Intracardiac impedance response during acute AF internal cardioversion using novel rectilinear and capacitor-discharge waveforms.

Intracardiac impedance (ICI) is a major determinant of success during internal cardioversion of atrial fibrillation (AF). However, there have been few studies that have examined the dynamic behaviour of atrial impedance during internal cardioversion in relation to clinical outcome. In this study, voltage and current waveforms captured during internal cardioversion of acute AF in ovine models using novel radiofrequency (RF) generated low-tilt rectilinear and conventional capacitor-discharge based shock waveforms were retrospectively analysed using a digital signal processing algorithm to investigate the dynamic behaviour of atrial impedance during cardioversion. The algorithm was specifically designed to facilitate the simultaneous analysis of multiple impedance parameters, including: mean intracardiac impedance (Z M), intracardiac impedance variance (ICIV) and impedance amplitude spectrum area (IAMSA) for each cardioversion event. A significant reduction in ICI was observed when comparing two successive shocks of increasing energy where cardioversion outcome was successful. In addition, ICIV and IAMSA variables were found to inversely correlate to the magnitude of energy delivered; with a stronger correlation found to the former parameter. In conclusion, ICIV and IAMSA have been evidenced as two key dynamic intracardiac impedance variables that may prove useful in better understanding of the cardioversion process and that could potentially act as prognostic markers with respect to clinical outcome.

A prospective randomized trial of cannulation technique in ERCP: effects on technical success and post-ERCP pancreatitis.

BACKGROUND AND STUDY AIMS: Inadvertent injection of contrast agent into the pancreatic duct is believed to be an important contributor to pancreatitis occurring after endoscopic retrograde cholangiopancreatography (post-ERCP pancreatitis, PEP). Our aim was to examine whether primary deep biliary cannulation with a guide wire is associated with a lower rate of PEP than conventional contrast-assisted cannulation. PATIENTS AND METHODS: From August 2003 to April 2006 all patients with an intact papilla who were referred for ERCP were eligible. Patients with pancreatic or ampullary cancer were excluded. Patients were randomized to undergo sphincterotomy biliary cannulation using either contrast injection or a guide wire. The ERCP fellow attempted initially for 5 minutes. If unsuccessful, the consultant attempted for 5 minutes using the same technique, followed by crossover to the other technique in the same sequence and then needle-knife sphincterotomy where appropriate. Patients were assessed clinically after the procedure, then followed up with telephone interviews after 24 hours and 30 days, and serum amylase and lipase tests after 24 hours. RESULTS: Out of 1654 patients undergoing ERCP, 413 were included in the study. PEP occurred in 29/413 (7.0 %): 16 in the guide-wire arm, 13 in the contrast arm ( P = 0.48). The overall cannulation success rate was 97.3 %. Cannulation was successful without crossover in 323/413 patients (78.2 %): 167/202 (81.4 %) in the guide-wire arm and 156/211 (73.9 %) in the contrast arm ( P = 0.03). Multivariate analysis demonstrated female sex (OR = 2.7, P = 0.04), suspected sphincter of Oddi dysfunction (OR = 5.5, P = 0.01), and complete filling of the pancreatic duct with contrast agent (OR = 3.5, P = 0.02) to be independently associated with PEP. The risk of PEP increased incrementally with each attempt at the papilla (OR 1.4 per attempt, P = 0.04) to greater than 10 % after four or more attempts. CONCLUSIONS: The guide-wire technique improves the primary success rate for biliary cannulation during ERCP but does not reduce the incidence of PEP compared to the conventional contrast technique. The incidence of PEP increases incrementally with each attempt at the papilla.

Mediastinal adenopathy: finding the answer with endoscopic ultrasound-guided fine-needle aspiration biopsy.

