had occurred. Dendritiform keratitis, corneal erosion, and stromal necrosis with vascularization of the cornea was seen in all the eyes. The disease resolved within 4 to 5 weeks of inoculation, leaving opaque, vascularized corneas. Histologic studies showed that inflammatory cells and viral antigens were widespread throughout the diseased corneas. A high titer of anti-SVV antibody (IgG) was detected in the immunosuppressed monkeys, but no evidence of systemic viral infection was observed. CONCLUSIONS: The authors propose that inoculation of the eyes of methylprednisolone-treated African green monkeys with simian varicella virus provides an appropriate animal model for studies of the virology and immunopathology of ocular varicella virus infection.

Animals↗

Effect of lidocaine and quinidine on focal ventricular arrhythmias induced by subepicardial epinephrine in cats.

Subepicardial infusion of epinephrine (EP) in the dose of 3 x 10(-3) M in 2.5 x 10(-3)M CaCl2-0.9% NaCl (calcium-saline vehicle) at the rate of 10 microliters/min in the right ventricular myocardium of mongrel cats weighing between 2.7 and 3.3 kg produced uniform reversible and reproducible focal ventricular arrhythmias of varying intensity and duration. Infusion of two antiarrhythmic agents, lidocaine (LD) and quinidine (QD) in the same site of arrhythmogenesis in equimolar concentration of 3 x 10(-3) M along with EP in the same vehicle reduced incidence, duration, peak and mean frequencies of arrhythmias while the latent period of onset of arrhythmias increased significantly. In present study, quinidine, in equimolar concentration of 3 x 10(-3) M was found to be more effective than lidocaine in antagonizing EP-induced ventricular arrhythmias.

Animals↗

[Restenosis after optimal coronary atherectomy and influence on left ventricular function].

The authors prospectively assessed 95 patients undergoing optimal guided atherectomy to assess the incidence of restenosis at 6 months. The coronary lesions were measured by a system of quantitative angiography to ensure reproducibility. Ventricular volumes, ejection fraction and segmental wall motion were assessed by ventriculography performed in the right anterior oblique projection. Sixty-three patients underwent atherectomy of the left anterior descending artery and 32 patients of the right coronary artery. The reference diameter was 3.58 +/- 0.65 mm. Atherectomy increased the minimal diameter of the lesion from 1.19 +/- 0.44 to 3.03 +/- 0.45 mm, with a residual stenosis of 14 +/- 10% of the diameter. At 6 months, 23% of patients had restenosed (> 50% stenosis) with a residual lumen at 1.16 +/- 0.39 mm. In the absence of restenosis, there was no significant change in left ventricular volumes or pressures and the global ejection fraction increased by +4 +/- 9% (p < 0.01), mainly in the group undergoing left anterior descending atherectomy. Moreover, fractional shortening increased in the anterior segments (+11 +/- 18%; p < 0.001). The authors conclude that optimal atherectomy is associated with acceptable rates of restenosis and that medium-term benefits of segmental wall motion are observed in patients without angiographic restenosis, mainly in those undergoing the procedure on the left anterior descending artery.

Adult↗

Effect of calcium-channel blocking drugs on focal ventricular arrhythmias induced by sub-epicardial epinephrine infusion in cats.

Sub-epicardial infusion of epinephrine (EP) in the dose of 3 x 10(-3) M in 2.5 x 10(-3) M CaCl2-0.9% NaCl (calcium-saline vehicle) at the rate of 10 microliters in the right ventricular myocardium of mongrel cats weighing between 2.8 and 3.3 kg, produced uniform, reversible and reproducible focal ventricular arrhythmia (VA) of varrying intensity and duration. Infusion of two calcium-channel blocking agents, verapamil (VP) and nifedipine (ND) at the site of arrhythmogenesis, in equimolar concentration of 3 x 10(-3) M alongwith EP in the same vehicle reduced the incidence, duration, peak and mean frequencies of arrhythmias while, the latent period of onset of arrhythmias increased significantly. Verapamil in equimolar concentration of 3 x 10(-3) M was found to be more effective than nifedipine in antagonizing EP-induced ventricular arrhythmias.

