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PubMedDate not supplied

133Xenon inhalation method. Analysis of reproducibility: some of its physiological implications.

Regional cerebral blood flow (rCBF) was simultaneously measured at seven locations in each hemisphere by the Obrist 133Xenon inhalation method. In each of 35 healthy right-handed subjects two rest measurements were performed on consecutive days. The data analysis comprises the two-compartmentally derived parameters for flow (f1), relative tissue weight (w1), and fractional flow (FF1) respectively of the first compartment, and in addition the initial slope index (ISI). At each detector location the coefficient of variation (C.V.) of the change from first to second measurement was on average 10.4% (ISI), 14.2% (f1), 7.2% (w1), and 2.9% (FF1) respectively. However, when each regional measurement was expressed as a percentage of its hemispheric mean, the C.V. of the intermeasurement change was on average 4.4% (ISI), 7.0% (f1), 7.7% (w1), and 1.9% (FF1) respectively; that of the hemispheric means of ISI, f1, and FF1 was found to be distinctly larger, whereas that of w1 was about equal in size. The interhemispheric coefficient of variation for the change of the hemispheric means from first to second measurement was only 2.3% (ISI), 4.4% (f1), 1.6% (w1), and 1.1% (FF1) respectively. The findings suggest that (1) the variability of rCBF from subject to subject and in consecutive measurements in the same subject is to a substantial degree of physiological origin, and that (2) there are two determinants of rCBF which may operate independently: a determinant of the hemispheric mean level, probably a single determinant for both hemispheres, and a set of determinants for each separate regions superimposed on the hemispheric mean level.

Adolescent↗
PubMed2004

Krypton laser-induced photothrombotic distal middle cerebral artery occlusion without craniectomy in mice.

Recent advances in genetical engineering of the mouse have highlighted the importance of reproducible and less invasive models of cerebral ischemia in mice. In this paper, we developed minimally invasive and reproducible model of distal middle cerebral artery (MCA) occlusion in mice using krypton (Kr) laser-induced photothrombosis. C57BL/6 or BALB mice (n=8 each) were anesthetized with halothane. The skin was cut, the temporal muscle was retracted, and the right distal MCA was observed through the skull. A Kr laser beam of wavelength 568 nm was focused onto the MCA over the intact skull. Upon laser irradiation, intravenous administration of a rose bengal solution was begun. After 4 min of irradiation, the laser beam was refocused on the MCA just proximal to the first spot, and another 4-min irradiation was performed. Then, the right common carotid artery (CCA) was ligated. Three days later, the brain was removed, and infarct volume was determined. Infarction confined almost solely to the cortical area was produced in each mouse. Mean infarct volume in C57BL/6 mice was 25.2+/-13.7 mm3. The BALB mice group showed significantly larger and more reproducible infarction (44.1+/-5.2 mm3; the coefficient of variation was 12%) than did C57BL/6 mice (P<0.005). Our photothrombosis model of stroke in mice can be performed without craniectomy, and its reproducibility is satisfactory when using BALB mice.

Animals↗
PubMed1991

[Quantitative analysis of myocardial fibrosis in myocardial biopsies--a comparison between computer analysis and point counting method].

To select an appropriate method to analyze quantitatively myocardial fibrosis in myocardial biopsies, two methods, the computer analysis and the point-counting method observed at magnifications of x200 and x400, were compared. Our targeted points of examination were the accuracy and reproducibility of these methods. Twenty patients (10 with dilated cardiomyopathy and 10 with hypertrophic cardiomyopathy) were randomly selected, and the percent area of myocardial fibrosis in myocardial biopsies obtained from the right ventricular septum was measured by both the computer analysis and the point-counting method. Two observers measured the same area twice on the different days, independently. In the area of analysis, the endocardium was excluded to avoid the observer's bias. By comparing the data obtained from two observers, it was shown that the point-counting method tended to give a larger mean value and standard deviation than the computer analysis method, but that the latter indicated better reproducibility than the former. Our result showed that the degree of myocardial fibrosis varied according to methods of analysis and observer's experiences. It is recommended that the comparison of myocardial fibrosis should be made only when the methods of analysis of fibrosis are identical.

