Why the study?
Cardiac sympathetic denervation had been reported in variant transthyretin amyloidosis, but had never been investigated in wild-type transthyretin amyloidosis.
Do patients with wild-type transthyretin (ATTRwt) cardiomyopathy exhibit cardiac sympathetic denervation, and does it correlate with amyloid burden and perfusion?
Do patients with wild-type transthyretin (ATTRwt) cardiomyopathy exhibit cardiac sympathetic denervation, and does it correlate with amyloid burden and perfusion?
Patients with ATTRwt cardiomyopathy exhibit significant cardiac sympathetic denervation that correlates with regional hypoperfusion but not directly with amyloid burden.
ATTRwt denervation associates with hypoperfusion but not amyloid burden; leaves open prognostic value and therapeutic targeting.
Background Tissue accumulation of misfolded transthyretin (TTR) may occur because of TTR gene mutations (variant amyloid TTR amyloidosis, ATTRv), or as an age-related phenomenon (wild-type ATTR, ATTRwt). Cardiac sympathetic denervation has been reported in ATTRv, but has never been investigated in ATTRwt.Methods Fifteen consecutive patients with ATTRwt cardiomyopathy (81% men, median age 82 years, no one with prior myocardial infarction) underwent Cadmium Zinc Telluride tomographic imaging for amyloid burden (99mTc-hydroxymethylene diphosphonate – 99mTc-HMDP), innervation (123I-metaiodobenzylguanidine – 123I-MIBG), and perfusion (99mTc-tetrofosmin).Results Median summed 99mTc-HMDP score was 60 (58–62), denoting a severe and diffuse amyloid burden. Planar 123I-MIBG examination showed decreased early and late H/M ratios (late H/M ratio: 1.5 [1.3–1.6], range 1.2–1.9, reference value ≥2.0). Summed 123I-MIBG score was 12 (6–22), with the most prominent denervation in the infero-septal, inferior, and infero-lateral regions; summed rest score was 7 (5–11), with lowest degrees of myocardial perfusion in the inferior and infero-septal regions. The correlation between amyloid burden (as relative 99mTc-HMDP uptake) and innervation (as relative 123I-MIBG uptake) did not achieve statistical significance at both segmental (p = .252) and regional level (p = .251). Nevertheless, denervation tended to worsen in parallel with the amyloid burden, and 123I-MIBG scores increased with 99mTc-HMDP scores. Segments and regions with prominent hypoperfusion also showed a higher degree of denervation (r = 0.500 and 0.591, respectively; both p < .001).Conclusions Patients with ATTRwt cardiomyopathy display cardiac sympathetic denervation, particularly in the inferior and septal myocardial wall. Myocardial hypoperfusion has a similar regional pattern, while the amyloid burden is more extensive.
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Gimelli et al. (2020) studied this question.
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