Animals↗

Bilateral symmetry of human carotid artery atherosclerosis.

BACKGROUND AND PURPOSE: Atherosclerosis is a principal cause of stroke and myocardial infarction. The carotid arteries provide a site at which progression of atherosclerosis can be monitored reproducibly and noninvasively. This study was conducted to determine the similarity of atherosclerotic plaques in the left and right carotid arteries. This question was explored with the use of perfusion-fixed cadaveric carotid arteries and 2 noninvasive clinical imaging techniques, MRI and electron-beam CT. METHODS: Fifty pairs of carotid arteries from cadaveric donors (aged 48 to 98 years) were imaged with MRI and electron-beam CT. Thirty-eight of the pairs met the criteria for rigorous analysis. Carotid artery wall volumes were measured from the MRI images, and calcification scores were computed from the electron-beam CT images. RESULTS: Total wall volumes of the left (972.5+/-241.6 mm3) and right (1016.3+/-275.0 mm3) carotid arteries were moderately correlated (concordance correlation coefficient [r(c)]=0.71). Calcification scores were highly correlated, with r(c)=0.95 for the Agatston scores and r(c)=0.94 for the calcium volume scores. CONCLUSIONS: Total wall volume and plaque calcification in the left and right human carotid arteries are substantially similar. These results suggest that atherosclerosis of the human carotid arteries is generally a bilaterally symmetrical disease. This evidence of symmetry suggests that diagnostic information about atherosclerotic plaque in one carotid artery can be used to infer information about the composition and volume of atherosclerotic plaque in the contralateral artery.

Aged↗

Modified RV short axis series--a new method for cardiac MRI measurement of right ventricular volumes.

PURPOSE: The current standard image orientation employed in the MRI assessment of right ventricular volumes uses a series of short axis cine acquisitions located with respect to a horizontal long axis view with the first slice placed across the atrio-ventricular valve plane at end diastole. Inherent inaccuracies are encountered with the use of this image orientation due to difficulty in defining the tricuspid valve and the border between atrium and ventricle on the resultant images. Our experience indicates that because the tricuspid valve is usually not in-plane in the slice the atrio-ventricular margin is difficult to distinguish. This leads to inaccuracies in measurements at the base of the RV and miscalculation of the RV volume. The purpose of this study was to assess an alternative method of image orientation aimed at increasing the accuracy of RV volume measurements using current commercially available CMRI sequences. This technique, the modified RV short axis series, is oriented to the outflow tract of the right ventricle. METHOD: We undertook a prospective study of 50 post cardiac transplant patients. A series of LV short axis multi-slice cine acquisition FIESTA images was acquired using the current standard technique. From this data set, LV and RV stroke volumes were derived on an Advantage Windows workstation using planimetry of the endocardial and epicardial borders in end systole and end diastole. Our new technique involved obtaining a set of multi-slice cine acquisition FIESTA images in a plane perpendicular to a line from the centre of the pulmonary valve to the apex of the RV. Planimetry of the RV was then performed and a stroke volume calculated using the same method of analysis. RV stroke volumes obtained from both techniques were compared with LV stroke volumes. Three operators independently derived RV data sets. RESULTS: On the images acquired with the new technique, the tricuspid valve was easier to define leading to more accurate and reproducible planimetry of ventricular borders. RV stroke volumes calculated from the new method showed better agreement with LV stroke volumes than with the current method. These results were consistent across the three operators. CONCLUSIONS: This new method improves visualisation of the tricuspid valve and makes analysis easier and less prone to operator error than the current standard technique for MRI assessment of RV volumes.

Heart Diseases↗

[Subdural location of a catheter. A complication of peridural anesthesia].

