The Incidence of Popliteal Artery Aneurysms in Patients with Abdominal Aortic Aneurysms

Purpose

We sought to evaluate the incidence of popliteal artery aneurysms (PAAs) in patients who have a diagnosis of abdominal aortic aneurysm (AAA).

Methods

It has been previously documented that patients with AAA have a greater incidence of PAA. During the past 11 years, 163 patients presented to the Vascular Laboratory at Harborview Medical Center with an AAA. Seventy-one (44%) of these patients had popliteal arteries evaluated using duplex ultrasound (Advanced Technology Laboratory 3000, 5000, 9000). The popliteal artery was measured in the anteroposterior and transverse diameters. A PAA was defined as an artery larger than 1.5 cm and/or an ectatic artery with thrombus present.

Results

Fourteen patients had a PAA; six patients (43%) had PAA bilaterally, for a total of 20 aneurysms. Nineteen (95%) aneurysms had thrombus present. Various interventional treatments were used: five limbs (25%) received an arterial bypass graft, two (10%) underwent amputation, and two (10%) received thrombolytic therapy

Conclusions

There is a high incidence of PAA in patients with AAA (19.7% in this series). Patients with a diagnosis of AAA should be screened for PAA and considered for elective repair to prevent the high rate of complications associated with these lesions.

Coagulopathy After Ruptured Abdominal Aortic Aneurysm

Although potentially treatable, coagulopathy is often included among the predictors of a poor outcome after ruptured abdominal aortic aneurysm (rAAA). The purpose of this review was to define the incidence of coagulopathy among patients presenting with rAAA and to identify the factors contributing to its development.

The medical records of 89 consecutive patients presenting with a rAAA were retrospectively reviewed. Laboratory results (international normalized ratio [INR], partial thromboplastin time [aPTT], platelet count, fibrinogen, and fibrin degradation products [D-dimer]) measured on admission and perioperatively were recorded and related to features of the patients' prehospital and hospital course.

At least one admission coagulation study was obtained in 70 of 89 patients. All measured coagulation values were within the normal range in only 10 (14%) patients, whereas at least one value was in the coagulopathic bleeding range in 17 patients (24%). Profound abnormalities of the INR (> 2.0) were present in 24%, of the aPTT (> 60 sec) in 12%, and of the platelet count (< 50) in 7% of patients. In a multivariate model, hematocrit was the only significant predictor of an INR > 2.0, while hematocrit and degree and duration of hypotension predicted an aPTT > 60 sec. Fluid volume prior to admission did not independently predict either the INR or aPTT, although it was the only significant predictor of a platelet count <50. Admission D-dimer levels were elevated in 79% of patients and were not significantly associated with either the degree of hemorrhage or volume resuscitation. All coagulation studies showed deterioration following admission, with profound abnormalities observed in 90% and 52% of patients intraoperatively and postoperatively, respectively. Mortality was 74% among those undergoing operation and was significantly associated with advanced age and lowest systolic blood pressure, but not with admission INR or aPTT.

The majority of rAAA patients present with disordered coagulation, profound abnormalities being more related to the degree of hemorrhage than to the volume of fluid resuscitation. Evidence of intravascular fibrinolysis is even more common and may be more closely related to the aneurysm itself than to acute hemorrhage.

Sequelae of untreated venous insufficiency

Untreated venous insufficiency results not only in a gradual loss of cosmesis but also in variety of complications including persistent pain and discomfort, hemorrhage, superficial thrombophlebitis, and progressive skin changes that may ultimately lead to ulceration. In rare instances, chronic soft tissue changes may lead to stiffness of the ankle joint, fixed plantar flexion, and periostitis. This article reviews the variety of complications caused by venous insufficiency.

Chronic venous insufficiency: clinical assessment and patient selection

Chronic venous insufficiency is a complex condition, with widely varied clinical manifestations, etiologies, and underlying pathophysiology. An orderly workup is mandatory to assess the nature of a patient's underlying venous disease. This begins in the office setting with a careful medical history, physical examination, and bedside diagnostic tests. These are augmented by confirmatory diagnostic testing, including duplex ultrasonography, venography, plethysmography, and ambulatory venous pressure measurement. Based upon the results of these examinations, the patient's venous disease can be classified according to standardized classification schemes, which in turn leads to the selection of an appropriate treatment strategy. This article outlines the steps in the clinical assessment and classification of patients with chronic venous insufficiency.