Cardiomyopathy, Dilated↗
PubMed1993

Reproducibility of myocardial contrast echocardiography in human studies.

Experimental and clinical studies were performed to assess the ability of myocardial contrast echocardiography for quantitation of regional myocardial blood flow. To evaluate whether myocardial contrast echocardiography is a reproducible technique in humans, 18 nonselected patients undergoing coronary angiography were studied. A total of 107 intracoronary injections into either the left or the right coronary artery were analyzed by computer assisted videodensitometry for peak intensity, contrast decay half-time, and area under the curve. By means of these parameters intraobserver, interobserver, and interinjection variability were determined. Intraobserver measurements showed lowest variability with correlation coefficients of 0.83 for contrast decay half-time, 0.93 for peak intensity, and 0.95 for area under the curve. Mean percent error varied between 6.8% (peak intensity) and 11.2% (area under the curve). The correlation coefficients for interobserver variability ranged from 0.73 for area under the curve to 0.97 for peak intensity. Mean percent error revealed a range between 7.5% for peak intensity and 19% for area under the curve. For interinjection variability, the correlation coefficient for contrast decay half-time was lower (0.56) than for peak intensity (0.73) and area under the curve (0.84). Mean percent error were higher than for intraobserver and interobserver variability (range 24.1% to 34.2%). Thus, intraobserver and interobserver variability for parameters derived from time-intensity curves after intracoronary injection of echo contrast agent in humans are sufficient and comparable to data from animal studies. Interinjection variability, however, showed a higher mean percent error.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed2006

Evaluation of global and regional right ventricular systolic function in patients with pulmonary hypertension using a novel speckle tracking method.

This study sought to demonstrate that a novel speckle-tracking method can be used to assess right ventricular (RV) global and regional systolic function. Fifty-eight patients with pulmonary arterial hypertension (11 men; mean age 53 +/- 14 years) and 19 age-matched controls were studied. Echocardiographic images in apical planes were analyzed by conventional manual tracing for volumes and ejection fractions and by novel software (Axius Velocity Vector Imaging). Myocardial velocity, strain rate, and strain were determined at the basal, mid, and apical segments of the RV free wall and ventricular septum by Velocity Vector Imaging. RV volumes and ejection fractions obtained with manual tracing correlated strongly with the same indexes obtained by the Velocity Vector Imaging method in all subjects (r = 0.95 to 0.98, p < 0.001 for all). Peak systolic myocardial velocities, strain rate, and strain were significantly impaired in patients with pulmonary arterial hypertension compared with controls and were most altered in patients with the most severe pulmonary arterial hypertension (p < 0.05 for all). Pulmonary artery systolic pressure and a Doppler index of pulmonary vascular resistance were independent predictors of RV strain (r = -0.61 and r = -0.65, respectively, p < 0.05 for both). In conclusion, the new automated Velocity Vector Imaging method provides simultaneous quantitation of global and regional RV function that is angle independent and can be applied retrospectively to already stored digital images.

Echocardiography, Doppler↗
PubMed1998

Effect of electrode length on atrial defibrillation thresholds.