A case of an involuntarily placed subdural catheter (between arachnoid and dura) is described. The catheter was thought to be in the epidural space. It was placed at T9/10 in order to achieve postoperative epidural analgesia in a patient with colonic surgery. Administration of 4 ml bupivacaine 0.5% was followed by segmental analgesia (left: C7 to T9, right: T2 to T8) 10 min later. The systolic blood pressure fell from 85 to 50 mmHg. No motor block was detectable. After 150 min remission of analgesia was complete. All effects were reproducible. Using 1.3 ml of a radiopaque fluid, a spinal X-ray film showed a typical subdural picture with radiopacity detectable on the left from C8 to T8 and on the right from T1 to T7. An additional 2.7 ml did not visualize the lumbar subdural space as well. No radiopaque fluid entered the epidural or intrathecal space. It may be that accidental subdural catheter placement in regional anesthesia is not as rare as it was thought to be a few years ago. There is at present no available epidural technique that guarantees the avoidance of this complication. In addition, the symptoms of 'subdural analgesia' vary to a great extent. Therefore, the diagnosis can only be verified by X-ray examination. If patients with epidural analgesia are supervised with care and uncommon dose responses are recognized, subdural catheter placement will not lead to a severe and dangerous situation for the patient.

Adult↗

Development and reversal of fatigue in human tibialis anterior.

The lack of easily measurable, objective physiologic indices of muscle fatigue in humans has hampered the evaluation of interventions that putatively inhibit muscle fatigue. In 6 healthy subjects, isometric fatigue of right and left tibialis anterior (TA) was produced using 180 s of intermittent electrical stimulation to the motor point (40 Hz, 650-ms or 250-ms trains, 1 train/s). The time course, magnitude, and reproducibility of fatigue and recovery from fatigue was established, and the effect of duty cycle measured. During fatigue, force fell rapidly in all subjects over the first 70 s, then fell more slowly. Recovery was also biphasic--force increased rapidly over the initial 30 s then slowly--and was incomplete at 300 s. Comparing duty cycles of 0.65 versus 0.25, the longer duty cycle caused a greater fall in force (-65% versus -29%; P < 0.001) and lower recovery (P < 0.02). In all subjects, left leg muscles fatigued more than right. We conclude that this noninvasive fatigue and recovery protocol is highly reproducible and that it may prove useful for evaluating the effects of pharmacologic or restorative interventions on human muscle fatigue.

Adult↗

Advances in monitoring in intensive care: continuous mixed venous oxygen saturation and right ventricular ejection fraction.

Direct cardiorespiratory measurements and the use of optimum values to guide therapy have been associated with improved survival in a number of conditions causing critical illness. Increasingly sophisticated monitoring that provides more accurate and reproducible assessment of the cardiorespiratory system at the bedside is pivotal to this better outcome. The inclusion of fibreoptic filaments and fast response thermistors in pulmonary artery catheters makes possible the continuous monitoring of mixed venous oxygen saturation and the measurement of right ventricular ejection fraction. Although the place of measurement and manipulation of these variables in critically ill patients has yet to be fully defined, clinical studies are promising. We discuss some practical aspects of the use of these measurements and some potential clinical applications. Additionally, some of the studies in which the use of these measurements is increasing our knowledge of the pathophysiology of critical illness and contributing to improved management of critically ill patients, are highlighted.

Cardiopulmonary Bypass↗

A simple single slice method for measurement of left and right ventricular enlargement by electron beam tomography.

