Ultrasonographic correlates of carotid atherosclerosis in transient ischemic attack and stroke.

BACKGROUND AND PURPOSE: Atherosclerotic plaques in extracranial carotid arteries, particularly in the bifurcation of the common carotid and internal carotid arteries, may cause transient cerebral ischemia and stroke by lumen stenosis or plaque-related thromboembolism. B-mode ultrasound imaging has the capability of providing information on plaque thickness, characteristics, and location in carotid arteries. METHODS: A retrospective analysis of 242 stroke and 336 transient ischemic attack (TIA) patients, recruited for the B-Scan Ultrasound Imaging Assessment Program, was performed to determine the ultrasonographic correlates of carotid atherosclerosis and acute cerebral ischemia. A matched case-control study design was used to compare brain hemispheres with ischemic lesions ("cases") to unaffected contralateral hemispheres ("controls") with regard to the presence and characteristics of carotid artery plaques. RESULTS: The first set of analyses examined the association between the presence of carotid plaques ipsilateral to the brain lesion and the occurrence of stroke or TIA and showed an association with recent episodes of TIA and stroke (odds ratio [OR], 1.6; P = .03) but not with past episodes. In a subset (n = 232) of patients with plaques in both carotid arteries and recent cerebral ischemic events, stroke was associated with ipsilateral carotid artery occlusion (P = .02). Lumen measurements at the site of the minimum residual lumen (MRL) diameter showed a significant association between a narrower lumen diameter in the carotid artery ipsilateral to case hemisphere and stroke (difference, 1.0 mm; P = .0003). TIA patients showed an association between both hypoechoic carotid plaques (OR, 3.0; P = .005) and the presence of longitudinal lesion motion (OR, 3.0; P = .02) with ipsilateral brain involvement. Plaque thickness at the MRL was positively correlated with both ipsilateral TIA (ipsilateral side, 4.4 +/- 0.15 mm; contralateral side, 3.9 +/- 0.16 mm; P = .007) and stroke (ipsilateral side, 4.2 +/- 0.23 mm; contralateral side, 3.3 +/- 0.21 mm; P = .0006). CONCLUSIONS: These data demonstrate significant relationships between carotid artery ultrasound plaque characteristics and ischemic cerebrovascular events. These findings encourage further prospective studies in asymptomatic subjects focused on echographic carotid plaque characteristics as predictors of subsequent TIA or stroke.

Measurement variability of carotid atherosclerosis: real-time (B-mode) ultrasonography and angiography.

To quantify the within- and between-reader agreement of carotid B-mode ultrasonography and angiography interpretation, images from 117 patients examined by both modalities were read multiple times. Angiographic measurements were more reproducible than those of B-mode scans for all parameters except lesion width, but variations for B-mode scan measurements were similar to those for angiographic measurements. Within-reader agreement on the presence of ulceration was substantial for both modalities, whereas between-reader agreement was poor for B-mode scan and only moderate for angiography.

Multicenter validation study of real-time (B-mode) ultrasound, arteriography, and pathologic examination.

The ability of high-resolution ultrasound, angiography, and pathologic examination of endarterectomy specimens to identify and quantitate atherosclerosis was compared in a five-center study. The carotid bifurcation in 900 patients was evaluated by angiography and ultrasound. In 216 cases, high-quality endarterectomy specimens were available for comparison with the preoperative images. All comparisons were made in a blinded fashion. Results indicate that ultrasound is able to differentiate angiographically normal from abnormal arteries with a sensitivity of 88% (1077 of 1233 arteries) and accuracy of 79% (1251 of 1578 arteries). Angiographic stenoses equal to or greater than 50% diameter were accurately identified by ultrasound imaging in 72% (1133 of 1578 arteries) of cases, and this was improved by the addition of other functional data (i.e., Doppler spectral analysis and oculoplethysmography). There was only modest correlation of absolute measurements of lesion width, minimal lumen, and standard lumen by the two imaging techniques (r = 0.28 to 0.55). Ultrasound measurements of lesion width were on the average 2 mm greater than those of angiography. The lumen averaged 1.5 mm larger when measured by ultrasound techniques. In the subset in which data were available from endarterectomy specimens, ultrasound showed the best correlation with lesion width (mean difference -1.1 mm) and angiography correlated best with minimal lumen (mean difference -0.1 mm). Neither examination consistently identified ulcerated plaques. Although ultrasound imaging alone has limited usefulness in quantitating luminal stenosis, this can be improved by the use of Doppler spectral analysis and oculoplethysmography. Ultrasound is superior to angiography for quantifying atherosclerotic plaque (lesion width) and will be an important tool for further study of atherosclerotic lesions.

Long-term mandibular adaptations to protrusive function: an experimental study in Macaca mulatta.

