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Biomedical subjects

K Ouriel

Publications and source records attributed to K Ouriel.

At least 19 recordsLinked to original sources

A volumetric index for the quantification of deep venous thrombosis.

PURPOSE: The evaluation of treatment strategies for deep venous thrombosis (DVT) is assessed through the use of a reliable method of quantifying the extent of the thrombotic process. Previous indices of thrombus burden have suffered from various limitations, including lack of clinical relevance, poor correlation with actual thrombus mass, and failure to include important venous segments in the methodology. The use of a novel scheme of quantifying venous thrombus was evaluated as an alternative method that would avoid some of the drawbacks of existing indices. METHODS: The volumes of 14 venous segments (infrarenal inferior vena cava, common iliac, hypogastric, external iliac, common femoral, profunda, superficial femoral, and popliteal and six tibial veins) were calculated from computed tomography (pelvic vein diameter), duplex ultrasound scan (infrainguinal vein diameter), and contrast venography (length of all segments) measurements. A venous volumetric index (VVI) was assigned with the normalization of the values to the volume of a single calf vein. The VVI was validated with the assessment of the ability to discriminate between asymptomatic and symptomatic DVT and between those DVT that were associated with pulmonary emboli and those that were not. RESULTS: With the imaging data, the VVI ranged from 1 for a single calf vein thrombus to 26 for the infrarenal inferior vena cava. Each VVI unit represented 2.3 mL of thrombus, with a maximum possible score of 63 representing a thrombus burden of 145 mL for a single extremity, including the infrarenal inferior vena cava. In 885 patients with DVT, the VVI ranged from 1 to 56, averaging 3.9 +/- 0.2 in patients who were asymptomatic and 8.7 +/- 0.3 in patients who were symptomatic (P <.001). The VVI was similar in the patients with pulmonary emboli as compared with those without (9.6 +/- 1.2 vs 7.7 +/- 0.2, respectively). In comparison with the three existing methods of quantifying venous thrombus burden, the receiver operating characteristic curve analysis results suggested that the VVI and the Venous Registry index were better than the other two indices in the discrimination of patients with symptomatic and asymptomatic DVT (P <.001). CONCLUSION: A novel index of venous thrombus burden, on the basis of actual venous volume measurements, was more accurate than present indices in the differentiation between clinical categories of patients with DVT. As such, it offers an acceptable alternative to current scoring systems.

Diagnostic Imaging

Photoplethysmography and calf muscle pump function after subfascial endoscopic perforator ligation.

OBJECTIVE: Subfascial endoscopic perforator surgery (SEPS) results in acceptable healing and recurrence rates. The role of hemodynamic venous testing in this situation, however, is poorly understood and inconsistently used. Our ongoing experience was reviewed to explore how SEPS affects the photoplethysmographic assessment of the leg. METHODS: Preoperative and postoperative venous refill times (VRTs) were measured with photoplethysmography in 30 limbs in 28 patients who underwent SEPS and superficial ablation, when indicated, with complete clearing of the anterolateral surface of the tibia, thus opening the deep posterior compartment from mid calf to close to the malleolus. Postoperative healing and duplex scanning were used to assess clinical and anatomic success, respectively. The VRTs were classified as "interpretable" if the leg emptied or "uninterpretable" if the calf could not empty. The "interpretable" study results were further classified as "normal" if the refill took 20 seconds or more or "abnormal" if less. RESULTS: Before the patients underwent SEPS, six study results (20%) showed inability of the calf to empty and thus were judged uninterpretable. After the patients underwent SEPS, 12 study results (40%) were uninterpretable (NS; P =.09 with the chi(2) test). Of the 24 preoperative interpretable study results, two (8%) were normal, and of the 18 postoperative interpretable study results, seven (39%) were normal (P <.03). With the consideration of only interpretable study results, the mean VRT increased slightly from 12.0 +/- 5.1 seconds (mean +/- standard deviation) to 14.3 +/- 8.1 seconds (NS). Seventeen of 19 ulcers (89%) had healed at a mean follow-up period of 8.6 +/- 4.8 months. CONCLUSION: Although VRT is unpredictably affected by SEPS, the most consistent finding is the inability of the calf to empty, which invalidates the remainder of the test. In addition, most ulcers heal, even with uninterpretable or abnormal postoperative VRTs. This suggests that photoplethysmography is a poor method of assessment of venous reflux after SEPS.

