P5992Why aortic valve disease may persist after surgery? A joint basic science - Clinical effort

Abstract

Abstract Background Diseases of the aortic valve are a common reason for heart surgery. Aortic stenosis (AS) is associated with pressure and aortic regurgitation (AR) with a volume overload of the left ventricle (LV). Over time both pathologies lead to systolic and diastolic heart failure, while progressive downregulation of β-adrenoceptors occurs. While LV re-remodeling occurs in the majority of patients after aortic valve surgery, LV dysfunction persists in one fourth of such patients and leads to a terminal heart failure. We aimed to investigate whether differential remodeling in the protein kinase A (PKA) dependent inotropic response in myocytes and myocardial tissue obtained from patients undergoing aortic valve surgery is associated with the LV re-remodeling after surgery. Methods Preoperatively, pro BNP levels were measured and left ventricular strain analysis via echocardiography was performed. Interventricular septal biopsy was obtained intraoperatively in 10 patients who underwent aortic valve surgery. In-vitro contractility was analyzed in myocardial tissue paced with 4 Hz at 37 °C. Freshly isolated cells were transduced with an adenovirus expressing a cytosolic Förster resonance energy transfer (FRET) based cAMP biosensor (Epac1-camps). After 48 hours of culture, Föster-resonance energy transfer (FRET) was used for the first time to measure cAMP in 60 isolated human ventricular myocytes. Isoprenaline (10 nM – 10 μM) was used for β-adrenoceptor activation and forskolin (10 μmol) to activate adenylyl cyclase directly. Results We found a significantly downregulated β-adrenergic sensitivity in cardiomyocytes of patients with aortic valve disease, although contractile response to forskolin was maintained. Furthermore, we found a clear association between reduced sensitivity to isoprenaline (i.e., high EC50 values) and low maximum effect size to isoprenaline in myocardial tissue of patients with aortic valve disease, pointing out relevant β-adrenoceptor dysfunction. There were no significant differences in basal myocardial force between tissue samples of patients with AR and AS. Conclusion Collectively, our data show a profound remodelling in the cAMP/PKA pathway in patients with aortic valve disease. These disturbances may have an impact on the postoperative ventricular function and possibly on the long-term LV re-remodelling after aortic valve surgery.