Antithrombotic therapy in cardiac disease: an approach based on pathogenesis and risk stratification

Managing anticoagulation in patients with atrial fibrillation

Patients with nonvalvular atrial fibrillation have an increased risk of cerebral thromboembolism. Oral anticoagulation therapy, however, provides primary and secondary stroke prevention in these patients. Here, update your knowledge of warfarin initiation, titration, monitoring, and adjustment.

Oral anticoagulation in nonvalvular atrial fibrillation

Chronic nonvalvular atrial fibrillation is associated with an overall risk of thromboembolic complications of 4.5% per year. Advancing age, prior stroke or transient cerebral ischaemia, diabetes, hypertension, and impaired function of the left ventricle are known risk factors. Placebo-controlled trials have demonstrated that oral anticoagulant therapy with warfarin is effective for primary and secondary prevention of ischaemic stroke, reducing the risk by 68%. The effect of aspirin is still controversial, reducing the risk by 18-44%. Recent clinical trials have investigated the effect of warfarin given at a very low intensity alone or combined with aspirin. The results from the SPAF III study demonstrated that a combination of mini-intensity warfarin plus aspirin was insufficient for stroke prevention in atrial fibrillation. More trials have now confirmed that oral anticoagulation at INR-values below 2.0 is not effective for prevention of thromboembolic events in these patients. It is currently recommended that patients at a high risk of stroke are treated with warfarin at an intensity of INR 2.0-3.0. Patients younger than 65 years without other risk factors can be given aspirin 325 mg day-1.

Antiplatelet and anticoagulant therapy in the prevention of thromboemboli in chronic heart failure

Thromboembolism is an important complication in patients with heart failure. Several recent clinical trials have established the efficacy of anticoagulant therapy in patients with heart failure and atrial fibrillation. There is renewed interest in examining the role of antiplatelet and anticoagulation therapy in patients with heart failure in sinus rhythm. There is a need to identify patients at risk for thromboembolism in heart failure. However, there are data to suggest that occult thromboembolic events may contribute to disease progression, ischemic events, and sudden cardiac death. This review summarizes the incidence, potential mechanism, and therapeutic approaches for management of thromboembolism in heart failure.

Thrombosed prosthetic valve in tricuspid position. Successful therapy with intravenous streptokinase

The successful use of streptokinase therapy in a child with chronic thrombosis of a prosthetic valve (Carbomedics) in the tricuspid position is presented.

Submaximal exercise thallium-201 SPECT for assessment of interventional therapy in patients with acute myocardial infarction

Submaximal thallium-201 stress testing has been shown to provide important diagnostic and prognostic information in patients with acute myocardial infarction. The purpose of this investigation was to evaluate the diagnostic value of early submaximal stress testing and thallium-201 single photon emission computed tomography (SPECT) after interventional therapy. Scintigraphic results from 56 patients with infarctions, who underwent acute thrombolytic therapy, angioplasty, or both, were compared with late (6 weeks) functional outcome as assessed by radionuclide ventriculography and with results of discharge coronary angiography. A linear correlation was found between the extent of thallium-201 SPECT perfusion defect and late ventricular function (r = 0.74, p less than 0.01). Forty-two percent of patients with large SPECT perfusion defects had normal left ventricular ejection fractions, suggesting an overestimation of infarct size by early imaging. Sensitivity and specificity of thallium-201 SPECT for detection of coronary artery stenosis in noninfarct territories was 57% and 46%, respectively, indicating limited diagnostic definition of extent of underlying coronary artery disease. Results of follow-up coronary angiography showed a significant relationship between the size of the initial perfusion defect and early restenosis or reocclusion of the infarct artery. Thus the extent of early thallium-201 perfusion defects correlates with late functional outcome but appears to overestimate the degree of injury. Submaximal thallium-201 stress testing allows only limited characterization of underlying coronary artery disease. Early assessment of infarct size may identify a patient population at high risk for reocclusion of the infarct artery.