Response to warfarin and other oral anticoagulants: effects of disease states.

BACKGROUND: Warfarin is associated with numerous drug and food interactions, and much attention has been appropriately focused on this subject. Because several disease states may also affect response to oral anticoagulants, we present a summary of the literature. METHODS: We searched MEDLINE for original articles on the effect of disease states on response to warfarin. RESULTS: Liver disease and thyroid dysfunction are well-documented as affecting warfarin response. Further study is needed to establish whether febrile illness, congestive heart failure, and other disease states enhance the effect of warfarin in some patients. CONCLUSION: Careful monitoring of anticoagulant therapy in patients with diseases that have the potential to affect warfarin response could increase safety and efficacy of this important agent.

Graded exercise testing for diagnosis of coronary artery disease in elderly patients.

We tested the clinical utility and predictive value of graded exercise testing in the diagnosis of coronary artery disease in 153 patients aged 65 years or more. Based on changes of the ST segment from baseline, the test was considered positive with 1 mm of depression lasting 0.08 seconds, negative with no changes despite 85% of predicted maximal heart rate, probably positive with 1 mm of depression at rest becoming 2 mm with exercise, probably negative with no changes at maximal heart rate (within 10 beats per minute of 85% of predicted maximal), and uninterpretable with baseline electrocardiographic changes (eg, digitalis effect, left bundle branch block, left ventricular hypertrophy, etc). A test was considered inadequate when the exercise tolerance was less than or equal to 5 METs (metabolic equivalent of the task) and/or maximal heart rate was less than 100 beats per minute. The 153 patients had 163 tests. Only 33 (20%) were considered inadequate or uninterpretable, and there were no complications requiring medical intervention. Of 82 patients who had coronary angiography, 52 (63%) had 50% stenosis of at least one major epicardial artery; 44 of these patients had positive results of exercise testing. Nine patients with negative exercise tests had negative angiograms. There were eight false-negative and seven false-positive results. These results revealed a sensitivity of 85%, a specificity of 56%, and a predictive value of 86% for a positive test.