RATIONALE AND OBJECTIVE: We devised to test the feasibility of measuring the left and right ventricular sizes by non-contrast electron beam tomographic images. METHODS: Ventricular sizes consist of the sum of the intracavitary cavity and myocardial mass for each ventricle. A total of 50-image studies from subjects undergoing contrast-enhanced studies were used to develop the measurement methodology. About 20 contrast studies were used to test the measure. The methodology was then prospectively tested on 75 patients with non-contrast studies to estimate the intra-observer, inter-observer and inter-study reproducibility. RESULTS: Multiple linear regression analysis was completed and the correct regression formulas to calculate ventricular volumes were acquired by using the area and span from the contrast studies. There was excellent correlation between the estimate of LV (r > 0.97, p < 0.001) and RV (r > 0.93, p < 0.001) sizes between measured and calculated (contrast, single slice) left and right ventricular volumes. The intra-observer, inter-observer and inter-study reproducibility demonstrated excellent results with < 7% difference in absolute values and a high correlation (r > 0.89, p < 0.001). CONCLUSION: We conclude that the left and right ventricular sizes can be accurately estimated from a single mid-ventricular slice on non-contrast electron beam tomographic images.

Case-Control Studies↗

Quantitative perfusion mapping of the human lung using 1H spin labeling.

PURPOSE: To evaluate the feasibility and reproducibility of a noninvasive, rapid and quantitative pulmonary perfusion mapping method using a two-compartment tissue model in combination with a (1)H spin labeling technique. MATERIALS AND METHODS: Ten healthy volunteers and three patients with cystic fibrosis (CF) were examined on a 1.5-T whole-body scanner. Global and selective lung T(1) maps based on an inversion recovery Snapshot FLASH technique were acquired from each subject with breath-holds at end-expiration. For comparison, corresponding Gd-DTPA-enhanced (1)H MR perfusion images were also obtained from each CF patient. RESULTS: Quantitative perfusion maps were calculated from the global and selective T(1) maps. The measured perfusion rates of the upper right lung in volunteers ranged from 400 to 600 mL/100 g/minute. The method showed a high intra-study reproducibility and low relative errors. In CF-patients, perfusion defects detected using Gd-DTPA-enhanced MR imaging were also detected using the spin labeling method. The perfusion rates of diseased lung tissues were less than 200 mL/100 g/minute. CONCLUSION: Noninvasive, robust and quantitative (1)H MR mapping of pulmonary perfusion was successfully performed using a rapid lung T(1) mapping in combination with spin labeling within the imaging slice. The proposed method has the potential to provide both important qualitative functional information and quantitative pulmonary perfusion rates in various lung diseases at various stages without the need of contrast agents.

Adult↗

Accuracy of reproducing hand position when using active compared with passive movement.

BACKGROUND AND PURPOSE: Evaluating proprioception is relevant to physical rehabilitation because of its significance in motor control. One method of proprioceptive testing involves having subjects either imitate or point at a joint position or movement which was presented via a passive movement. However, as the muscle spindles are subject to central fusimotor control, the proprioceptive system may be better-tuned to movements created by active muscular contraction than to passive movements. The objective of the present study was to determine whether accuracy of reproducing hand position is dependent on whether proprioceptive input is obtained via an active or a passive movement. METHOD: Thirty-nine healthy volunteers (mean age (+/- SD) 24.6 (+/- 3.6) years) participated in the study. Subjects' right hands, which were obscured from view, were acoustically guided to five targets on a digitizer tablet with either an active or passive upper extremity movement. Subjects were then asked to reproduce the targets' location by either reaching to them with the unseen hand or by use of a laser beam. Distance from target and angular deviations were calculated in both absolute and relative terms. Repeated measures analysis of variance (ANOVA) was performed for each variable followed by predetermined contrasts. RESULTS: Comparison between the active and passive conditions when reconstruction of target location was guided kinaesthetically indicates significant differences in absolute distance, range and angular deviation. The comparison when reconstruction of target location was guided visually indicates significant differences in absolute distance, absolute angle and angular deviation. CONCLUSIONS: The ability to reproduce hand position accurately is enhanced when position is encoded by active upper extremity movement compared with passive movement. The results have implications for the design of strategies for evaluating as well as treating patients with impaired proprioception and limited movement.

Adult↗

Continuous ambulatory right heart pressure measurements with an implantable hemodynamic monitor: a multicenter, 12-month follow-up study of patients with chronic heart failure.