Failure of peripheral arterial thrombolysis due to elevated plasminogen activator inhibitor type 1

To reduce the risk of intracerebral hemorrhage during thrombolytic therapy, a lower dose of tissue plasminogen activator (t-PA) or urokinase is used for acute peripheral arterial thrombi versus coronary thrombi. We hypothesized that elevated plasminogen activator inhibitor-1 (PAI-1) activity could neutralize infused t-PA or urokinase, resulting in lysis failure. Active PAI-1, active t-PA and total t-PA antigen were measured in 20 patients receiving t-PA, and active PAI-1 was measured in four patients receiving urokinase for acute peripheral arterial thrombosis. The 18 patients that successfully lysed their thrombi all had low active PAI-1 levels (10 +/- 19 pmol/l) during infusion of thrombolytic therapy, while six patients that failed to lyse their thrombi had high active PAI-1 levels (1533 +/- 1384 pmol/l, P = 0.00007) during infusion. Active t-PA levels during t-PA infusion were higher in the group that lysed their thrombi (536 +/- 423 pmol/l versus 42 +/- 45 pmol/l, P = 0.04) even though total t-PA levels were lower (1240 +/- 493 pmol/l versus 1956 +/- 709 pmol/l, P = 0.03). In the patients that failed to lysed their thrombi, > 95% of infused t-PA was neutralized by PAI-1. We conclude that elevated PAI-1 during acute peripheral arterial thrombolysis is associated with an increased risk of lysis failure due to reduced levels of circulating active t-PA or urokinase.

Performance characteristics of the venous clinical severity score

OBJECTIVE

To facilitate study of the natural history and management of venous disease, a 10-component venous clinical severity (VCS) score has been proposed as an objective measure of disease severity. The purpose of this study was to evaluate the validity and reliability of this instrument.

METHODS

VCS component scores (0 to 3) for pain, varicose veins, edema, pigmentation, inflammation, induration, stocking use, and ulcer size, duration, and number were measured in consecutive patients with chronic venous disease. Differences between observers (n = 3) and on serial evaluation by the same observer were determined.

RESULTS

One hundred twenty-eight limbs in 64 patients were evaluated. Mean VCS score increased from CEAP class 0 (1.7 +/- 1.8) to class 6 (14.7 +/- 3.0; R =.84; P <.0001). Scores in 68 limbs evaluated twice by the same observer differed by a mean of only 0.8 (P =.15), with a reliability coefficient of 0.6. Mean scores of 8.0 (+/- 5.1), 7.2 (+/- 5.1), and 8.0 (+/- 5.4) were obtained in 63 limbs evaluated by all three investigators (P =.02). Only the component scores for pain, inflammation, and pigmentation showed significant (P <.05) interobserver variability. Interobserver agreement on the absence of disease or presence of severe disease as defined by scores of 3 or less or 8 or more was good (kappa = 0.59 and 0.65, respectively).

CONCLUSION

The VCS score is a critically needed tool for evaluating changes in venous disease over time. The score is reliable and shows good correlation with CEAP clinical classification.

Seat belt aorta: endovascular management with a stent-graft

PURPOSE

To report the endovascular treatment of a relatively uncommon type of deceleration injury to the abdominal aorta.

CASE REPORT

A 21-year-old backseat passenger was wearing a single lap belt without shoulder harness when the car was involved in a collision. He sustained a transverse (Chance) fracture of the third lumbar vertebra and a circumferential dissection of the infrarenal abdominal aorta with pseudoaneurysm. As an interim measure while a stent-graft was obtained, a Wallstent was deployed to tack down the dissection and prevent distal embolization. Thirty-six hours later, an AneuRx endograft was successfully implanted inside the Wallstent to seal the pseudoaneurysm. The patient's recovery was uneventful, and the endograft remains secure and the pseudoaneurysm excluded at 10 months after the accident.

CONCLUSIONS

Endovascular repair of "seat belt aorta" is a minimally invasive, straightforward method of management for this type of aortic injury. The potential for infection in a contaminated peritoneal cavity and the long-term outcome of this treatment have not been determined.

Predicting death from ruptured abdominal aortic aneurysms

BACKGROUND

We have previously reported preoperative and immediate postoperative formulae to estimate mortality in patients with ruptured abdominal aortic aneurysms (rAAA). In this study, we prospectively compared these formulae in patients with rAAA with their actual outcomes.

METHODS

Information was collected on 134 patients from two centers over a 3-year period. Preoperative mortality risk was estimated using coefficients for age, level of consciousness, and cardiac arrest. Mortality risk in the immediate postoperative state was based on the presence of coagulopathy, ischemic colitis, prolonged requirement for inotropes, time from arrival at hospital to surgery, patient age, perioperative myocardial infarction, renal failure, and pre-operative hemoglobin level.

