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The worldwide burden of valvular heart disease (VHD) continues to grow as a result of increases in life expectancy combined with the high incidence of rheumatic heart disease in developing nations.1 Patients with VHD and certain comorbid conditions or prosthetic heart valves (PHVs) are at high risk for thromboembolic complications and often require antithrombotic therapy (Table 53–1). Although bleeding is a risk with all antithrombotic agents, the frequency and consequences of a stroke make drug therapy appropriate in many patients with VHD.2
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Antithrombotic therapy among individuals with native valve disease (defined as VHD in absence of PHV or mitral stenosis [MS]) is based on the presence of concomitant risk factors (Fig. 53–1). The most common risk factors for thromboembolism include atrial fibrillation (AF) and left ventricular (LV) systolic dysfunction.
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Nonvalvular AF has been defined as AF in the absence of rheumatic MS, a mechanical or bioprosthetic heart valve, or mitral valve repair.3 Multiple randomized controlled trials have demonstrated the clinical benefits of antithrombotic therapy with either warfarin or aspirin compared with placebo or no treatment in reducing ischemic events among individuals with “nonvalvular” AF. Based on a meta-analysis of over 28,000 patients comprising 29 trials, adjusted-dose warfarin therapy was associated with a 60% and 40% reduction in ischemic stroke compared with placebo and antiplatelet therapy, respectively.4 Antiplatelet therapy alone reduced the risk by 20%.4 The addition of clopidogrel to aspirin further reduced ischemic events, including stroke, among patients with AF who were unsuitable for vitamin K antagonist therapy,5 but was inferior to warfarin in warfarin-eligible patients.6 Data from contemporary trials have shown that there has been a significant reduction in stroke event rate over the past two decades as a result of greater time spent in therapeutic anticoagulation (stroke or systemic embolism rate of 1.66% per year).7 The benefits of anticoagulation are graded, increasing as the risk for ischemic stroke increases. Multiple risk stratification schemes exist ...