Prevalence and prognostic value of autonomic neuropathy assessed by Sudoscan® in transthyretin wild-type cardiac amyloidosis

Correlation between a commercial electrophysiological test of sudomotor function and intraepidermal nerve fiber density in hereditary transthyretin amyloidosis

INTRODUCTION/AIMS

In the early stage, hereditary transthyretin (ATTRv) amyloidosis predominantly affects small nerve fibers, resulting in autonomic dysfunction and impaired sensation of pain and temperature. Evaluation of small fiber neuropathy (SFN) is therefore important for early diagnosis and treatment of ATTRv amyloidosis. Herein, we aimed to investigate the accuracy of a quick and non-invasive commercial sudomotor function test (SFT) for the assessment of SFN in ATTRv amyloidosis.

METHODS

We performed the SFT in 39 Japanese adults with ATTRv amyloidosis, and we analyzed the correlations between electrochemical skin conductance (ESC) values obtained via the SFT and the parameters of other neuropathy assessment methods.

RESULTS

ESC in the feet demonstrated significant, moderate correlations with intraepidermal nerve fiber density (IENFD) results (Spearman's rank correlation coefficient [rs ], 0.58; p < .002) and other neuropathy assessment methods including the sensory nerve action potential amplitude in the nerve conduction studies (rs , 0.52; p < .001), the Neuropathy Impairment Score (rs , -0.45; p < .01), the heat-pain detection threshold (rs , -0.62; p < .0001), and the autonomic section of the Kumamoto ATTRv clinical score (rs , -0.53; p < .0001).

DISCUSSION

In this study, we found that ESC values in the feet via the SFT demonstrated significant, moderate correlations with IENFD and other SFN assessment methods in patients with ATTRv amyloidosis, suggesting that the SFT appears to be an appropriate method for assessment of SFN in this disease.

The ventilatory component of the muscle metaboreflex is overstimulated in transthyretin cardiac amyloidosis patients with poor aerobic capacity

Background: The exercise pressor reflex, i.e., metabo- and mechano-reflex, partially regulates the control of ventilation and cardiovascular function during exercise. Abnormal exercise pressor reflex response has been associated with exaggerated ventilatory drive, sympathovagal imbalance and exercise limitation in chronic heart failure patients. Whether metaboreflex is over-activated and participate to poor aerobic capacity in patients with hereditary transthyretin cardiac amyloidosis (CA-TTR) is unknown. Methods: Twenty-two CA-TTR patients (aged 76 ± 7, 68% male) with the V122I (p.Val142Ile) transthyretin underwent a thorough evaluation including heart rate variability metrics, electrochemical skin conductance (ESC), physical function cardiopulmonary exercise testing, and muscle metaboreflex assessment. Eleven control subjects were chosen for muscle metaboreflex assessment. Results: Age-matched controls (n = 11) and CA-TTR patients (n = 22) had similar metaboreflex sensitivity for heart rate, stroke volume, cardiac index and mean systemic arterial pressure. Compared with age-matched controls, metaboreflex sensitivity for systemic vascular resistance (-18.64% ± 6.91% vs 3.14% ± 23.35%) and minute-ventilation responses (-9.65% ± 14.83% vs 11.84% ± 23.1%) was markedly increased in CA-TTR patients. Values of ESC displayed positive correlations with stroke volume (r = 0.53, p = 0.011) and cardiac index (r = 0.51, p = 0.015) components of metaboreflex sensitivity, an inverse correlation with systemic vascular resistance (r = -0.55, p = 0.008) and a trend with mean arterial (r = -0.42, p = 0.052) components of metaboreflex sensitivity. Peak aerobic capacity (peak VO₂%) displayed an inverse correlation with the ventilation component of metaboreflex sensitivity (r = -0.62, p = 0.015). Conclusion: Consistent with the "muscle hypothesis" in heart failure, it is proposed that deterioration of skeletal muscle function in hereditary CA-TTR patients may activate muscle metaboreflex, leading to an increase in ventilation and sensation of breathlessness, the perception of fatigue, and overall sympathetic activation.

