Jack Hirsh - Academia.edu (original) (raw)

Papers by Jack Hirsh

Archives of Internal Medicine, 1993

The use of subcutaneous heparin, the therapy of choice for women requiring anticoagulant prophyla... more The use of subcutaneous heparin, the therapy of choice for women requiring anticoagulant prophylaxis during pregnancy, is problematic because of the discomfort produced by repeated injections. An indwelling subcutaneous Teflon catheter that can be left in place for 1 week recently became available for use as an entry port for parenteral therapy. Since the use of this catheter has the potential to overcome some of the problems of long-term heparin therapy, we decided to compare this Teflon catheter with twice-daily subcutaneous injections in women requiring heparin during pregnancy. In a randomized, multiple-crossover study, patients alternated every 2 weeks between having heparin administered through the indwelling Teflon catheter and receiving heparin via subcutaneous injections. After each 4-week cycle, patients completed a questionnaire designed to determine their preferred method of heparin administration. The side effects, doses, and anticoagulant activity of heparin with the two delivery systems were also compared. Twelve patients completed one to five 4-week cycles of heparin therapy. Ten of the patients selected the Teflon catheter as the preferred route of heparin administration (P = .04) and 11 patients reported that the catheter caused less pain and bruising than twice-daily subcutaneous injections (P < .01). Five patients developed urticarial reactions at the sites of heparin injections. These reactions tended to be more severe when the Teflon catheter was used, and two women discontinued using the catheter after the first cycle because of this complication. There were no differences in heparin dose requirements or achieved activated partial thromboplastin times between the two routes of heparin administration. Most pregnant women in our study preferred to have subcutaneous heparin administered through an indwelling Teflon catheter rather than by twice-daily injections. Heparin given through the Teflon catheter was bioavailable and caused less local bruising than twice-daily injections. Urticarial reactions to heparin tended to be more severe with the use of the Teflon catheter and resulted in the discontinuation of the device's use in two of 12 patients.

VIIIth International Congress on Thrombosis and Haemostasis, 1981

Heparin enhances the rate of inactivation of thrombin (IIa) and other coagulant proteases by anti... more Heparin enhances the rate of inactivation of thrombin (IIa) and other coagulant proteases by antithrombin III (AT III). The anticoagulant activity of heparin is associated with heparin moieties which have high affinity to AT III. However, the contribution of the IIa affinity to the anticoagulant activity has not been as clear. Standard porcine mucosal heparin was fractionated on affinity columns consisting of purified human AT III and IIa immobilized on agarose to determine the effect of heparins of various affinities on the second order rate constant (K") for the inactivation of IIa by AT III. Results are expressed as the rate enhancement factor (REF) which is defined as the ratio of the K" in the presence of 50 ng/ml heparin to the K" in the absence of heparin. The REF for unfractionated heparin was 9.5. Chromatography on either AT III-agarose or IIa-agarose resulted in elution of three heparin fractions corresponding to a void volume fraction, a low affinity fracti...

Annals of Internal Medicine, 1992

To estimate the prevalence of objectively proven thrombotic complications in antithrombin-III-def... more To estimate the prevalence of objectively proven thrombotic complications in antithrombin-III-deficient persons. Cross-sectional study and a critical review of the literature. The prevalence of thrombosis in antithrombin III-deficient and -nondeficient family members of a large kindred was estimated by history, review of diagnostic tests, and examination for venous reflux by Doppler ultrasonography, as an indicator of previous venous thrombosis. A MEDLINE search and literature review of the published English- and French-language literature from 1966 to 1990 that described antithrombin-III-deficient families was done, and the following information was obtained: the prevalence of thrombosis in deficient and nondeficient family members, the presence or absence of risk factors for thrombosis (surgery, pregnancy, the postpartum state, use of oral contraceptives, immobilization, metastatic cancer, major trauma) at the time of the thrombotic event, and age of onset of the first episode of thrombosis. The validity of the studies was assessed according to predetermined criteria. Sixty-seven research subjects were evaluated. Six of 31 (19.4%) antithrombin-III-deficient subjects compared with none of 36 (0%) nondeficient subjects had had one or more thrombotic events. The initial episode in five of six subjects had occurred in association with risk factors for thrombosis. The literature search indicated that the pooled prevalence of symptomatic venous thrombosis among the deficient subjects was 51%, but objective testing was done in only 17% of these subjects at the time of presentation. Based on the data from this antithrombin-III-deficient kindred, lifelong anticoagulant prophylaxis does not appear to be warranted in asymptomatic carriers, and prophylaxis could be limited to periods of high risk for thrombosis.

