Acute changes in circulating natriuretic peptide levels in relation to myocardial ischemia.

OBJECTIVES: The aim of this study was to determine the effect of transient myocardial ischemia on circulating natriuretic peptide levels.
BACKGROUND: Natriuretic peptides are released by the heart in response to wall stress. We hypothesized that transient myocardial ischemia would cause acute changes in circulating natriuretic peptide levels.
METHODS: B-type natriuretic peptide (BNP), N-terminal fragment of BNP pro-hormone (NT-pro-BNP), and N-terminal fragment of atrial natriuretic peptide pro-hormone (NT-pro-ANP) levels were measured in 112 patients before, immediately after, and 4 h after exercise testing with nuclear perfusion imaging.
RESULTS: Baseline levels of BNP were associated with the subsequent severity of provoked ischemia, with median levels of 43, 62, and 101 pg/ml in patients with none, mild-to-moderate, and severe inducible ischemia, respectively (p = 0.03). Immediately after exercise, the median increase in BNP was 14.2 pg/ml in patients with mild-to-moderate ischemia (p = 0.0005) and 23.7 pg/ml in those with severe ischemia (p = 0.017). In contrast, BNP levels only rose by 2.3 pg/ml in those who did not develop ischemia (p = 0.31). A similar relationship was seen between baseline NT-pro-BNP levels and inducible ischemia, but the changes in response to ischemia were less pronounced. NT-pro-ANP levels rose with exercise in both ischemic and non-ischemic patients. When added to traditional clinical predictors of ischemia, a post-stress test BNP >or=80 pg/ml remained a strong and independent predictor of inducible myocardial ischemia (odds ratio 3.0, p = 0.025).
CONCLUSIONS: Transient myocardial ischemia was associated with an immediate rise in circulating BNP levels, and the magnitude of rise was proportional to the severity of ischemia. These findings demonstrate an important link between the severity of an acute ischemic insult and the circulating levels of BNP.