RESULTS

The average age was 73 years (range 30 to 92 y) and 20 of 134 (15%) patients were women. Sixty-three patients (47%) survived. For patients with a calculated preoperative mortality risk of >90%, the sensitivity, specificity, and positive and negative predictive values were 25%, 98%, 95%, and 54%, respectively. For a mortality risk >80%, these values were 37%, 94%, 87%, and 57%, respectively. For patients with an estimated immediate postoperative mortality risk > or = 90%, the sensitivity, specificity, and positive and negative predictive values were 17%, 87%, 60%, and 49%, respectively. For a predicted mortality > or = 80%, these values were 22%, 84%, 60%, and 50%, respectively.

CONCLUSIONS

Our formula for predicting mortality for preoperative rAAA patients may be useful for patients with an estimated mortality risk >/=90%, based on the high positive predictive value. The formula for immediate postoperative rAAA patients was not useful in predicting death.

Peripheral arterial embolization: Doppler ultrasound scan diagnosis

Use of intraoperative monitoring with transcranial Doppler scanning during carotid endarterectomy has enabled identification of embolus signals in the ultrasound spectrum. Extension of this technique to preoperative screening has enabled identification of actively embolizing lesions and correlation with neurologic deficits. We report embolus signals in the peripheral circulation before operation, which aided diagnosis and decision to operate. The patient had been transferred from another institution after multiple revascularization procedures, including posterior tibial artery thrombectomy. Angiography performed on arrival at our institution confirmed an open bypass graft, although a small indentation was noted at the site of the previous posterior tibial artery thrombectomy. Runoff was intact to the plantar arch where there was attenuation of that vessel and occlusion of most digital branches. Duplex monitoring revealed no embolic signals in the graft or in the posterior tibial artery proximal to the previous arteriotomy. Distal to this site, embolic signals were detected. At the time of operation, a large platelet thrombus was identified at the site of the previous arteriotomy, and platelet thrombus was obtained from the plantar artery. It is concluded that doppler ultrasound scanning enables detection of peripheral embolization and the identification and location of lesions with such embolic activity. Diagnostic accuracy may be improved when there is clinical suspicion of embolization, enabling better patient selection for surgical procedures. This report provides the first clinicopathologic characterization of the emboli detected.

Management of aortobronchial fistula with an aortic stent-graft

Aortobronchial fistula presenting as massive hemoptysis is a rapidly fatal process that is extremely difficult to manage. We report a case in which endovascular occlusion of a fistula between a thoracic aortic pseudoaneurysm and lung was successfully managed by placement of an aortic endovascular stent-graft. Stent-grafting is a promising technique in managing complications of thoracic aneurysms and grafts.

Rupture in small abdominal aortic aneurysms

BACKGROUND

The decision of whether to repair small abdominal aortic aneurysms (AAAs), which are those that are less than 5 cm in diameter, remains controversial.

METHODS

We describe 161 consecutive patients who were seen at a single urban hospital with ruptured AAAs (rAAAs) and in whom aneurysm size was measured with ultrasound scanning, or rarely computed tomography, en route to the operating room. Eleven patients (6.8%) had AAAs that measured less than 5.0 cm. This group was compared with 150 patients who had rAAAs that were more than 5 cm.

RESULTS

The mortality rates were similar in both of the groups 70% for small rAAAs versus 66% for large rAAAs. No significant differences were seen between the patients with small and large ruptured aneurysms with respect to the prevalence rates of hypertension (60% vs 50%) or of cardiac disease (20% vs 22%). However, the prevalence rate of obstructive lung disease was significantly different (64% vs 25%; P =.02) as was the rate of diabetes (28% vs 3%; P =.004). Five aneurysms were measured at exactly 5 cm. This suggests that approximately 10% of all aneurysms that rupture in this series do so at 5 cm or less.

CONCLUSION

In view of the safety of elective repair as compared with the prohibitive risk associated with aneurysm rupture, patients who are at good risk with small AAA (between 4 and 5 cm) should be considered for elective aneurysm resection. For unclear reasons, obstructive lung disease and diabetes are associated with a significantly greater risk for rupture of small AAA. Patients with these risk factors should be given special consideration.

Venous thromboembolism: detection by duplex scanning

PURPOSE

The usefulness of transcranial Doppler monitoring in identifying emboli in the arterial circulation has been established. We attempted to extend this technique to identify embolism in the venous circulation and to note any changes in embolism rate with anticoagulation.

METHODS

From March to July 1993, 218 patients were evaluated by duplex scan for deep venous thrombosis.

