Three-dimensional echocardiographic evaluation of left ventricular volume: comparison of Doppler myocardial imaging and standard gray-scale imaging with cineventriculography--an in vitro and in vivo study

BACKGROUND

Standard gray-scale imaging (GSI), three-dimensional (3D) echocardiography has been shown to be superior to two-dimensional echocardiography in measuring left ventricular volume. However, the often relatively poor quality of transthoracic gray-scale data can limit the potential application of this technique. Doppler myocardial imaging (DMI) is a new ultrasound technique that potentially offers higher-quality 3D images with a transthoracic approach than the 3D GSI technique. This study was designed to compare the accuracy of standard GSI and DMI 3D left ventricular volume measurements in vitro and in vivo.

METHODS AND RESULTS

In vitro, the minimum and maximum volume of the contracting single-chamber, tissue-mimicking phantom was calculated by using both techniques. In vivo, GSI and DMI 3D left ventricular volume measurements were performed in 16 patients. End-diastolic and end-systolic left ventricular volumes were computed for both techniques and compared with those calculated by cineventriculography. In vitro, both methods tended to underestimate the true phantom volume, but the systematic error was smaller for DMI than for GSI (-1.2% +/- 1.5% vs. -4.3% +/- 3%; p < 0.01) and was more constant in the case of DMI over the range of different sizes of true volume. In vivo, for GSI the end-diastolic volume mean difference was -12.6 ml and the limits of agreement were +/-18 ml, and for DMI the corresponding values were -4.2 and +/- 10.6 ml, respectively. The difference for end-systole was -6.5 +/- 10.6 ml and -1.5 +/- 10 ml for GSI and DMI, respectively. The magnitude of the difference in volume measurement between 3D echocardiography and cineventriculography was significantly smaller when using the Doppler technique.

CONCLUSIONS

The results of this in vitro and in vivo study indicate that DMI is superior to GSI as a transthoracic acquisition technique for 3 D volume computation.

Contextual dependencies during perceptual-motor skill performance: influence of task difficulty

The present experiment was designed to address the role of task difficulty for the development of contextual-dependent behaviour during perceptual-motor task acquisition. Task difficulty in the present study was manipulated by restricting the time that the subject; (a) viewed task-relevant information, and (b) was afforded to execute a sequence of key presses. Assuming these manipulations made the acquisition of the key press tasks more difficult, it was hypothesised that reducing the time for either of these processes would result in a greater dependence on reinstating the training context at the time of test. This was based on previous findings reported by Wright and Shea (1991) which indicated that task difficulty can contribute to the development of context-dependent behaviour. The results of the study revealed that viewing time was a potent difficulty manipulation. This is supported by the slower acquisition rates for subjects exposed to short as opposed to long viewing conditions during training. More importantly, the impact of changing the intentional-incidental stimuli relationship that was apparent during training, during the test was greatest for the individuals who experienced shorter viewing times during the training phase. Thus, the proposed influence of task difficulty on contextual-dependent performance was supported. This dependency was manifested as a slowing in both the initiation and execution of the correct key presses. It is proposed that individuals trained in the more difficult viewing condition during training, when faced with an incongruence in the acquisition and test stimuli, must engage additional data-driven verification processes to supplement their extant knowledge in order to execute an appropriate response.

An acoustic injection test object for colour flow imaging systems

There are few test objects suitable for colour-flow ultrasound scanners. An acoustic injection device is described that enables the production of a 2-D region of colour on a colour-flow image. The device involves detection of the transmitted ultrasound pulse from the scanner, followed by the emission of a synthesized echo that consists of a radiofrequency burst modulated by an audiofrequency signal in such a way that, on reception by the ultrasound scanner, it is interpreted as a signal arising from a region of flow. The depth of the colour region may be controlled by adjustment of the length of the synthesised echo. The audiofrequency content may be altered as desired, enabling examination of the relationship between the displayed colour and the signal spectral content.

