Monitoring of somatosensory evoked responses during carotid endarterectomy.

During carotid endarterectomy (CEA), we monitored somatosensory evoked responses (SERs) ipsilaterally over the scalp following stimulation of the contralateral median nerve at the wrist. Thirty-eight CEAs in 36 patients were studied. Of the 10 CEAs performed with patients under general anesthesia, three involved marked changes in SERs, reversed by shunt insertion. The remaining 28 CEAs were done with patients under local anesthesia. The SERs remained stable during an average clamp time of 30 minutes in all except one patient, in whom SER changes developed within a minute of clamping; the changes were reversed by shunt placement. Four of the 38 CEAs required a shunt based on SER changes, although measurement of stump pressure (less than 50 mm Hg) would have indicated the necessity of a shunt in eight additional operations. We concluded that SERs are useful in signaling cerebral ischemia and the need for a shunt during CEA.

Progression of atherosclerosis in diabetics.

Two hundred seventy-four diabetic patients were studied over a 2-year period to evaluate the progression of lower extremity atherosclerotic occlusive disease (ASO). At initial evaluation, ASO was noted in 98 patients (36%). Incidence of new or more severe disease was noted in 92 patients (34%) at follow-up. Increased age, longer duration of diabetes, lower percent ideal body weight, elevated systolic blood pressure, and elevated serum cholesterol levels were all significantly associated with disease progression. Patients with disease progression were found to have significantly lower nerve motor velocities and sensory conduction, higher serum creatinine levels, and a higher prevalence of retinopathy, proteinuria, and carotid artery disease (perhaps indicating concomitant neuropathy and microvascular disease). Diastolic pressure, race, fasting and postprandial glucose, fasting and postprandial insulin, fasting and postprandial C peptides, and glycosylated hemoglobin levels did not correlate with disease progression. The strongest prognostic indicator of disease progression appeared to be preexisting disease. Significant disease progression over a relatively short period indicates that treatment of the diabetic patients who have symptoms should be early and aggressive.

Efficacy of balloon catheter dilatation for lower extremity atherosclerosis.

Since there are few data regarding complications and long-term efficacy of balloon catheter dilatation for advanced lower extremity atherosclerosis, we are reporting our experience with 132 attempted dilatations in 88 patients. Dilatation was attempted on 51 aortoiliac-common femoral lesions, 80 superficial femoral-popliteal lesions and 1 peroneal lesion. Twenty procedures were technically unsuccessful and led to urgent surgery in three patients. Thirty-one complications in the 109 technically successful dilatations led to emergency surgery in only one, but another required closure of an arteriovenous fistula at the site of catheterization. There were three episodes of embolism, but none required operation. In 109 dilatations monitored for 1 month, there was significant hemodynamic improvement in 52 and mild to moderate improvement in 37; 10 had no change; 10 occluded at the site of dilatation. Of the 42 patients observed 6 months or longer, 11 maintained a significant increase, and 15 had mild to moderate improvement; 11 reverted to predilatation levels; 1 had progressive worsening; 4 occluded. Sixteen patients who had significant increases in flow after dilatation and were followed longer than 6 months showed a trend to restenosis as the length of follow-up increased. We conclude that dilatation is a useful adjunctive procedure in treating lower extremity atherosclerosis, that the early results are good, and that the incidence of recurrent stenosis is high. Indications for dilatation and its complications are similar to those for operations. It should not be done without hemodynamic monitoring.

Restenosis following carotid endarterectomy. Evaluation by duplex ultrasonography.

This study evaluated the efficacy of duplex ultrasonographic scanning in assessing the status of carotid arteries after 155 endarterectomies in 131 patients. Duplex studies were done as early as one month and as late as 96 months postoperatively; 33 patients had serial studies. Only 59 (42%) of 142 arteries had no evidence of irregularity or reduction in diameter at the operative site. An additional 41 (29%) had a reduction in diameter between 10% and 29%; 19 (13%) had reductions of 30% to 49%; nine (6%) from 50% to 69%; six (4%) from 70% to 99%; and eight (6%) were occluded. In 51 vessels, angiographic studies confirmed the duplex findings. Symptoms suggestive of recurrent cerebrovascular disease occurred postoperatively in 25 instances; in only three were the anatomic findings suggestive of lesions appropriate to the symptoms. We conclude that duplex ultrasonographic scanning is a useful technique for assessing carotid arteries after endarterectomy and that postoperative narrowing of vessels occurs more commonly than suspected.

Balloon catheter dilation for limb salvage.

Balloon catheter dilation was attempted as the initial treatment for limb salvage in 83 patients, of whom 38 had rest pain only, 32 had ischemic ulcers, and 13 had gangrene. One month 87 (78%) of these dilations showed an increase in flow, 14 (13%) had no change, and ten (9%) had thrombosis at the site of dilation. After six months, 23 of 49 dilations showed evidence of restenosis, though 27 maintained flow greater than predilation levels. Only six of 19 lesions in 14 patients who had no surgery maintained improved flow after one year. Overall limb salvage for patients with successful dilation was 71% (51 of 72 patients), and the rate of limb salvage after dilation alone was 34%. Transluminal dilation appears to be a useful method of treatment for patients with limb-threatening ischemia and should be considered complementary to other methods. The tendency for recurrence of stenosis mandates careful, frequent follow-up.