Adult

Intracerebral hemorrhage after carotid endarterectomy: incidence, contribution to neurologic morbidity, and predictive factors.

PURPOSE: With a diminishing rate of cardiac and neurologic events after carotid endarterectomy, intracerebral hemorrhage is gaining increasing importance as a cause of perioperative morbidity and mortality. To date, information has been largely anecdotal, and there has been no comparison with a control group of patients. METHODS: The records of all patients experiencing symptomatic intracerebral hemorrhage after carotid endarterectomy were reviewed and compared with data from 50 randomly selected patients who did not experience intracranial bleeding. Univariate analyses were performed, using the Fisher exact test for dichotomous data and the Student t test for continuous data. RESULTS: During a 6-year period, symptomatic intracranial hemorrhage developed in 11 (0.75%) of 1471 patients undergoing carotid endarterectomy, accounting for 35% of the 31 total perioperative neurologic events. Hemorrhage occurred a median of 3 days postoperatively (range, 0 to 18 days). Signs and symptoms included hypertension in all 11 patients, headache in 7 conscious patients (64%), and bradycardia in 6 patients (55%). Massive hemorrhage with herniation and death occurred in 4 patients (36%). Moderate hemorrhage developed in 5 patients (45%); 3 of these patients had partial recovery, and 2 had complete recovery. Petechial hemorrhage occurred in the remaining 2 patients (18%), 1 with partial and 1 with complete recovery. In comparison with the control group, there were no differences in respect to sex, indication for operation, smoking or diabetic history, and antiplatelet therapy or perioperative heparin management. Patients with intracranial hemorrhage were, however, younger, more frequently hypertensive, had a higher degree of ipsilateral and contralateral carotid stenosis, and had a higher rate of contralateral carotid occlusion. CONCLUSION: Intracranial hemorrhage occurs with notable frequency after carotid endarterectomy and accounts for a significant proportion of neurologic morbidity and mortality. Younger patients, hypertensive patients, and patients with severe cerebrovascular occlusive disease appear to be at greatest risk for the complication.

Age Factors

Developments in diagnosis and classification of venous disorders: non-invasive diagnosis.

PURPOSE: This review examines the many techniques that have been used for the non-invasive diagnosis of acute and chronic venous disease and was conducted by members of the Committee on Research of the American Venous Forum. It proposes to identify those techniques with the greatest clinical potential, to suggest algorithms for the clinical application of non-invasive techniques in the identification of acute deep venous thrombosis and chronic venous insufficiency, and to identify areas of deficient knowledge and potential areas for future research initiatives. METHODS: Review of pertinent clinical and research material. RESULTS: Impedance plethysmography and ultrasonic imaging are the primary non-invasive tools used in the diagnosis of acute deep venous thrombosis. At present, ultrasonic imaging techniques are recommended on the basis of greater diagnostic accuracy in recent comparative clinical trials. Data would suggest that serial evaluation should probably be viewed as the preferred option for symptomatic patients with a negative initial examination and the presence of risk factors or physical findings suggesting a proximal deep venous obstruction/thrombosis. Chronic venous disease is the result of valvular incompetence, with or without associated venous obstruction. Duplex imaging can be used to determine the location and extent of reflux; however, there are reported procedural variations in the performance and interpretation of such studies. Recent innovations in air plethysmography may provide a means of quantifying volume changes, and permit an objective characterization of venous reflux and calf pump efficiency. CONCLUSIONS: There are still significant questions that need to be answered by well-designed research initiatives. Research applications that incorporate non-invasive diagnostic techniques may involve the diagnosis, treatment and natural history of acute deep venous obstruction/thrombosis and chronic venous insufficiency, assessment prior to and following venous reconstruction, and the basic science aspects of acute and chronic venous disease. At present, a lack of common standards is, by far, the greatest impediment to an organized research approach to venous disease.

Acute Disease

Prourokinase versus urokinase for recanalization of peripheral occlusions, safety and efficacy: the PURPOSE trial.

