Inverse Association Between Myocardial B-Type Natriuretic Peptide Release and Functional Capacity in Healthy Humans

BACKGROUND
B-type natriuretic peptide (BNP) has been found to be inversely related to peak oxygen consumption (peak VO2) in various patient populations. However, in these studies, circulating plasma BNP, i.e. the net effect of release and elimination, rather than cardiac BNP release has been measured. We assessed the relationship between the transcardiac BNP gradient [ΔBNPCS-A, i.e. the difference between BNP in coronary sinus (BNPCS) and arterial (BNPA) plasma] and peak VO2 in healthy subjects with a view to better understanding the regulation of cardiac BNP release in humans.

METHODS
We studied 10 asymptomatic subjects (age 64±11 years, two females) with preserved left ventricular function (left ventricular ejection fraction 62±5%, averaged early diastolic mitral annular velocity 9±3cm/s) and low BNP (BNP in venous plasma [BNPV] <100ng/l). Subjects underwent measurement of BNPA and BNPCS for the calculation of ΔBNPCS-A, maximal cardiopulmonary exercise testing, echocardiography and resting and submaximal exercise right heart catheterisation.

RESULTS
The median (range) BNPV, BNPA, BNPCS, and ΔBNPCS-A were 62 (14, 82), 60 (13, 79), 110 (25, 157), and 44 (1, 103) ng/l. The median peak VO2 during cardiopulmonary exercise testing was 21.5 (18, 54) ml/min/kg. There was an inverse correlation between higher ΔBNPCS-A and lower peak VO2 (r=-0.84; p=0.002) and oxygen pulse (r=-0.64, p=0.049). There was a trend towards an inverse correlation between ΔBNPCS-A and the exercise arteriovenous oxygen content difference (r=-0.58; p=0.08).