Original ArticleSerial changes in cardiac sympathetic nervous function after transcatheter aortic valve replacement: A prospective observational study using 123I-meta-iodobenzylguanidine imaging
Introduction
Aortic stenosis (AS) is one of the leading causes of cardiac morbidity and mortality among elderly patients.1 While surgical aortic valve replacement is considered as the established treatment for severe symptomatic AS, transcatheter aortic valve replacement (TAVR) is another important treatment option, particularly for elderly adults or patients with prohibitive surgical risk.2
Patients with AS exhibit impairments in cardiac sympathetic nervous function (CSNF), and several studies have indicated improvements in CSNF consequent to TAVR.3,4 Our previous research has demonstrated that CSNF, as assessed by 123I-meta-iodobenzylguanidine (MIBG) imaging, significantly improves within a short duration (i.e., < 2 weeks) after TAVR.4 However, whether such short-term improvement in CSNF will be sustained thereafter remains unclear.
Functional improvement in cardiac sympathetic nerve endings is generally thought to require substantial time (i.e., more than a few months). Previous studies on the effects of beta-blockers or angiotensin-converting enzyme inhibitors (ACEIs) evaluated changes in MIBG parameters, including the heart–mediastinum ratio (H/M) and washout rate (WR), over a period of 6 to 12 months.5,6 To adequately evaluate the effects of TAVR on CSNF, it is necessary to observe not only the short-term as well as long-term changes in CSNF indices; hence, it is important to examine whether TAVR-dependent early improvements in CSNF are transitory or sustainable. To address this, the present study aimed to investigate the mid-term effects of TAVR on CSNF using serial cardiac MIBG imaging.
Section snippets
Study Population
This single-center, prospective, observational study enrolled consecutive patients who were scheduled to undergo TAVR for severe AS between October 2017 and June 2019. Severe AS was defined according to the current American College of Cardiology/American Heart Association guidelines.2 Cardiac MIBG imaging was scheduled at baseline, within 2 weeks after TAVR, and at 6 to 12 months after TAVR to evaluate the H/M and WR. All baseline and procedural data, including laboratory and echocardiographic
Patient Characteristics
Of 183 consecutive patients who underwent TAVR, 65 were excluded from the initial evaluation, whereas 7 were excluded from post-TAVR evaluation due to periprocedural complications. During the follow-up period, 21 patients who required additional medical treatment, eight patients who were followed up at other hospitals, and seven patients who died before the final MIBG imaging were excluded from the final MIBG evaluation. The final study population comprised 75 patients (Figure 1).
The baseline
Discussion
The present study yielded the following two main findings: (i) CSNF, as denoted by late H/M, demonstrated a sustained improvement from within 2 weeks after TAVR until 6–12 months later, and (ii) higher baseline mPG was an independent predictor of mid-term improvement in late H/M after TAVR. As no studies have evaluated the long-term (> 6 months) effects of TAVR on CSNF, our study could provide physicians with new insights into this field.
New Knowledge Gained
The late H/M assessed using MIBG imaging displayed a clearer trend toward improvement at 6 to 12 months than immediately after TAVR. Higher baseline mPG was an independent predictor of mid-term improvement in late H/M after TAVR.
Study Limitations
The present study has certain limitations. First, the relatively small sample size of this study may be insufficient to fully reveal the long-term effects on CSNF by TAVR procedure. In addition, the final study population comprised only 75 of the 183 consecutive patients enrolled, which raises concern about the external validity of this study. The applicability of certain imaging modalities, including MIBG scintigraphy, can be limited by the patient’s background and the presence of
Conclusion
CSNF, as denoted by late H/M, demonstrated a sustained improvement from within 2 weeks after TAVR until 6–12 months later. Such improvement was related to baseline hemodynamic AS severity. Patients with very high baseline mPG would gain the greatest prognostic benefit from TAVR.
Disclosures
Yoshito Kadoya, Kan Zen, Nagara Tamaki, Shunsuke Nakamura, Tomotaka Fujimoto, Masaki Yashige, Kazuaki Takamatsu, Nobuyasu Ito, Michiyo Yamano, Tetsuhiro Yamano, Takeshi Nakamura, Hidetake Kawajiri, Satoshi Numata, Hitoshi Yaku, and Satoaki Matoba have no conflicts of interest.
Funding
This study was not supported by any funding.
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