The Journal of Thoracic and Cardiovascular Surgery, 2012

Objective: To compare the potency, reversibility, and perioperative bleeding risk of Hepalean wit... more Objective: To compare the potency, reversibility, and perioperative bleeding risk of Hepalean with those of PPC heparin. Methods: Because in vitro testing failed to detect differences in the potency or protamine reversibility of the 2 heparin preparations, we conducted a parallel group, single-center, double-blind, randomized, controlled trial to compare the anticoagulant effects of Hepalean to those of PPC heparin in patients undergoing coronary artery bypass grafting with cardiopulmonary bypass. Results: From June 1, 2011, to June 30, 2011, we randomly assigned 11 patients to receive PPC heparin and 10 to receive Hepalean. Despite similar initial doses of heparin, the median initial activated clotting time was numerically lower in the PPC heparin group than in the Hepalean group (median, 516.0 seconds; interquartile range, 481.0-633.0; vs median, 584.0 seconds, interquartile range, 520.0-629.0; P ¼ .418). Those given PPC heparin required a greater total heparin dose (median, 46,000.0 U; interquartile range, 39,500.0-60,000.0 vs median, 34,500.0 U; interquartile range, 32,250.0-37,000.0; P ¼ .011) and a greater dose of heparin per kilogram than those given Hepalean (median, 572.9 U/kg; interquartile range, 443.0-659.7 vs median, 401.1 U/kg; interquartile range, 400.0-419.4; P ¼ .003). The key secondary results included an increased median total protamine dose (median, 600.0 mg; interquartile range, 550.0-700.0; vs median, 500.0 mg; interquartile range, 425.0-542.5; P ¼ .026) and a trend toward increased chest tube output within 24 hours (median, 830.0 mL; interquartile range, 425.0-1135.0; vs median, 702.5 mL; interquartile range, 550.0-742.5; P ¼ .324). Conclusions: PPC heparin use was associated with greater heparin and protamine dose requirements than Hepalean. These findings indicate that heparin preparations are not interchangeable and suggest that a direct comparison of the potency with the brand in use is needed if a change is made to ensure that the agents exert similar anticoagulant effects in vivo. (

$Research paper thumbnail of Effects of heparin fractions of different affinities to antithrombin III and thrombin on the inactivation of thrombin and factor Xa by antithrombin III$

Canadian journal of biochemistry and cell biology, Oct 1, 1984

Thrombosis and Haemostasis, 1987

Thrombosis Research, 1981

Blood, Oct 1, 1980

Affinity chromatography of human cryosupernatants on anti-human factor VIll-Sepharose yielded a p... more Affinity chromatography of human cryosupernatants on anti-human factor VIll-Sepharose yielded a plasma devoid of detectable factor VIIIC, VIIIR:Ag. and VIIIR:WF activities. This plasma was indistinguishable from severe congenital hemophilic plasma when used as substrate in factor VIII coagulant assays.

