Elevated B-type natriuretic peptide despite normal left ventricular function on rest and exercise stress echocardiography in mitral regurgitation.

Abstract

To determine whether elevated B-type natriuretic peptide (BNP) predicts left ventricular (LV) contractile dysfunction on exercise stress echocardiography in patients with severe mitral regurgitation (MR). Thirty three patients with moderate-to-severe or severe MR, a LV ejection fraction > or =60% and New York Heart Association Class I or II symptoms, and 12 controls underwent resting and exercise stress echocardiography. In 20 MR patients, BNP was within the normal range (mean +/- SD, 7.7 +/- 2.7 pmol/L), and in 13 MR patients, BNP was >12 pmol/L (19.6 +/- 7.6 pmol/L). LV end-systolic volume index after exercise was lower in controls than patients with MR (P < 0.0001), but similar in MR patients with normal and elevated BNP, respectively (controls 8.5 +/- 3.9, MR 20 +/- 7 vs. 20 +/- 9 cm(2)/m(2), P > 0.05). However, pulmonary artery systolic pressure (PAP) after exercise was higher in MR with high BNP (70 +/- 20 vs. 48 +/- 11 mmHg, <0.0001) and controls (38+/-11 mmHg). A two-fold increase in plasma BNP was associated with an average increase in resting PAP of 7.6 (95% CI 2.9, 12.2) mmHg, an increase in post-exercise PAP of 14.4 (95% CI 9.0, 19.9) mmHg and increase in left atrial area index of 2.1 (95% CI 0.5, 3.8) cm(2)/m(2). However, there was no significant association between the plasma level of BNP and any rest or post-exercise measure of LV systolic function (r < 0.25, P > 0.05 for all). The plasma level of BNP may be within the normal range in patients with moderate-to-severe or severe MR despite significant increases in LV end-systolic volume. Increase in BNP is associated with pulmonary artery hypertension on exercise and left atrial enlargement even when LV systolic function on exercise stress echocardiography is normal.