Sabah S. Tumeh

RANDOMISED CONTROLLED TRIAL OF RECOMBINANT TISSUE PLASMINOGEN ACTIVATOR VERSUS UROKINASE IN THE TREATMENT OF ACUTE PULMONARY EMBOLISM

The effect of intravenous recombinant human tissue-type plasminogen activator (rt-PA) was compared with that of urokinase in 45 patients with angiographically documented pulmonary embolism (PE) in a randomised controlled trial. The two principal end-points were clot lysis at 2 h, as assessed by angiography, and pulmonary reperfusion at 24 h, as assessed by perfusion lung scanning. All patients received the full dose of rt-PA but urokinase infusions were terminated prematurely (on average after 18 h) in 9 patients because of allergy in 1 and uncontrollable bleeding in 8. By 2 h, 82% of rt-PA-treated patients showed clot lysis, compared with 48% of urokinase-treated patients (p = 0.008; 95% CI for the difference = 10-58%). Improvement in lung scan reperfusion at 24 h was identical in the two treatment groups. The reduction in fibrinogen did not differ significantly between the rt-PA and urokinase groups (45% vs 39% at 2 h and 34% vs 40% at 24 h). The results indicate that in the dose regimens employed, rt-PA acts more rapidly and is safer than urokinase in the treatment of acute PE.

Utility of cross-linked fibrin degradation products in the diagnosis of pulmonary embolism

Blood samples from patients with suspected pulmonary embolism (PE) were obtained at the time of diagnostic lung scanning to determine whether identification of those with activation of endogenous fibrinolytic pathways could serve as a screening test for PE. Cross-linked fibrin degradation products (XDPs) were measured by a quantitative enzyme-linked immunoassay with a specific monoclonal antibody (MabCO Dimertest EIA) that recognizes cross-linked D-dimer fragments and related high molecular weight fibrin derivatives containing D-dimer but that does not cross-react with fibrinogen or its plasmin degradation products. PE was present in 19 with positive pulmonary angiograms and absent in 50 with completely normal lung scans. Elevated levels of XDPs (greater than 144 ng/ml) were present in 17 of 19 patients (89%) with PE and in 28 of 50 (56%) without PE (p = 0.30). Among those with PE present, the XDP levels were (means +/- sd) 864 +/- 1,068 ng/ml (median = 470 ng/ml) compared with 285 +/- 395 ng/ml (median = 155 ng/ml) among those with PE absent (p = 0.003). For PE detection, elevated XDP levels provided a sensitivity of 89%, a specificity of 44%, a positive predictive value of 38%, a negative predictive value of 92%, and an accuracy of 57%. Among those with elevated XDP levels and PE absent, 75% had no apparent reason for XDP elevations. These data indicate that XDPs are significantly elevated in patients with PE but that, in contrast to earlier reports, measurement of XDPs among individuals with suspected PE may not be sufficiently accurate to be clinically useful in screening.

Myocardial clearance of Tc-99m hexakis-2-methoxy-2-methylpropyl isonitrile (MIBI) in patients with coronary artery disease.

Myocardial clearance of the new cationic, lypophilic myocardial perfusion agent, Tc-99m-hexakis-2-methoxy-2-methylpropyl isonitrile (MIBI) was studied in nine patients with coronary artery disease. Regional time-activity curves were determined from serial postexercise myocardial SPECT images after a single dose of Tc-99m MIBI. There were significant differences between the clearance rates from normal and ischemic myocardium. Tc-99m MIBI washout from normal myocardium was 27 ± 8% by 6 hours after injection. Clearance from mild myocardial defects (initial activity greater than 60% of the activity in normal myocardium) was 16% by 6 hours in six patients. No washout was detected by 6 hours in the three patients with severe myocardial defects. The ratio between the activity in ischemic and normal myocardium increased from 0.70 ± 0.08 to 0.80 ± 0.13 and 0.84 ± 0.13 at 4 and 6 hours after injection in the patients with mild defects. In the patients with large defects, the ratio increased from 0.42 ± 0.09 to 0.54 ± 0.07 at 6 hours. It is concluded that, while redistribution is substantially slower than with TI-201, image interpretation and data evaluation should be approached cautiously when imaging is delayed 4 hours or more after injection of Tc-99m MIBI. Quantitative techniques aimed at evaluating the extent and intensity of myocardial ishemia will be particularly affected.

Bile duct disruption after laparoscopic cholecystectomy

The reported prevalence of biliary tract disruption following laparoscopic cholecystectomy has ranged from 0% to 7% in early reports. We have reviewed the first 823 laparoscopic cholecystectomies performed at our institution and found 13 symptomatic biliary complications necessitating further therapy (prevalence 1.6%). This finding represents a decrease from the 2.7% prevalence found in our earlier series. The incidence of biliary complications will likely continue to vary depending on patient selection, operator experience, and new developments in laparoscopic technique. Bile duct injury and bile leaks are often difficult to diagnose but must be strongly considered in postoperative patients with abdominal pain, fever, jaundice, or continued bilious drainage from a surgical drain. Whereas computed tomography (CT) and sonography are sensitive in detecting perihepatic or free peritoneal fluid collections, they are nonspecific and definitive diagnosis of biliary tract injury requires hepatobiliary scintigraphy, endoscopic retrograde cholangiopancreatography (ERCP), percutaneous transhepatic cholangiography (PTC), or percutaneous aspiration. Disruption of the biliary tree has commonly been treated with reoperation or percutaneous drainage. More recently, endoscopic management has shown encouraging results for bile leaks and strictures in small series.

