Management of carotid restenosis.

Carotid endarterectomy is the preferred method for cerebral revascularization in patients with symptomatic and asymptomatic high-grade extracranial carotid artery stenosis. Carotid artery stenting has recently emerged as a less invasive alternative to endarterectomy. Carotid stenting has been demonstrated to be technically feasible and safe in high-risk patients with current data indicating clinical equipoise with respect to endarterectomy. It is clear that carotid stenting will continue to be performed at increasing rates after these encouraging outcomes. Therefore, it is anticipated that there will be a corresponding increase in the number of in-stent restenosis cases. Considerable controversy exists regarding the clinical significance, natural history, threshold for management, and appropriate intervention of recurrent carotid stenosis after endarterectomy and after stenting. This review analyses current information on this important clinical problem and presents evidence-based recommendations for the diagnosis and management of recurrent carotid stenosis.

A comparison of cilostazol and pentoxifylline for treating intermittent claudication.

PURPOSE: We performed a randomized, double-blind, placebo-controlled, multicenter trial to evaluate the relative efficacy and safety of cilostazol and pentoxifylline. PATIENTS AND METHODS: We enrolled patients with moderate-to-severe claudication from 54 outpatient vascular clinics, including sites at Air Force, Veterans Affairs, tertiary care, and university medical centers in the United States. Of 922 consenting patients, 698 met the inclusion criteria and were randomly assigned to blinded treatment with either cilostazol (100 mg orally twice a day), pentoxifylline (400 mg orally 3 times a day), or placebo. We measured maximal walking distance with constant-speed, variable-grade treadmill testing at baseline and at 4, 8, 12, 16, 20, and 24 weeks. RESULTS: Mean maximal walking distance of cilostazol-treated patients (n = 227) was significantly greater at every postbaseline visit compared with patients who received pentoxifylline (n = 232) or placebo (n = 239). After 24 weeks of treatment, mean maximal walking distance increased by a mean of 107 m (a mean percent increase of 54% from baseline) in the cilostazol group, significantly more than the 64-m improvement (a 30% mean percent increase) with pentoxifylline (P <0.001). The improvement with pentoxifylline was similar (P = 0.82) to that in the placebo group (65 m, a 34% mean percent increase). Deaths and serious adverse event rates were similar in each group. Side effects (including headache, palpitations, and diarrhea) were more common in the cilostazol-treated patients, but withdrawal rates were similar in the cilostazol (16%) and pentoxifylline (19%) groups. CONCLUSION: Cilostazol was significantly better than pentoxifylline or placebo for increasing walking distances in patients with intermittent claudication, but was associated with a greater frequency of minor side effects. Pentoxifylline and placebo had similar effects.

Operative confirmation of Doppler ultrasound in evaluation of intestinal ischemia.

The prediction at operation of viability of ischemic intestine frequently is difficult and has resulted in recommendations for reoperation to assess intestine of questionable viability. This report describes the use of the Doppler ultrasonic flowmeter in three patients with ischemic intestine caused by acute superior mesenteric arterial thrombosis. Reliability of the Doppler technique was confirmed at second-look operations in each patient.

Fibromuscular dysplasia of the internal carotid arteries.

Seven patients with fibromuscular dysplasia of the internal carotid arteries have been operated upon at Walter Reed Army Medical Center. One lesion was treated by graduated dilatation with Bake's dilators combined with resection, end-to-end anastomosis, and vein patching of a tortuous segment. All other lesions were treated by graduated dilatation with an arterial dilator-shunt. All of these patients are asymptomatic presently. One patient has been operated upon recently because of symptoms related to the previously unoperated side as well as mild symptoms related to the previous operation. Two other patients with arteriographic evidence of fibromuscular dysplasia are being followed clinically. One is asymptomatic and one has minimal symptoms. Both are being treated with acetylsalicylic acid in hopes of preventing microembolization from these lesions. Important technical considerations in treating this condition are meticulous dissection of the internal carotid artery as near to the base of the skull as possible, confining the arteriotomy to the region of the carotid bulb, and straightening the carotid artery while passing the dilator under direct vision. A technique for routine shunting in these patients now is available.

Regional hemodynamics of large and small femoral arteriovenous fistulas in dogs.

