Cardiac Sympathetic Nerve Function in Patients with Severe Aortic Stenosis Prior and After Transcatheter Aortic Valve Implantation: Evaluation by 5-Year Risk Model

Background: While the non-invasive assessment of cardiac sympathetic nerve dysfunction is readily accessible, its applicability in invasive intervention for structural heart disease has received limited investigation. Our study aimed to clarify the cardiac sympathetic nerve function in patients with severe Aortic stenosis (AS) and its postoperative changes after transcatheter aortic valve implantation (TAVI) using 123I-metaiodobenzylguanidine scintigraphy (MIBG) in combination with 5-year mortality prediction model. Methods: Consecutive 26 patients (83 ± 5ys, male 4) with severe AS who underwent MIBG prior TAVI procedures were retrospectively enrolled. Of those, 15 patients underwent postoperative-follow up MIBG. The early and delayed heart-to-mediastinum ratio (e- and d-H/M), and washout rate (WR) were obtained from MIBG planner imaging. The MIBG 5-year mortality prediction model was employed to compare pre and after TAVI. Cardiac function and wall thickness were evaluated with transthoracic echocardiography. Results: Preoperative e-H/M, d-H/M, and WR were 2.4 ± 0.5, 2.3 ± 0.4, and 29 ± 14% respectively, and WR showed significant correlation to LVEF and BNP (r=-0.4 and 0.6; p=0.03, and 0.001 for LVEF and BNP, respectively). 102 ± 28 days after TAVI, either H/M or WR did not show significant improvement among enrolled patients (2.5 ± 0.3, 2.3 ± 0.4, and 30 ± 11% for e-, d-H/M, and WR for after TAVI), while the BNP level was significantly reduced (128 ± 691 and 94 ± 194 pg/dl, for pre vs. after, p=0.008). Five patients showed a significant recovery in WR (37.0 ± 13.8 and 28.8 ± 8.5% for pre and post, p=0.04), and left ventricular wall thickness was significantly thinner compared to those who did not recover (15.2 ± 3.2 vs 11.2 ± 2.4, p=0.02; 14.2 ± 2.9 vs 10.8 ± 1.8, p=0.02 for intraventricular septum and posterior wall, respectively). In 5-year prediction risk model, 7 patients showed a significant reduction in mortality risk, and the patients who did not show risk reduction had significantly reduced renal function (eGFR 57.5 ± 18.8 vs. 38.2 ± 11.3 ml/min/1.73m², p=0.03 for recovered vs. not recovered). Conclusion: After a 3-month follow-up after TAVI, diverse response in cardiac MIBG parameters were observed among patients with severe AS, despite successful valve replacement. Cardiac MIBG serves as a non-invasive tool that can comprehensively evaluate and surrogate the severity of heart failure resulting from a multi-factorial condition.