BACKGROUND: Endoscopic ultrasound-guided fine-needle aspiration biopsy (EUS FNA) is a relatively new imaging modality that has been reported to be useful for mediastinal nodal staging of lung cancer and for the evaluation of mediastinal adenopathy of unknown cause. However, the technique is not commonly used in Australia. METHODS: A retrospective review of all patients who had mediastinal EUS FNA was undertaken. Of a total of 787 patients who had undergone endoscopic ultrasound (EUS) studies from November 1999 to March 2004, 27 patients were identified to have had mediastinal EUS FNA. Details were recorded including study indication, history of malignancy, source of referral, prior attempts for tissue diagnosis, EUS and EUS FNA findings, complications, surgical pathology if available and clinical outcome after diagnosis. RESULTS: Mediastinal EUS FNA was performed on an outpatient basis and no complications were recorded. Diagnostic material was obtained from all patients with a mean number of three passes. Nodal stations sampled included left paratracheal, subcarinal, aortopulmonary window and inferior mediastinum. Indications for the studies included mediastinal adenopathy of uncertain cause (17), lung cancer staging (7) and gastrointestinal cancer staging (3). EUS FNA confirmed malignancy in 16/27 patients, sarcoidosis in three patients, tuberculosis in one patient and seven patients were deemed to have reactive adenopathy. Primary cytopathological diagnosis of malignancy was determined by EUS FNA in nine patients. CONCLUSIONS: EUS FNA is a safe, efficient and effective modality for mediastinal staging of lung cancer and for the diagnosis of mediastinal adenopathy of uncertain origin. EUS FNA has the potential to significantly impact on patient management, avoiding more invasive procedures as well as unnecessary operations.

Adjunctive use of endoscopy during acoustic neuroma surgery.

OBJECTIVE/HYPOTHESIS: In specific clinical situations, endoscopes offer better visualization than the microscope during acoustic neuroma (vestibular schwannoma) surgery and can therefore decrease the incidence of the postoperative complications of cerebrospinal fluid (CSF) leakage and recurrence of tumor. This study was undertaken to determine if the use of adjunctive endoscopy provides complementary information to the operating surgeon during surgery for acoustic neuromas. METHOD: Seventy-eight patients with acoustic neuromas underwent tumor excision by two neurotologists (PAW., D.S.P.), together with their respective neurosurgical partners, via a retrosigmoid (suboccipital) approach (n = 68), translabyrinthine approach (n = 7), or middle cranial fossa approach (n = 3). Endoscopy with a rigid glass lens endoscope was used during tumor removal to examine posterior fossa neurovascular structures, and after tumor excision to inspect the internal auditory canal (IAC), inner ear, and middle ear, depending on the approach used. One of the authors (D.S.P.) has not used adjunctive endoscopy during resections via the translabyrinthine and middle cranial fossa approaches, and therefore, these cases were excluded from the data collection and analysis. RESULTS: Complete tumor excision was achieved in 73 patients. Endoscopy allowed improved identification of tumor and adjacent neurovascular relationships in all cases. In addition, residual tumor at the fundus of the IAC (n = 11) and exposed air cells (n = 24) not seen with the microscope during retrosigmoid approaches were identified endoscopically. In one of the translabyrinthine cases, the endoscope allowed identification of open air cells not visualized with the microscope. None of the 78 patients developed CSF rhinorrhea. Incorporating the endoscope did not significantly increase operative time. CONCLUSIONS: Endoscopy can be performed safely during surgery to remove acoustic neuromas. The adjunctive use of endoscopy may offer some advantages including improved visualization, more complete tumor removal, and a lowered risk of CSF leakage.

Single-voxel proton MR spectroscopy of nonneoplastic brain lesions suggestive of a neoplasm.

BACKGROUND AND PURPOSE: MR spectroscopy is used to characterize biochemical components of normal and abnormal brain tissue. We sought to evaluate common histologic findings in a diverse group of nonneoplastic diseases in patients with in vivo MR spectroscopic profiles suggestive of a CNS neoplasm. METHODS: During a 2-year period, 241 patients with suspected neoplastic CNS lesions detected on MR images were studied with MR spectroscopy. Of these, five patients with a nonneoplastic diagnosis were identified retrospectively; a sixth patient without tissue diagnosis was added. MR spectroscopic findings consistent with a neoplasm included elevated choline and decreased N-acetylaspartate and creatine, with or without detectable mobile lipid and lactate peaks. RESULTS: The histologic specimens in all five patients for whom tissue diagnoses were available showed significant WBC infiltrates, with both interstitial and perivascular accumulations of lymphocytes, macrophages, histiocytes, and (in one case) plasma cells. Reactive astrogliosis was also prominent in most tissue samples. This cellular immune response was an integral component of the underlying disorder in these patients, including fulminant demyelination in two patients, human herpesvirus 6 encephalitis in one patient, organizing hematoma from a small arteriovenous malformation in one patient, and inflammatory pseudotumor in one patient. Although no histologic data were available in the sixth patient, neoplasm was considered unlikely on the basis of ongoing clinical and neuroradiologic improvement without specific therapy. CONCLUSION: Nonneoplastic disease processes in the CNS may elicit a reactive proliferation of cellular elements of the immune system and of glial tissue that is associated with MR spectroscopic profiles indistinguishable from CNS neoplasms with current in vivo MR spectroscopic techniques. Such false-positive findings substantiate the need for histologic examination of tissue as the standard of reference for the diagnosis of intracranial mass lesions.

