Background Anticoagulation during percutaneous coronary intervention (PCI) balances the thromboembolic risk of coronary intubation with an increased risk of bleeding. The optimal dose of heparin during elective PCI in patients with stable angina is unknown. Existing guidelines are based on limited data. Our objective was to assess two different dosing strategies of unfractionated heparin during elective PCI.

Methods We interrogated data from a PCI database over a 4-year period. Patients undergoing planned PCI for stable angina were included. We compared a fixed heparin dose (3000 U unfractionated heparin; UFH) to a weight-adjusted dose (70 U/kg). The primary endpoint was periprocedural myocardial infarction (MI). MI was defined as a troponin value greater than three times the 99th percentile upper reference limit for our laboratory, in keeping with the Joint Eueopean Society of Cardiology/American College of Cardiology Foundation/American Heart Association/World Heart Federation Task Force recommendations. Serum samples for troponin I (TnI) measurement were taken 10−48 h post-procedure. Preprocedural TnI measurements were not recorded as all patients underwent elective PCI for stable angina. For patients who had more than one elective angioplasty during the study period, only the first procedure was included. Routine care before and after PCI was similar for all patients, which included pretreatment with 300 mg aspirin and 300 mg clopidogrel. Glycoprotein IIb/IIIa inhibitors were administered at the operators’ discretion.

Results We studied 1837 patients (table). 422 (23.0%) received fixed-dose (3000 U) UFH and 1415 (77.0%) received 70 U/kg weight-adjusted UFH. The median troponin level was significantly higher in the fixed dose group; 0.29 versus 0.15 ng/ml; p<0.001; z  =  5.7 (Mann–Whitney U test). The proportion of troponin-positive patients was significantly higher in the fixed-dose group (71.6% vs 58.6%; p<0.0005, χ² test). The periprocedural MI rate was significantly higher in the fixed-dose group (71.6% vs 58.4%; p<0.0005, χ² test). There were no deaths or major ischaemic events during hospitalisation, and no bleeding requiring transfusion or delaying hospital discharge.

Conclusions This retrospective observational study of elective PCI demonstrated that a reduced, fixed dose of periprocedural heparin was associated with a significant increase in the MI rate compared with a standard weight-adjusted regime. Our study further questions the optimal dose of heparin during elective PCI and suggests a need for further studies.