warfarin and Thyrotoxicosis

Hyperthyroidism and atrial fibrillation (AF) are both common in the Australian community, and often encountered in general practice.. This article discusses the risk of AF and thromboembolism in hyperthyroidism, the role of antithrombotic therapy in this setting, and appropriateness and safety of various antithrombotic agents in thyroid disease.. Prevention of thromboembolism is an important consideration in the care of patients with AF and hyperthyroidism. However, the evaluation of thromboembolic risk and management in this setting is challenging. Thyroid disease results in a pro-coagulant state via disruption of coagulation pathways and alters the pharmacodynamics of anticoagulants. Currently, guidelines regarding anticoagulation in AF do not incorporate hyperthyroidism as an additional risk factor. Until further evidence becomes available, we recommend warfarin as the oral anticoagulant of choice in thyroid disease because of ease of monitoring and reversibility.

Topics: Anticoagulants; Atrial Fibrillation; Humans; Male; Middle Aged; Thromboembolism; Thyrotoxicosis; Warfarin

Due to the narrow therapeutic range and high drug-to-drug interactions (DDIs), improving the adequate use of warfarin for the elderly is crucial in clinical practice. This study examines whether the effectiveness of using warfarin among elderly inpatients can be improved when machine learning techniques and data from the laboratory information system are incorporated.. Having employed 288 validated clinical cases in the DDI group and 89 cases in the non-DDI group, we evaluate the prediction performance of seven classification techniques, with and without an Adaptive Boosting (AdaBoost) algorithm. Measures including accuracy, sensitivity, specificity and area under the curve are used to evaluate model performance.. Decision tree-based classifiers outperform other investigated classifiers in all evaluation measures. The classifiers supplemented with AdaBoost can generally improve the performance. In addition, weight, congestive heart failure, and gender are among the top three critical variables affecting prediction accuracy for the non-DDI group, while age, ALT, and warfarin doses are the most influential factors for the DDI group.. Medical decision support systems incorporating decision tree-based approaches improve predicting performance and thus may serve as a supplementary tool in clinical practice. Information from laboratory tests and inpatients' history should not be ignored because related variables are shown to be decisive in our prediction models, especially when the DDIs exist.

Topics: Aged; Aged, 80 and over; Algorithms; Anticoagulants; Artificial Intelligence; Body Weight; Clinical Laboratory Information Systems; Comorbidity; Cross-Cultural Comparison; Decision Trees; Dose-Response Relationship, Drug; Drug Interactions; Ethnicity; Female; Heart Failure; Humans; Male; Medical History Taking; Middle Aged; Quality Improvement; Risk Factors; Taiwan; Thyrotoxicosis; Warfarin

Many patients with cardiac arrhythmias require concomitant therapy with warfarin and amiodarone. Beyond the predictable pharmacokinetic drug-drug interaction requiring a significant warfarin dose reduction, the iodine-rich amiodarone affects the thyroid gland, causing overt hypothyroidism or thyrotoxicosis in 14%-18% of cases. In turn, thyroid disorders may affect warfarin sensitivity, with hypothyroidism and thyrotoxicosis resulting in increased or decreased warfarin requirements, respectively. We describe 3 patients on concomitant amiodarone and warfarin who developed amiodarone-induced thyrotoxicosis heralded by a significant decrease in warfarin requirements. We review the literature on the mechanisms of the complex drug-drug and drug-disease interactions within the thyroid gland, warfarin, and amiodarone triad. Given that significant thyroid disorders may be only mildly symptomatic and thus may escape clinical detection, we suggest that thyroid function should be tested in any patient with otherwise unexplained changes in warfarin dose requirements, particularly if concomitantly treated with amiodarone.

Topics: Adult; Amiodarone; Anti-Arrhythmia Agents; Anticoagulants; Arrhythmias, Cardiac; Drug Interactions; Female; Humans; Male; Middle Aged; Risk Factors; Thyroid Gland; Thyrotoxicosis; Warfarin

A 73-yr-old Korean man with permanent atrial fibrillation visited outpatient clinic with severely increased International Normalized Ratio (INR) values after taking a usual starting dosage of warfarin to prevent thromboembolism. We found out later from his blood tests that he had hyperthyroidism at the time of treatment initiation. His genetic analysis showed CYP2C9*1/*3 and VKORC1+1173TT genotypes. We suspect that both hyperthyroidism and genetic variant would have contributed to his extremely increased INR at the beginning of warfarin therapy. From this case, we learned that pharmacogenetic and thyroid function test might be useful when deciding the starting dosage of warfarin in patients with atrial fibrillation.