Evaluation of case reports of aplastic anemia among patients treated with felbamate

PURPOSE

Felbamate (FBM) is a new antiepileptic drug (AED) that is often effective in seizure disorders refractory to other treatments; its use has been greatly restricted after cases of aplastic anemia were reported. To elucidate the putative association between FBM and aplastic anemia, we made a detailed evaluation of the first 31 reports.

METHODS

Hematologic review according to the criteria of the International Agranulocytosis and Aplastic Anemia Study (IAAAS) confirmed 23 cases (74%) as aplastic anemia; FBM was judged to be the only plausible cause for three; confounding (mostly by other drugs) was considered possible, but FBM remained the most likely cause for 11; and there was at least one other plausible cause for 9.

RESULTS

Using a denominator from sales data of 110,000 persons exposed and a numerator of the cases for which FBM was considered the only plausible cause, we established a lower limit of incidence of 27 cases of aplastic anemia per million users as compared with the general population rate of 2.0 per million per year. With all confirmed cases used as the numerator, the upper limit of incidence was 209 per million. The 'most probable" incidence was estimated to be 127 per million.

CONCLUSIONS

Intensive, systematic investigation can maximize the utility of case reports for assessing risks of newly released drugs. The present evaluation confirmed an association between FBM and aplastic anemia; however, confounding was significant for most cases and there was a tenfold range in the "best case" and "worst case" incidence estimates among users.

Earliest evidence for arthrogryposis multiplex congenita or Larsen syndrome?

A sixteenth-century illustrated pamphlet from Great Britain suggests that documentary evidence may permit accurate diagnosis of pathological conditions in earlier societies. The document is of particular importance, since the presented congenital abnormalities, including cleft lip, spina bifida cystica, genu recurvatum, and talipes deformity are reported rarely in archaeological skeletal material. It is suggested that the combination of abnormalities may represent the earliest case of arthrogryposis multiplex congenita or Larsen syndrome.

A comparison of two motion analysis systems for the measurement of two-dimensional rearfoot motion during walking

The purpose of this study was to compare two-dimensional rearfoot motion during walking measured by a traditional video-based motion analysis system to that of an electromagnetic analysis system. Twenty-five individuals (15 men, 10 women) with a mean age of 29.8 years served as subjects for this study. The results of the study showed that there was a high correlation (r = 0.945) between the mean motion paths produced by the two systems, indicating that they were very similar. The electromagnetic motion analysis system was able to produce these similar results in a fraction of the time required by the video-based system.

Sense of time in children with ADHD: effects of duration, distraction, and stimulant medication

A recent theory of ADHD predicts a deficiency in sense of time in the disorder. Two studies were conducted to test this prediction, and to evaluate the effects of interval duration, distraction, and stimulant medication on the reproductions of temporal durations in children with ADHD. Study I: 12 ADHD children and 26 controls (ages 6-14 years) were tested using a time reproduction task in which subjects had to reproduce intervals of 12, 24, 36, 48, and 60 s. Four trials at each duration were presented with a distraction occurring on half of these trials. Control subjects were significantly more accurate than ADHD children at most durations and were unaffected by the distraction. ADHD children, in contrast, were significantly less accurate when distracted. Both groups became less accurate with increasing durations to be reproduced. Study II: Tested three doses of methylphenidate (MPH) and placebo on the time reproductions of the 12 ADHD children. ADHD children became less accurate with increasing durations and distraction was found to reduce accuracy at 36 s or less. No effects of MPH were evident. The results of these preliminary studies seem to support the prediction that sense of time is impaired in children with ADHD. The capacity to accurately reproduce time intervals in ADHD children does not seem to improve with administration of stimulant medication.

Use of household pesticides and the risk of aplastic anaemia in Thailand. The Aplastic Anemia Study Group

BACKGROUND

Aplastic anaemia is a severe blood dyscrasia that is more common in Thailand than in Western countries. Its a etiology remains poorly understood.

METHODS

A case-control study was conducted in Bangkok and two rural regions of Thailand. The effect of household pesticides was evaluated among 253 incident cases of aplastic anaemia and 1174 hospital controls.