Duplex ultrasonography, digital subtraction angiography, and conventional angiography in assessing carotid atherosclerosis.

We prospectively compared duplex ultrasonography with digital subtraction angiography (DSA) and conventional angiography in the evaluation of carotid atherosclerosis by studying 494 arteries. Arteries were graded independently as normal, mildly stenotic, moderately stenotic, severely stenotic, or occluded. There was absolute agreement between duplex ultrasonography and DSA as to disease severity in 296 (68%) of 434 vessels, good correlation in an additional 119 vessels (28%), and poor correlation in 19 vessels (4%). When duplex studies were compared with conventional angiograms, the correlations were similar: absolute for 60 (71%) of 85 vessels, good for 17 (20%) of 85 vessels, and poor for eight (9%) of 85 vessels. With conventional angiography as the standard, duplex studies tended to overestimate the severity of disease in 64% of vessels and underestimate it in 36%, v 28% and 72%, respectively, for DSA. We concluded that duplex ultrasonography is as accurate as DSA in assessing carotid bifurcation atherosclerosis. The tendency of DSA to underestimate disease severity may lead to diagnostic errors in patients with nonobstructive plaques.

Pitfalls of the Doppler examination for venous thrombosis.

In a prospective study comparing Doppler ultrasound and contrast venography in 112 patients, we identified all false-negative and false-positive results obtained by Doppler and are reporting those errors that we believe are commonly occurring pitfalls of this technique. There were 21 false-negative and nine false-positive examinations. False-negative examinations were caused by the following factors: thrombi isolated to the veins of the calf (13 patients); nonocclusive clot involving or proximal to the popliteal vein (3); incorrect interpretation of examinations done by inexperienced personnel (2); acute thrombosis masked by changes of severe chronic disease (1); misinterpretation of increased saphenous flow in the presence of an occluded superficial femoral vein (1); and bilateral clot with one leg having significantly more evidence of venous obstruction than the other (1). Factors in the nine false-positive examinations were chronic disease interpreted as acute thrombosis (3), interpretation of weak signals in the calf as thrombosis (3), weak signals due to obesity (2), and excess Doppler probe pressure distorting venous flow (1). We conclude that results of the Doppler examination should be questioned when there is a suspicion of thrombus in the deep veins of the calf, the question of a nonocclusive thrombus, or the presence of chronic venous changes related to previous deep venous thrombosis.

Maintenance of adequate hemodialysis access. Prevention of neointimal hyperplasia.

The maintenance of adequate hemodialysis vascular access is frequently complicated in the patient with polytetrafluoroethylene (PTFE) A-V hemodialysis grafts by venous anastomotic stenosis. This stenosis is caused by neointimal hyperplasia (NIH), a response to vascular injury. In this study, the authors prospectively analyzed the effect of a short-term regimen consisting of administration of two medications, heparin and low molecular weight dextran, on the development of NIH at the venous anastomosis in 79 patients with PTFE A-V hemodialysis grafts. In addition, they evaluated other parameters' effects on the development of NIH. In comparison with control subjects, heparin had some effect in minimizing the development of NIH in the PTFE grafts when evaluated radiologically at 3 months, although this effect was not statistically significant. Low molecular weight dextran, however, had no trend or statistically significant effect on this venous anastomotic narrowing. Interestingly, patient age, use of calcium channel blockers, and presence of diabetes mellitus (DM) all appeared to affect the development of NIH. Increasing age and use of calcium channel blockers was associated with decreased development of NIH; conversely, DM was associated with worsened NIH. In evaluation of access survival (time to first access failure), degree of venous anastomosis stenosis at 3 months was not predictive. Patient time on dialysis pre graft placement was the only measured parameter related to access failure. The method of dialysis pre graft placement (hemodialysis versus peritoneal dialysis) was not a significant factor in early access failure. Pharmacologic treatment of venous anastomotic narrowing in PTFE hemodialysis grafts due to NIH continues to be difficult. Short-term treatment with the tested medication failed to statistically affect NIH. Patient age, use of calcium channel blockers, and presence of DM were all factors in the development of NIH. Of measured parameters, time on dialysis pre graft placement was the only factor correlated with early access failure. In future treatment regimens, one should consider more prolonged treatment. In addition, noted risk factors should be considered when determining type of renal replacement therapy.

Transcutaneous detection of subcritical arterial stenoses by Doppler signal spectrum analysis.