British Journal of Haematology, Jun 1, 1984

Platelets and phosphilipids have been shown to protect factor Xa from inhibition by the heparin-a... more Platelets and phosphilipids have been shown to protect factor Xa from inhibition by the heparin-antithrombin I11 complex. The studies reported herein investigated the effects of gel filtered platelets, activated platelets, brain phospholipids (cephalin), and brain tissue factor on the inactivation of thrombin and factor Xa by the heparin-antithrombin I11 complex. In addition, the relative anticoagulant effects of heparin on the extrinsic and intrinsic coagulation pathways were investigated. Our results suggest that gel filtered platelets, activated platelets, cephalin and tissue factor protect thrombin, as well as factor Xa, from inactivation by the heparinantithrombin 111 complex. Tissue factor had the greatest anti-heparin activity. Activated platelets, gel filtered platelets, cephalin and tissue factor did not alter the protease-antithrombin I11 reaction rates measured in the absence of heparin. These observations are consistent with the hypothesis that platelets, brain phospholipids, and tissue factor, in the presence of calcium, partition heparin from antithrombin 111, and thus prevent full expression of the antithrombin 111-dependent anticoagulant activity of heparin. A variety of assays, such as thrombin clotting time, factor Xa clotting time, activated partial thromboplastin time (APTT), and chromogenic assays for thrombin and factor Xa, are currently in use for monitoring plasma heparin levels (Tien & Abilgaard, 1976; Denson & Bonnar, 1973; Tien et al, 1976). While the factor Xa clotting time and the APTT require both calcium and brain phopholipids (Proctor & Rapaport, 1961; Denson & Bonnar, 1973; Walsh & Biggs, 1972; Yin et al, 1973), the thrombin clotting time is performed with or without calcium and does not require phospholipid (Denson & Bonnar, 1973). The chromogenic assays are usually performed in the absence of both calcium and phospholipid (Tien et al, 1976; Nordeman et al, 1980). Brain phospholipids (cephalin) and activated platelets have been shown to protect factor Xa from inhibition by the heparin-antithrombin I11 complex.

Thrombosis Research, Aug 1, 1981

ABSTRACT

Thrombosis Research, Nov 1, 1982

Standard unfractionated heparin is known to have two actions on blood clotting. Unfractionated he... more Standard unfractionated heparin is known to have two actions on blood clotting. Unfractionated heparin enhances the rates at which antithrombin III inactivates activated clotting factors, and inhibits the activation of both Factor X and prothrombin by disrupting the calcium and phospholipid dependent assembly of the Factor X and prothrombin activator complexes. This latter inhibitory action of heparin occurs independently of antithrombin III. A heparin fraction with low affinity to antithrombin III was prepared from standard heparin by affinity chromatography on antithrombin-III-Sepharose and its properties compared with unfractionated heparin. The low affinity heparin fraction and the unfractionated heparin had equivalent inhibitory effects on prothrombin activation in antithrombin III depleted plasma. In normal plasma, the low affinity fraction inhibited the activation of prothrombin. Unlike the unfractionated heparin, however, the fraction of heparin with low affinity to antithrombin III did not enhance the inactivation of either Factor Xa or thrombin. This antithrombin III independent inhibition of the activation of prothrombin was also evident when activated platelets were used as the source of the procoagulant phospholipids. The antithrombin III independent effect of heparin is unlikely to be important therapeutically, however, if this property of heparin is shared by other naturally occurring glycosaminoglycans, it could be important in maintaining the fluidity of blood under physiological conditions.