Human head-neck biomechanics under axial tension.

A significant majority of cervical spine biomechanics studies has applied the external loading in the form of compressive force vectors. In contrast, there is a paucity of data on the tensile loading of the neck structure. These data are important as the human neck not only resists compression but also has to withstand distraction due to factors such as the anatomical characteristics and loading asymmetry. Furthermore, evidence exists implicating tensile stresses to be a mechanism of cervical spinal cord injury. Recent advancements in vehicular restraint systems such as air bags may induce tension to the neck in adverse circumstances. Consequently, this study was designed to develop experimental methodologies to determine the biomechanics of the human cervical spinal structures under distractive forces. A part-to-whole approach was used in the study. Four experimental models from 15 unembalmed human cadavers were used to demonstrate the feasibility of the methodology. Structures included isolated cervical spinal cords, intervertebral disc units, skull to T3 preparations, and intact unembalmed human cadavers. Axial tensile forces were applied, and the failure load and distraction were recorded. Stiffness and energy absorbing characteristics were computed. Maximum forces for the spinal cord specimens were the lowest (278 N +/- 90). The forces increased for the intervertebral disc (569 N +/- 54). skull to T3 (1555 N +/- 459), and intact human cadaver (3373 N +/- 464) preparations, indicating the load-carrying capacities when additional components are included to the experimental model. The experimental methodologies outlined in the present study provide a basis for further investigation into the mechanism of injury and the clinical applicability of biomechanical parameters.

Biomechanics of skull fracture.

This study was conducted to determine the biomechanics of the human head under quasistatic and dynamic loads. Twelve unembalmed intact human cadaver heads were tested to failure using an electrohydraulic testing device. Quasistatic loading was done at a rate of 2.5 mm/s. Impact loading tests were conducted at a rate of 7.1 to 8.0 m/s. Vertex, parietal, temporal, frontal, and occipital regions were selected as the loading sites. Pathological alterations were determined by pretest and posttest radiography, close-up computed tomography (CT) images, macroscopic evaluation, and defleshing techniques. Biomechanical force-deflection response, stiffness, and energy-absorbing characteristics were obtained. Results indicated the skull to have nonlinear structural response. The failure loads, deflections, stiffness, and energies ranged from 4.5 to 14.1 kN, 3.4 to 16.6 mm, 467 to 5867 N/mm, and 14.1 to 68.5 J, respectively. The overall mean values of these parameters for quasistatic and dynamic loads were 6.4 kN (+/- 1.1), 12.0 mm (+/- 1.6), 812 N/mm (+/- 139), 33.5 J (+/- 8.5), and 11.9 kN (+/-0.9), 5.8 mm (+/- 1.0), 4023 N/mm (+/- 541), 28.0 J (+/- 5.1), respectively. It should be emphasized that these values do not account for the individual variations in the anatomical locations on the cranium of the specimens. While the X-rays and CT scans identified the fracture, the precise direction and location of the impact on the skull were not apparent in these images. Fracture widths were consistently wider at sites remote from the loading region. Consequently, based on retrospective images, it may not be appropriate to extrapolate the anatomical region that sustained the impact forces. The quantified biomechanical response parameters will assist in the development and validation of finite element models of head injury.

Quality assurance in a large reference laboratory.

