D.E. Strandness

The natural history of carotid arterial disease in asymptomatic patients with cervical bruits.

A prospective study was initiated in January 1980 to follow with Duplex scanning a consecutive series of 167 asymptomatic patients with cervical bruits. Patients were seen at six month intervals for the first year and yearly thereafter. Based on previously validated criteria, disease at the carotid bifurcation was classified into 6 categories: Normal, 1-15% diameter reduction, 16-49%, 50-79%, 80-99%, and occlusion. Patients were evaluated to assess: the occurrence of new neurological symptoms, the stability of the lesions at the carotid bifurcation, and the possible role of risk indicators on disease changes. During follow-up, ten patients became symptomatic (6 with TIAs and 4 with stroke). The development of symptoms was accompanied by disease progression in 8 patients. By life table analysis, the annual rate occurrence of symptoms was 4%. The mean annual rate of disease progression to a greater than 50% stenosis was 8%. When progression in all categories was considered, 60% of the sides showed some disease aggravation. The presence of or progression to a greater than 80% stenosis was highly correlated (p = 0.00001) with either the development of a total occlusion of the internal carotid artery or new symptoms. The major risk factors associated with disease progression were cigarette smoking, diabetes mellitus, and age. Those patients under 65 years of age were most likely to show progression. Despite high rates of disease progression, this study further supports the contention that it is prudent to follow a conservative course in the management of asymptomatic patients presenting with a cervical bruit.(ABSTRACT TRUNCATED AT 250 WORDS)

A prospective study of disease progression in patients with atherosclerotic renal artery stenosis

The natural history of renal artery stenosis (RAS) has been difficult to document because serial arteriography is rarely justified. Duplex scanning is a noninvasive technique that is ideally suited for both screening and follow-up of RAS. In this approach, renal arteries are classified as normal, < 60% stenosis, > or = 60% stenosis, or occluded, and disease progression is defined as a change in the duplex classification. The purpose of this study was to determine the rate of disease progression in atherosclerotic RAS by serial duplex scanning. At least one abnormal renal artery was identified in each of 76 patients being screened for RAS. Of the 152 renal arteries, 20 were excluded (14 prior interventions, 5 occlusions, 1 technically inadequate duplex scan), leaving 132 for the natural history follow-up protocol. The patient group included 36 men and 40 women, with a mean age of 67 years, who were followed for a mean of 32 months (maximum 55 months). The initial status of the 132 renal arteries was normal in 36, < 60% stenosis in 35, and > or = 60% stenosis in 61. The cumulative incidence of progression from normal to > or = 60% RAS was 0% at 1 year, 0% at 2 years, and 8% at 3 years. The cumulative incidence of progression from < 60% to > or = 60% RAS was 30% at 1 year, 44% at 2 years, and 48% at 3 years. All 4 renal arteries that progressed to occlusion had > or = 60% stenoses at the initial visit, and for those arteries with a > or = 60% stenosis, the cumulative incidence of progression to occlusion was 4% at 1 year, 4% at 2 years, and 7% at 3 years. Progression of RAS occurred at an average rate of 7% per year for all categories of baseline disease combined. Progression of atherosclerotic RAS is relatively common, particularly from < 60% to > or = 60% stenosis.

Carotid artery velocity patterns in normal and stenotic vessels.

Duplex scanning prorides real time B-raode images of the carotid bifurcation Teasels along with a single gate pulsed Doppler flow Telocity detector. By using the B-mode output of the duplex system to measure the Doppler angle and spectrum analysis to measure the frequency content of the Doppler signal, instantaneous flow Telocity can be calculated. Mean velocity at peak systole was calculated retrospecthely in 68 common (CCA) and internal (ICA) carotid arteries of 39 patients who had undergone prlor angiography and prospecthely in 30 arteries of 15 healthy young controls. The ratio of mean peak ICA Telocity to mean peak CCA Telocity at systole (VlCA/VCCA) was below 0.8 in all 36 normal arteries and above 1.5 in all 21 high-grade stenoses of 60% or greater diameter reduction. Sixty-one percent of 41 Tessels with less than 10 to 55% diameter redaction had a velocity ratio between 0.8 and 1.5. Only 10% of all ICAs with any stenotic lesion were incorrectly classified as normal. VlCA/VCCA appears to be an accurate Indicator of the degree of ICA stenosis.

