Carotid bifurcation atherosclerosis. Quantitative correlation of plaque localization with flow velocity profiles and wall shear stress

The distribution of nonstenosing, asymptomatic intimal plaques in 12 adult human carotid bifurcations obtained at autopsy was compared with the distribution of flow streamline patterns, flow velocity profiles, and shear stresses in corresponding scale models. The postmortem specimens were fixed while distended to restore normal in vivo length, diameter, and configuration. Angiograms were used to measure branch angles and diameters, and transverse histological sections were studied at five standard sampling levels. Intimal thickness was determined at 15 degrees intervals around the circumference of the vessel sections from contour tracings of images projected onto a digitizing plate. In the models, laser-Doppler anemometry was used to determine flow velocity profiles and shear stresses at levels corresponding to the standard specimen sampling sites under conditions of steady flow at Reynolds numbers of 400, 800, and 1200, and flow patterns were visualized by hydrogen bubble and dye-washout techniques. Intimal thickening was greatest and consistently eccentric in the carotid sinus. With the center of the flow divider as the 0 degree index point, mid-sinus sections showed minimum intimal thickness (0.05 +/- 0.02 mm) within 15 degrees of the index point, while maximum thickness (0.9 +/- 0.1 mm) occurred at 161 +/- 16 degrees, i.e., on the outer wall opposite the flow divider. Where the intima was thinnest, along the inner wall, flow streamlines in the model remain axially aligned and unidirectional, with velocity maxima shifted toward the flow divider apex. Wall shear stress along the inner wall ranged from 31 to 600 dynes/cm2 depending on the Reynolds number. Where the intima was thickest, along the outer wall opposite the flow divider apex, the pattern of flow was complex and included a region of separation and reversal of axial flow as well as the development of counter-rotating helical trajectories. Wall shear stress along the outer wall ranged from 0 to -6 dynes/cm2. Intimal thickening at the common carotid and distal internal carotid levels of section was minimal and was distributed uniformly about the circumference. We conclude that in the human carotid bifurcation, regions of moderate to high shear stress, where flow remains unidirectional and axially aligned, are relatively spared of intimal thickening. Intimal thickening and atherosclerosis develop largely in regions of relatively low wall shear stress, flow separation, and departure from axially aligned, unidirectional flow. Similar quantitative evaluations of other atherosclerosis-prone locations and corresponding flow profile studies in geometrically accurate models may reveal which of these hemodynamic conditions are most consistently associated with the development of intimal disease.

Selective infusion of streptokinase for arterial thrombosis

We have treated 13 patients with limb-threatening ischemia caused by acute arterial thrombosis with selective arterial infusion of streptokinase. The indications for thrombolytic therapy included medical contraindication to surgery, surgically inaccessible thrombi, arterial thrombosis following percutaneous transluminal angioplasty, and thrombosed distal arterial bypass. Patients were evaluated with arteriography, Doppler segmental arterial pressure studies, and coagulation profile. Objective evidence of complete or partial thrombolysis was demonstrated in 11 of the 13 patients (85%). Treatment after thrombolytic therapy included percutaneous transluminal angioplasty in six patients and distal bypass in two patients. Of five patients who had received no additional treatment, three required amputation. Overall limb salvage was achieved in 10 of the 13 patients. The most serious complications were puncture site bleeding in five patients, acute renal failure in one patient, and retroperitoneal hemorrhage in another patient. Bleeding was more frequent in patients with decreased serum fibrinogen levels. Although lysis of acute arterial thrombi can be achieved, thrombolytic therapy alone will allow limb salvage in only a few patients. Selective thrombolytic therapy with streptokinase must be used with caution and is associated with serious complications.

Arterial disruption and remodeling following balloon dilatation

We studied immediate and long-term alterations in human atherosclerotic arteries subjected to balloon dilatation. Pathologic material included vessels obtained at amputation or autopsy that had been previously dilated in vivo and cadaver vessels dilated under physiologic pressure and temperature. All vessels were pressure-perfusion fixed, and morphologic observations were correlated with sequential angiograms obtained in 36 patients. Balloon dilatation resulted in disruption of both the plaque and the artery wall, with separation of the plaque from the tunica media, rupture of the tunica media, and stretching of the tunica adventitia to increase lumen cross-sectional area. The intimal plaque protruded into the lumen, accounting for the angiographic appearance of local flaps and dissection channels. Remodeling occurred by readherence of the intimal flaps with little change in plaque volume. Achievement of a sufficient radius of curvature may be necessary to achieve long-term patency. Restenosis may occur because of insufficient dilatation but may also result from extention of dissection channels into nondilated segments of the artery.