Early clinical studies showed significant data overlap when Doppler signal spectral analysis was used to differentiate normal carotid vessels from those with slight stenoses. A canine common carotid model has been used to study the ability of spectral analysis to detect subcritical stenoses, i.e., those with 20 to 50 per cent diameter reductions. Using the ratio of peak systolic frequency at the stenosis site to that proximal to the stenosis, significant differences from controls were found for all degrees of stenosis. The mean peak frequency ratio was 1.15 +/- 0.05 for 20 per cent stenoses, increasing to 1.68 +/- 0.50 for 50 per cent stenoses. The peak frequency ratios for Doppler signal spectra recorded from a site 1 cm distal to the stenosis exceeded control values only for 40 and 50 per cent stenoses; at a site 3 cm from the stenosis no spectra were significantly different from controls. Spectral analysis can be a direct, sensitive method to evaluate slight carotid arterial stenoses, but careful examination technique is necessary and Doppler signals must be taken from the stenotic site itself.

Duplex carotid sonography: correlation with digital subtraction angiography and conventional angiography.

Duplex sonography is a relatively new technique for noninvasive evaluation of the extracranial carotid arteries. In a prospective, double-blind study of 453 vessels (229 patients) over a one-year period, an excellent correlation was found with intravenous digital subtraction angiography (DSA) in 66.3 per cent of vessels, good correlation in an additional 28.4 per cent of vessels, and poor correlation in only 5.3 per cent. Duplex was compared with conventional biplane angiography in 86 vessels (45 patients); there was excellent correlation in 71 per cent, good correlation in 20 per cent, and poor agreement in 9 per cent of vessels. Duplex sonography is a highly accurate method of evaluating the cervical carotid system and it has a complementary role with DSA.

Efficacy of noninvasive modalities of diagnosis of thrombophlebitis.

In a blind prospective study of 158 limbs, Doppler ultrasound, pneumoplethysmography, and radionuclide venography (RNV) using 99mTc-MAA were compared to phlebography as methods of detecting thrombophlebitis. All three noninvasive modalities were very insensitive to isolated thrombus below the knee. In patients with extension of thrombus above the knee and isolated thrombus in the deep veins of the upper limb, Doppler ultrasound had a sensitivity of 81% and RNV had a sensitivity of 77%. All of the noninvasive modalities were found to be dependent on venous occlusion. Overall, pneumoplethysmography had a sensitivity of 28% and specificity of 96%, compared with 56% and 91%, respectively, for Doppler ultrasound and 51% and 84% for RNV. Based on these findings, phlebography would still seem to be the modality of choice in the diagnosis of thrombophlebitis.

Contrast extravasation through Dacron grafts: a sequela of low-dose streptokinase therapy.

Local transcatheter administration of low-dose streptokinase for the treatment of thrombosed Dacron grafts was performed in four patients. Angiography after the infusion revealed extravasation of contrast material through the interstices of the graft. In each case the graft material was knitted Dacron, Surgically placed 1 month to 6 years before infusion with streptokinase. The fibrinolytic activity of streptokinase is likely responsible for lysis of the fibrin in the interstices of the graft with resultant extravasation of contrast material.

Local thrombolytic therapy for subclavian and axillary vein thrombosis. Treatment of the thoracic inlet syndrome.

Four patients with primary subclavian-axillary vein thrombosis are described. Each patient received local thrombolytic therapy, resulting in reestablishment of antegrade flow via the axillary and subclavian veins. An intrinsic venous abnormality (perimural fibrosis and/or intimal dissection) identified at the first rib-clavicle junction (subclavian-axillary vein junction) was thought to be responsible for the thrombosis. One of the four patients subsequently underwent a surgical venous bypass of the abnormal segment, and a second underwent percutaneous transluminal angioplasty.

Thrombolytic agents: effects of local infusion on microvascular physiology and macrovascular ultrastructure.

Microvascular responses in live preparations of rat cremaster muscle were studied with intravital light microscopy following infusions of streptokinase, streptokinase-plasminogen complex, or urokinase into the iliac artery. Structural changes occurring in the endothelium of the iliac arteries were documented by electron microscopy. Though no functional microvascular changes were documented, endothelial cell injury and luminal surface fibrin deposits were identified in the iliac arteries locally infused with the thrombolytic agents. In addition, platelets in various stages of activation were identified. It is concluded that the commonly employed thrombolytic agents, urokinase and streptokinase, caused injury to the endothelial cells of our animal model. It is further concluded that platelet activation, due to local endothelial injury or some other mechanism, occurred following local infusion in our animal model. The long-term effects and potential clinical implications of the findings are not known.

Low-dose fibrinolytic therapy. Results and new concepts.

The authors report their experience with the first 57 infusions (50 patients) in an ongoing study of local low-dose fibrinolysis for treatment of thromboembolic disease. Complete lysis occurred in nearly half of cases, while some therapeutic effect was demonstrable in more than two thirds. Success seems to be most directly related to the type of vessel infused, with the greatest success seen in vessels with no alternate pathways for egress of the fibrinolytic agent. Chronic fibrin deposits could also be treated with this technique. Since new thrombus formation occurs in a significant percentage of patients during local fibrinolytic therapy, the authors recommend cautious use of concomitant continuous intravenous heparin at a dosage sufficient to maintain the partial thromboplastin time at 1.5 times normal. While fibrinolytic therapy is usually not curative, it frequently facilitates detection of the underlying lesion, permitting definitive therapy.