BACKGROUND: We describe the performance of an implantable hemodynamic monitor (IHM) that allows continuous recording of heart rate, patient activity levels, and right ventricular systolic, right ventricular diastolic, and estimated pulmonary artery diastolic pressures. Pressure parameters derived from the implantable monitor were correlated to measurements made with a balloon-tipped catheter to establish accuracy and reproducibility over time in patients with chronic heart failure (CHF). METHODS AND RESULTS: IHM devices were implanted in 32 patients with CHF (left ventricular ejection fraction, 29% +/- 11%; range, 14%-62%) and were tested with right heart catheterization at implantation and 3, 6, and 12 months later. Hemodynamic variables were digitally recorded simultaneously from the IHM and catheter. Values were recorded during supine rest, peak response of Valsalva maneuver, sitting, peak of a 2-stage (25-50 W) bicycle exercise test, and final rest period. The median of 21 paired beat-to-beat cardiac cycles was analyzed for each intervention. A total of 217 paired data values from all maneuvers were analyzed for 32 patients at implantation and 129 paired data values for 20 patients at 1 year. The IHM and catheter values were not different at baseline or at 1 year (P >.05). Combining all interventions, correlation coefficients were 0.96 and 0.94 for right ventricular systolic pressure, 0.96 and 0.83 for right ventricular diastolic pressure, and 0.87 and 0.87 for estimated pulmonary artery diastolic pressure at implantation and 1 year, respectively. CONCLUSIONS: The IHM and a standard reference pressure system recorded comparable right heart pressure values in patients with CHF. This implantable pressure transducer is accurate over time and provides a means to precisely monitor the hemodynamic condition of patients with CHF in a continuous fashion.

Adult↗

Reproducibility of quantitative, spirometrically controlled CT.

Quantitative spirometrically controlled computed tomography (with 1-mm-thick sections) was performed twice (with a 5-minute break) in 24 adult patients with pulmonary disease to objectively evaluate parenchymal changes in the lung. Twelve measurements of attenuation were made on apical, carinal, and basal scans (right, left, total of each level, total right, total left, total of all three scans), obtained at 50% vital capacity. Since differences in measurements between the first and second examination were not significant, the method provides highly reproducible results.

Adult↗

Estimation of right ventricular volume by modified echocardiographic subtraction method.

To evaluate the accuracy and clinical utility of right ventricular volume estimated by a modified echocardiographic subtraction method versus Krebs' original subtraction method, an experiment was performed on hearts excised from 25 animals (dogs, pigs, and cows) followed by a clinical study of 41 patients with heart disease. Right ventricular volume was measured by subtracting the left ventricular volume from that of the whole heart based on echocardiographic apical two- and four-chamber views by means of the area-length method. In the animal heart study, the coefficient of variation between the right ventricular volume estimated by the modified method and the true volume was +/- 13%. The regression equation was y = 0.94x + 4.15 (r = 0.987, p less than 0.001) and showed good correlation, whereas the right ventricular volume obtained by the original method underestimated the true volume (coefficient of variation = +/- 25%, y = 0.59x + 1.11; r = 0.976, p less than 0.001). In the clinical study, the coefficient of variation between right ventricular volume estimated by the modified echocardiographic method and RV volume estimated by radionuclide ventriculography was +/- 15%. The regression equation was y = 0.80x + 13.3 (r = 0.935, p less than 0.001). This correlation was better than that obtained by the original method (coefficient of variation = +/- 16%), where the regression equation was y = 0.60x + 2.43 (r = 0.888, p less than 0.001). Thus the accuracy of the modified subtraction method was validated, and this method showed a better correlation than the original method both experimentally and clinically.

Adolescent↗

Quantitation of intracardiac shunts by cine-CT.