RESULTS

Sixty patients had positive study results; 26 scans (43%) demonstrated embolism. In five patients (19%) the emboli were also seen on a B-mode image, enabling us to estimate embolus size, which ranged from 200 to 5000 micrometer. Embolus counts varied from 5 to 800 per minute. Deep venous thrombosis was located in the iliofemoral vein in 2 patients, superficial femoral/profunda vein in 8, saphenofemoraal junction in 1, popliteal vein in 1, and the calf in 10. Concomitantly, studies in 158 patients were negative for deep venous thrombosis; embolism was detected in 4 patients (3%) in this group. In patients taking heparin, the embolus counts decreased 50% or more within 24 hours, and all embolism was abolished within 72 hours. Two patients died of pulmonary embolus.

CONCLUSIONS

Patients with duplex scans that are positive for deep venous thrombosis have a high incidence of ongoing embolism. Heparin appears effective in eliminating the microemboli detected. The relationship among microembolism, deep venous thrombosis, and clinically significant pulmonary embolism remains to be elucidated.

Transcranial Doppler and angiographic findings in adolescent stretch syncope

The clinical, angiographic, and Doppler findings are reported for two young patients with recurrent syncope induced by neck hyperextension during stretching. Transcranial Doppler monitoring of both posterior cerebral arteries was performed during head manoeuvres. There were reproducible rapid decreases in blood flow velocities in both patients to an average of 28% and 41% of baseline values when they performed neck hyperextension. These decreases were regularly associated with the patients' symptoms and were not found during rotation or flexion. On return to a neutral head position there was a transient increase of the blood flow velocities to an average of 131% and 136% of baseline values (reactive hyperaemia). Routine four vessel angiography was normal except for the demonstration of very small posterior communicating arteries in one patient. Dynamic angiography showed evidence of extracranial compression of the craniocervical arteries in both patients. It is concluded that decreased blood flow to the posterior circulation is an important factor in the pathogenesis of adolescent stretch syncope.

Iliofemoral venous thrombosis following fascial excision of a deep burn of the lower extremity: case report

Burned patients with deep venous thrombosis present a particularly perplexing challenge. They frequently require central venous catheters. Their altered skin integrity does not permit correlation with the typical changes described by the classic terminology for thrombophlebitis or its most severe forms, phlegmasia cerulea dolens or phlegmasia alba dolens. They are at risk of exsanguination or massive graft loss with lytic therapy or anticoagulation. Venous thrombectomy may be a necessary limb-saving surgical option.

Flow separation in the carotid bulb: prognostic significance

It has been previously shown that boundary layer or flow separation occurring in the carotid bulb and detected by duplex scanning denotes minimal or no carotid atherosclerotic disease as demonstrated by angiography and reliably predicts aetiology other than carotid artery disease in symptomatic patients. To evaluate outcome at long-term follow-up we prospectively studied 94 patients (48 males, 46 females) who demonstrated bilateral flow separation. Mean age was 61.2 years (27 to 86 years). Mean follow-up was 57 months (5 to 113 months). There was one death during follow-up at 69 months. It was stroke related. Using age and sex specific death rates for the general population 14.3 deaths would be expected for the same average period. By life table analysis, survival was 98.7% at five years compared to a general population expected 5 year survival of 85.9%. There were no strokes at 5 years of follow-up. (Age and sex specific stroke-free survival for Rochester, MN 1970-1974 is 98% at 5 years). TIA-free survival was 99% at one year (n = 87) and 96% at five years (n = 46). It is concluded that the presence of boundary layer separation in the carotid bulb not only indicates absent or minimal atherosclerotic disease, but is predictive of a favourable long-term outcome with respect to mortality and neurological events.

Proteolytic processing of the Plasmodium falciparum merozoite surface protein-1 produces a membrane-bound fragment containing two epidermal growth factor-like domains

The amino-terminal sequence has been obtained for 2 fragments of the Plasmodium falciparum T9/94 merozoite surface protein precursor (PfMSP1) and these have been compared with the sequence predicted from the gene. These data define the position of these fragments in the precursor and indicate that the C-terminal sequence which is carried into the red cell during invasion consists of 2 epidermal growth factor (EGF)-like domains. A homologous cleavage sequence and domain structure can be identified in the MSP1 molecules of other malarial species. In addition the results suggest that the smaller fragment is not N-glycosylated.

