The use of thrombolysis to treat ST elevation myocardial infraction (MI) is well supported. Serious adverse events occur in 1–2% of patients.¹ Warfarin is increasingly prescribed to patients at high cardiovascular risk and it is inevitable that these patients will present with an MI that warrants thrombolytic treatment. The British National Formulary and the American Heart Association both advise that patients on warfarin present a relative contraindication to thrombolysis, but this has resulted in uncertainty in providing patients with the optimum medical management.

Streptokinase and tissue plasminogen activators activate the conversion of plasminogen to plasmin, which rapidly degrades formed thrombus. In contrast, warfarin inhibits the carboxylation of the vitamin K dependent clotting factors II, VII, IX and X (extrinsic system) rending these factors inactive.

Anecdotally physicians differ in their advice regarding thrombolysis for patients prescribed warfarin. Before the present study, all acute care physicians and cardiologists at the University Hospitals of Leicester NHS Trust were surveyed anonymously about their use of thrombolysis for such patients. Three respondents (of 38 replies received) advised thrombolysis regardless of the international normalised ratio (INR). Of the others, 24 would advise thrombolysis only if the INR was less than 3. This was irrespective of grade and specialty.

Primarily, the objective of this study was to investigate the thrombolysis complication rate among patients prescribed warfarin at the time of admission for an MI. For this purpose, we retrospectively …