Operative versus nonoperative management of asymptomatic high-grade internal carotid artery stenosis: Improved results with endarterectomy

In a 4-year period, 129 asymptomatic high-grade (80-99%) internal carotid artery stenoses were identified in 115 patients. Because we previously demonstrated a strong relation between degree of carotid stenosis and subsequent development of ipsilateral related events (stroke, transient ischemic attack, and carotid occlusion), we changed our previous policy and began to offer carotid endarterectomy to good surgical risk patients referred to us with asymptomatic high-grade carotid stenosis. A total of 56 carotid endarterectomies were performed while 73 lesions were followed nonoperatively. Operated and nonoperated groups were similar with regard to age, prevalence of hypertension, cardiac disease, diabetes, and aspirin use. Life table analysis to 24 months revealed a higher rate of stroke (19 vs. 4%, p = 0.08), transient focal neurologic deficits (28 vs. 5%, p = 0.008), and carotid occlusion (29 vs. 0%, p = 0.003) in the nonoperated group. Eight of the 9 strokes in the nonoperated group occurred within 9 months of diagnosis of the high-grade lesion; none were preceded by a transient ischemic attack. There was 1 perioperative stroke (1.8%) but no in-hospital operative deaths and no difference in the late death rates of the two groups. This suggests that the preservation of neurologic status in patients with asymptomatic high-grade internal carotid artery stenosis can be improved by carotid endarterectomy.

Observer variability in evaluating extracranial carotid artery stenosis.

One hundred twenty eight cervical carotid arteriograms were twice viewed by three readers for the evaluation of atherosclerotic disease at the carotid bifurcation. Stenoses were estimated using calipers to the nearest 5% and lesions were qualitatively characterized as smooth, irregular, or ulcerated. The intraobserver correlation coefficient between estimates of percent stenosis was .94 overall and .98 for the internal carotid artery. The average intraobserver variability in estimating percent stenosis was 5.23% for all vessels and 6.04% with a standard deviation of 8.09% for the internal carotid artery. The intraobserver percent agreement at a fixed stenosis is defined as the percent of the time one reader on two readings would read at least the fixed percent stenosis among cases that might be read as having the fixed percent stenosis. The intraobserver percent agreement rate for the internal carotid artery was 95.9% at greater than 0% stenosis, 90.4% for 50% or greater stenosis, and 96.8% for 100% stenosis (total occlusion). The interobserver correlation coefficient between readers was .92 overall and .97 for the internal carotid artery. The absolute difference in percent stenosis between readers was 7.21% for all vessels and 8.64% for the internal carotid artery with a standard deviation of 9.5%. The interobserver agreement rate for the internal carotid artery at greater than 0% stenosis was 93.0%, 85.4% for 50% or greater stenosis and 96.8% at 100% stenosis. The addition of oblique views had no statistical effect on estimates of percent stenosis but increased the frequency with which irregularity and ulceration were diagnosed in the internal carotid artery.

Carotid artery occlusion: Natural history

During a 5-year period, 212 patients (170 men and 42 women, median age 65 and 64 years, respectively) were diagnosed as having internal carotid artery occlusion. Mean follow-up was 24.9 months. Five-year cumulative survival and stroke-free rates by life-table analysis were 62% and 75%, respectively. Deaths were due to stroke in 7 of 40 patients (17%) and were of cardiac origin in 22 of 40 patients (55%). The strokes were ipsilateral in 20 of 31 patients (65%). No statistically significant difference between the sexes could be demonstrated for either death or stroke, nor was age correlated with stroke during follow-up. Diabetes and hypertension increased the risk of stroke, whereas gender and aspirin consumption had no discernible effect. Endarterectomy of the opposite carotid artery did not significantly affect the natural history but did reduce the stroke rate in the territory of the operated artery. Presenting symptoms were useful for estimating prognosis. Twenty-two of 111 patients referred for stroke (20%) suffered a further stroke and 21 of 111 patients (19%) died (three were stroke-related), whereas of those patients referred for transient ischemic attack (TIA), only 2 of 42 patients (5%) suffered a stroke and none died. TIAs occurred in 23 patients (11%) during follow-up, and these were premonitory for stroke in three cases (13%). The limited value of TIA in predicting stroke and the high mortality rate unrelated to stroke in this group are important considerations when therapy is considered for these patients.