Clinical significance of retrograde flow in the vertebral artery

Although retrograde vertebral artery flow was described over 100 years ago, its relationship to symptoms remains unclear. We documented 43 patients who were found by duplex scanning to have reverse flow in the vertebral artery. Of this group, seven patients (16%) were found to have symptoms described as typical for the "subclavian steal" syndrome. Nearly one-third were asymptomatic. Of the remaining patients, 13 (30%) presented with nonhemispheric symptoms while nine (21%) had hemispheric symptoms. Nine patients had "to and fro" flow in the vertebral artery. This variant was not found in subclavian steal patients but correlated with nonhemispheric symptoms. During follow-up (mean: 19 months) none of the asymptomatic patients became symptomatic, and there were no strokes or stroke-related deaths. Surgical procedures which restored antegrade vertebral artery flow did not necessarily improve symptoms of posterior circulation ischemia. In some patients improvement in posterior circulation symptoms was noted following carotid endarterectomy. It is concluded that retrograde flow in the vertebral artery is, per se, a benign entity. Accurate selection of surgical candidates remains imprecise. It will require not only identification of vertebrobasilar disease but as yet undefined tests to assure symptoms are due to these stenoses.

Ruptured abdominal aortic aneurysm: the Harborview experience

During the last decade (1980 to 1989) 186 patients with ruptured abdominal aortic aneurysm were admitted to a single urban hospital. Ninety-six percent of these patients had a prehospital systolic blood pressure less than 90 mm Hg. Management included paramedic field resuscitation and transport, an emergency department diagnostic protocol completed in an average of 12 minutes, rapid transport to a dedicated emergency operating room, aneurysmorrhaphy by general surgery chief residents under the supervision of specialist vascular surgeons, and skilled postoperative intensive care unit care. Nevertheless, 130 (70%) patients died in the first 30 postoperative days--3% in the emergency department, 13% in the operating room, 51% in the intensive care unit, and 3% on the ward or at home. Certain features--age greater than 80 years, female gender, persistent preoperative hypotension despite aggressive crystalloid and blood replacement, admission hematocrit less than 25, transfusion requirements exceeding 15 units--were associated with a greater than 90% likelihood of death. No patient with preoperative cardiac arrest survived more than 24 hours. From this experience we conclude that, although "optimal" prehospital, emergency department, operating room, and postoperative care can improve the outcome of patients with ruptured abdominal aortic aneurysms in shock, most such patients will die. Certain clinical features predict such excessive mortality rates after ruptured abdominal aortic aneurysms that withholding operation may be reasonable. Screening of patients at high risk for abdominal aortic aneurysm, followed by elective aneurysmorrhaphy, is clearly indicated.

Detection of middle cerebral artery emboli during carotid endarterectomy using transcranial Doppler ultrasonography

The purpose of our study was to define the signal characteristics and clinical circumstances associated with emboli detected in the middle cerebral artery using 2-MHz pulsed transcranial Doppler ultrasound in patients undergoing carotid endarterectomy. Signals designating emboli were transients displaying harmonic qualities the signatures of which were clearly different from those of mechanical and electronic artifacts. We reviewed the audio/video tape recordings from 91 patients for signals of air bubble emboli occurring upon release of common carotid artery crossclamps; recordings from 35 patients (38%) demonstrated air bubble emboli. Transients with signatures identical to those of air bubble emboli were also discovered when bubbles in the bloodstream were improbable; we defined these transients as representing formed-element emboli. Such signals were found in recordings from 24 patients (26%), and they occurred before (both spontaneously and upon common carotid artery compression), during, and after surgical dissection. Signals indicating formed-element emboli were associated with intraluminal platelet thrombus, with ulcerations in the carotid artery, and with transient ischemic attacks or stroke. Most postoperative formed-element emboli did not cause symptoms but, when persisting for hours, they were associated with strokes and cerebral infarction. This Doppler ultrasound method of detecting emboli will be useful in the study of stroke mechanisms and as a clinical test to guide the medical and surgical treatment of patients at risk of stroke.

Concurrent Monitoring of Brainstem Auditory and Somatosensory Evoked Potentials During Carotid Endarterectomy

Intraoperative management of a 68-year-old man with a 3-month history of presyncopal attacks presenting for left carotid endarterectomy is reported. Preoperative angiograms revealed that the patient had a 90% stenosis of his left internal carotid artery and a 35% stenosis of right internal carotid artery, absent posterior communicating arteries, a totally occluded left vertebral artery, and a right vertebral artery that became compressed upon turning his head to the right, often precipitating the presyncopal attacks. The surgical procedure was managed with intraoperative monitoring of both brainstem auditory and somatosensory evoked potentials. The patient had an uneventful outcome. The anesthetic management is discussed.