BACKGROUND: The intraarterial administration of thrombolytic agents is associated with clinical benefits in patients with acute peripheral arterial occlusion, and urokinase has been the agent that has become the standard of care in the United States. Recombinant prourokinase (r-ProUK) offers potential as a novel agent with improved fibrin specificity and, as such, may offer advantages as an attractive alternative to urokinase. METHODS: A randomized, double-blind, parallel, phase II, prospective multicenter trial was undertaken to compare three doses of intra-arterial, catheter-directed r-ProUK (2 mg, 4 mg, or 8 mg/hr for 8 hrs, then 0.5 mg/hr) versus one dose of tissue-culture urokinase (4,000 IU/min for 4 hrs, then 2,000 IU/min) for the treatment of acute lower extremity arterial occlusion of 14 days' duration or less (n = 241). The primary endpoint was complete (>95%) lysis of the occluding thrombus after 8 hours of infusion. RESULTS: Increased clot lysis at 8 hours, decreased fibrinogen concentration, and an increased rate of hemorrhagic events were observed as the r-ProUK dose was increased from 2 mg/hr to 8 mg/hr. Similarly, a decreased duration of study drug infusion was seen, decreasing from 16.7 +/- 0.90 hours in the 2 mg/hr group to 12.7 +/- 0.97 hours in the 8 mg/hr group. The results for the urokinase group decreased to a level between those observed for the 2 mg and 8 mg r-ProUK group with respect to clot lysis at 8 hours, fibrinogen decrement, and bleeding complications, approximating those observed in the 4 mg/hr r-ProUK group. These results were achieved with a relatively low rate of major bleeding events and no episodes of intracranial hemorrhage. CONCLUSIONS: The 8 mg/hr dose of r-ProUK was associated with an increased rate of thrombolysis relative to the other treatment groups, associated with a slightly increased frequency of bleeding complications and decrements in fibrinogen concentration. Conversely, the 2 mg/hr r-ProUK dose was associated with a slightly slower rate of thrombolysis, but bleeding complications and fibrinogenolysis were diminished. r-ProUK is a novel thrombolytic agent with a dose-related safety and efficacy profile. As such, it offers potential as a useful tool in the treatment of peripheral vascular occlusion.

Aged

Femoral-infrapopliteal bypass with prosthetic grafts.

BACKGROUND: Patients who require prosthetic infrapopliteal of the lower extremity have historically had dismal long-term results. This study examined the outcome of patients undergoing femoral-distal arterial bypass with expanded polytetrafluoroethylene (ePTFE) grafts. METHODS: Femoral to infrapopliteal artery bypasses with ePTFE performed between 1990 and 1997 were reviewed. Graft patency, limb salvage, and survival rates were calculated by actuarial analysis. Different anastomotic adjuncts (direct end-to-side anastomosis, vein patch anastomosis, and arteriovenous fistula [AVF] anastomosis) were compared with the log-rank test. RESULTS: Seventy-four femoral-infrapopliteal bypasses with ePTFE were performed in 67 patients for limb salvage. At 24 months the primary patency, assisted primary patency, and secondary patency rates were 40% +/- 10% (SEMAI), 48% +/- 11%, and 52% +/- 11%, respectively. Limb salvage was successful in 62 % +/- 10% of the bypasses at 24 months. Forty-six percent of the bypasses were performed with an AVF; 35% were performed with direct end-to-side anastomosis, and 19% were performed with a vein patch anastomosis. Apparent trends in favor of the AVF group did not attain statistical significance with 24-month patency rates of 65% +/- 19%, 44% +/- 16%, and 35% +/- 20%, respectively, in the 3 subgroups. Limb salvage rates were similar (64% +/- 17%, 56% +/- 15%, and 76% +/- 22%, respectively) at 24 months. CONCLUSIONS: Patency and limb salvage rates are sufficient to justify the use of ePTFE grafts in infrapopliteal bypass when adequate autogenous material is unavailable.

Adult

A comparison of recombinant urokinase with vascular surgery as initial treatment for acute arterial occlusion of the legs. Thrombolysis or Peripheral Arterial Surgery (TOPAS) Investigators.