Alterations in regional hemodynamics were determined after construction of side-to-side femoral arteriovenous fistulas in dogs to quantitate the relationship between fistula size and reversal of distal arterial blood flow. When fistula size exceeded the transverse diameter of the femoral artery and vein (large fistula group), reversal in distal arterial blood flow was observed in all fistulas and measured 48 +/- 7 ml. per minute. If the fistula size were approximately equal to these critical transverse diameters (small fistula group), distal arterial flow was reduced but reversal did not occur. Distal arterial and venous pressures were 42 +/- 5 and 35 +/- 4 mn. Hg, respectively, for the large fistula group, and these pressures were 79 +/- 5 and 17 +/- 2 mn. Ht, respectively, for the small fistula group. These pressure changes for the two groups were significantly different and may provide a better understanding of the physiology of the reversal phenomenon.

The effect of microaggregates in stored blood on canine pulmonary vascular resistance.

Microaggregates have been implicated as a contributory cause of respiratory distress syndrome. Blood flow and resistance changes are compared between the right and left lungs following the selective administration of stored autologous heparinized blood into the left pulmonary artery. Eight dogs were bled 1,160 +/- 47 c.c. over 3 days. Following storage for 5 days the volume, number and size of microaggregates were measured by multichannel particle size analyzer and compared to 14-day-old human blood. Distribution of blood flow and resistance were calculated from data derived from injection of radioactively tagged microspheres into the right atrium and determination of cardiac output and pulmonary artery and wedge pressures. These measurements were made during a control period, following resuscitation from a 2 hour hemorrhagic shock period with the stored blood and 3 hours after resuscitation. Despite the administration of stored blood with massive amounts of microaggregates into the left pulmonary artery, the distribution of blood flow immediately and 3 hours following resuscitation was the same as in the control period. The pulmonary vascular resistance increased across both lungs but the increase was the same on the left as the right. These data suggest that microaggregates may not be important in the development of the respiratory distress syndrome.

Hemodynamic effects of intra-arterial injection of drugs of abuse.

Acute vascular insufficiency following intra-arterial injection of a variety of drugs has been recognized for many years. The present study addresses the hypothesis that this vascular insufficiency may be due to vasospasm. Intra-arterial injections of logarithmic doses of drugs of abuse from the barbiturate, narcotic, non-narcotic analgesic, and amphetamine groups were studied in baboons. All drugs except amphetamine produced significant increases in femoral flow. Dextroamphetamine produced insignificant alteration in flow. Solid excipients, cornstarch, and talcum powder when injected intra-arterially decreased flow, and vascular obstruction was shown angiographically. These data suggest that vasospasm is not a primary response of intra-arterial injection of drugs of abuse.

Adrenergic mechanisms in the cephalic and cerebral circulations of the subhuman primate.

Effects of circulating adrenergic amines on the cerebral circulation remain contraversial. Common carotid (CCF) and internal carotid (ICF) arterial flows were determined electromagnetically in eight lightly anesthetized baboons to evaluate alterations in the cephalic and cerebral vascular beds, respectively. Epinephrine (E), norepinephrine (NE), phenylephrine (PE), and isoproterenol (I) were injected randomly in doses of 10-3, 10-2, 10-1, and 1 mug (base) per kilogram into each carotid artery. Measurements were repeated in four animals after alpha-adrenergic blockade with phenoxybenzamine and in another four animals after beta-adrenergic blockade with propranolol. Baseline CCF was 75 plus or minus 10 (S.E.M.) ml. per minute and ICF was 58 plus or minus 8 ml. per minute. Significant (p smaller than 0.05) CCF changes without arterial pressure alterations occurred with 10-1 mug per kilogram doses. Alpha blockade significantly (p smaller than 0.05) attenuated the effects of E, NE, and PE on CCF while beta blockade significantly (p smaller than 0.05) attenuated the effect of I on CCF. ICF did not change significantly (p greater than 0.05) after injection of any of the vasoactive amines, unless associated with pressure changes at the highest dose. Our data suggest the presence of alpha- and beta-adrenergic receptor sites within the cephalic circulation resulting in significant flow responses to intra-arterial adrenergic amines. The absence of responses in the cerebral circulation suggests that circulating catecholamines do not significantly influence or regulate the cerebral vasculature. In addition the data suggest that use of adrenergic agonists to alter the hemodynamics of the cerebral circulation is limited.