Intimal fibromuscular hyperplasia at the venous anastomosis of PTFE grafts in hemodialysis patients. Clinical, immunocytochemical, light and electron microscopic assessment

Failure of arteriovenous communications used for chronic hemodialysis was studied during sequential 5-year periods after placement of either endogenous Brescia-Cimino (B-C) fistulas (50 patients) or polytetrafluoroethylene (PTFE, Gore-Tex) grafts (66 patients). Venous stenosis near the anastomosis was the reason for failure in 45% of PTFE grafts compared with 16% of B-C fistulas (p less than 0.001). Failure occurred, on average, 16 months after PTFE graft placement compared with 22 for B-C fistulas (p = NS). Proximal vein segments removed from five failed and two functioning PTFE graft communications were studied using light and electron microscopy and immunocytochemical techniques. All venous segments removed during surgical shunt repair exhibited a marked intimal hyperplasia. The intimal cellular component was almost exclusively smooth muscle. Accumulation of intracellular lipid droplets was not seen. Foam cells as well as extracellular lipid deposits were absent; macrophages and lymphocytes were absent from the zone of proliferation. Ultrastructural examination revealed a large proportion of extracellular matrix surrounding smooth muscle cells in the neointima. Collagen and elastin were present in the extracellular matrix, in greatest concentration deeper in the intima. Closer to the lumen, most of the extracellular volume consisted of proteoglycan. Hemosiderin was absent from the lesions as were consistent signs of luminal and intimal fibrin. Uniform intimal gradients of actin, collagen, and proteoglycan suggest that this is a steadily progressive, rather than episodic, proliferative response. These clinical and histologic observations and an analysis of hemodynamic stresses support the postulate that upstream release of platelet-derived growth factor, and possibly, shear-induced intimal injury stimulate this response. This myointimal proliferative process provides a readily accessible model of fibromuscular hyperplasia in humans; its understanding may lead to effective methods for its prevention and may provide clues to the pathogenesis of arteriosclerosis.

Long-term follow-up and clinical outcome of carotid restenosis

The efficacy of carotid endarterectomy is dependent on the inherent ability of the operation to prevent stroke as well as the incidence of restenosis and associated symptoms. To examine the long-term effects of restenosis, 301 patients having carotid endarterectomy were followed by serial duplex scanning for an average of 4 years. Carotid restenosis, defined as 50% or greater diameter reduction by duplex scanning, occurred after 78 of the endarterectomies; regression of recurrent stenosis occurred in 20 arteries. By life-table analysis the cumulative incidence of restenosis at 7 years was 31%, and the cumulative incidence of regression was 10%. Thus the prevalence of recurrent stenosis at 7 years was 21%. Restenosis developed in women more frequently than men (p = 0.01). Transient ischemic attack occurred in 12% of patients with restenosis, and stroke occurred in 3%; however, the cumulative incidence of stroke or transient ischemic attack was not statistically different in those patients with and without restenosis. Similarly, cumulative survival at 7 years was no different. Carotid restenosis usually occurs early in the postoperative period and tends to regress or remain stable during long-term follow-up. A conservative approach to treatment appears justified, since transient ischemic attacks and stroke were rarely associated with restenosis.

Neurologic sequelae of unilateral carotid artery occlusion: immediate and late

Over a 7-year period (1980 to 1987) 24 patients (18 men: mean age 67 years; range, 52 to 78 years, and six women: mean age 67 years; range, 46 to 82 years) undergoing serial carotid artery duplex scans were observed to progress to unilateral carotid artery occlusion. The occlusions were associated with ipsilateral strokes in six (25%), ipsilateral transient ischemic attacks in four (16%), and the onset of nonhemispheric symptoms in one (5%). Thirteen patients had no symptoms. Follow-up ranged from 4 months to 96 months (mean 39.4 months). Late neurologic events comprised two strokes, three transient ischemic attacks and the onset of nonhemispheric symptoms in six, which in some were disabling. Thirteen patients had no symptoms. Three deaths occurred (one was stroke related). For late events by life-table analysis, the average annual rate over the first 2 years for stroke was 10% and for transient ischemic attack 13%. The combined rate for transient ischemic attack and stroke was 20% per annum. For nonhemispheric symptoms the rate for the first year was 31%. It is concluded that unilateral carotid artery occlusion is associated with an unacceptable incidence of immediate neurologic sequelae and that such patients continue to have a high rate of late neurologic deficits at follow-up. Therefore it seems appropriate that patients who are observed to progress to high-grade stenosis and are therefore at risk for immediate occlusion should undergo prophylactic carotid endarterectomy.

