Drug Treatment Associated with Heart Valve Replacement

Abstract

This article reviews a number of specific pharmacological considerations for patients with prosthetic heart valves. All patients with mechanical heart valves should be anticoagulated. In the past, an International Normalised Ratio (INR) of 2.5 to 4.5 has been recommended. Recent nonrandomised studies have suggested that a patient with a prosthetic valve who is at low risk for thromboembolic events could have an INR ranging from 1.8 to 3.5. The lower end of this range should only be used for patients at higher than average risk of haemorrhage, until randomised data show that levels below 2.5 may be applied universally. In high-risk patients (particularly those with previous thromboembolic events) low dose aspirin should be added. During noncardiac surgery, a patient at low risk for thromboembolic events could be managed by discontinuing anticoagulation 3 days before the operation, with warfarin recommenced as soon as possible afterwards. Perioperative heparinisation would be appropriate in a higher risk patient. Women with prosthetic heart valves wishing to become pregnant should be converted to the use of twice-daily subcutaneous heparin injections. Patients with bioprosthetic valves can be managed without anticoagulation unless they have some other reason to require it. Patients at high risk should be treated with aspirin or warfarin. Thrombolytic therapy for acute valve thrombosis should be used for those who are haemodynamically compromised and therefore have a high risk of mortality from operative intervention. All patients with prosthetic heart valves undergoing invasive procedures potentially causing bacteraemia should receive antibiotic prophylaxis for endocarditis. The actual drugs used depend on the likely nature of the bacteraemia, and any possible patient hypersensitivity.

Thrombin generation and its inhibition: a review of the scientific basis and mechanism of action of anticoagulant therapies

“…This is especially the case in patients with prosthetic cardiac valves. 15 One other recent review suggested that withholding warfarin for 48 h was associated with a 1 point fall in the INR from about 3.5 to 2.5 in patients with prosthetic valves. This value was not associated with increased bleeding or increased thrombotic episodes over the transient period of drug withdrawal.…”

Correlation between Metabolic Parameters and Warfarin Dose in Patients with Heart Valve Replacement of Different Genotypes

“…Patients with mechanical heart valve replacement need to have life-time anticoagulation with warfarin [ 9 ]. Since warfarin metabolism is affected by the patient’s age, gender, genotype, drugs and other factors, the therapeutic window of warfarin is narrow and serious complications such as bleeding or thrombosis may occur.…”

Anticoagulant therapy in special circumstances

“…Reported thromboembolism rates of bioprosthetic valves range from 0.5% to 3% per year without the use of anticoagulants [26,27]. This thromboembolism rate is comparable to anticoagulated patient with mechanical valves.…”

“…This risk is not well established and may be less than 1% per day. For example, the average yearly risk of thromboembolic events with a mechanical valve without anticoagulation is 10% per year or 0.2% per day [26,30]. However, valve thrombosis or an embolic event can be catastrophic.…”