The success of a quality assurance system is contingent on close adherence to each protocol, from preparation of the patient to issuance of the final result. In the event that the system experiences failures at any point, the quality of laboratory data may be jeopardized. Again, the system requires support not just from management and personnel employed at the technical level, but from the entire organization. It requires a complete commitment to quality and to the provision of a high level of service. Such quality assurance programs have been highly successful in the manufacturing industry. For an example, one need look no further than the domination of certain world markets by Japanese industries. Their commitment to quality and their system-wide quality control efforts have been essential to the success and growth of their organizations. Currently, systems that provide high levels of quality assurance are under scrutiny in an effort to reduce costs. As more effort is placed into monitoring an organization's quality, the expenditure of non-revenue producing dollars increases. A large organization should question these expenditures. However, when evaluating such a program, it should be realized that the costs associated with the pursuit of quality are often offset by savings realized through improved processes. Further, quality is a salable commodity. Its lack may be costly. According to Westgard et al., costs of quality can be grouped into prevention costs, appraisal costs, and failure costs. Prevention costs include those costs incurred through the development of sound analytic procedures and adequate training of technical personnel. Appraisal costs comprise those costs incurred as a result of challenging the analytic procedure as well as the entire system. Failure costs represent the dollars spent when out-of-control assays have to be repeated. An important step in evaluating potential savings produced by a quality control program is assigning a dollar value to the cost of repeating an assay. In general, as the quality of an organization's product increases, the expense of providing the product decreases. Likewise, as productivity increases, the cost of testing decreases. Increased quality and productivity provide a higher percentage of profit. As the profitability of an organization increases, the additional resources required to investigate new methods, themselves a valuable contribution to quality assurance, are provided.(ABSTRACT TRUNCATED AT 400 WORDS)

Comparison of single-photon emission computed tomography with [123I]iodoamphetamine and xenon-enhanced computed tomography for assessing regional cerebral blood flow.

Regional CBF (rCBF) images obtained from xenon-enhanced computed tomography (XeCT) and single-photon emission computed tomography (SPECT) with N-isopropyl-p-[123I]iodoamphetamine (IMP) done with a rotating gamma-camera were compared in nine patients. Both XeCT and SPECT/IMP demonstrated flow abnormalities at all sites of infarction identified by CT, while detecting reduced rCBF in areas normal by CT in eight of the nine patients. All areas that were abnormal on XeCT were abnormal on the comparable SPECT/IMP images. The major advantages of XeCT are its greater resolution and potential for noninvasive quantitation of rCBF, while the major advantage of SPECT/IMP is its visualization of the entire brain on transverse, coronal, and sagittal sections.

Evoked potential studies of the effects of impact acceleration on the motor nervous system.

The initial results of a continuing investigation into the effects of various levels of impact acceleration on the functional integrity of the motor nervous system are summarized. The results are based on the measurement of alterations in neural transmission along the motor pathway of the Rhesus monkey as revealed by latency and amplitude changes in the motor pathway evoked potential (EP) following the delivery of various levels of impact acceleration to a test vehicle. The EPs were produced by electrical stimulation of and recording from the motor pathway of experimental animals subjected to -Y (lateral impact) acceleration and animals subjected to -X (frontal impact) acceleration. High resolution latency and amplitude measures of the EP recorded from these animals before and after impact were tracked so that the time course of recovery of nerve propagation following impact could be accurately assessed. Analysis of these EP measures revealed that the time course of recovery to preimpact values is directly related to the intensity of the acceleration impulse delivered to the test vehicle.

Distraction rod stabilization in the treatment of metastatic carcinoma.

Stabilization of the spinal column with Harrington distraction rods and acrylic fusion was the primary form of treatment in a select group of patients with metastatic carcinoma of the spinal column. Clinical criteria included patients in poor general medical condition with intractable pain originating from metastatic tumor involvement in the ventral components of the thoracic or upper lumbar spinal column and minimal evidence or absence of spinal cord compression. After stabilization, pain relief was almost total and sustained, and neurological status generally remained unchanged from preoperative findings without any evidence of improvement of preexisting abnormalities or occasions of rapid neurological deterioration. This form of spinal stabilization may offer significant relief of debilitating pain, lessen the risk of pathological fracture-dislocation of the thoracic or upper lumbar vertebral column, and reduction in the local compressive effects on the spinal cord caused by ventrally situated metastatic tumor.

A simplified radioimmunoassay for plasma 11-deoxycortisol.

