Midregional Pro-atrial Natriuretic Peptide (MR-proANP)

Midregional pro-atrial natriuretic peptide (MR-proANP)

Midregional pro-atrial natriuretic peptide (MR-proANP) is a stable fragment of the prohormone of atrial natriuretic peptide. The prognostic value of mid regional proANP in acute ischemic strokes was evaluated by Katan and associates [1]. They measured the plasma levels of mid regional proANP in over three hundred and sixty patients with acute ischemic stroke. Higher MR-proANP levels were noted in cardioembolic strokes. The investigators also found that MR-proANP is useful as a prognostic marker in the acute phase of stroke, independently predicting post stroke mortality and functional outcome. MR-proANP was also useful in improving the discriminatory values of the National Institutes of Health Stroke Scale (NIHSS) score.

Earlier studies had shown that level of atrial natriuretic peptide (ANP) is elevated in acute phase of ischemic stroke. This has been further validated by immunohistochemical studies which showed that cerebral ischemia directly induces the secretion of ANP in the brain tissue. Midregional pro-ANP is released in same molar quantities as atrial natriuretic peptide. MR-proANP is more stable than the N-terminal or C-terminal fragments of proANP and hence more applicable in clinical practice. In the study by Katan et al, MR-proANP levels at admission were about three fold increased in the 44 patients who died within 90 days, as compared to survivors. A similar two fold higher level of MR-proANP was found in those who had an unfavourable functional outcome at 90 days.

MR-proANP levels were also higher in those with associated chronic heart failure. The prognostic value of midregional pro-ANP was independent of age, clinical scores, chronic heart failure and atrial fibrillation. Another biomarker which has been shown to have predictive value in the outcome of stroke is copeptin, the c-terminal prohormone of arginine vasopressin. It is thought that copeptin has a higher prognostic efficacy in predicting functional outcome while MR-proANP is a better predictor of mortality after stroke.

MR-proANP is independently associated with cardioembolic stroke and improves risk stratification for 90 day mortality when measured within 2 to 3 days of onset of symptoms in those with acute ischemic stroke. A study by Arnold et al [2] further extended the prognostic value of MR-proANP at least up to 5 days, though repeated measurements did not improve the prognostic value. MR-proANP levels were shown to decrease modestly over the initial 5 days.

References

1. Mira Katan, Felix Fluri, Philipp Schuetz, Nils G Morgenthaler, Christian Zweifel, Roland Bingisser, Ludwig Kappos, Andreas Steck, Stefan T Engelter, Beat Müller, Mirjam Christ-Crain. Midregional pro-atrial natriuretic peptide and outcome in patients with acute ischemic stroke. J Am Coll Cardiol. 2010 Sep 21;56(13):1045-53.
2. Arnold M, Nakas C, Luft A, Christ-Crain M, Leichtle A, Katan M. Independent Prognostic Value of MRproANP (Midregional Proatrial Natriuretic Peptide) Levels in Patients With Stroke Is Unaltered Over Time. Stroke. 2020 Jun;51(6):1873-1875. doi: 10.1161/STROKEAHA.120.029333. Epub 2020 Mar 27. PMID: 32216532.