Mr-Proanp Rises during Exercise Even after Surgical Closure of the Left Atrial Appendage:A Sub-Study of the Laacs Randomized Study

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Objectives:The atrial appendages play a regulatory role in the fluid homeostasis and in the secretion of atrial natriuretic peptide (ANP).ANP is a 28-amino-acid peptide synthesized in the cardiac myocytes, where it is stored as a pro-hormone in cardiomyocyte granules.When released, it participates in cardiovascular volume and pressure homeostasis.We hypothesized that patients with surgical closure of the Left Atrial Appendage (LAA) -would have lower increase of Mid Region-pro-hormone ANP (MR-proANP) during exercise compared to patients with open LAA.Patients were randomized into two groups -one with surgical closure of the LAA during planned cardiac surgery and one with open LAA.Methods: A group of 19 patients who had undergone elective open heart surgery, and who had been randomized to either the LAA-closure group (n=9), or to the LAA-open group (n=10) performed a standard bicycle exercise test, at least six weeks after the operation.Closure of the LAA was confirmed by Transesophageal Echocardiography (TEE).Venous blood samples were collected before the test, and within the first two minutes of recovery after maximum work-load.Results: Baseline ANP showed (non-closed vs. closed LAA): 163.3pM (95% CI: 121.9 -204.8) vs. 137.5 pM (95% CI: 69.5 -205.6), p=0.4575.Maximum work-load was similar for both groups.MR-proANP concentration rose significantly: Max ANP (non-closed vs. closed LAA): 197.4pM (95% CI: 146.9 -247.9) vs. 164.3pM(95% CI: 89.1 -239.6), p=0.4061MR-proANP increase was not different between the groups.Delta ANP (non-closed vs. closed LAA): 34.1pM (95% CI: 22.1 -46.1) vs. 26.8pM(95% CI: 15.3 -38.3), p=0.3352 Conclusion:This study shows that plasma MR-proANP increases during exercise, and that surgical LAA closure did not reduce the increase of MR-proANP in response to physical exercise.These findings indicate that other areas of the heart elicit most of the MR-proANP production Journal of Cardiology and Vascular Medicine

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