Referral of impotent patients to a sexual dysfunction clinic

The referral pattern of impotent men from a urology clinic to a sexual dysfunction clinic was investigated. Only 62% of referred patients made such recommended appointments. Of the patients for whom sex therapy was recommended, only 32% accepted this recommendation. Of those accepting a recommendation for treatment, 57% prematurely terminated treatment against medical advice. The implications of this for referring physicians and alternative treatment approaches are discussed.

Doppler ankle pressure: an evaluation of three methods of expression

We studied 133 patients with arteriographic evidence of lower limb arterial disease and 34 normal volunteers to determine the most useful means of expressing ankle pressure. Representative ranges were determined for each of six symptomatic categories. Receiver operating characteristic curve analysis showed that ankle index (ankle to brachial pressure ratio) and brachial-ankle pressure gradient were more valuable than absolute pressure in discriminating between normal and disease extremities. In contrast, absolute ankle pressure was the best predictor of nonviability (limb requiring bypass for salvage or amputation). An absolute pressure cutoff of 6mm Hg correctly identified 86% of viable limbs and 77% of nonviable limbs. Thus, the diagnostic accuracy of the three methods of expressing ankle pressure depends on the context in which they are to be used, and it appears that ankle index and gradient are most appropriate for defining the presence of disease, while absolute pressure correlates best with viability.

Critical evaluation of stress testing in the diagnosis of peripheral vascular disease

We studied 218 patients (372 limbs) and 25 normal subjects (50 limbs) with resting ankle index (RAI), treadmill exercise (TE), and postocclusive reactive hyperemia (PORH) to determine whether diagnostic accuracy is improved through the use of stress testing. In addition, we studied 10 patients with stable claudication (20 limbs) to determine the reproducibility of the three measures. RAI was the most reproducible measure, with the smallest variance between testing days (P less than 0.001). RAI differentiated between arteriographically diseased and normal limbs with a sensitivity of 97% and a specificity of 100%, whereas the corresponding values for TE were 97% and 96% and for PORH 89% and 96%. Recovery to baseline index was prolonged in the diseased group compared with normal (p less than 0.001 for both TE and PORH), but this was of limited discriminative value. Receiver-operating characteristic curve analysis documented that RAI was as diagnostically useful as TE and that both were more valuable than PORH (P less than 0.02). However, the routine addition of stress testing increased diagnostic yield by only 1.6% and cost $1100 for each limb correctly diagnosed through the addition of stress testing. RAI is a simple, accurate, and reproducible test. Routine stress testing is not cost effective, adding little diagnostic information to RAI, and it should be reserved for the small subset of symptomatic patients with normal RAI.

Diagnosis of upper extremity deep venous thrombosis using noninvasive technique

Forty-two patients suspected of having unilateral upper extremity deep venous thrombosis (DVT) were evaluated with Doppler ultrasonography and phleborheography (PRG). Venography was performed on 23 upper extremities (54%). Doppler ultrasonography and PRG produced similar accuracy (82%) in detecting upper extremity DVT when compared with venography. The accuracy improved to 91% when the results of both tests were considered together. It is concluded that Doppler ultrasonography and PRG, when used together, are useful, rapid, and accurate techniques for diagnosing upper extremity DVT.

Analysis of 122 unselected impotent men subjected to multidisciplinary evaluation

Erectile impotence is not a simple problem and it is important to recognize that the presence of a possible organic cause does not rule out emotional difficulties or sexual maladjustment. Behavioral therapy and surgery have an important role in treating this symptom. By careful pre-treatment evaluation the most appropriate therapy can be selected. It has been our general rule that when neither clear organic nor psychogenic problems lie at the root of the difficulty, a trial of behavioral therapy is the most appropriate procedure. If no success is achieved after an adequate trial of therapy re-evaluation and recommendation for a prosthetic implant can be made.