A simple, specific, accurate, precise and sensitive radioimmunoassay procedure developed for plasma 11-deoxycortisol is described. 1. The assay employs an anti-11-deoxycortisol serum generated against 11-deoxycortisol-3-(0-carboxymethyl) oxime coupled to bovine serum albumin, crystalline 11-deoxycortisol as standard, and [3H] 11-deoxycortisol as the radioactive ligand. 2. Cross-reactivity studies performed with structurally related steroids indicated cross reactivities with 17 alpha-hydroxyprogesterone, deoxycorticosterone and progesterone of 2.0%, 1.3% and 0.4% respectively; cortisone, corticosterone, cortisol, testosterone, less than 0.1%; and estrone, 17-beta-estradiol, estriol, and metyrapone less than 0.001%. Due to the high specificity of the anti-11-deoxycortisol serum, the method is simplified by the lack of need for chromatographic purification of the organic solvent extract of the plasma prior to the radioimmunoassay. The procedure was validated by comparing values for plasma 11-deoxycortisol with and without preliminary purification by chromatography on Sephadex LH-20 columns (y = 0.99 R/-x + 4.0, r = .98). Pretreatment of the plasma with n-hexane was found to eliminate interferences from high concentrations of 17 alpha-hydroxyprogesterone or progesterone. 3. Parallel dose-response curves were demonstrated between dilutions of plasma with elevated 11-deoxycortisol concentrations and the standard reference preparation. A non-specific binding less than 4% of the total [3H] 11-deoxycortisol was routinely observed. The detection limit of the assay was approximately 10 pg of 11-deoxycortisol which corresponds to a plasma concentration of approximately 0.7 micrograms/L 4. The analytical recovery of 11-deoxycortisol added to human plasma varied from 88 to 108%, with a mean recovery of 100%. The inter-assay variation was determined by assaying (n = 30) three different quality control pools. The following data were obtained: x 1 = 3.8 +/- 0.6 micrograms/L (CV = 15.8%); x 2 = 18.5 +/- 2.0 micrograms/L (CV = 10.8%); x 3 = 43.0 +/- 3.7 micrograms/dl (CV = 8.6%).

A simplified radioimmunoassay for plasma aldosterone.

The analytical evaluation is described of a [125I]-aldosterone radioimmunoassay method for measuring aldosterone in human plasma, which requires no chromatographic purification before quantification by radioimmunoassay but does require organic solvent extraction. Rabbit anti-aldosterone serum is used, generated against aldosterone-3-oxime coupled to thyroglobulin. The antibody demonstrates negligible cross reactions with structurally-related steroids. The proposed method uses [125I]-labeled aldosterone as the radioactive ligand. The recovery of D-aldosterone added to human plasma averaged 98 percent. The parallelism and precision of the method are excellent. Seventy specimens were assayed by the proposed method and a [3H]-aldosterone reference procedure, which includes LH-20 column chromatographic purification prior to the radioimmunoassay step (y = 1.03X - 3.0; r = 0.99; p less than 0.01). The [3H]-aldosterone reference procedure uses an anti-aldosterone serum prepared against aldosterone-3-oxime coupled to rabbit serum albumin.

Measurement of gentamicin by radioimmunoassay.

A sensitive, specific and precise procedure for the measurement of serum gentamicin by radioimmunoassay is presented. The method is rapid, convenient, and highly reliable for this very important measurement. Studies designed to evaluate the validity and reproducibility of the assay are presented and discussed.

A clinical evaluation of xenon enhancement for computed tomography.

Xenon increases the attenuation coefficients of tissues in which it dissolves and, therefore, enhances lipid-rich material. The authors evaluated xenon enhancement for computed tomography. Patients and normal subjects were given xenon in subanesthetic concentrations and were scanned in a large aperture CT scanner. Patients tolerated 30-50% inhaled xenon well. Cerebral tissues and lung were enhanced by this concentration of xenon. Xenon inhalation in subanesthetic concentrations will be a useful technique for characterizing abnormal lipid tissues and for estimating cerebral blood flow.

Evoked potentials in experimental myelopathy.

Evoked potentials recorded from the cerebral cortex and spinal cord secondary to peripheral stimulation are reversibly reduced in amplitude by both pathologic distraction and pathologic flexion of the vertebral column. While the cerebral responses are lost within two minutes after complete occlusion of the ascending aorta, the responses recorded from the spinal cord persist without change for approximately ten minutes and then gradually disappear. During the first few minutes after aortic occlusion, changes produced by spinal distraction and spinal flexion are indistinguishable from those produced when the same maneuvers are made with the aorta patent. The responses mediated by dorsal columns and corticospinal tracts are affected in the same way by flexion and distraction, suggesting that somatosensory evoked potential recordings should be a reliable means of detecting spinal cord dysfunction during surgical procedures affecting the spinal cord. It may also be possible to differentiate a mechanical from a vascular insult by the time required for the evoked potential to become abnormal following a particular surgical maneuver.