INTRODUCTION: Catheter-based electrodes have been used previously to terminate episodes of atrial fibrillation in animals and man. Typically, these electrodes span 6 to 7 cm, and lowest energy requirements are achieved when these electrodes are positioned in the distal coronary sinus and in the right atrium. The purpose of this study was to evaluate the use of longer electrode lengths for atrial defibrillation. METHODS AND RESULTS: In 15 patients, two decapolar catheters were inserted, one into the distal coronary sinus and one in the right atrium. To provide longer electrodes lengths, a third catheter was inserted and alternated positioned in the right atrium or coronary sinus. A 6-cm electrode span was obtained by using the distal 8 rings on the coronary sinus catheter or 8 consecutive electrodes on the right atrial catheter and increased from 6 to 11 cm by connecting 5 consecutive, nonoverlapping rings of the third catheter with the 10 rings of the initial right atrial or coronary sinus catheter. Atrial defibrillation thresholds were determined twice, in a randomized order, in each patient for each of the three combinations of electrode lengths. All 15 patients could be successfully converted to sinus rhythm without complications; however, one patient could be converted reproducibly with only 2 of the 3 electrode combinations. Mean thresholds were 306 +/- 102 V, 5.9 +/- 4.0 J for the 6 cm/6 cm electrode length combination with an impedance of 72 +/- 18 omega. For the electrode combination using the 11-cm electrode in the right atrium, the defibrillation threshold was 296 +/- 107 V, 5.8 +/- 3.9 J with an impedance of 61 +/- 17 omega and was 294 +/- 91 V, 5.6 +/- 3.6 J with an impedance of 55 +/- 11 omega for the 11-cm electrode in the coronary sinus. There were no significant differences in defibrillation voltage or energy (P > 0.05) associated with the longer electrode lengths; however, the longer electrode lengths did significantly lower shock impedance (P < 0.05). CONCLUSION: The use of longer electrodes, when using the right atrium to coronary sinus shock vector, does not lower the defibrillation requirements for restoration of sinus rhythm.

Adult↗
PubMed1999

Specimen collection and handling.

Pre-analytical factors should be known and standardized to obtain reliable laboratory test result. If they could not be standardized they should be recognized. The specimen should be representative, properly collected, preserved, and labeled. It is also important to prevent any infection to the patients, the phlebotomists and the environment. The ideal is to get the right sample for the right test at the right time.

Blood Specimen Collection↗
PubMed1997

Reproducibility of ventricular fibrillation characteristics in patients undergoing implantable cardioverter defibrillator implantation.

INTRODUCTION: The purpose of this study was to evaluate the immediate reproducibility of local electrogram characteristics recorded during repeated episodes of induced ventricular fibrillation (VF) in patients undergoing implantable cardioverter defibrillator (ICD) implantation. METHODS AND RESULTS: Power spectral analysis (using a fast Fourier transform algorithm) of electrograms recorded during 3 seconds of VF were analyzed in 24 patients undergoing ICD implantation using a Medtronic Transvene lead. Patients had 2 to 7 episodes of VF that were induced during defibrillation threshold testing. VF was induced by burst pacing (n = 20) or T wave shock (n = 4). Simultaneous electrograms during VF were recorded from a Medtronic Transvene lead with the following configurations: (1) a narrow spaced (12 mm) dedicated bipole used clinically for sensing; (2) a unipolar electrogram from the right ventricular coil; and (3) a widely spaced (18.3 mm) integrated bipole using the distal tip and the coil. Intraclass correlation coefficients (ICCs) were determined to examine the reproducibility of these VF characteristics among VF episodes in each patient. Recordings from both bipolar configurations had ICCs from 0.40 to 0.55, whereas unipolar recordings ICCs were below 0.40. Reproducibility was similar for dedicated and integrated recordings. CONCLUSIONS: Frequency characteristics of repeated episodes of VF induced in the same subjects show fair-to-good but not excellent reproducibility. Bipolar recordings were far more reproducible than unipolar recordings, but both bipolar configurations had similar reproducibility. These findings have implications for both the pathophysiology of induced VF and the design of VF detection algorithms.

Adult↗
PubMed2000

Prognostic usefulness of the tricuspid annular plane systolic excursion in patients with congestive heart failure secondary to idiopathic or ischemic dilated cardiomyopathy.

The prognostic value of ultrasound evaluation of right ventricular (RV) performance in patients with congestive heart failure (CHF) is still a matter of investigation. We studied 140 consecutive patients with chronic CHF and a left ventricular ejection fraction <35%. All patients underwent a complete echocardiographic evaluation that systematically included the measurement of the tricuspid annular plane systolic excursion (TAPSE). During a follow-up period of 24 +/- 14 months, 45 patients died and 7 underwent emergency heart transplantation. At the multivariate survival analysis (Cox regression model) backward stepwise selection identified a prognostic model with 2 parameters: New York Heart Association (NYHA) class III or IV and TAPSE < or =14 mm (p <000). In a subgroup of 97 patients in sinus rhythm in whom mitral inflow Doppler variables could be measured, survival was further analyzed according to a model in which the significant parameters were included in the same order as usually used in routine clinical practice: clinical variables first, left ventricular function data second, mitral Doppler variables third, and indexes of right ventricular (RV) function last. TAPSE < or =14 mm added significant (p <0.03) prognostic information to NYHA class III or IV, left ventricular ejection fraction of <20%, and mitral deceleration time of < 125 ms. In conclusion, in patients with CHF, TAPSE adds significant prognostic information to the NYHA clinical classification, to the echocardiographic evaluation of left ventricular function, and to mitral Doppler variables. Furthermore, the measurement of TAPSE is easy to obtain in all patients, irrespective of heart rate and rhythm.

