Serial BNP assay in monitoring exercise tolerance in patients with diastolic dysfunction

Abstract

Brian natriuretic peptide (BNP) is a peptide with important diuretic, natriuretic and vasodilating effects produced and released from ventricular myocytes in the healthy subjects and throughout the myocardium in heart failure. BNP was demonstrated to have an important diagnostic role in patients with isolated left ventricular diastolic dysfunction (ILVDD) [1]. This prospective studywas aimed to evaluate if the increment of BNP levels from baseline to follow-up might be predictive for exercise tolerance impairment over time in patients with LV diastolic dysfunction and preserved systolic function. Twenty-seven consecutive outpatients presenting in the heartfailure out-patient clinic of the University of L'Aquila and Hospital of Atri with ILVDD and preserved systolic function (EF>45%) were enrolled in this prospective study. Sixteen (59.2%) patients reported dyspnoea (NYHA class II) and 11 (40.8%) NYHA class I. Mean age was 61±9 years (38–75); 8 patients were females and 19 males. At the enrolment (baseline), diastolic dysfunction was assessed by trans-thoracic echocardiogram (MyLab 30, Esaote, Florence—Italy) and classified into 3 categories according to definition already reported [1]; BNP was measured using the commercially available Shionoria BNP (Shionogi USA, Inc) sandwich immunoassay Kit; 6 minute walking test (6MWT) was conducted as previously described by Guyatt et al. [2]: Covered distance (meters) and symptoms were considered. Echocardiogram, BNP assay and 6MWTwere repeated at follow-up (18±6 months). Exercise tolerance impairment (or improvement) was defined as the percent reduction (or increase) of 6MWT covered distance of at least 20% from baseline to follow-up [3]. The study conforms to the principles outlined in the Declaration of Helsinki and it was approved by the local ethics committee. Baseline echocardiography showed altered relaxation (pattern 1) in 10 (37.0%) patients, pseudonormalization (pattern 2) in 10 and restrictive pattern (3) in the remaining 7 cases (26.0%). Significantly different BNP levels were found among the 3 diastolic dysfunction