Cardiac sympathetic nerve activity following mitral transcatheter edge-to-edge repair verified by 123I-metaiodobezylguanidine (MIBG) scintigraphy among disproportionate secondary mitral regurgitation

This study evaluated the cardiac sympathetic nerve (CSN) activity following mitral transcatheter edge-to-edge repair (M-TEER) using 123I-metaiodobenzylguanidine (MIBG) scintigraphy among disproportionate secondary mitral regurgitation (SMR). Among the 31 patients who underwent M-TEER between November 2018 and December 2020, 20 patients who underwent pre-procedural and 1-year post-procedural MIBG scintigraphy were included. The ratio of the pre-procedural effective regurgitant orifice area (EROA) to the left ventricular end-diastolic volume (LVEDV) was retrospectively assessed. Patients with higher EROA/LVEDV ratios were classified as MR-dominant/MR-LV-co-dominant (MD/MLCD), indicating disproportionate SMR. The changes of MIBG scintigraphy parameters were assessed among disproportionate SMR patients. All patients presented with heart failure due to moderate-to-severe (3+) or severe (4+) SMR. Following M-TEER, all patients achieved an MR grade of ≤ 2+. Of the 20 patients, 17 (85%) were classified as MD/MLCD, representing disproportionate MR. In terms of MIBG parameters, early and delayed heart-to-mediastinum ratio (e-H/M, d-H/M) showed no significant changes, but washout rate (WR) significantly decreased post-M-TEER (e-H/M; 2.07 ± 0.39 vs. 2.01 ± 0.43, P = 0.35, d-H/M; 1.86 ± 0.41 vs. 1.87 ± 0.44, P = 0.96, WR; 38.8 ± 17.5 % vs. 32.1 ± 15.2 %, P = 0.01). The brain natriuretic peptide level was significantly decreased post-M-TEER (476.7 ± 387.1 pg/mL to 306.7 ± 309.2 pg/mL, P < 0.01). The 5-year mortality prediction model showed no significant difference post-TEER (25.9 ± 15.7 % vs. 20.4 ± 11.3 %, P = 0.45). This study found a significant reduction in CSN tone, evidenced by a reduction in WR, among disproportionate SMR patients who underwent M-TEER. Further research is warranted to elucidate the association between reduced CSN tone and long-term outcomes after M-TEER.