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.

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Triglyceride deposit cardiomyovasculopathy (TGCV) is an emerging rare heart disease with high mortality, characterized by defective intracellular lipolysis of triglycerides (TG). We developed diagnostic criteria for TGCV, in which low washout rate of BMIPP (BMIPP-WR) is a key factor. The working group of the Japan Society of Nuclear Cardiology recently published practice recommendations for measuring BMIPP-WR. We reported that hemodialysis (HD) patients with TGCV exhibited a markedly higher cardiovascular risk than those without TGCV. Secondary carnitine deficiency is common in patients undergoing HD, as carnitine is removed from the circulation. However, clinical evidence linking carnitine levels to BMIPP-WR is limited. Here we report the effect of L-carnitine administration on the BMIPP-WR in 9 chronic HD patients with TGCV in a retrospective cohort. The mean age at TGCV diagnosis was 59 years. Following standard doses of oral L-carnitine administration, plasma free carnitine levels significantly increased. However, BMIPP-WR was not changed. In normal condition, most BMIPP taken up were esterified/incorporated into TG pool, hydrolyzed by intracellular lipases, and then transported by carnitine shuttle to mitochondria. In TGCV, intracellular TG lipolysis is defective. During the intracellular metabolism of BMIPP, carnitine shuttling occurs downstream of TG lipolysis. Therefore, even when carnitine levels were increased, BMIPP-WR did not change in patients with TGCV who underwent chronic HD. A phase IIb/III clinical trial for TGCV, is underway (jRCT2051210177). Increased awareness of the disease concept of TGCV, along with its diagnostic principles and procedures using BMIPP scintigraphy, is warranted.

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Purpose: We aimed to clarify the clinical characteristics of global and regional myocardial perfusion in patients with transthyretin type of cardiac amyloidosis (ATTR) using dual single-photon emission computed tomography (SPECT) with ^99mTc pyrophosphate (PYP) and ²⁰¹TL (TL).
Methods: Consecutive 178 (mean age 78 ± 12, male 79) patients known or suspect of ATTR who underwent PYP-TL dual SPECT were retrospectively enrolled. Patients were categorized according to the visual grading for planar PYP uptake using Perugini grading, and the patients with grade greater than or equal to 2 were analyzed. In planar analysis, the heart/ contralateral ratio (H/CL) for PYP, and heart/lung ratio (H/L) for TL were obtained to evaluate global myocardial uptake. In TL-SPECT polar map analysis, the heterogeneity of myocardial uptake was evaluated using segmental mean %uptake. Cardiac function and left ventricular function and end-diastolic ventricular mass (LVmass) were measured by echocardiography.
Results: Among 178 patients, 39 patients showed PYP uptake with grade 2 or 3 and H/CL >1.3 (81 ± 5 ys, male 28). Of those, 4 patients showed significant perfusion defect in TL scan. Among 35 patients without perfusion defect, H/L showed a significant inverse correlation to H/CL, and LVmass (r=-0.3, p=0.02; r=-0.4, p=0.03. 95% confidence interval -0.4 to 0.2, and -0.7 to -0.04 for H/CL and LVmass). Polar map analysis demonstrated significantly lower mean %uptake for TL in septum compared to lateral (79.4 ± 8.4 vs. 84.3 ± 6.2, p=0.006 for TL in septum vs. lateral, respectively).
Conclusion: In ATTR, TL uptake surrogated the reduction of global myocardial perfusion. A significant regional heterogeneity was observed with a notable reduction in septum despite the diffuse hypertrophy.

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