title: Antithrombin-III plasma activity during and after prolonged use of heparin in unstable angina.
abstract: Heparin effectively prevents the complications of unstable angina but disease reactivation has been documented following its discontinuation. To investigate whether this could be related to antithrombin-III depletion, 50 patients with unstable angina had serial determinations of activated partial thromboplastin time and of the plasma levels of heparin, antithrombin-III activity and of the thrombin-antithrombin-III complex before, during and, in a subgroup of 8 patients, 4 hours after heparin discontinuation. Heparin was administered intravenously at therapeutic doses for a mean of 7.6 +/- 4.1 days. Plasma antithrombin-III activity decreased rapidly from 1.05 +/- 0.03 to 1.0 +/- 0.03 U/ml (p < 0.03) following heparin initiation with no further significant subsequent decrease. Antithrombin-III activity returned to the control values 4 hours after the discontinuation of heparin. Thus, heparin treatment is associated with small, non-cumulative and rapidly reversible decrease in antithrombin-III activity. Reactivation of unstable angina after discontinuation of heparin must be explained by a mechanism other than antithrombin-III deficiency.
authors.affiliation: Department of Medicine, Montreal Heart Institute, Quebec, Canada.
authors.forename: R M
authors.initials: RM
authors.lastname: Lidón
authors.forename: P
authors.initials: P
authors.lastname: Théroux
authors.forename: D
authors.initials: D
authors.lastname: Robitaille
mesh_terms: D000789:Angina, Unstable / Q000097:blood* / Q000188:drug therapy; D000990:Antithrombin III / Q000032:analysis; D020152:Antithrombin III Deficiency; D001241:Aspirin / Q000627:therapeutic use; D005260:Female; D006493:Heparin / Q000627:therapeutic use*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010314:Partial Thromboplastin Time; D010447:Peptide Hydrolases / Q000032:analysis; D011446:Prospective Studies
chemical_list: C046193:antithrombin III-protease complex; D000990:Antithrombin III; D006493:Heparin; D010447:Peptide Hydrolases; D001241:Aspirin