Cardiac Catheterization↗
PubMedDate not supplied

A standard method for repeated recording of skin blood flow using laser Doppler flowmetry.

We investigated the simple method of non-invasive Laser Doppler Flowmetry (LDF), and its use as a reproducible standard method for measuring skin blood flow. Microcirculatory blood flow shows both considerable temporal as well as regional variation. The study of reactive changes in skin blood flow, e.g. in irritancy tests, requires repeated measurements. The normal variation of skin blood flow was studied on the forearms of healthy volunteers. Males showed higher values than females. Differences between left and right arms, and recordings in the morning and the afternoon were not significant. Differences between lateral and medial aspects were borderline significant; and significant differences were measured between proximal and distal test sites. To improve the reproducibility of the measurements, a probeholder was designed with a considerably larger test area than that of the original probeholder. Fixation at both ends of the probeholder allows for repeated measurements without affecting skin blood flow. Recommendations are given for repeated testing by LDF.

Adult↗
PubMed2006

Tricuspid annular velocity in patients undergoing cardiac operation using transesophageal echocardiography.

BACKGROUND: The complex geometry of the right ventricle (RV) and poor endocardial definition make quantitative assessment of RV function difficult. Doppler tissue imaging may be helpful in quantifying RV function through measurement of tricuspid annular velocity (TAV). This prospective study assessed the feasibility of using color Doppler tissue imaging to measure TAV using a novel transgastric RV inflow view in patients undergoing cardiac surgery. METHODS: We used the transgastric RV inflow view and measured the TAV using Doppler tissue imaging and quantitative analysis software. We also measured left ventricular fractional area of contraction and hemodynamic variables. We compared values before and after cardiopulmonary bypass in patients undergoing coronary artery bypass graft. RESULTS: TAV could be measured in 19 of 23 patients (83%) undergoing coronary artery bypass graft. There was a significant decrease postbypass in TAV: isovolumic acceleration was 1.71 +/- 0.59 versus 1.32 +/- 0.66 m/s2, isovolumic velocity was 4.34 +/- 1.19 versus 3.13 +/- 1.35 cm/s, and systolic annular descent velocity was 5.15 +/- 1.15 versus 3.77 +/- 1.18 cm/s. There was a significant change in heart rate and cardiac index without any change in stroke volume index. There was no change in left ventricular function (fractional area of contraction: 54 +/- 10 vs 52 +/- 10%). CONCLUSION: Determination of TAV using the transgastric RV inflow view is feasible and may provide quantitative information on systolic RV function in patients undergoing coronary artery bypass graft. We found a decrease in systolic TAV after cardiopulmonary bypass without a significant change in stroke volume index.

Aged↗
PubMed1998

Improved reproducibility of magnetic stimulation-evoked motor potentials in the human masseter by a new method for locating stimulation sites on the scalp.

In magnetic-stimulation studies where motor-evoked potentials (MEP) are measured on different occasions, accurate relocation of the stimulation site on the scalp is essential. Here a novel method of locating neural stimulation sites was tested and the reproducibility of MEPs in the human masseter assessed. The heads of the participants were immobilized in a plastic mask that incorporated a grid overlying the left cerebral hemisphere. A figure-of-eight coil was oriented with a micromanipulator. Electrodes were placed over the right masseter using a standardized method. Two discrete sites on the grid were stimulated alternately at threshold + 10% whilst participants clenched their teeth. Recordings were repeated after the mask and electrodes had been removed and replaced. Within individual participants, the latency and amplitude of the MEP were reproducible between trials and when the mask and electrodes were replaced. The new method appears to be accurate and practical when recording longitudinal MEP data in the masseter.