Traumatic arteriovenous fistulas and false aneurysms: a review of 558 lesions.

Through the Vietnam Vascular Registry which was established in 1966 at Walter Reed Army Medical Center, copies of medical records of 509 combat casualties with 558 arteriovenous fistulas and false aneurysms have been analyzed. This represents approximately 7 percent of the vascular injuries in American casualties from Southeast Asia, from 1963 to 1972, which are included in the Registry effort. Contributions of several hundred individuals are included in this documentation, however, more than one fourth of the patients, 149 or 29.3 percent, have been evaluated in our clinic. There were 296 false aneurysms and 262 arteriovenous fistulas. Multiple lesions occurred in 7.9 percent of the casualties. Fragment wounds accounted for 487 or 87.3 percent of the lesions with 85.5 percent in extremity vessels. Early recognition and definitive surgical treatment usually were accomplished: 52.8 percent within the first 30 days following injury. Ligation was either accepted or required in about 50 percent of the lesions. The mortality rate was 1.8 percent and the morbidity associated with the vascular injury was 6.3 percent. There were eight amputations for an amputation rate of 1.7 percent. Potential complications of heart failure, proximal arterial dilatation, and endocarditis were essentially absent.

A comparison of autografts and frozen, irradiated homografts in canine femoral venous reconstruction.

Autogenous veins are the ideal substitute for bridging venous defects. Experimentally, fresh homografts have patency rates comparable to autografts. However, a method of preservation must be employed if homografts become practical for clinical use. In this study, homografts were frozen, irradiated, and stored for a total of 6 weeks. Following femoral venous reconstruction, patency rates between frozen, irradiated homografts and fresh autografts were compared and found to be similar over a 6 month period. Recanalization of the frozen, irradiated homografts occurred at the same rate as did that of the autografts. This study concludes that cryopreservation and irradiation are suitable methods of preservation that do not adversely affect patency. In addition irradiation will sterilize tissue and may decrease the potential of the graft to stimulate the recipient's immunologic system.

Effects of intravenous and intra-arterial infusions of prostaglandin E1 on canine hindlimb blood flow distribution.

Prostaglandin E1 (PGE1) has been used clinically in the treatment of ischemic peripheral vascular disease. However, the preferred route of administration and its influence on the distribution of blood flow to the skin, muscle, bone, and arteriovenous anastomoses ( AVAs ) have yet to be established. Bilateral femoral arterial blood flow was measured electromagnetically in 10 anesthetized adult mongrel dogs (mean weight 16.5 kg). The distribution of femoral arterial flow to the skin, muscle, bone, and AVAs was determined with use of femoral intra-arterial injections of radioactively tagged microspheres (15 +/- 1 mu) before, during, and 1 hour after 20 minutes of intravenous and intra-arterial infusions of PGE1 at 0.1 microgram kg-1 min-1. Intra-arterial infusions caused a significant (P less than 0.003) increase in femoral arterial flow (462 +/- 58 ml X min-1), which was sustained throughout the infusion. The distribution of flow to the skin increased significantly (P less than 0.01) to 24.1 +/- 2.1%, whereas that through AVAs was significantly (P less than 0.05) decreased to 3.2 +/- 0.9%. Femoral arterial blood flow did not change during intravenous infusions; however, there was a significant (P less than 0.01) reduction in the distribution to muscle (41.1 +/- 10.5%) associated with a significant (P less than 0.02) increase in distribution through AVAs (30.8 +/- 11.5%). These data demonstrate the superiority of intra-arterial infusion over intravenous infusions of PGE1 in the canine hindlimb. There was a significant increase in femoral arterial blood flow with increased distribution to the skin and decreased shunting. Femoral arterial blood flow did not change during intravenous infusions; however, a reduction in the distribution of flow to the muscle was accompanied by an increase in shunting.

Differential patency and limb salvage for polytetrafluoroethylene and autogenous saphenous vein in severe lower extremity ischemia.

