Cardiomyopathy and autonomic neuropathy in hereditary amyloidosis: Defining the cart and the horse
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Division of Cardiology and The Heart and Vascular Institute, University of Pittsburgh Medical Center, Pittsburgh, PA
Received Nov 29, 2018; accepted Nov 29, 2018 doi:10.1007/s12350-018-01560-4
See related article, https://doi.org/10.10 07/s12350-018-01477-y. Autonomic dysfunction is common in patients with AL amyloidosis and hereditary (mutant) ATTR polyneuropathy and cardiomyopathy (m ATTR). It has also been infrequently described in wild-type ATTR cardiomyopathy.1,2 As described by Wang et al,3 the term autonomic dysfunction implies the presence of one of more of an exhaustive list of symptoms including blurred vision or glare (pupillary dysfunction), dry eyes, or mouth (impaired cholinergic sympathetic innervation to lacrimal or salivary glands), gustatory sweating or heat intolerance (abnormal sudomotor function), cold hands and feet (peripheral sympathetic dysfunction), orthostatic hypotension, gastrointestinal symptoms of early satiety, alternating diarrhea and constipation, urinary frequency, urgency retention or incontinence, and sexual dysfunction. In their study of autonomic dysfunction in 65 patients with biopsy-proven amyloidosis,3 Wang et al used an autonomic reflex screen (ARS), a group of tests designed to test the adrenergic (blood pressure and heart-rate response to tilt, beat-to-beat blood pressure response to the Valsalva maneuver), cardiovagal (heartrate response to deep breathing at 6 breaths/min, the Valsalva ratio calculated from the maximal and minimal heart rates during the Valsalva maneuver), and sudomotor (the quantitative sudomotor axon reflex test, Reprint requests: Prem Soman, MD, PhD, MASNC, Division of Cardiology and The Heart and Vascular Institute, University of Pittsburgh Medical Center, A-429 Scaife Hall, 200 Lothrop Street, Pittsburgh, PA 15213; [email protected] J Nucl Cardiol 1071-3581/$34.00 Copyright Ó 2018 American Society of Nuclear Cardiology.
QSART) components of autonomic dysfunction. The results of these individual components were integrated into the composite autonomic severity score (CASS), resulting in a semiquantitative measure of autonomic dysfunction (mild, moderate, and severe—depending on the score). Most other studies of autonomic dysfunction in amyloidosis patients have used a more limited symptom screen and battery of tests. While Wang et al describe comprehensive autonomic testing, their study also highlights a major difficulty with the assessment of autonomic function, namely the variety and nonspecific nature of potential symptoms, and the range of testing needed for a complete evaluation of all subcomponents. I-123 mIBG imaging has been used to evaluate myocardial sympathetic function more objectively.4 The tracer was approved by the US FDA for this purpose in 2013. The uptake of I-123 mIBG by the myocardium is a reflection of the integrity of the NET-1 uptake mechanism, which is impaired in patients with heart failure and presumably, in other causes of sympathetic nerve terminal dysfunction or denervation. Its retention by the myocardium is impaired
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