Gallium-67 imaging and computed tomography in early retroperitoneal fibrosis.

Retroperitoneal fibrosis is characterized by symptoms associated with gradual compression of retroperitoneal structures. This case report demonstrates the use of Ga-67 imaging and CT in the early diagnostic work-up of this disorder.

Tc-99m MIBI SPECT in the Assessment of Myocardial Reperfusion after Percutaneous Transluminal Coronary Angioplasty

Tc-99m MIBI SPECT was used to assess the early benefits of successful percutaneous transluminal coronary angioplasty (PTCA) in nine consecutive patients. SPECT stress studies were done by artificial cardiac pacing just prior to PTCA and 16–20 hours later, with perfusion images obtained 2–3 hours after pacing stress and Tc-99m MIBI injection. Angiographic restenosis was demonstrated in three patients at a later date, and all of these showed no significant improvement on the perfusion study after PTCA. All four patients asymptomatic at 7 months following PTCA had an average 15% improvement in segmental perfusion after the procedure. In two patients symptomatic after PTCA, one showed angio-graphic patency and had >15% improvement in perfusion, while the second showed no scintigraphic improvement (no angiographic data obtained). This preliminary study suggests that Tc-99m MIBI is an important adjunct to angiography in estimating the amount of myocardium “at risk” before and after PTCA.

Platelet activation and aggregation after endothelial injury. Assessment with indium-111-labeled platelets and angiography.

Although platelet activation and aggregation after endothelial injury are well documented, the time course of platelet deposition and the relationship between platelet aggregation and the release of vasoactive products have not been fully clarified in vivo. To study the effect of platelet vasoactive products, a collateral blood supply was induced by ligating the superficial femoral artery in male New Zealand white rabbits. Two weeks later, endothelial injury to the distal abdominal aorta was produced by cytologic brush or mimicked with a metal coil embolus. Platelet aggregation was assessed with indium-111 (111In)-labeled platelets, and scintigraphy demonstrated significant, progressive platelet deposition up to 3 hours after injury and evidence of residual activity 24 hours later. Angiography showed that the time course of peripheral vasoconstriction matched closely that of platelet deposition, indicating release of vasoactive substances from the aggregating platelets. These pathophysiologic changes secondary to endothelial injury may have significant implications for intravascular interventional procedures.

Detection of hepatic metastases in diffuse fatty infiltration by CT: the complementary role of imaging

Six patients undergoing computed tomographic (CT) evaluation for possible abdominal and pelvic metastases were shown to have diffuse fatty infiltration of the liver and findings indeterminate for hepatic metastases. In two patients with diffuse fatty infiltration and no focal hepatic lesions on CT, technetium-99m sulfur colloid imaging demonstrated focal hepatic defects confirmed to represent metastases. In four patients with diffuse fatty infiltration and hyperdense liver foci on CT, radionuclide imaging demonstrated normal uptake in the hyperdense foci confirmed to represent areas of normal liver spared by fatty infiltration. In each of the six patients, clinical management was altered by the radionuclide findings.

Unusual solitary soft tissue metastases from renal cell carcinoma

Adenocarcinoma of the kidney may metastasize to many organs and remain undetected for years. We present three illustrative cases of patients who had solitary recurrences in unusual locations; two of the three presented more than eight years after having undergone nephrectomy. Recognition of these unusual presentations is important in proper patient management.

Embolization of platelets after endothelial injury to the aorta in rabbits. Assessment with 111indium-labeled platelets and angiography.

This study exploits the ability of a collateral arterial network to trap platelet aggregates in order to document the frequency of macroembolization in rabbits after endothelial damage. Two weeks after ligation of the right superficial femoral artery, endothelial injury was induced in the distal aorta; within 3 hours the rabbits were studied using either angiography or 111indium-labeled (111In) platelet scintigraphy. Angiography indicated visible aggregates in the thigh region in eight of 19 and arterial occlusion in three of 19 rabbits. The collateral-dependent thigh also showed more 111In-labeled platelet activity than the contralateral side (P less than .001), whether platelets were injected before or 2 hours after injury. Radioactivity in the limbs of rabbits with no injury was distributed symmetrically. Blood pool volume, assessed with technetium-99m-labeled red blood cells, was the same in both thighs, and could not account for these observations. The findings indicate that platelet activation and aggregation after endothelial injury lead to microembolization much more frequently than it leads to macroaggregate formation and visible artery occlusion.