Polytetrafluoroethylene (PTFE) was compared to autogenous saphenous vein (ASV) in 133 femoropopliteal and femorotibial or peroneal bypass procedures performed in limb salvage during a 4-year period. PTFE was used as an alternative prosthesis in the absence of a suitable ASV. Sixty-nine femoropopliteal bypasses (FPBPs) were studied--36 with ASV and 33 with PTFE. Sixty-four femorotibial or peroneal bypasses were categorized as femoral distal bypasses (FDBPs)--34 with ASV and 30 with PTFE. With a 3-year clinical follow-up, cumulative function rate (CFR)--patency including thrombectomy--for FPBP with ASV was 65% as compared to 53% for PTFE (P greater than 0.05), whereas the limb salvage rate (LSR) was 75% with ASV and 56% for PTFE (P greater than 0.05). However for FDBP, the GFR was 55% for ASV and 7% for PTFE, whereas the LSR was 55% with ASV and 26% for PTFE. The cumulative patency rate (CPR)--initial thrombosis of a prosthesis as an endpoint--was not significantly (P greater than 0.05) different from CFR, suggesting that thrombectomy with or without distal anastamotic revision does not contribute to patency of the PTFE prosthesis in these limb salvage cases. PTFE was a suitable alternative to ASV for FPBP; however, PTFE is recommended for FDBP in selected cases only.

Atherosclerotic aneurysms of the subclavian artery.

The case reports of three adult men, in whom four atherosclerotic aneurysms of otherwise normal subclavian arteries were detected in the absence of thoracic outlet syndrome or a history of trauma, are detailed. Two patients complained of supraclavicular discomfort--one having a history suggestive of peripheral arterial emboli and the other was asymptomatic. These aneurysms can be resected safely using a supraclavicular incision with resection of the medial clavicle. In cases requiring more proximal arterial control, median sternotomy is advisable. Our one patient with bilateral atherosclerotic aneurysms appears to be the first such reported case in the surgical literature.

Comparison of pulsed Doppler and real-time B-mode echo arteriography for noninvasive imaging of the extracranial carotid arteries.

Accuracy and clinical applications of noninvasive imaging of the extracranial carotid arteries were compared using pulsed Doppler and real-time B-mode ultrasonography. During the period December, 1977, to February, 1979, 530 ultrasonograms (265 patients) were performed. Angiographic correlations were available in 90 patients (172 arteries) using the pulsed Doppler technique, and both techniques were employed in 43 patients (84 arteries). Greatest accuracy with pulsed Doppler ultrasonography occurred in confirmation of normal vasculature (73%) and diagnosis of occluded internal carotid arteries (96%). Estimation of the percentage of stenosis was less accurate; however, this determination could be made somewhat more accurately by B-mode ultrasonography. Incidence of false positive and negative results for the pulsed Doppler technique was 11% and 14%, respectively, whereas for the corresponding incidence for B-mode imaging it was 11% and 59%. The higher incidence of false negative results with the B-mode technique related to its inaccuracy in diagnosis of occlusion (18%). Current clinical applications of carotid ultrasonography include confirmation of normalcy and diagnosis of occlusion, visualization of atheroslerotic plaques with characterization of their size and ultrasonic morphology, and an anticipated reduction in the requirements for contrast arteriography in selected patients.

Below-knee bypass for limb salvage. Comparison of autogenous saphenous vein, polytetrafluoroethylene, and composite dacron-autogenous vein grafts.

Autogenous saphenous vein was used preferentially for 92 below-knee bypass procedures (44 femoral-distal popliteal and 48 femoral-distal tibial or peroneal) performed for limb salvage in 87 adult male patients during a 30-month period of study. When a saphenous vein was unavailable or of unsuitable length or diameter, we randomly used expanded polytetrafluoroethylene (PTFE) and composite Dacron-autogenous vein (DV) grafts. With good run-off, all grafts have remained patent. However, with poor run-off, cumulative patency by the life table method decreased to 54% for autogenous saphenous vein and 45% for PTFE, which was not significantly different. All composite DV grafts used with poor run-off became occluded within the first ten months of the study. We continue to recommend use of autogenous saphenous vein for revascularization of the ischemic lower extremity. When a suitable saphenous vein is unavailable, PTFE is a satisfactory alternative graft that is superior to composite DV grafts.

Ultrasonic blood flow assessment in colon esophageal bypass procedures.

Colonic serosal and mesenteric blood flows were assessed by use of the Doppler ultrasound device during three colon bypass procedures for obstructing esophageal carcinoma. The technique allowed confirmation of pulsatile blood flow in large and small vessels after mobilization of the colon and following completion of critical anastomoses. We recommend use of this technique to eliminate serious compromise of colonic blood flow in colon bypass procedures.

