A Case of Heparin resistance?
Patient A.B..- 23 y/o wf started on oral contraceptive (OC) 5 months ago presents with dyspnea x 5 days followed by severe pleuritic chest pain. V/Q scan shows no perfusion to left lung. BP stable.
Hematology consult obtained because of : (a) difficulty in elevating her PTT- on 1600 u/hr with PTT only 42 sec (b) Role for low molecular weight heparin as access is poor (c) hypercoaguable w/u...what underlying congenital hypercoaguable state may she have?
Ultimately this patient needed 2800 u/hr to keep PTT in 60 sec range, she is 105 kg which may explain in part increased heparin requirement though she could have ATIII deficiency, unfortunately an immunologic ATIII assay was not done while on heparin (a low level would have prompted use of ATIII concentrate), the ATIII bioassay drawn while on Coumadin was WNL. Unfortunately, also, the physician who prescribed the OC did not ask about family history- her father who cuts trees and wears a strap around each calf had a DVT at age 45, his mother has had 2 DVTs though associated with pelvic surgery. In this patient's case the onset of clot < 6 months since starting OCs implicates OCs in part though obviously the family history strongly suggests additional hypercoaguable states- FV Leiden raises chance to clot in person on OC from 3 fold to 80 fold. However, an exhaustive work-up for congenital thrombophilia is negative to date: screen for Factor V Leiden ("Resistance to activated Protein C Assay"), PCR for PT 20,210; Protein C and S levels , total homocysteine level. Work-up for Anti-Phospholipid Antibody Syndrome was also negative. Low molecular weight heparin was discouraged not because she had a PE but because of her weight > 100 kg wherein its not clear if dosing remains linear, certainly LMWH levels could be followed but as a practical issue the weekend was coming up and LMWH levels could not be easily set up around the clock.
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