Cloning and expression of a trypomastigote-specific 85-kilodalton surface antigen gene from Trypanosoma cruzi

An 85-kDa trypomastigote-specific surface antigen gene from Trypanosoma cruzi has been identified by screening a genomic library in lambda gt10 with trypomastigote and epimastigote cDNA. The 1.3-kb genomic clone (pTt34) hybridizes to a single trypomastigote mRNA of 3.7 kb and to multiple bands in genomic Southern blots. Dot-blot experiments show that there are 5-10 copies of this sequence per haploid genome, and these are arranged in a non-tandem manner. pTt34 has been expressed as an anthranilate synthetase fusion protein in Escherichia coli, and inclusion bodies have been used to raise antiserum in rabbits. This antiserum immunoprecipitates a cell surface trypomastigote-specific protein of 85 kDa. The DNA and predicted amino acid sequences of pTt34 are given. Four further clones obtained from a PvuII/HpaI partial genomic library in pUC13 have extended the sequence of the 3' end of pTt34; each of these clones has regions of sequence divergence and each could represent a different member of the gene family.

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.

Management of internal carotid artery occlusion

Although attempts to restore patency of occluded internal carotid arteries are now rarely made, endarterectomy in the contralateral artery, external carotid endarterectomy and until recently EC/IC bypass have remained surgical options in the management of such patients. Over a four-year period at this institution 104 patients underwent carotid endarterectomy for stenosis. In this group the contralateral carotid was patent (Group A). Fifty-four patients with unilateral carotid artery occlusion underwent contralateral endarterectomy (Group B), 8 underwent ECA/ICA bypass (Group C) and 4 an ECA endarterectomy (Group D). No statistically significant difference was noted in perioperative stroke and death rates for Groups A and B were (1% and 1%) and (3.7% and 1.9%) respectively. One Group C patient died from perioperative stroke (12.5%). For late events the life table adjusted annual rates for stroke and mortality were similar, Group A (stroke 2.1% and death 5%), and Group B (stroke 1.6% and death 5%). In Group C stroke rate was 10% and death 3%. All four patients undergoing ECA endarterectomy were relieved of their symptoms. It is concluded that in patients with internal carotid artery occlusion TEA may be performed with perioperative morbidity and mortality rates comparable to those when the opposite carotid artery is patent. The late outcome for stroke compares favorably with the reported natural history of the disease and outcome for such patients treated medically in the Joint Study of Extracranial Occlusion and EC-IC Bypass Study. External carotid artery endarterectomy appears useful in the treatment of embolic events on the occluded side. ECA/ICA bypass does not appear to confer benefit.

Diagnostic significance of flow separation in the carotid bulb

Pulsatile blood flow within the normal carotid sinus involves at least two distinct components. That near the flow divider is laminar and antegrade, whereas a boundary layer separation zone in the posterolateral aspect exhibits transient blood flow reversal. It is now possible to document these flow velocity components using pulsed Doppler ultrasound methods. When atherosclerosis develops, it preferentially involves the posterolateral bulb region, obliterating the normal configuration of the sinus with consequent loss of the flow separation zone. It was therefore hypothesized that if flow separation could be detected, it should be predictive of a normal angiogram. To assess this, we evaluated 20 symptomatic patients and two with only bruits found by duplex scanning to have flow separation in either one or both carotid bulbs and who also underwent cerebral angiography. Initial diagnoses were stroke in seven, reversible ischemic neurologic deficit in one, transient ischemic attack in 12, and bruit in two. Flow separation was bilateral in 13 patients (59%). There were 15 patients with symptoms in the territory of a carotid bulb exhibiting flow separation. By angiography, of the 35 bulbs with boundary layer separation, 27 (77%) were normal, with the remainder showing lesions that reduced the diameter of the vessel by 20% or less. Final diagnoses of the 15 patients with symptoms ipsilateral to a carotid sinus exhibiting flow separation were fibromuscular disease in two, lacunar stroke in three, dissection in two, subclavian steal in one, cardiogenic embolus in three, migraine in one, hyperventilation syndrome in one, kink of the mid-internal carotid artery in one, and no diagnosis in one.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunization against Plasmodium falciparum with recombinant polypeptides produced in Escherichia coli

Two proteins produced in recombinant Escherichia coli and containing amino acid sequences from the Plasmodium falciparum precursor to major merozoite surface antigens (PMMSA) have been partially purified. These proteins, together with a preparation of merozoites, have been used to immunize animals. The antibody response and the degree of protection were compared. Animals immunized with merozoites produced antibodies reacting with many P. falciparum proteins, whereas a response specific for PMMSA was detected in those receiving the recombinant material. Incomplete protection was conferred to both groups and there was no apparent correlation between antibody levels and protection.

An S antigen gene from Plasmodium falciparum contains a novel repetitive sequence

The complete sequence of the gene coding for the S antigen from the Wellcome (West African) strain of Plasmodium falciparum has been obtained. It contains a central repetitive region consisting of 65 copies of a partially degenerate 24 bp sequence, coding for a conserved 8 amino acid repeat (Gly Pro Asn Ser Asp Gly Asp Lys). The repeat sequence is different from those of S antigens characterised in other strains and thus represents a new S antigen serotype.