Heparin decreases ischemia-reperfusion injury in isolated canine gracilis model.

The mechanisms of ischemia-reperfusion injury in skeletal muscle remain controversial. Some investigators have demonstrated that heparin can ameliorate ischemic injury to heart, brain, and renal tissue. We investigated the ability of heparin sodium to decrease ischemia-reperfusion injury in an isolated gracilis muscle model in ten anesthetized mongrel dogs. One gracilis muscle was perfused normally while the contralateral muscle was subjected to six hours of ischemia followed by one hour of reperfusion. Five dogs were given a preischemic bolus of heparin sodium (200 U/kg, intravenously followed by a continuous infusion (15 U/kg/h, intravenously), and five control dogs received no heparin. Quantitation of skeletal muscle ischemia-reperfusion injury was determined by histochemical staining with triphenyl tetrazolium-chloride and computerized planimetry of the infarct size. Results from the ischemic muscle demonstrate a significant beneficial effect of heparinization. The nonheparinized dogs had a 72% +/- 5% infarct size, which was significantly reduced to 24% +/- 8% in the heparinized dogs. The mechanism of this protective effect may be due to heparin's anticoagulant, antiplatelet, or anti-inflammatory action.

Ultrasonic imaging and oculoplethysmography in diagnosis of carotid occlusive disease.

Pulsed Doppler ultrasonic imaging (UI) of the cervical carotid artery provides flow-dependent anatomic detail of the carotid bifurcation, while oculoplethysmography (Kartchner) (OPG-K) and ocular pneumoplethysmography (Gee) (OPG-G) reflect changes in flow and pressure resulting from hemodynamically significant lesions. We examined 66 patients prospectively with UI, OPG-K, and OPG-G to compare the relative accuracy of these techniques with contrast arteriography. Both UI and OPG-G were significantly more accurate than OPG-K. While the accuracies of UI and OPG-G were not significantly different, their combined use resulted in a significant increase in sensitivity compared with that of Doppler imaging alone. In addition, UI correctly identified 22 (85%) of 26 occlusions of the internal carotid artery. The use of UI and OPG-G together provided accurate anatomic and hemodynamic information useful in the evaluation of carotid occlusive disease.

Prostacyclin (epoprostenol): its effect on canine splanchnic blood flow during hemorrhagic shock.

Prostacyclin (epoprostenol, prostaglandin I2) is a vasodilator of the splanchnic circulation during normotensive states. To confirm the persistence of its effects after hemorrhagic shock, six anesthetized, previously splenectomized, adult mongrel dogs were subjected to hemorrhagic shock using a modified Wigger's technique in which a mean arterial pressure of 30 mm Hg was maintained until 25% of the shed blood spontaneously returned. The animals were randomly resuscitated with normal saline solution or a similar volume of saline solution containing prostacyclin. Organ blood flow was calculated by measuring the distribution of radioactively tagged microspheres. During shock, blood flows to the liver, small intestine, pancreas, and carcass were reduced. During a 60-minute infusion, prostacyclin selectively caused a significant increase in hepatic arterial blood flow. This improvement in arterial blood flow may prove beneficial in the clinical management of hemorrhagic shock.

Determination of intestinal viability by Doppler ultrasound.

The Doppler ultrasonic flowmeter was used to determine intestinal serosal and mesenteric blood flows in 130 patients who underwent abdominal aortic vascular procedures and in 14 patients who underwent general surgical procedures. Temporary occlusion of the inferior mesenteric artery (IMA) during aortic surgery resulted in the absence or marked diminution of collateral blood flow over the left side of the colon in eight patients. One patient had the flow in the IMA preserved by proper placement of an end-to-side aortofemoral Dacron prosthesis, whereas the other seven patients underwent replantation of the IMA into the Dacron prosthesis. All patients did well postoperatively. In the 14 general surgical patients, intestinal viability and collateral mesenteric blood flows were determined, which demonstrated that the presence of audible arterial blood flow correlated with ultimate bowel viability. We recommend the use of the Doppler ultrasonic flowmeter in abdominal aortic revascularization procedures to determine the need for IMA reconstruction as well as in general surgical procedures where the surgeon desires a more objective assessment of intestinal viability.