RESULTS

A total of 54% of the cases and 61% of the controls were exposed 1-6 months previously. For most individual household pesticides and for groups classified according to chemical type (organophosphates, pyrethrins, and organochlorines), the relative risk (RR) estimates approximated 1.0; upper 95% confidence limits were below 2.0 for many comparisons. A significant association was observed for exposure to combination products containing dichlorvos and propoxur, with an overall RR estimate of 1.7 (95% confidence interval [CI]: 1.1-2.6); the estimate for regular use was 1.6 (95% CI: 0.9-2.9).

CONCLUSIONS

The absence of a higher risk for the regular use of dichlorvos/propoxur reduces the credibility of the apparent association, which could well have been an artefact of multiple comparisons. We conclude that most household pesticides used in Thailand do not appear to increase the risk of aplastic anaemia.

Low drug attributability of aplastic anemia in Thailand. The Aplastic Anemia Study Group

From 1989 to 1994, a population-based, case-control study of aplastic anemia was conducted in Thailand, including the regions of Bangkok, Khonkaen in the northeast, and Songkla in the south. An annual incidence in Bangkok of 3.7 cases per million population, about twice as high as in Western countries, has been reported. To evaluate the etiologic role of drugs, 253 subjects were compared with 1,174 hospital controls. With multivariate adjustment for confounding, a significant association was identified for exposure 2 to 6 months before admission to thiazide diuretics (relative risk estimate 7.7; 1.5 to 40). There were crude associations with sulfonamides (relative risk estimate, 7.9; P = 0.004) and mebendazole (6.3; P = 0.03) (there were insufficient data for multivariate adjustment). Excess risks for the three drugs were in the range of 9 to 12 cases per million users. There was no significant association with chloramphenicol, although the multivariate relative-risk estimate was elevated (2.7; 0.7 to 10). Other drugs that have been reported to increase the risk of aplastic anemia, such as nonsteroidal anti-inflammatory drugs and anticonvulsants, were not commonly used. There were no associations with commonly used drugs, including benzodiazepines, antihistamines, oral contraceptives, and herbal preparations. For all associated drugs, the overall etiologic fraction (the proportion of cases attributable to an exposure) was 5%, compared with 25% in Europe and Israel. Drugs are uncommon causes of aplastic anemia in Thailand, and their use does not explain the relatively high incidence of the disease in that country.

Association of seropositivity for hepatitis viruses and aplastic anemia in Thailand

Aplastic anemia is more common in the Orient than in western countries, with an incidence in Thailand that is 2- to 3-fold higher than in Europe. Aplastic anemia after hepatitis is a well characterized clinical entity, and clinical hepatitis is also prevalent in the Far East. We performed a prospective case-control study to determine risk factors for aplastic anemia in Bangkok and two rural regions during 1989 to 1994. A total of 375 cases were identified, along with 1,174 hospital controls matched for age and sex. Historical data were collected by trained interviewers. Sera from a subset of cases (N = 177) and controls (N = 183) were tested for antibodies to hepatitis viruses A, B, and C and hepatitis B surface antigen. There was no evidence of association of aplastic anemia with hepatitis B or hepatitis C. Previous exposure to hepatitis A, as determined by immunoglobulin G (IgG) seropositivity, was significantly associated with aplastic anemia: the relative risk adjusted for confounding was 2.9 (95% confidence interval 1.2-6.7). The same association also existed for persons under age 25 years, in whom the prevalence of hepatitis A IgG was lower than in the total population. However, no patients showed evidence of recent infection with hepatitis A (immunoglobulin M [IgM] seropositivity). These results indicate that exposure to a hepatitis virus is a risk indicator for aplastic anemia in Thailand, and while itself unlikely to be etiologic, hepatitis A may be a surrogate marker for another enteric microbial agent.