BACKGROUND: Recent controlled trials suggest that thrombolytic therapy may be an effective initial treatment for acute arterial occlusion of the legs. A major potential benefit of initial thrombolytic therapy is that limb ischemia can be managed with less invasive interventions. METHODS: In this randomized, multicenter trial conducted at 113 North American and European sites, we compared vascular surgery (e.g., thrombectomy or bypass surgery) with thrombolysis by catheter-directed intraarterial recombinant urokinase; all patients (272 per group) had had acute arterial obstruction of the legs for 14 days or less. Infusions were limited to a period of 48 hours (mean [+/-SE], 24.4+/-0.86), after which lesions were corrected by surgery or angioplasty if needed. The primary end point was the amputation-free survival rate at six months. RESULTS: Final angiograms, which were available for 246 patients treated with urokinase, revealed recanalization in 196 (79.7 percent) and complete dissolution of thrombus in 167 (67.9 percent). Both treatment groups had similar significant improvements in mean ankle-brachial blood-pressure index. Amputation-free survival rates in the urokinase group were 71.8 percent at six months and 65.0 percent at one year, as compared with respective rates of 74.8 percent and 69.9 percent in the surgery group; the 95 percent confidence intervals for the differences were -10.5 to 4.5 percentage points at six months (P=0.43) and -12.9 to 3.1 percentage points at one year (P=0.23). At six months the surgery group had undergone 551 open operative procedures (excluding amputations), as compared with 315 in the thrombolysis group. Major hemorrhage occurred in 32 patients in the urokinase group (12.5 percent) as compared with 14 patients in the surgery group (5.5 percent) (P= 0.005). There were four episodes of intracranial hemorrhage in the urokinase group (1.6 percent), one of which was fatal. By contrast, there were no episodes of intracranial hemorrhage in the surgery group. CONCLUSIONS: Despite its association with a higher frequency of hemorrhagic complications, intraarterial infusion of urokinase reduced the need for open surgical procedures, with no significantly increased risk of amputation or death.

Acute Disease

Animal models for the study of lower extremity chronic venous disease: lessons learned and future needs.

The purpose of this review is to define animal models of chronic venous disease and to demonstrate how animal studies can impact our understanding and treatment of this disorder. To this end an extensive literature search was conducted highlighting potential animal models of chronic lower extremity venous disease. Scientific investigations using animals to study particular aspects of this disease are also reviewed. This review was conducted by members of the Committee on Research of the American Venous Forum to help provide direction for future venous research endeavors. Useful models of chronic venous occlusive disease involve controlled ligation of a major lower limb vein and multiple tributaries. Such a model can provide sustained venous hypertension and studies using this model have confirmed that an isodiametric graft can provide early hemodynamic relief. Models of primary, postphlebitic, and isolated chronic deep venous insufficiency are available for study. Valve repair or transplantation can positively impact the insufficiency observed in these models. Investigations into valve substitutes have generally been disappointing or are undergoing early evaluation. In conclusion, animal models for the study of some aspects of chronic venous disease do exist and have already affected our clinical approach to patients. The scientific study of basic pathophysiology, diagnostics, end-organ response, and long-term surgical treatments of this disorder in well-controlled animal experiments have not been conducted.

Animals

A model for merging vascular surgery and interventional radiology: clinical and economical implications.

BACKGROUND: The traditional separation of vascular surgery and interventional radiology into distinct units is associated with inefficiencies in patient care, practice management, and training. Traditional departmental politics, discrepant clinical backgrounds and philosophies, fear of decreasing remuneration, and basic differences in education, training, and practice have all rendered mergers difficult. METHODS: We have implemented a model that incorporates all the clinical, fiscal, and educational activities of the 2 former entities into a single unit. A 5-physician vascular surgery group, its noninvasive laboratory, and a 3-physician interventional radiology group were unified. The revenue was deposited into a single account from which all the expenses were paid. The net income of the joint unit was apportioned on a predetermined pro rata basis, with scaled percentages for each practitioner. In an effort to separate clinical decision making from economic pressures, the individual physician remuneration was not on the basis of productivity. Clinical volume, gross revenue, and remuneration were compared with the 12-month period that immediately preceded the merger and contrasted to the previous 3-year historical trend (HT). RESULTS: The number of vascular surgical procedures fell after the merger (-9.3%; HT, +4.7%). By contrast, the number of interventional radiology procedures rose (+56.1%; HT, +15.2%), as did the number of noninvasive testing (+9.2%; HT, +3.5%). In concordance with the number of procedures, the gross revenue of vascular surgery fell (-23.7%; HT, +1.1%) and that of interventional radiology rose (+53.5%; HT, +46.0%). The increased efficiencies allowed the total expenses of the 2 units to fall (-13.2%; HT, +7. 5%), and, despite the reduced revenue, the vascular surgeon remuneration was preserved (+0.7%; HT, -3.9%) and the radiology remuneration rose (+22.3%; HT, +8.3%). The merger allowed the vascular surgery fellows to actively participate in 26 interventional cases per month and the interventional radiology fellows to actively participate in 8 open surgical cases per month. CONCLUSION: The merger of vascular surgery and interventional radiology resulted in a decrease in the surgical procedures and revenue, with a corresponding increase in the interventional radiology procedures and revenue. Despite these effects, the physician remuneration increased as a result of the improved efficiencies in practice management and the reduction in expenses. The merger of the 2 units excludes the economic pressures from clinical decision making and appears to be warranted on the basis of the fiscal and educational benefits that are achieved.

