Abstract
B-type natriuretic peptide (BNP) secretion is stimulated by cardiac dysfunction. However, it is unclear how finely myocardial ischaemia contributes to BNP secretion and whether increases in BNP secretion contribute to coronary vasodilation. This study investigated the direct interaction between plasma BNP levels and cardiac ischaemia using the baseline distal-to-aortic pressure ratio (Pd/Pa). We examined the baseline Pd/Pa and fractional flow reserve (FFR) in 167 patients with intermediate coronary stenosis. The plasma BNP level appeared to be associated with the baseline Pd/Pa in the study population, and this association appeared to become clear only in patients with an FFR ≤ 0.80. To examine the effect of the baseline Pd/Pa on the BNP level in these patients, structural equation modeling (SEM) was performed. The baseline Pd/Pa significantly affected the BNP level (β: −0.37, p = 0.003) and the left ventricular ejection fraction (β: 0.43, p = 0.001). To examine the role of BNP in coronary vasodilation, we proposed another path model using a novel value obtained by dividing the FFR by the baseline Pd/Pa (FFR/baseline Pd/Pa) as an index of the hyperaemic response. The BNP level significantly affected the FFR/baseline Pd/Pa (β: 0.48, p = 0.037). This study demonstrated that BNP finely responded to an exacerbation of cardiac ischaemia and that increases in BNP secretion effectively ameliorated coronary vasoconstriction.
Highlights
B-type natriuretic peptide (BNP) is secreted mainly by the ventricles in heart failure, whereas normal atria secrete A-type natriuretic peptide (ANP) as well as BNP1–5
The major findings of this study were as follows: 1) cardiac ischaemia, as represented by the nonhyperaemic baseline Pd/Pa, had a causative impact on the plasma BNP level, suggesting the presence of a fine regulatory system of BNP by cardiac ischaemia; 2) BNP had a positive impact on the fractional flow reserve (FFR)/baseline Pd/Pa ratio, suggesting that a vasodilating action of BNP occurred in a compensatory manner; and 3) increasing BNP secretion was effective for palliation of the coronary arterial tonus, but the produced quantity of BNP was still inadequate for full coronary vasodilatation even in patients with high plasma BNP levels
This association appeared to become clear only in patients with coronary stenosis with an FFR of 0.80 or less, which is widely recognized as being suggestive of an ischaemic circumstance[18]
Summary
B-type natriuretic peptide (BNP) is secreted mainly by the ventricles in heart failure, whereas normal atria secrete A-type natriuretic peptide (ANP) as well as BNP1–5. Increases in the plasma BNP level are considered a compensatory response of the heart to ischaemia, because several reports have shown that BNP has a vasodilatory effect on the coronary artery system in humans[13,14]. We devised a new investigative method to examine the relationship between the BNP level and coronary ischaemia and performed simultaneous measurements of the plasma BNP level and the baseline Pd/Pa in patients with intermediate coronary artery stenosis. Studies of this type are faced with another degree of intractableness. We tried to propose a path model based on SEM to explain a complex phenomenon
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