Brain Natriuretic Peptide and the Risk of Cardiovascular Events and Death in Patients with Atrial Fibrillation

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Subjects and methods SubjectsThis study included 371 consecutive outpatients with AF in the Tsuchida Clinic of Internal Medicine and Cardiology (23-93 years with an average age of 69.5±10.8years; 205 men and www.intechopen.com Atrial Fibrillation -Basic Research and Clinical Applications 200166 women; 231 paroxysmal AF and 140 chronic AF), whose BNP levels were measured to evaluate left ventricular function from 1999 to 2002.The patients were treated according to the relevant guidelines and followed up until 31 December 2006.The mean follow-up period was 5.4years (max: 7.5 years).Diagnosis was based on history, physical examination, laboratory findings, chest X-rays, electrocardiograms and echocardiograms.Paroxysmal AF was defined as AF that terminated spontaneously within 7 days after onset.Chronic AF was defined clinically when defibrillation of paroxysmal AF was unsuccessful (permanent AF) or AF was continuously observed for more than 6 months (persistent AF). MethodsBNP levels were measured by the immunoradiometric assay method using a Shionoria BNP assay kit (Shionogi, Osaka, Japan) for the one-point blood sample taken in a sitting position.Some studies of patients with heart failure (Latini et al., 2004;Tsutamoto et al., 1997) showed that BNP levels of more than about 100 pg/ml were significantly related to mortality and morbidity, so the patients were stratified into two groups based on cut-off levels of BNP (<100 pg/ml and ≧100 pg/ml).The primary endpoint was a composite of cardiovascular events (hospitalization and death).Components of the endpoints included the following: heart failure, coronary heart disease events (acute myocardial infarction, unstable angina), stroke (ischemic, hemorrhagic), arrhythmia, dissecting aneurysm, peripheral arterial disease, infective endocarditis, acute myocarditis, renal infarction, pulmonary infarction, embolism of the superior mesenteric artery, and sudden cardiac death.The first of these events was noted as the primary event.Any component of a composite primary endpoint, for which a patient could be counted once in each category, was treated as a second endpoint.Death from any cause was also designated a secondary endpoint.Furthermore, patients with paroxysmal AF were observed for the development of chronic AF.The study protocol was approved by the Ethics Committee of Tsuchida Clinic of Internal Medicine and Cardiology. Statistical analysisValues are shown as mean±standard deviation (SD).Time-to-event curves for the endpoints were estimated by the Kaplan-Meier method for the entire follow-up period.The log-rank test was used to examine the association of BNP levels.Hazard ratio (HR) and 95% confidence interval (CI) were calculated and adjusted for age, sex, the presence or absence of hypertension, diabetes mellitus, and hyperlipidemia with the Cox's proportional hazards model.All analyses were performed with the use of StatView (version 5.0).Significance levels were p < 0.05 in these analyses. Results Patient characteristicsClinical characteristics are summarized in Table 1.This study included 371 patients: valvular disease was found in 57 (15%); congestive heart failure (CHF) in 58 (16%); coronary artery disease (CAD) in 47 (13%), old myocardial infarction (OMI) in 16 (4%), angina pectoris (ANG) in 31 (8%); prior stroke in 35 (9%); hypertrophic cardiomyopathy (HCM) in 19 (5%); dilated cardiomyopathy (DCM) in 10 (3%); prior pacemaker operation in 12 (3%); hypertension in 228 (62%); diabetes mellitus in 63 (17%); dyslipidemia in 104 (28%); including some patients with more than one disease.In comparing chronic AF with paroxysmal AF, there were more valvular disease, CHF, and prior stroke in patients with www.intechopen.com

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.