Hospital Departments

Fetal internal iliac artery: case report and embryologic review.

A 25-year-old woman with anomalous circulation to the right leg was seen with a symptomatic aneurysm of the abnormal vessel. The artery, which did share some features of the classic persistent sciatic artery, also had important differences that were not previously described in the literature. The patient manifested several associated vascular and nonvascular congenital anomalies. She underwent resection of the aneurysm and primary operative repair of the artery without difficulty. An embryologic interpretation is offered, and the clinical implications and management strategy are discussed.

Adult

Endovascular treatment of renal artery thrombosis caused by umbilical artery catheterization.

Renal arterial thrombosis, usually in association with aortic thrombosis, has been reported as a result of prolonged neonatal umbilical artery catheterization. A case of renal artery thrombosis attributable to umbilical artery catheterization, resulting in malignant renovascular hypertension, in a 15-day-old neonate, treated by catheter-directed thrombolysis through the involuting umbilical artery, was studied. Resolution of systemic hypertension and partial return of right renal function followed rapid thrombus dissolution.

Catheterization

Ruptured popliteal artery aneurysm.

Popliteal artery aneurysms rarely rupture. We treated a 91-year-old man who presented with a deep venous thrombosis and anemia; rupture of a popliteal artery aneurysm was suspected only after compartment syndrome isolated to the thigh developed as the result of bleeding. Although fasciotomy was required on the basis of the clinical examination alone, the cause of the problem, operative strategy, and definitive treatment (i.e., resection and bypass) were clarified by the preoperative computed tomography scan. Ruptured popliteal aneurysm can manifest as a massively swollen leg with anemia and should be suspected if no other cause is evident.

Aged

Value of preoperative EEG for carotid endarterectomy.

PURPOSE: This study was designed to determine whether the preoperative, baseline electroencephalogram (EEG) can be used for intraoperative decision making during carotid endarterectomy, and to identify circumstances where the EEG can be eliminated. METHODS: The charts of all patients undergoing carotid endartectomy at the authors' institution from June 1991 to May 1995 were reviewed to identify those patients that had adequate pre- and intraoperative EEG monitoring. EEGs during 331 carotid endartectomies in 303 patients were coded without knowledge of outcome; primary and secondary endpoints were EEG changes with clamping and clinical outcome, respectively. RESULTS: The incidence of mortality and major neurological morbidity was 1.8%. Baseline-EEGs were abnormal in 105 patients (32%). Whereas baseline-EEG changes were highly predictive of EEG changes after anesthetic induction (P < .0001), they were not predictive of EEG changes with clamping or of clinical outcome. Prior stroke (CVA) predicted abnormal baseline-EEGs (P < .0001) and abnormal post-anesthetic EEGs (P < .0001) but did not predict changes with clamping or perioperative CVA. EEG changes with clamping occurred during 18% of operations; such changes were predicted only by contralateral occlusion (P < .0016) and EEG changes during a prior contralateral carotid endartectomy (P < .0001). The only variable that predicted an adverse neurological outcome was the presence of contralateral occlusion, which increased the likelihood of a perioperative neurological event seven-fold (P = .0038). Clinical outcomes in the 57 of 105 patients with abnormal baseline-EEGs and the 49 of 83 with prior CVA who were shunted were not different from those who were not. CONCLUSIONS: baseline-EEG is not of value for the prediction of adverse events during carotid endartectomy and can be eliminated. Because contralateral occlusion is highly predictive of changes with clamping, and patients undergoing a second carotid endartectomy will usually manifest EEG changes identical to those at the first, operative EEG monitoring can also be eliminated from both these circumstances. Finally, prior stroke does not lead to a higher incidence of clamp-induced EEG changes, and thus is not an indication for shunting in and of itself.