Adult↗
PubMed2004

Quantitative assessment of right ventricular function using doppler tissue imaging in fetuses with and without heart failure.

BACKGROUND: Previous reports have established the use of Doppler tissue imaging (DTI) for noninvasive assessment of ventricular function, but the technique has not been validated for diagnosis of fetal cardiac failure. OBJECTIVE: The purpose of this study was to assess right ventricular (RV) function in fetuses with heart failure using DTI. METHODS: In all, 43 fetuses (36 control, 7 heart failure) were assessed using pulsed Doppler echocardiography combined with DTI. RV peak myocardial velocities during early diastole (Ea), atrial contraction, and systole were measured; and tricuspid peak velocities during early diastole (E) and atrial contraction. The ratio of E/Ea was used as an index of filling pressure were measured. From DTI, a Doppler-derived index of combined systolic/diastolic myocardial performance (DTI-Tei index) was measured. RESULTS: Compared with control fetuses, the mean Ea was significantly lower and the mean E was significantly higher in fetuses with heart failure, although these parameters did overlap between the 2 groups. The mean RV myocardial wall-motion velocity during atrial contraction, ratio of Ea/RV myocardial wall-motion velocity during atrial contraction, and RV myocardial wall-motion velocity during systole did not differ between the 2 groups. Compared with control fetuses, the mean E/Ea was significantly higher (9.71 +/- 0.91 vs 6.20 +/- 0.97; P <.0001) and the mean DTI-Tei index was significantly greater (0.79 +/- 0.11 vs 0.55 +/- 0.05; P <.0001) in fetuses with heart failure. In addition, the DTI-Tei index z score was >2 in all fetuses with heart failure. CONCLUSIONS: This study demonstrated a clinically important application of DTI-derived tricuspid annular velocities in fetuses with heart failure. Although DTI velocities were not sufficiently sensitive to identify fetuses with heart failure versus control fetuses, DTI-Tei index and E/Ea were useful and sensitive indicators of global RV dysfunction.

Blood Flow Velocity↗
PubMed1999

Novel brain ischemic change on MRI. Delayed ischemic hyperintensity on T1-weighted images and selective neuronal death in the caudoputamen of rats after brief focal ischemia.

BACKGROUND AND PURPOSE: Specific change of persistent hyperintensity/hypointensity on T1-weighted (T1W) and T2-weighted (T2W) MRI, respectively, has been reported to develop in the human basal ganglia after brief hemispheric ischemia. We investigated whether this ischemic change observed in humans could be reproduced experimentally in rats after brief middle cerebral artery (MCA) occlusion (MCAO), and if so, what the neuroradiological change represented histologically. METHODS: The origin of the right MCA of male Wistar rats (n=25) was occluded for 15 minutes by inserting a silicon-coated nylon thread from the external carotid artery into the internal carotid artery. After 15 minutes' MCAO, coronal MR images (T1W, T2W, and T1W with fat saturation pulse) were obtained once at 3-day reperfusion (n=5) and twice at 3- and 7-day reperfusion (n=20). Brain specimens were examined histologically immediately after the last MRI study in all rats. RESULTS: Neither T1W nor T2W MRI showed marked signal changes 3 days after reperfusion following 15-minute MCAO. However, the ischemic change of hyperintensity and hypointensity on T1W and T2W MRI, respectively, appeared in the striatum following 7-day reperfusion after 15-minute MCAO (n=19/20). Histological examination revealed that the specific lesion in the rat striatum on MRI corresponded to selective neuronal death and proliferation of reactive astrocytes and microglia without infarct, hemorrhage, lipid accumulation, or calcification. CONCLUSIONS: Brief MCAO with reperfusion induces the delayed ischemic changes of hyperintensity and hypointensity on T1W and T2W MRI, respectively, in the rat striatum with high reproducibility. This specific ischemic change on MRI histologically corresponded to selective neuronal death and gliosis with preservation of the macroscopic structure of the brain. A similar MRI pattern reported in patients who have sustained brief ischemia may represent similar histology. We speculate that the ischemic change reflects some biochemical changes affecting the magnetic field as the brain tissue undergoes subtle structural changes.

