Prevalence of heparin/platelet factor 4 antibodies before and after cardiac surgery.
BACKGROUND
The clinical significance of heparin/platelet factor 4 (PF4) antibodies in subjects undergoing cardiac surgery has not been systematically studied. We prospectively investigated whether the presence of heparin/PF4 antibodies would predict clinical thrombosis in this population.


METHODS
In 299 patients scheduled for cardiac surgery between October 2003 and March 2005, the heparin/PF4 antibodies and platelet count were measured immediately prior to, and 5 days after, surgery. The patients were followed up at 30 days for thrombotic complications.


RESULTS
The prevalence of the heparin/PF4 antibodies was 4.3% (13 of 299) prior to surgery and increased more than fivefold to 22.4% (62 of 277) postoperatively (p < 0.0001). Thromboembolic events occurred in 8.8% of patients with negative antibody and in 6.3% of patients with positive antibody (p = 0.77). Of the 62 patients with positive heparin/PF4 antibodies postoperatively, 22 (35.5%) were treated with a nonheparin anticoagulant. There was a trend toward higher rates of thromboembolic events in subjects who were thrombocytopenic compared with those who were not (17.1% and 6.7%, respectively, p = 0.06), regardless of antibody status. Two out of 8 patients (25%) with both thrombocytopenia and a positive antibody (clinical heparin-induced thrombocytopenia [HIT]) suffered a thromboembolic event, compared with 17 of 222 (7.7%) without clinical HIT (p = 0.13).


CONCLUSIONS
The high prevalence of antibodies to the heparin/PF4 complex after cardiac surgery and the low rate of thromboembolic complications in this population suggest that the antibody alone does not confer an increased risk of thrombotic complications. Monitoring for thrombocytopenia is recommended.
Everett
Brendan M
BM
Department of Medicine, Cardiology Division, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114, USA.
Yeh
Robert
R
Foo
Shi Yin
SY
Criss
David
D
Van Cott
Elizabeth M
EM
Laposata
Michael
M
Avery
Edwin G
EG
Hoffman
William D
WD
Walker
Jennifer
J
Torchiana
David
D
Jang
Ik-Kyung
IK
D000368:Aged; D000906:Antibodies / Q000097:blood*; D000925:Anticoagulants / Q000009:adverse effects / Q000276:immunology* / Q000627:therapeutic use; D006348:Cardiac Surgical Procedures / Q000009:adverse effects*; D005260:Female; D006493:Heparin / Q000009:adverse effects / Q000276:immunology*; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D010978:Platelet Factor 4 / Q000276:immunology*; D011184:Postoperative Period; D011237:Predictive Value of Tests; D011300:Preoperative Care; D011446:Prospective Studies; D013921:Thrombocytopenia / Q000139:chemically induced; D013923:Thromboembolism / Q000453:epidemiology / Q000209:etiology* / Q000517:prevention & control
D000906:Antibodies; D000925:Anticoagulants; D010978:Platelet Factor 4; D006493:Heparin