The objective of this study was to systematically investigate cardiac and peripheral vasomotor autonomic functions in late-onset transthyretin Val30Met familial amyloid polyneuropathy (FAP ATTR Val30Met) patients from non-endemic areas. The coefficient of variation of R-R intervals (CVR-R), responses to the Valsalva manoeuvre, head-up tilt test with impedance cardiography, noradrenaline infusion test, and (123)I-metaiodobenzylguanidine (MIBG) myocardial scintigraphy were assessed in eight patients. Although only four patients manifested orthostatic hypotension during the head-up tilt test, CVR-R, responses to the Valsalva manoeuvre, and myocardial MIBG uptake indicated a higher prevalence of cardiac sympathetic and parasympathetic dysfunction. Total peripheral resistance at 60° tilt did not increase from baseline values in five of six examined patients. An infusion of low-dose noradrenaline induced an increase in systolic blood pressure in all patients. The extent of the change in systolic blood pressure negatively correlated to that in total peripheral resistance (p < 0.05). Patients with poor vasoconstrictor responses to orthostatic stress tended to exhibit severe reduction of unmyelinated fibres in sural nerve biopsy specimens. In conclusion, both cardiac and peripheral vasomotor autonomic dysfunctions were prevalent in late-onset FAP ATTR Val30Met patients from non-endemic areas, even in those without orthostatic intolerance. However, vasoconstriction by alpha-adrenoceptor agonists was preserved even after denervation, carrying important implications for the management of orthostatic hypotension in FAP.
Keywords: Amyloid; Amyloidosis; Familial amyloid polyneuropathy; Resistance vessels; Transthyretin.