Annals of the New York Academy of Sciences, Dec 1, 1986

Biochemical Journal, May 1, 1992

Hirudin and hirulog-1 {D-Phe-Pro-Arg-Pro-[Gly]4-desulphohirudin-(54-65)} abrogate the enzyme acti... more Hirudin and hirulog-1 {D-Phe-Pro-Arg-Pro-[Gly]4-desulphohirudin-(54-65)} abrogate the enzyme activities of a-thrombin by binding the enzyme simultaneously at its catalytic centre and fibrin(ogen)-recognition exosite. In contrast, hirugen [hirudin-(54-65)] binds a-thrombin solely at the fibrin(ogen)-recognition exosite, and competitively inhibits fibrinopeptide A release. To investigate the extent to which the fibrin(ogen)-recognition exosite is involved when a-thrombin catalyses the amplification reactions of coagulation, we compared the abilities of hirudin, hirulog-1 and hirugen to inhibit simultaneously Factor X, Factor V and prothrombin activation. Whereas 0.1 tM-hirudin and 0.1 uM-hirulog-(i.e. less than 10% of the concentration of prothrombin in plasma) inhibited Factor X, Factor V and prothrombin activation, 10 /M was the minimum concentration of hirugen to achieve a similar anticoagulant action. Concentrations of hirudin and hirulog-equimolar to and 5 times greater than those of a-thrombin respectively abrogated Factor V activation by exogenous a-thrombin. In contrast, a 500-fold molar excess of hirugen could not. The inability of hirugen to inhibit the activation of the three clotting factors effectively suggests that the fibrin(ogen)-recognition exosite does not play a mandatory role when thrombin activates Factor V.

Thrombosis and Haemostasis, 1993

To determine whether functional antithrombin III (AT-III) levels measured by a factor Xa inhibiti... more To determine whether functional antithrombin III (AT-III) levels measured by a factor Xa inhibition (AT-III-Xa) assay identifies AT-III deficient individuals more reliably than functional AT-III levels measured by a thrombin inhibition (AT-III-IIa) assay. Cross-sectional study. Sixty-seven members of a large family with type 2 AT-III deficiency. DNA analysis was used as the reference diagnostic standard for AT-III status and subjects were classified as AT-III deficient or non deficient according to these results. Functional AT-III levels were measured in all subjects using: 1) a chromogenic substrate for thrombin and added human thrombin (AT-III-IIa), and 2) a chromogenic substrate for factor Xa and added bovine factor Xa (AT-III-Xa). Functional heparin cofactor II (HC-II) levels were measured using a commercially available kit. The proportions of 125I-alpha-thrombin complexed to AT-III and HC-II were measured by polyacrylamide gel electrophoresis and autoradiography. Thirty-one (46%) individuals were classified as AT-III deficient and 36 (54%) as AT-III non deficient. AT-III-Xa assay measured a significantly lower mean AT-III value and a narrower range for individuals classified as AT-III deficient than the AT-III-IIa assay. Using the AT-III-IIa assay, six subjects had borderline AT-III levels compared to none with the AT-III-Xa assay.(ABSTRACT TRUNCATED AT 250 WORDS)

British Journal of Haematology, Aug 1, 1985

SummaryThe effects of standard heparin, three low molecular weight derivatives of heparin, dermat... more SummaryThe effects of standard heparin, three low molecular weight derivatives of heparin, dermatan sulphate and pentosan polysulphate on the intrinsic coagulation pathway were compared in order to evaluate the contributions of the anti‐factor Xa and anti‐thrombin activities to their anticoagulant activities. The anticoagulant potency was measured by the ability of each sulphated polysaccharide to inhibit the generation of thrombin activity in plasma. Similarly, the ability of the six sulphated polysaccharides to enhance the rates of inactivation either factor Xa or thrombin in defibrinated plasma containing calcium chloride and cephalin were also determined. Standard heparin was the only sulphated polysaccharide that could equally inhibit thrombin generation and enhance the inactivation of factor Xa and thrombin by plasma. Dermatan sulphate and pentosan polysulphate were more effective as inhibitors of thrombin generation than potentiators of factor Xa inactivation. The two smallest derivatives of heparin, which had high anti‐factor Xa (but low antithrombin) activity, were the poorest inhibitors of thrombin generation. Our results therefore suggest that only sulphated polysaccharides that enhance the inactivation of thrombin by plasma and/or inhibit the generation of thrombin activity in plasma are good anticoagulants. These two activities of sulphated polysaccharides appear to be good predictors of the relative antithrombotic potency in vivo.