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.

Assessment of pressure gradient by Doppler ultrasound: experimental and clinical observations

Three methods for estimating peripheral artery pressure gradients from ultrasound data were assessed by means of an acute canine aortic coarctation with a variable stenosis and retrospective data from 18 patients with iliac stenoses who had duplex scanning studies and pressure measurements at the time of angiography. The measured pressure difference was correlated with end-diastolic velocity, the presence or absence of reverse flow in diastole, and a pressure difference calculated with the modified Bernoulli equation. Although the calculated pressure gradients correlated well with measured values in animal studies (11 animals, r = 0.78, n = 224, SD = 8.1), they did not in the clinical studies (r = 0.54, n = 33, SD = 28). In both cases, pressure gradients were consistently overestimated for mild stenoses. There was a strong correlation between end-diastolic velocity and pressure gradient (r = 0.71, n = 94, SD = 5.2 for animal studies; r = 0.81, n = 36, SD = 23 for clinical studies), but the data were too variable to provide useful pressure estimates. In clinical studies the absence of reverse flow in diastole at the site of the stenosis was the best indicator of a resting pressure gradient of greater than 15 mm Hg. We conclude that the modified Bernoulli equation and end-diastolic velocity correlate highly with the pressure gradient but are not clinically useful because the variability is too great. The absence of reverse flow in diastole is a more reliable indicator of hemodynamically significant stenosis.

Processing of the precursor to the major merozoite surface antigens of Plasmodium falciparum

Specific sequences derived from the gene for the precursor to the major merozoite surface antigens (PMMSA) of Plasmodium falciparum have been expressed in Escherichia coli and the products have been used to produce antibodies. These antibodies, together with monoclonal antibodies, have been used to investigate the form of the PMMSA protein associated with merozoites. Polypeptide fragments derived by processing from the PMMSA protein have been detected in extracts of merozoites and assigned to locations within the PMMSA coding sequence.

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.

Noninvasive diagnosis of renal artery stenosis by ultrasonic duplex scanning

We retrospectively studied the results of duplex scanning for evaluation of renal artery disease in 158 patients. Satisfactory examinations were achieved in 144 patients (90%). Arteriograms were available for 43 renal arteries. We used the ratio of the peak velocities in the renal artery and the aorta (RAR) to separate nonstenotic arteries (less than 60% diameter reduction) from stenotic arteries (greater than 60% diameter reduction). With an RAR of greater than 3.5 to indicate stenotic lesions, duplex scanning had a sensitivity of 91% (20 of 22 diseased arteries correctly identified) and specificity of 95% (20 of 21 normal or insignificantly diseased arteries correctly identified). One of four occluded arteries was incorrectly interpreted as patent because of misidentification of a collateral vessel. Prospective studies will be necessary to validate this test and establish other criteria for a more detailed classification of renal artery stenosis. The ratio of the end-diastolic to peak systolic velocities in the renal artery (EDR) tended to decrease with increasing serum creatinine levels, presumably because renal vascular resistance increases with end-stage parenchymal disease. EDR may prove useful in the detection of advanced parenchymal disease before renal artery revascularization is attempted.

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 vessel's 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.

Diastolic flow as a predictor of arterial stenosis

With a pulsed Doppler imaging system, it is now possible to interrogate sites from the aorta to the popliteal trifurcation. To determine which velocity parameters could be correlated with the degree of disease as determined by angiography, 34 arterial stenoses identified by scanning were also evaluated by contrast arteriography and classified in 10% increments. The angiographic readings were blinded with respect to the scan results. Four hand-measured parameters from velocity waveforms obtained at the site of stenosis were correlated with the angiogram--peak systolic velocity, systolic rise time, diastolic reverse velocity, and diastolic reverse flow time. When diastolic reverse flow was absent, diastolic forward flow was recorded. To describe diastolic flow along a continuum, diastolic reverse velocity was ascribed a positive value and diastolic forward velocity was ascribed a negative value. A systolic velocity gradient (peak velocity/rise time) was also calculated. The relationship between the angiographic categories and the measured parameters was evaluated with the Jonkheere-Terpstra trend test. A trend was determined with diastolic flow (diastolic reverse flow or diastolic flow velocity) that was significant (p less than 0.01). The linear regression was calculated (y = 40.8 + [-5.6X]), and correlation coefficient was obtained (r = 0.76) that was statistically significant (p less than 0.01). The method enables mapping and calculation of arterial stenoses by noninvasive means. This can be expected to obviate the need for diagnostic angiograms in certain and select cases in which angioplasty can be expected to be beneficial. It also affords a convenient quantitative means of following lesions over time.