Abdominal aortic aneurysm and Behçet's disease

A case of abdominal aortic aneurysm with Bechçet's disease and a review of two similar cases previously reported are presented. This case and additional review of other reported major vascular complications of Behçet's disease lead us to conclude that the pathogenesis of the abdominal aneurysm is related to involvement of the aortic wall or vasa vasorum by the Behçet's disease process. Surgical treatment of this rare complication by Behçet's disease should include extra-anatomic bypass if the possibility of infection cannot be definitely excluded.

The effect of a thigh tourniquet on the incidence of deep venous thrombosis after operations on the fore part of the foot

We performed a prospective randomized clinical study to determine whether use of a thigh tourniquet influences the incidence of deep venous thrombosis. The lower limbs of patients who were scheduled for elective surgery on the fore part of the foot were randomized and assigned to one of three treatment categories: Group I, no tourniquet; Group II, exsanguination by an Esmarch bandage before tourniquet application; and Group III, exsanguination by elevation of the extremity prior to application of a tourniquet. The 117 limbs of seventy-one patients included in this study were evaluated preoperatively and twenty-four and seventy-two hours postoperatively with 125I-labeled fibrinogen, and preoperatively and seventy-two hours postoperatively with Doppler ultrasound studies and phleborheography. The findings in all of the Doppler ultrasound studies and all of the phleborheograms were normal. Two of the 125I-fibrinogen studies were positive, but subsequent contrast venography revealed that these were false-positive findings. We therefore concluded that the use of a thigh tourniquet does not increase the risk of deep venous thrombosis in patients who have had an operation on the fore part of the foot.

Percutaneous transluminal angioplasty for limb salvage

Thirty patients with end-stage atherosclerosis, being considered for amputation, were treated by percutaneous transluminal angioplasty (PTA). All had very poor run-off, and none was a candidate for arterial reconstruction. Occluded segments of the iliac, femoral, popliteal, and tibial arteries measuring up to 21 cm were recanalized, resulting in an increased ankle/brachial systolic pressure index despite significant distal occlusive disease. Ischemic symptoms were relieved in 22 patients, and the overall limb salvage rate (2- to 17-month follow-up) was 73%.

Long-segment arterial occlusion: percutaneous transluminal angioplasty

In cases of occlusion of the superficial femoral artery exceeding a length of 10 cm, accompanied by involvement of the popliteal artery and poor runoff, percutaneous transluminal angioplasty is unfavorable. However, when such advanced occlusive disease is present in patients for whom vascular surgery is not feasible, this technique can be of value by averting or at least postponing amputation. Percutaneous transluminal angioplasty was used to recanalize long segments (10-36 cm) of occluded or stenotic femoropopliteal arteries in 21 patients. Results were evaluated by means of pre- and postangioplasty arteriograms and measurements of pressure indices. The initial success rate was 76%; the success rate on 5-24 month follow-up was 67%. The long-term benefit can be improved by other measures, such as stopping cigarette smoking, exercise, long-term anticoagulation therapy, and early detection and treatment of restenosis.

Local effects of stenoses: increased flow velocity inhibits atherogenesis

Thoracic aortic coarctations were produced in cynomolgus monkeys by one of three methods: circumferential banding to produce a symmetric channel with a rigid wall, lateral plication to provide an asymmetric channel with splitting on one side, and lateral plication plus banding to provide a rigid asymmetric channel. The degree of luminal constriction was 58 +/- 12%, with no significant difference among groups. After 3-12 months on an atherogenic diet, the coarctation channels were remarkably free of lesions compared with the aorta immediately proximal to the coarctation (p less than 0.001). Banding resulted in sharp circumferential termination of the lesions just proximal to constriction. Lateral plication resulted in an oblique termination of proximal disease wtih sparing opposite the plication. Lesions distal to coarctations occurred in a pattern related to the configuration of the coarctation channel and tended to form immediately below the plication. Sparing in and immediately beyond the constriction was independent of the rigidity of the aortic wall or of previous disruptive endothelial or medial injury associated with the operative procedure. Endothelium was preserved within the coarctation channel and over all lesions and distal to the constriction. The findings suggest that flow separation and instability tend to favor atherogenesis, whereas increased flow velocity per se may exert a protective effect.

