LETTER TO THE EDITOR
Reply
Pierre-Yves Marie, MD
Service de Médecine Nucléaire,
Chu Nancy-Brabois,
54511 Vandoeuvre Cedex,
France
Paul M. Mertes, MD
(Email: py.marie{at}chu-nancy.fr).
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 additional
independent predictors of the exercise increase in peptide concentrations. Because
both parameters were unrelated to the peptide concentrations at rest, we
postulated that they might have a specific impact on the triggering of peptide
release from secretory granules. For beta-blockers, this impact could be related not
only to higher wall tension and cavity size at exercise, as mentioned in the letter
by Drs. Win and Zoghbi, but mainly to an imbalance between alpha- and beta-adrenergic
stimulations at exercise (1).
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Footnotes
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This LR is paired w/LE JACC030504-0763
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References
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- Marie PY, Mertes PM, Hassan-Sebbag N, et al. Exercise release of cardiac natriuretic peptides is markedly enhanced when patients with coronary artery disease are treated medically by beta-blockers J Am Coll Cardiol 2004;43:353-359.[Abstract/Free Full Text]
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