Abstract 3156: Prevalence of Unrecognized and Recognized Myocardial Infarction in Older Individuals with Elevated NT-pro-BNP
Background: Higher BNP is associated with poor prognosis. Underlying mechanisms are not well understood and may carry important treatment implications. We used contrast-enhanced cardiac magnetic resonance (CMR) to examine the pathophysiology leading to increased NT-proBNP in ambulatory older subjects.
Methods & Results: In 616 older subjects (median age 75 yrs, range 68 to 93) from the ICELAND MI substudy of the AGES-Reykjavik Study, clinically recognized or unrecognized myocardial infarctions (MI) were defined according to 1) delayed enhancement on CMR involving the subendocardium in a coronary distribution, and 2) hospital records and/or surveillance records collected since 1968. Both recognized (p<0.001) and unrecognized MI (p=0.005) were significantly related to NT-proBNP levels in linear regression models adjusting for age, sex, diabetes, LVEF, glomerular filtration, and LV mass/BSA. Receiver operator characteristic analysis identified a NT-proBNP value of 235 pg/mL as the cut point that optimally discriminated whether MI was present. MI was more prevalent when BNP was >235 than <235 (37% vs. 12%). A similar relationship held for recognized MI (13% vs. 3%) and unrecognized MI (24% vs. 9%; p<0.001 for all). Even in patients with normal LVEF and no history of (recognized) MI, NT-proBNP levels > 235 pg/mL remained strongly associated with a high prevalence of unrecognized MI (23% vs. 8%, p<0.001). When the analysis was repeated using the 90th percentile as a cut point (698 pg/mL), similar findings were observed.
Conclusions: Both recognized and unrecognized myocardial infarction are strongly related to NT-proBNP and are commonly found with elevated NT-proBNP. Careful assessment for MI is warranted in this setting, even if left ventricular systolic function is normal.