Generalized anxiety and sleep architecture: a polysomnographic investigation

The sleep of 15 adult subjects who reported heightened generalized anxiety in the absence of other psychiatric syndromes and a 15-adult contrast group were studied by means of nocturnal polysomnography. Analysis of polysomnography variables revealed a significant discriminant function that accounted for 79% of the variance between groups, indicating that high-anxiety/worry subjects took longer to fall asleep, had a smaller percentage of deep (slow-wave) sleep, and more frequent transitions into light sleep [stage 1 nonrapid eye movement (NREM)]. Additional analyses indicated that high-anxiety/worry subjects had a greater percentage of light sleep, more early microarousals, a lower rapid eye movement (REM) density relative to low-anxiety subjects. These subjects also showed more electrodermal storming when slow-wave sleep and REM sleep variables were covaried. Results indicated disrupted sleep depth and continuity similar to that documented in clinical anxiety disorder patients and distinct from that of depressed patients. These results indicate that generalized anxiety and worry in otherwise healthy individuals may act to produce a clinically significant sleep disturbance in the absence of other psychiatric symptoms.

UVA II exposure of human skin results in decreased immunization capacity, increased induction of tolerance and a unique pattern of epidermal antigen-presenting cell alteration

The risks incurred from increased exposure to UVA II (320-340 nm) (i.e. during sunscreen use and extended outdoor exposure, tanning parlors) are not well understood. Therefore, we explored the effects of UVA II on skin immune responses in humans. After a single local exposure (4 minimum erythemal dose [MED]) using a xenon are lamp filtered with a narrow bandpass filter (335 +/- 5 nm full width at half maximum), individuals were contact-sensitized with dinitrochlorobenzene (DNCB) through a UVA II exposure site or through normal skin. UVA II induced a marked decrease in the magnitude of skin immune responses (P < 0.0001). The UVA II group had only 29% successful sensitizations, as compared to 83% in the control group. The percentage of individuals who remained tolerant to DNCB after two sensitizations was 23.6% for the UVA II-exposed group, as compared to 3.8% in the controls (P = 0.006). UVA II also uniquely altered the type of antigen-presenting cells present in the epidermis. Human leukocyte antigen (HLA)-DR+ cells in control epidermal cell suspensions (C-EC) comprised a single, homogeneous population of Langerhans cells (LC) with the phenotype: CD1ahi DRmid CD11b CD36 (1.5 +/- 0.3% of EC). UVA II irradiation reduced the number of such LC to 0.6 +/- 0.2% of EC. Although cells expressing the macrophage phenotype: CD1a- DRhi CD11b+ CD36+ were increased in UVA II skin, relative to C-EC, these comprised only 10.1 +/- 6.1% of the DR+ cells, which is less than that after UVB exposure. Also distinct from UVB, a third population was found in UVA II-EC, which exhibited a novel phenotype: CD1a+ DR+ CD36+ CD11b+; these comprised 11.1 +/- 6.9% of the DR+ UVA II-EC. In conclusion, despite the above differences in infiltrating DR+ cells, both UVB and UVA II reduce the skin's ability to support contact sensitization, induce active suppression (tolerance) and induce a reduction in LC.

Diagnostic bone scanning in oncology

Over the last several decades bone scanning has been used extensively in the evaluation of oncology patients to detect bone involvement. It can provide information about disease location, prognosis, and the effect of therapy. Bone scanning offers the advantages of whole body evaluation and the detection of lesions earlier than other techniques. However, as newer diagnostic tools become available, indications for bone scanning must be revised and the results combined with these other tests in order to provide optimum patient care. Advances in instrumentation and the subsequent improvement in image quality have allowed nuclear medicine physicians to provide more accurate bone scan interpretations. By optimizing image acquisition, it is often possible to determine lesion characteristics, which are more likely to represent malignancy. Knowledge of disease pathophysiology and other specific properties of the patient's primary tumor, along with subsequent correlation of scan abnormalities to patient history, physical examination, previous studies, and other radiological examinations, is essential for determining lesion significance. The differential diagnosis of a scan abnormality should also include consideration of both false normal and abnormal causes. The final interpretation should be clearly communicated to the clinician with appropriate recommendations for further evaluation. Only through careful attention to the patient, the clinician, and appropriate study acquisition parameters will bone scanning maintain its place in the evaluation of oncology patients.