Increased cerebral blood flow after external carotid artery revascularization

Ten patients with symptoms of cerebral ischemia were found to have totally occluded internal carotid arteries with significant external carotid artery stenosis or occlusion. Eight patients underwent external carotid endarterectomy, and two patients underwent saphenous vein bypass to the external carotid artery from the subclavian artery. Cerebral blood flow was measured with 133Xe in six patients preoperatively and in five postoperatively. Four of the six patients had diminished mean flow on the affected side, and three had diminished flow in the contralateral side. All patients had abnormalities in regional cerebral blood flow. Postoperatively, all patients had significant improvement in mean blood flow on the side treated with operation (15% to 39%), and four had improvement of blood flow on the contralateral side (12% to 52%). All had improvement in regional cerebral blood flow. Nine of the 10 patients were relieved of their symptoms. One patient, despite improvement in cerebral blood flow, continued to have diminished cerebral flow and symptoms postoperatively. Subsequent extracranial-intracranial bypass relieved his symptoms and his cerebral blood flow returned to normal. Thus external carotid artery revascularization is effective in increasing total and regional cerebral blood flow and in relieving symptoms of internal carotid artery occlusion and external carotid stenosis. Cerebral blood flow measurement with 133Xe is useful in preoperative patient selection and objective assessment of operative results.

Characteristics of erectile dysfunction as a function of medical care system entry point

The scientific literature on the treatment of penile erectile dysfunction contains numerous contradictory reports on the relative frequency of organic causes of impotence and the treatment results of behavioral sex therapy. One explanation for these contradictory findings is the hypothesis that different investigators are studying different subsamples of the symptomatic population. This study investigated differences in characteristics of men who initially consulted a urologist with a complaint of impotence versus those who self-referred themselves to a sexual dysfunction clinic. Self-referred sexual dysfunction patients were more often white, more often had psychogenic etiologies to their difficulties, were more often of higher socioeconomic class, and had a much better response to psychological interventions. This study suggests that future studies concerning the etiology and treatment of impotence need to specify population characteristics such as referral source and screening criteria. It may be necessary to develop alternative treatment techniques for men who present to nonpsychiatric sources for help with psychogenic impotence.

Does reduced colloid oncotic pressure increase pulmonary dysfunction in sepsis?

Starling's hypothesis of forces governing fluid movement across capillary membranes suggests that any unopposed decrease in intracapillary colloid oncotic pressure (COP) or increase in capillary permeability should result in increased interstitial fluid. Iso-oncotic increase in pulmonary artery wedge (PAW) causes pulmonary dysfunction. Isobaric reduction of COP with normal capillary permeability does not result in pulmonary interstitial edema. Because sepsis is a frequent antecedent of clinical pulmonary dysfunction, the question was asked: does reduction in the COP-PAW gradient in the presence of sepsis result in increased pulmonary dysfunction? Twenty baboons were studied: group 1--control, group 2--4-h constant infusion of E. coli, group 3--plasmapheresis alone, group 4--plasmapheresis followed by sepsis. Ringer's lactate was infused to keep PAW constant. Arterial and mixed venous blood gases were drawn and the intrapulmonary shunt (QS/QT) was calculated. The data were compared using Tukey's HSD test and one way analysis of variance. Plasmapheresis alone resulted in a 68% reduction in COP (15 +/- 2.9 (SD) torr to 4.6 +/- 0.6 in group 3 and 16.5 +/- 4.3 to 5.7 +/- 0.9 in group 4, p less than 0.05). Sepsis resulted in an increase in QS/QT in all septic animals. There was no increased QS/QT in those animals that had sepsis added to plasmapheresis, group 4 (p less than 0.05). These data indicate that sepsis leads to pulmonary dysfunction but that this dysfunction appears to be independent of colloid oncotic forces.

Discrimination of organic versus psychological impotence with the DSFI: a failure to replicate

Patients with a presenting complaint of erectile dysfunction were extensively investigated by a research team consisting of a urologist, vascular surgeon, psychiatrist and psychiatric social worker. Patients were assigned to organic and psychogenic groups according to specified criteria. Multiple comparisons of psychogenic and organic impotence cases on scores derived from the Derogatis Sexual Functioning Inventory (DSFI) did not differentiate the two groups. This inventory did, however, manifest numerous relationships with demographic variables. Failure to identify a psychological profile characteristic of psychogenic impotence was attributed to the heterogenity of this diagnostic grouping and selection processes in seeking treatment for such disorders.