Archives of internal medicine, Sep 27, 1999

Blood, Sep 1, 1984

Heparan with a low affinity for antithrombin Ill has previously been demonstrated to inhibit thro... more Heparan with a low affinity for antithrombin Ill has previously been demonstrated to inhibit thrombin generation in both normal plasma and plasma depleted of antithrombin Ill. In addition. standard heparin and heparin with a low affinity for antithrombin Ill have been demonstrated to have equivalent inhibitory actions on thrombin generation in plasma depleted of antithrombin III. These observations prompted the investigation of the effects of four normal vessel wall glycosaminoglycans (heparan sulfate, dermatan sulfate. chondroitin-4-sulfate. and chondroitin-6-sulfate) on the intrinsic pathway generation of thrombin and factor Xa and on the inactivation of thrombin and factor Xa in plasma. Heparan sulfate inhibited thrombin generation and accelerated the inactivation of added thrombin and factor Xa in normal plasma but not in antithrombin Ill-depleted Sigma Chemical Co. St Louis. Porcine mucosal heparins (specific activity I 50 USP units/mg) were products of Riker Laboratories,

$Research paper thumbnail of Unfractionated heparin inhibits thrombin-catalysed amplification reactions of coagulation more efficiently than those catalysed by factor Xa$

Biochemical Journal, 1989

We have proposed previously that the steps in coagulation most sensitive to inhibition by heparin... more We have proposed previously that the steps in coagulation most sensitive to inhibition by heparin are the thrombin-dependent amplification reactions, and that prothrombinase is formed in heparinized plasma only after Factor Xa activates Factor VIII and Factor V. These propositions were based on the demonstration that both heparin and Phe-Pro-Arg-CH2Cl completely inhibited 1251I-prothrombin activation for up to 60 s when contact-activated plasma (CAP) was replenished with Ca2+. Furthermore, the addition of thrombin to CAP before heparin or Phe-Pro-Arg-CH2Cl completely reversed their inhibitory effects. Additional support for the above hypotheses is provided in this study by demonstrating that, when the activity of thrombin is suppressed by heparin (indirectly) or by Phe-Pro-Arg-CH2Cl (directly), exogenous Factor Xa reverses the ability of these two agents to inhibit prothrombin activation. Prothrombin activation was initiated by adding Factor Xa (1 nM) or thrombin (1 or 10 nM) simultaneously with CaCl2 to CAP. In the absence of heparin or Phe-Pro-Arg-CH2Cl, prothrombin activation was seen 15 s later in either case. Heparin failed to delay, and Phe-Pro-Arg-CH2Cl delayed for 15 s, prothrombin activation in CAP supplemented with Factor Xa. In contrast, heparin and Phe-Pro-Arg-CH2Cl completely inhibited prothrombin activation for at least 45 s in CAP supplemented with 1 nM-thrombin. Heparin failed to delay prothrombin activation in CAP supplemented with 10 nM-thrombin, whereas Phe-Pro-Arg-CH2Cl completely inhibited prothrombin activation in this plasma for 45 s. These results suggest that in CAP: (1) Factor Xa can effectively activate Factor VIII and Factor V when the proteolytic activity of thrombin is suppressed; (2) heparin-antithrombin III is less able to inhibit Factor Xa than thrombin; (3) suppression of the thrombin-dependent amplification reactions is the primary anticoagulant effect of heparin. MATERIALS AND METHODS Materials Activated-partial-thromboplastin-time (APTT) reagent was obtained from Organon Teknica, Toronto, Ont.,

