Archief Roodbont

Optimal level of anticoagulant therapy determined for heart conditions

15 July 2009

MedWire News: Patients with mechanical heart valve prostheses or atrial fibrillation should be treated with oral anticoagulant therapy (OAT) to an optimal international normalized ratio (INR) of 3, results of an observational study suggest.

Those patients recovering from a myocardial infarction (MI) meanwhile should be maintained at a slightly higher INR of 3.5, say Frits Rosendaal and colleagues from the Leiden University Medical Center in The Netherlands.

Oral anticoagulant therapy with vitamin K antagonists is recommended for the primary and secondary prevention of arterial thromboembolism.

Specifically, for patients with mechanical heart valve prostheses, OAT protects from valve thrombosis, while in patients with atrial fibrillation or ischemic heart disease it prevents ischemic stroke and recurrent MI.

However, the major drawback of OAT is the increased risk for hemorrhage, which is associated with the intensity of anticoagulation.

In the present study, the researchers evaluated 4202 patients visiting the Leiden Anticoagulation Clinic with mechanical heart valve prostheses, atrial fibrillation, or MI from 1994 to 1998.

During follow-up they recorded incidences of major hemorrhage and thromboembolism (untoward events) and took venous blood samples to determine prothrombin times expressed as an INR.

The optimal intensity of oral anticoagulation was calculated as the INR level that provided the lowest overall incidence of untoward events.

Incidence rates of untoward events were around 4% per year for all indications: 4.3 for patients with mechanical heart valve prostheses, 4.3 for patients with atrial fibrillation, and 3.6 per year for patients treated after MI.

The optimal intensity of anticoagulation for patients with mechanical heart valve prostheses was an INR of 2.5 to 2.9; for patients with atrial fibrillation, an INR of 3.0 to 3.4; and for patients after MI, an INR of 3.5 to 3.9.

“Our study suggests target INRs of 3.0 for patients with mechanical heart valve prostheses and atrial fibrillation and 3.5 after myocardial infarction as a starting point in future clinical trials,” Rosendaal and colleagues conclude in the Archives of Internal Medicine.

MedWire (www.medwire-news.md) is an independent clinical news service provided by Current Medicine Group, a part of Springer Science+Business Media. © Current Medicine Group Ltd; 2009

Arch Intern Med 2009; 169: 1203–1209