Four of 11 children with acute lymphoblastic leukemia on long‐term methotrexate therapy developed severe bone pain in their distal extremities. All were in good clinical and hematologic remission. Radiologic examination revealed severe osteoporosis with associated fractures in 5 of these 11 children. A trial of local radiotherapy was attempted in one patient with no response. Methotrexate therapy was stopped in 4 patients with marked improvement in their bone pain and osteoporotic lesions.

Correlative studies were carried out on the coronary arteriograms made during diagnostic procedures and on the specimens obtained at necropsy in 10 cases of coronary heart disease. Of the 134 segments of coronary arteries available for both studies, 44 (33%) were given false-negative arteriographic diagnosis of obstructive atherosclerosis.Factors which may underlie this discrepancy include (1) radiographic technic, (2) projection used, (3) a slitlike lumen adjacent to the atheroma, (4) comparison of severely obstructed segments involved but less severely obstructed, and (5) misinterpretation from the specimen of obstruction present in life.

SUMMARYDeposition of thrombotic material on catheters was observed following more than 50% of 93 diagnostic catheterizations. The incidence of deposition of thrombotic material on catheters remaining in the body for more than 1 day was 100%.Polyethylene and siliconized polyurethane catheters were less thrombogenic than Teflon end-occluded catheters.A definite time relationship between the thrombus formation and the duration of the catheterization procedure was noted.The growth of thrombi on the outside of catheters does not appear to be linear since catheters can remain in place for 10 days or more.Postcatheterization thrombosis is believed to be due to thrombi stripped from the catheter by the arterial wall. The thrombus which originally encases the catheter will pile up at the puncture site as the catheter is withdrawn. Received December 5, 1969; revision accepted for publication January 20, 1970. Circulation, Volume XLI, May 1970 Seldinger technic catheters, thrombi were noted about the catheters in 40%4 to 91%.5 The site from which the catheter was removed was described as a "fibrin channel' and a "cannulated thrombus." Jacobsson and co-workers6 demonstrated similar thrombotic encasement of the catheter in the arteries of dogs.Clinical signs of thrombotic vascular occlusion are much less common. In a survery of 6,160 cardiac catheterizations, clinical arterial thrombosis was diagnosed in 0.5%.7 By oscillographic monitoring of calf pulsations, Jacobsson and associates8 identified arterial occlusion in 1.4% of patients undergoing femoral artery catheterizations. With routine angiograms made prior to withdrawal of the catheter, Siegelman and associates' found surgical thrombectomy indicated following 2.3% of arteriograms.It is the purpose of this study to determine (1) the incidence of thrombus formation on catheters in clinical practice; (2) the relation of thrombus formation to the duration of the catheterization procedure; (3) the throm-833 by guest on

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