Quantitation of intracardiac shunts is important in the evaluation of congenital heart disease and ventricular septal defects postmyocardial infarction. Shunt detection and quantitation is currently performed by either oximetry or radionuclide angiography. Oximetry is an invasive technique and radionuclide angiography, although noninvasive, does not have sufficient spatial resolution to provide detailed anatomic information. The present study evaluated a new technique for quantitating right-to-left shunts by analysis of indicator dilution curves acquired noninvasively using cine-CT. This technique was evaluated in a phantom and in postoperative dogs with a surgically created variable shunt. The phantom model demonstrated the accuracy and reproducibility of the curve analysis algorithm, and the canine model permitted the comparison of oximetry with cine-CT for shunt quantitation. Cine-CT accurately estimated right-to-left shunt fraction when compared with oximetry (r = 0.91) and is more sensitive than oximetry in detecting small shunts. The results of this study suggest that contrast enhanced cine-CT provides a precise noninvasive technique for measuring shunt lesions in congenital and acquired heart diseases.

Animals↗

Measurement of left-to-right shunts by gated radionuclide angiography: concise communication.

Gated cardiac blood-pool scans allow comparison of left- and right-ventricular stroke volume. We have applied these measurements to the quantification of left-to-right shunts (QP/QS) in nine patients with atrial septal defects, one patients with partial anomalous pulmonary venous return, four patients with ventricular septal defects, and two patients with patent ductus arteriosus. None of these patients had combined lesions. QP/QS was measured as the right-ventricular (RV) stroke counts divided by the left-ventricular (LV) stroke counts and as the LV stroke counts divided by the RV stroke counts in patients with RV and LV diastolic volume overload respectively. All patients had also QP/QS measurements by oximetry and first-pass radionuclide angiography. The stroke-count measurements indicated the overloaded ventricle in all patients. QP/QS determined by equilibrium gated studies correlated well with those obtained by oximetry (r = 0.79). Reproducibility of the equilibrium measurements was good. We conclude that gated cardiac blood-pool scans can measure left-to-right shunts and can distinguish between shunts with RV and LV volume overload.

Adolescent↗

The Indiana pouch continent urinary reservoir.

The right colon reservoir using a stapled plicated ileal efferent limb (Indiana continent urinary reservoir) has been demonstrated to be a reproducible durable form of continent diversion. The overall day and nocturnal continence rate of 94% compares favorably with all other forms of continent cutaneous diversion. Carefully following the technique of stapling and plicating the ileal efferent limb and ileocecal valve as described in this article nearly ensures adequate competence of the outlet valve. In the rare case in which incontinence occurs, it is almost always on the basis of high-pressure unit contractions of the reservoir. On occasion, patients who develop incontinence are observed to have high pressures within the reservoir despite complete detubularization of the right colon segment. When this problem is encountered it can be corrected successfully by adding an ileal patch augmentation to the previously detubularized reservoir. The issue of ureteral implantation in continent urinary diversions is as yet unsettled. Many authors have not used ureteral tenial tunnels and have reported a reflux rate of < 13%. Furthermore, these patients have not developed any long-term sequelae of their reflux. Although favorable results have been obtained without creating tunneled tenial reimplantation, we believe that continent cutaneous reservoirs are almost always colonized with bacteria, and an antireflux mechanism may offer protection against subsequent pyelonephritis. Closure of the reservoir traditionally has been conducted by hand at our institution; however, the development of smaller absorbable gastrointestinal anastomosis stapling devices offers the theoretic advantage of shortening the operative time. We anxiously await follow-up, including larger patient numbers and longer term follow-up of the absorbable staple technique. The use of continent cutaneous urinary diversion clearly has decreased as bladder replacement has become a more viable procedure over the past decade. Despite this, the urologic reconstructive surgeon must maintain the ability to perform continent cutaneous diversion in patients who are unwilling to accept the potential for nocturnal incontinence observed in all forms of bladder replacement as well as the patients who have ineffective sphincter mechanism or who need a urethrectomy due to their primary disease.

Adolescent↗