Topics: Aged; Anticoagulants; Aspirin; Atrial Fibrillation; Chromatography, High Pressure Liquid; Cytochrome P-450 CYP2C9; Genotype; Humans; Male; Polymorphism, Single Nucleotide; Tandem Mass Spectrometry; Thromboembolism; Thyrotoxicosis; Vitamin K Epoxide Reductases; Warfarin

We report a case of cerebral venous thrombosis (CVT) due to tyrotoxicosis in a patient with methylenetetrahydro-folate-reductase (MTHFR) gene polymorphism C677T, (genotype 677TT), in which discontinuation of intravenous heparin was followed by clinical and radiological worsening despite warfarin treatment. We discuss the relationship between CVT, MTHFR hyperthiroidism and anticoagulant therapy.

Topics: Adult; Anticoagulants; Heparin; Humans; Male; Methylenetetrahydrofolate Reductase (NADPH2); Polymorphism, Genetic; Sinus Thrombosis, Intracranial; Thyrotoxicosis; Warfarin

Topics: Amiodarone; Anti-Arrhythmia Agents; Anticoagulants; Atrial Fibrillation; Humans; International Normalized Ratio; Thyroid Diseases; Thyrotoxicosis; Warfarin

The value of warfarin in preventing stroke in patients with chronic atrial fibrillation is well established. However, the prevalence of such treatment generally lags behind actual requirements. The aim of this study was to evaluate doctor- and/or patient-related demographic, clinical, and echocardiographic factors that influence decision for warfarin treatment.. Between 1990 and 1998, 1027 patients were discharged with chronic or persistent atrial fibrillation. This population was composed of (1) patients with cardiac prosthetic valves (n=48), (2) those with increased bleeding risks (n=152), (3) physically or mentally handicapped patients (n=317), and (4) the remaining 510 patients, the main study group who were subjected to thorough statistical analysis for determining factors influencing warfarin use.. The respective rates of warfarin use on discharge in the 4 groups were 93.7%, 30.9%, 17.03%, and 59.4% (P=0.001); of the latter, an additional 28.7% were discharged on aspirin. In the main study group, warfarin treatment rates increased with each consecutive triennial period (29.7%, 53.6%, and 77.1%, respectively; P=0.001). Age >80 years, poor command of Hebrew, and being hospitalized in a given medical department emerged as independent variables negatively influencing warfarin use: P=0.0001, OR 0.30 (95% CI 0.17 to 0.55); P=0.02, OR 0.59 (95% CI 0.36 to 0.94); and P=0.0002, OR 0.26 (95% CI 0.12 to 0.52), respectively. In contrast, past history of stroke and availability of echocardiographic information, regardless of the findings, each increased warfarin use (P=0.03, OR 1.95 [95% CI 1.04 to 3.68], and P=0.0001, OR 3.52 [95% CI 2.16 to 5.72], respectively).. Old age, language difficulties, insufficient doctor alertness to warfarin benefit, and patient disability produced reluctance to treat. Warfarin use still lags behind requirements.

Topics: Age Factors; Aged; Aged, 80 and over; Anticoagulants; Aspirin; Atrial Fibrillation; Chronic Disease; Communication Barriers; Comorbidity; Drug Prescriptions; Drug Utilization; Echocardiography; Female; Heart Diseases; Hospital Departments; Hospitalization; Humans; Israel; Lung Diseases, Obstructive; Male; Middle Aged; Physician-Patient Relations; Physicians; Practice Patterns, Physicians'; Recurrence; Refusal to Treat; Retrospective Studies; Risk Factors; Stroke; Thyrotoxicosis; Warfarin

Topics: Aged; Amiodarone; Anti-Arrhythmia Agents; Anticoagulants; Drug Synergism; Humans; International Normalized Ratio; Male; Prothrombin Time; Tachycardia, Supraventricular; Thyrotoxicosis; Thyroxine; Warfarin

Topics: Adult; Aged; Aged, 80 and over; Atrial Fibrillation; Chronic Disease; Female; Humans; Male; Middle Aged; Thromboembolism; Thyrotoxicosis; Warfarin

Embolic occlusion of lower extremity arteries caused by hyperthyroidism-induced atrial fibrillation occurs rarely. Severe end organ damage may be prevented by aggressive medical and surgical intervention. Subtle signs of hyperthyroidism should be sought when arterial occlusion and atrial dysrhythmia are discovered. About 25% of thyrotoxic patients have atrial fibrillation, and up to 40% of this subgroup have systemic emboli; thus, 3% to 10% of all thyrotoxic patients may have systemic emboli. This estimation supports the recommendation for anticoagulation in all hyperthyroid individuals with atrial fibrillation.

Topics: Adult; Atrial Fibrillation; Embolism; Female; Femoral Artery; Humans; Quinidine; Syndrome; Thyrotoxicosis; Warfarin