Author + information
- Paul M. Mertes, MD
When we started our study, we hoped that an enhanced secretion of atrial natriuretic peptide (ANP) and/or brain natriuretic peptide (BNP) might allow for detecting exercise ischemia. However, as it was already pointed out in our report, myocardial ischemia was documented by exercise-single-photon emission computed tomography (SPECT) in 63 of our 104 patients with coronary artery disease, and this ischemia was not a predictor of the exercise increase in blood levels of either ANP or BNP (1). More precisely, in the 63 patients with SPECT-ischemia, the difference between exercise and rest concentrations of BNP was, on average, 14 ± 20 ng/l. Equivalent values were observed in patients with normal SPECT: 14 ± 35 ng/l. By contrast, much higher values were observed in the remaining patients showing SPECT-necrosis: 49 ± 55 ng/l (p < 0.001).
As it was already discussed in our study (1), this is mainly an acute release of peptides from secretory granules that is likely to allow a prompt exercise rise in the blood concentrations of peptides. Therefore, this rise depends on 1) the amount of peptides, which may be previously stored within secretory granules, and 2) the mechanism of peptides release from these granules.
Granule storage is known to rise in parallel to the resting blood concentrations of natriuretic peptides and to the level of left ventricular dysfunction. This is presumably the reason why we found that the rest concentration of peptides was a main predictor of the exercise increase in peptide concentration. For both ANP and BNP, however, rest concentrations were related to age and to the extent of SPECT-necrosis, but not to exercise SPECT-ischemia.
As for the second point, exercise increases in heart rate and beta-blockers were the sole additionalindependent predictors of the exercise increase in peptide concentrations. Becauseboth parameters were unrelated to the peptide concentrations at rest, wepostulated that they might have a specific impact on the triggering of peptiderelease from secretory granules. For beta-blockers, this impact could be related notonly to higher wall tension and cavity size at exercise, as mentioned in the letterby Drs. Win and Zoghbi, but mainly to an imbalance between alpha- and beta-adrenergicstimulations at exercise (1).
This LR is paired w/LE JACC030504-0763
- American College of Cardiology Foundation