Prescription of vitamin K inhibitors in low-risk patients with atrial fibrillation

Abstract

Long-term treatment with vitamin K inhibitors (VKA) for stroke prevention is recommended in most patients with atrial fibrillation (AF) [1]. An exception to this rule are patients without clinical risk factors for stroke as those with a CHADS2 score = 0 [1]. To evaluate the rate of low risk patients with AF treated with VKA, we assessed the CHADS2 score of patients referred to our anticoagulation clinic. The presence of congestive heart failure, hypertension, age [75, diabetes, and previous stroke/TIA was ascertained by reviewing hospital records and directly interviewing each patient. Congestive heart failure was defined as a recent (\90 days) hospital admission for impaired left ventricular systolic function at transthoracic echocardiography (ejection fraction less than 50%). Hypertension was defined as a systolic blood pressure higher than 160 mmHg on two consecutive occasions or the use of antihypertensive drugs. Diabetes was defined according to the American Diabetes Association criteria [2]. Cerebral ischemia was a previous sudden neurological defect confirmed by cerebral imaging. From January 2004 to October 2008, 609 consecutive AF patients were considered. One-hundred and nine were excluded as data were incomplete (n = 51), an elective cardioversion was programmed (n = 32) or mitral valve disease was associated (n = 7). Remaining 19 patients refused to participate in the study. Of the 500 included patients, 96 (19.2%) had a CHADS2 score of 0. Sixty-eight were males and 28 females, with a mean age (±SD) of 65 ± 8.5 years. The reasons why they were prescribed VKA are shown in Table 1: most of them simply followed the recommendations of their physician (81.2%) without further specifications. Few reported gastrointestinal problems or aspirin intolerance, or had a family history positive for cerebral ischemia. A large proportion (62.8%) of these patients with CHADS2 score = 0 was referred to our Anticoagulation Clinic by a specialist (cardiologist or internist), and 20% by their general practitioner. Our actual major bleeding rate among CHADS2 0 patients reached 1.78 pts%/year (7 events). Bleeding was classified as major when fatal, intracranial (documented by imaging), ocular causing loss of sight, to major articulations, retroperitoneal, gastro-intestinal, when surgery was required or hemoglobin was reduced of 2 g/dl or more and/ or were requested more than two blood units for transfusion [3]. Among these, we had a rate of 0.51 pts%/year of intracranial bleeding (2 events). These data show that VKA are often prescribed in young patient with AF and no risk factors for stroke. Ischemic stroke is the most severe consequence of AF and the calculated risk is 4.5% per year [4]. However, the risk is different among AF patients varying between 1–2 and 12–18% a year according to the presence of risk factors [5]. In the last 20 years, many different risk stratification models have been proposed to identify AF patients at low, moderate and high risk of stroke. CHADS2 is a simple and widely used score that identifies low-risk patients (score = 0) in whom long-term aspirin therapy at a dose of S. Granziera G. Nante (&) E. Manzato Department of Medical and Surgical Sciences, Geriatric Clinic, Giustinianeo Hospital, University of Padova, via Giustiniani, 35128 Padua, Italy e-mail: giovanni.nante@sanita.padova.it