Biochemical Journal, Apr 15, 1987

Heparin catalyses the inhibition of two key enzymes of blood coagulation, namely Factor Xa and th... more Heparin catalyses the inhibition of two key enzymes of blood coagulation, namely Factor Xa and thrombin, by enhancing the antiproteinase activities of plasma antithrombin III and heparin cofactor II. In addition, heparin can directly inhibit the activation of Factor X and prothrombin. The contributions of each of these effects to the anticoagulant activity of heparin have not been delineated. We therefore performed experiments to assess how each of these effects of heparin contributes to its anticoagulant activity by comparing the effects of heparin, pentosan polysulphate and D-Phe-Pro-Arg-CH2CI on the intrinsic pathway of coagulation. Unlike heparin, pentosan polysulphate catalyses only the inhibition of thrombin by plasma. D-Phe-Pro-Arg-CH2Cl is rapid enough an inhibitor of thrombin so that when added to plasma no complexes of thrombin with its inhibitors are formed, whether or not the plasma also contains heparin. Heparin (0.66 ,ug/ml) and pentosan polysulphate (6.6 ,#g/ml) completely inhibited the intrinsic-pathway activation of '251-prothrombin to 125I-prothrombin fragment 1+2 and 1251-thrombin. On the addition of thrombin, a good Factor V activator, to the plasma before each sulphated polysaccharide, the inhibition of prothrombin activation was demonstrable only in the presence of higher concentrations of the sulphated polysaccharide. D-Phe-Pro-Arg-CH2Cl also completely inhibited the intrinsic-pathway activation of prothrombin in normal plasma. The inhibitory effect of D-Phe-Pro-Arg-CH2Cl was reversed if thrombin was added to the plasma before D-Phe-Pro-Arg-CH2Cl. The inhibition of the activation of prothrombin by the three agents was also abolished with longer times with re-added Ca2+. Reversal of the inhibitory effects of heparin and pentosan polysulphate was associated with the accelerated formation of 1251-thrombinantithrombin III and 1251-thrombin-heparin cofactor complexes respectively. These results suggest that the anticoagulant effects of heparin and pentosan polysulphate are mediated primarily by their ability to inhibit the thrombin-dependent activation of Factor V, thereby inhibiting the formation of prothrombinase complex, the physiological activator of prothrombin.

$Research paper thumbnail of A Comparison of Low-Molecular-Weight Heparin Administered Primarily at Home with Unfractionated Heparin Administered in the Hospital for Proximal Deep-Vein Thrombosis$

The New England Journal of Medicine, Mar 14, 1996

Background. Patients with acute proximal deep-vein thrombosis are usually treated first in the ho... more Background. Patients with acute proximal deep-vein thrombosis are usually treated first in the hospital with intravenous standard (unfractionated) heparin. However, the longer plasma half-life, better bioavailability after subcutaneous administration, and more predictable anticoagulant response of low-molecular-weight heparins make them attractive for possible home use. We compared these two approaches. Methods. Patients with acute proximal deep-vein thrombosis were randomly assigned to receive either intravenous standard heparin in the hospital (253 patients) or lowmolecular-weight heparin (1 mg of enoxaparin per kilogram of body weight subcutaneously twice daily) administered primarily at home (247 patients). The study design allowed outpatients taking low-molecular-weight heparin to go home immediately and hospitalized patients taking low-molecular-weight heparin to be discharged early. All the patients received warfarin starting on the second day. Results. Thirteen of the 247 patients receiving lowmolecular-weight heparin (5.3 percent) had recurrent thromboembolism, as compared with 17 of the 253 patients receiving standard heparin (6.7 percent; P ϭ 0.57; absolute difference, 1.4 percentage points; 95 percent confidence interval, Ϫ 3.0 to 5.7). Five patients receiving low-molecularweight heparin had major bleeding, as compared with three patients receiving standard heparin. After randomization, the patients who received low-molecular-weight heparin spent a mean of 1.1 days in the hospital, as compared with 6.5 days for the standard-heparin group; 120 patients in the low-molecular-weight-heparin group did not need to be hospitalized at all. Conclusions. Low-molecular-weight heparin can be used safely and effectively to treat patients with proximal deep-vein thrombosis at home.