Use of hemodynamic parameters in the diagnosis of mesenteric insufficiency

To evaluate the hemodynamic characteristics of the normal mesenteric circulation, five parameters of the velocity waveforms were measured in 15 normal subjects in the celiac and superior mesenteric arteries (SMA) in the pre- and postprandial periods. It was noted that changes in celiac artery flow after eating was minimal, indicating that this vessels major supply function is not to the gut. SMA parameters showing the most significant and consistent changes after a meal were the diastolic reverse flow and diastolic forward flow (DFF). Four patients referred with symptoms of intestinal angina underwent scanning and subsequent angiography of their mesenteric circulation. All four exhibited loss of reverse flow in the SMA. The change in DFF in the SMA was statistically significant (p = 0.01). Change in peak systolic velocity in the celiac artery was marginally significant (p = 0.05). Angiography revealed that three patients had greater than 90% stenosis of both vessels. The fourth patient had a 90% celiac artery and 65% SMA stenosis. The technique described offers the first noninvasive means of identifying mesenteric insufficiency. It is an effective screening method for a disease entity difficult to verify without selective arteriography. The use of velocity waveform parameters giving good discrimination between normal subjects and those with stenoses of the visceral arteries should reduce both the incidence of missed diagnosis and unnecessary angiography.

Computer based pattern recognition of carotid arterial disease using pulsed Doppler ultrasound

A minicomputer based system has been developed for studying carotid artery blood flow data obtained for a combined B-mode, pulsed Doppler ultrasound scanner. The goals of this work are to devise and improve techniques for estimating the extent of atherosclerosis at the carotid artery bifurcation. Features are automatically extracted from spectrum analyzed Doppler blood flow data. Five statistical pattern recognition algorithms are compared, with cross validation being used to improve the estimate of classification accuracy. A data collection protocol has been devised in which four sites are studied along each carotid arterial system. Classification of unknowns is done using a hierarchy of three decisions.

Immediate and long-term results of carotid endarterectomy.

We review the long-term results of carotid endarterectomy in 200 consecutive patients operated on from 1980 to 1987. The patients were part of an ongoing study using duplex scanning to assess the status of the carotid bifurcation before and after endarterectomy. The average follow-up for the patients was 31 months. The indications for surgery were transient ischemic attacks in 87 (43.5%) and stroke in 36 (18%) patients; 77 patients (38.5%) were asymptomatic. In 176 sides (88%), the degree of stenosis exceeded 50% in terms of diameter reduction. The perioperative stroke rate was 2.3% in patients with transient ischemic attacks, 2.8% in patients with strokes, and 1.3% in asymptomatic patients. There was one perioperative death (0.5%). There were five occlusions of the internal carotid artery, one during the perioperative period and four after discharge; in three patients the occlusion was associated with the development of a stroke. There was a restenosis rate of 19.7% secondary to myointimal hyperplasia; such lesions did not appear to contribute to new ischemic events during or after their development. The mean stroke incidence after the decision was made for carotid endarterectomy was 2.8%/yr in the patients with transient ischemic attacks, 6.2%/yr in the patients with stroke, and 0.65%/yr in the asymptomatic patients. The annual death rate was 6% for the entire group, 5.5%/yr in the patients with transient ischemic attacks, 9.2%/yr in the patients with stroke, and 4.6%/yr in the asymptomatic patients.

Carotid artery intraplaque hemorrhage and stenotic velocity.

Background and Purpose One of the proposed mechanisms for sudden expansion of a carotid bifurcation plaque is hemorrhage within the lesion. It has been postulated that the sudden increase in plaque size will acutely reduce blood flow to the ipsilateral hemisphere and induce either a transient ischemic attack or a stroke. In this study, the relation between peak systolic velocity at the site of narrowing and its potential role in the development of intraplaque hemorrhage were investigated. Methods Ten patients who had carotid endarterectomy were examined by duplex Doppler sonography before surgery to determine the peak systolic velocity at the site of maximal narrowing. The excised carotid plaques were sectioned at 1-mm intervals and examined for histological evidence of intraplaque hemorrhage. The recorded peak systolic velocities in patients with intraplaque hemorrhage were compared with the velocities in cases in which no hemorrhage was identified. Results Five of the ten patients had intraplaque hemorrhage. Four of the five patients with intraplaque hemorrhage had a peak systolic velocity of >420 cm/sec and diastolic velocities of >16 0 cm/sec; none of the patients without intraplaque hemorrhage had such high values. Conclusions Peak systolic velocity is significantly higher in patients with intraplaque hemorrhage. The specificity and sensitivity of a peak systolic velocity of >420 cm/sec in predicting intraplaque hemorrhage remains to be determined.