Twenty-three male juvenile rhesus monkeys (Macaca mulatta) were used in an experimental study of long-term mandibular adaptations to induced protrusive function. Serial protrusive appliances were placed in 11 experimental animals and mandibular adaptations were monitored cephalometrically. Twelve animals were used as controls. After 48 weeks significant increases in increments of condylar growth and in overall mandibular length were noted in the treated animals. At the end of the 144-week experimental period, the mandibles of the treated animals were 5 to 6 mm longer than those of the control animals. The results of this study do not support the hypothesis that the mandible has a genetically predetermined length.

Choice of payment plan in the Medicare capitation demonstration.

This article identifies factors that influence the choice between joining an HMO and remaining with the traditional fee-for-service system among aged Medicare beneficiaries in three communities. Sources of marketing information were found to be strongly and positively related to the decision to join the HMO. Among beneficiaries who had to switch providers to join, persons who had a prior usual source of care and those who were satisfied with the amount of paperwork required to use that source of care were less likely to enroll in the HMO. Persons who did not have to switch providers to join the HMO were more likely to enroll in the prepaid program if they were satisfied with the amount of paperwork involved in using the HMO prior to the demonstration. Differences among the three communities suggest that the barrier to HMO enrollment presented by having a prior source of care who is not affiliated with the HMO may attenuate as the number of competing HMOs in the community increases, making the medical care environment more competitive. In the community with the most HMOs, persons who already had supplemental insurance were less likely to enroll than those who did not. None of the six HMOs studied experienced adverse selection, based on pre-enrollment health status.

A survey approach for finding cases of epilepsy.

Identify persons with epilepsy by first looking for prescriptions for particular antiseizure drugs. Follow these prescriptions from the pharmacies to the physicians who wrote them for patients. Ask the physicians whether the patients have epilepsy. Finally, contact the patients who do have epilepsy to elicit information about the impact of that condition on their lives. With these steps, it may be possible to carry out successfully a probability survey of epilepsy in the United States population. To learn more about this approach, a field test was funded by the National Institute of Neurological and Communicative Disorders and Stroke (NINCDS) of the Public Health Service. From 1978 through 1982, the work was planned, carried out, and evaluated by Research Triangle Institute, Research Triangle Park, NC. Epilepsy is a sensitive topic to ask about in a survey. Also, the condition is sufficiently rare to render ordinary survey approaches inefficient. Even if rarity were not an issue, there would be the problem of response error because a person with epilepsy does not, as a rule, have much clinical information on his or her condition. Better information lies with the physician who provides the care, but many physicians are busy with their practices. Furthermore, their record systems are usually not designed for easy retrieval of information, unless the names of patients are available. In the survey approach considered here, the names of patients are obtained through a random sampling of prescriptions for antiseizure drugs. The field test was divided into three phases with special activities reserved for each. The most important problem confronted was how to safeguard the confidentiality of relationships between pharmacist and patient and between physician and patient.Special guidelines on confidentiality were put into effect for the data collection. These guidelines,however, contributed to serious problems of nonresponse-especially for physicians. This article provides a brief account of the field test, including a rationale for the survey strategy of finding cases of epilepsy through prescriptions for antiseizuredrugs.

Effects of an advance telephone call in a personal interview survey.

During October and November 1982, 1,260 Medicare-eligible senior citizens were interviewed in a survey focusing on health care of the elderly. As part of the survey, an experiment was conducted in each of the three survey sites to determine the effects of an advance telephone call to schedule an appointment for a personal interview. One random half sample in each site was sent a lead letter, followed by a telephone call to schedule a personal interview. The other half sample was sent a lead letter followed by a personal contact, with no intervening telephone call. Telephoning to arrange an appointment for a personal interview resulted in a 20 percent saving in data collection costs with only a 1 percent decrease in response rate.

Implications for health care policy. A social and demographic profile of hemodialysis patients in the United States.

Before 1973, selection of patients with end-stage renal diseases (ESRD) for treatment was necessary because of inadequate medical and financial resources. Patients were selected based partly on social worth rather than medical suitability. In 1973 ESRD patients became eligible for Medicare benefits, eliminating the financial barrier to treatment. Using data from two national surveys of hemodialysis patients in 1967 and 1978, two social and demographic profiles of patients illustrate the effect of extension of Medicare benefits on composition of the dialysis patient population. These data indicate that problems of patient selection have been resolved, and ESRD patients now have equal access to medical care. Nevertheless, there is growing pressure for cost efficiency for the ESRD program in the tightening economic climate. This may lead again to some form of restriction for future access to dialysis therapy.

Hemodialysis partners.

A 1976 national survey was made to obtain information about hjemodialysis patients and their partners. Results of the survey indicate that a suitable (willing and capable) partner is a principal consideration of both patient and physician when they select the site for carrying out dialysis treatment. Results also indicate that the majority of the partners of the home-hemodialysis population come from the immediate family (90%), are white (93%), and have at least a high school education (80.4%). That more than 50% of the patients' partners in the study had assisted 3 or more years indicates that a stable relationship is possible on home dialysis. Moreover, even though machine problems were found to be a continuing major dislike among partners, most partners (nearly 92%) express little or no worry over them. Furthermore, the results indicated that the length of time a partner helps with dialysis is not correlated with the level of concern with machine problems.