Animals↗
PubMed2004

Reproducibility of organ position using voluntary breath-hold method with spirometer for extracranial stereotactic radiotherapy.

PURPOSE: To evaluate in healthy volunteers the reproducibility of organ position using a voluntary breath-hold method with a spirometer and the feasibility of this method for extracranial stereotactic radiotherapy in a clinical setting. METHODS AND MATERIALS: For this study, 5 healthy volunteers were enrolled. After training sessions, they held their breath at the end-inspiration and the end-expiration phase under spirometer-based monitoring. Computed tomography (CT) scans were performed twice at each respiratory phase, with a 10-min interval, on 2 separate days. The total number of CT scans was four at each respiratory phase. After CT volume data were transferred to a three-dimensional treatment-planning system, digitally reconstructed radiographs (DRRs) were calculated for anterior-posterior and left-right beams. Verification was performed with DRRs relative to the diaphragm position, bony landmarks, and the isocenter in each healthy volunteer at each respiratory phase. To evaluate intrafraction reproducibility, we measured the distance between diaphragm position and bony landmarks. To evaluate interfraction reproducibility, we measured the distance between diaphragm position and the isocenter. Reproducibility and setup error were defined as the average value of the differences between each DRR with regard to the first DRR. RESULTS: Intrafraction reproducibility of the caudal-cranial direction was 4.0 +/- 3.5 mm at the end-inspiration phase and 2.2 +/- 2.0 mm at the end-expiration phase. Interfraction reproducibility of the caudal-cranial direction was 5.1 +/- 4.8 mm at the end-inspiration phase and 2.1 +/- 1.8 mm at the end-expiration phase. The end-expiration phase was more stable than the end-inspiration phase. CONCLUSIONS: The voluntary breath-hold method with a spirometer is feasible, with relatively good reproducibility. We are encouraged about the use of this technique clinically for extracranial stereotactic radiotherapy.

Diaphragm↗
PubMed1999

Cardiac motion of coronary arteries: variability in the rest period and implications for coronary MR angiography.

PURPOSE: To measure the duration of the rest period in the cardiac cycle, a parameter vital to data acquisition in coronary magnetic resonance (MR) angiography. MATERIALS AND METHODS: Motion of coronary arteries was measured in 13 patients by using breath-hold, biplane, conventional angiography, with frontal and lateral projections of the left and right coronary arteries acquired at 30 frames per second. The time courses of the coordinates of bifurcations of proximal parts of the coronary arteries were measured, from which the rest period (motion < 1 mm in orthogonal axes), velocity, displacement range, motion correlation, and reproducibility from heartbeat to heartbeat were estimated. RESULTS: Both the motion pattern and the amplitude varied substantially from patient to patient. The rest period varied from 66 to 333 msec (mean, 161 msec) for the left coronary artery and from 66 to 200 msec (mean, 120 msec) for the right coronary artery. CONCLUSION: The rest period for coronary arteries in the cardiac cycle varies substantially from patient to patient, which may cause quality to be inconsistent in current coronary MR angiography. A cardiac motion image prior to coronary data acquisition (preimage) may be used to estimate the optimal duration and timing in the cardiac cycle for coronary MR angiography.

Coronary Angiography↗
PubMed1986

Gated xenon scans for right ventricular function.

The complex geometry of the right ventricle makes the use of radionuclides an attractive method for assessing right ventricular function. The use of the gated 133Xe technique for this purpose offers several advantages. A short i.v. infusion over 20 sec of 133Xe permits scans to be obtained, gated to the electrocardiogram at rest and during maximal exercise using a standard gamma camera. The method is both reproducible (3.5%) and repeatable (2.8%), and because of the short half-life within the patient with most of the radioisotope being excreted by the lungs, scans may be repeated within a few minutes and the radiation dose to the patient is small. Right ventricular ejection fraction obtained from gated xenon scans is shown to correlate well with measurements obtained from both standard gated technetium scans and first-pass studies.

Female↗