Brain Ischemia

A multi-modal approach to the management of bypass graft failure.

Bypass graft failure is an unsolved problem in the contemporary treatment of peripheral arterial occlusion. Thrombolysis of a failed bypass graft is performed with instillation of plasminogen activators directly into the substance of the thrombus. Thrombolytic techniques can restore the bypass graft to its pre-occlusive state, clearing the inflow and outflow tracts of propagated thrombus and unmasking the causative lesion responsible for graft occlusion. Open surgery, or an endovascular modality, can then be employed to directly address these lesions. Recent randomized trials have demonstrated the safety and efficacy of a thrombolytic treatment strategy when the graft occlusion is acute, that is, when the patient presents within 2 weeks of the event. The appropriate management of the patient with an acutely occluded bypass graft includes thrombolysis, endovascular modalities and open surgery, employed in conjunction, to improve patient outcome over that observed with an immediate operation alone.

Angiography

Noninvasive diagnosis of upper extremity vascular disease.

The relative rarity of vascular disorders of the arm accounts for unfamiliarity with upper extremity diagnostic testing on the part of even experienced vascular clinicians. Understanding the wide variety of noninvasive tests is imperative if one is to appropriately diagnose and treat these disorders. The diagnosis and localization of arterial occlusive disease is dependent on the use of Doppler-derived arterial pressures, which may be measured serially from the upper arm to the digits. Plethysmographic digital waveforms can be used as an aid in the diagnosis of vasospastic disorders as well as in the assessment of therapy. Similarly, provocative testing with cold stimulation can assist in the diagnosis of Raynaud's and other vasospastic disorders. The use of duplex ultrasonography for venous occlusion, although not as accurate as when used for lower extremity problems, can be a useful aid in the diagnosis of upper extremity venous thrombosis. Symptoms associated with the thoracic outlet syndrome can be evaluated and confirmed noninvasively, measuring Doppler pressures and gauging venous outflow obstruction while the patient performs a variety of positional maneuvers. A thorough knowledge of upper extremity noninvasive tests will provide the clinician with confidence in the objective assessment of upper extremity vascular disease.

Arm

Acute lower limb ischemia: determinants of outcome.

BACKGROUND: Previous studies have documented high rates of morbidity and death after acute peripheral arterial occlusion. To date, however, few studies have identified parameters predictive of successful therapy. METHODS: The Thrombolysis or Peripheral Arterial Surgery Trial of intraarterial recombinant urokinase or immediate operation for acute lower extremity arterial occlusion provided data on 544 patients randomized at 113 centers. A Cox proportional hazards multifactor analysis was performed to identify those main effects predictive of amputation-free survival and to document any baseline variables useful in deciding whether a patient would be treated best initially with thrombolysis or operation. RESULTS: Of 28 variables analyzed, eight main effects were predictive of amputation-free survival. These included two demographic factors: white race (risk ratio [RR] = 1.75; p = 0.003) and younger age (RR = 1.015; p = 0.046). Comorbidities comprised four of the main effects: history of central nervous system disease (RR = 1.726; p = 0.005), history of malignancy (RR = 1.615; p = 0.024), congestive heart failure (RR = 2.202; p < 0.001), or low body weight (RR = 1.007 per pound; p = 0.006). The severity of the process was also predictive, as gauged by the presence of skin color changes (RR = 1.585, p = 0.007) or pain at rest (RR = 0.503; p = 0.003). All eight effects were similar in the two treatment groups; none of these variables predicted improved outcome with one form of initial therapy over the other (i.e., there was no therapy-by-variable interaction). The length of occlusion, however, predicted whether a patient would fare better with thrombolysis or operation. With a threshold occlusion length of 30 cm, the RR for longer occlusions to shorter occlusions was 43% better in patients who received thrombolysis, whereas the situation was reversed for those who were randomized to operation. CONCLUSIONS: A variety of baseline variables can be identified that are predictive of outcome after treatment for acute lower extremity ischemia. In addition, the length of the occlusive process appears to predict whether a patient will be best served with thrombolysis or operative intervention; longer occlusions appear to respond best with an initial thrombolytic strategy.

Acute Disease