The value of electrochemical skin conductance measurement by Sudoscan® for assessing autonomic dysfunction in peripheral neuropathies beyond diabetes

The diagnosis and follow-up of peripheral neuropathies involving small-diameter nerve fibers require specific examinations beyond conventional nerve conduction studies which only concern large-diameter nerve fibers. Among these tests, some are dedicated to the investigation of cutaneous innervation by the autonomic nervous system, mainly by unmyelinated sympathetic C fibers. To this end, various laboratory tests have been proposed, but the measurement of electrochemical skin conductance (ESC) by Sudoscan® is increasingly becoming the most widely used technique, because it allows a quick and simple assessment of the sudomotor function of the limb extremities. This technique is based on the principles of reverse iontophoresis and chronoamperometry and since its introduction in 2010, has been the source of nearly 200 publications. In the clinical field, most of these publications concern the evaluation of diabetic polyneuropathy, for which the value of Sudoscan® no longer needs to be demonstrated. However, there is also evidence for a role for Sudoscan® in the testing of the autonomic nervous system in various peripheral neuropathies of other origins or diseases primarily affecting the central nervous system. In this article, a comprehensive review of the literature on the clinical value of Sudoscan® outside of diabetes is presented, detailing ESC changes in neuropathies associated with various clinical conditions, such as hereditary amyloidosis or other genetic pathologies, chemotherapy neurotoxicity, dysimmune or infectious disorders, fibromyalgia, parkinsonism or other neurodegenerative diseases.

Central Sensitization and Small-fiber Neuropathy Are Associated in Patients With Fibromyalgia

OBJECTIVE

To study the prevalence of small-fiber neuropathy (SFN) in a large cohort of patients with fibromyalgia (FM) and to better characterize the subset of patients with both FM and SFN.

METHODS

This 1-year, retrospective, observational cohort study included 265 patients with FM. They all performed electrochemical skin conductance (ESC) using the Sudoscan device, 1 of the simplest and most reliable technique to assess the distal autonomic nerve fibers. They completed 4 self-assessment questionnaires: (1) the Central Sensitization Inventory (CSI), (2) the Neuropathic Pain Symptom Inventory (NPSI), and (3) the Hospital Anxiety and Depression Scale (HADS), the Fibromyalgia Impact Questionnaire (FIQ).

RESULTS

Fifty-three patients (20%) had reduced ESC values. These patients had higher CSI and HADS scores, and a larger intake of analgesic drugs compared with patients with no ESC abnormalities. Central sensitization, which was extreme in 69% of the patients (CSI score ≥60), was 1 of the main determinants of ESC abnormalities and was associated with a higher NPSI score, even though these 2 factors were not correlated.

CONCLUSION

Over the past 10 years, studies have shown that a significant proportion of patients with FM have signs of small nerve fiber impairment. The possible involvement of SFN, in the occurrence and presentation of clinical symptoms in FM patients, remains however unclear. This is the first study that showed an association between central sensitization and both small nerve fiber impairment and neuropathic pain features in FM patients, rather than a direct association between SFN and neuropathic pain.

Determinants of ventilatory inefficiency in transthyretin cardiac amyloidosis: The role of excessive ventilatory drive

Background and objective: Along with impaired aerobic capacity, increased slope of the relationship between ventilation (VE) and pulmonary CO2 output (VCO2), i.e., VE-VCO2 slope is a common finding in patients with cardiac amyloidosis (CA), which suggests ventilatory inefficiency. Little is known about mechanisms leading to ventilatory inefficiency in CA patients. The purpose of this investigation was to examine the factors that underlie the abnormal ventilatory efficiency in transthyretin hereditary CA patients, such as excessive ventilatory drive, inability of pulmonary blood flow to increase adequately during exercise and excessive sympathetic stimulation, which are known mechanisms of VE-VCO2 slope increase.

Methods: In this single-center retrospective observational study, consecutive patients (n = 41) with known familial transthyretin amyloidosis p.Val142Ile mutation carriers with confirmed cardiac phenotype were included.

Results: Compared with CA patients without ventilatory inefficiency (VE-VCO2 slope &lt; 36), patients with ventilatory inefficiency (VE-VCO2 slope ≥ 36) had increased inter-ventricular septum thickness, lower VO2 peak along with hyperventilation, and prolonged post-exercise heart rate recovery. By multivariate analysis, only excess of minute-ventilation at anaerobic threshold (β = 0.127; p = 0.011) remained an independent predictor of ventilatory inefficiency.

Conclusion: Our data suggest that high ventilatory stimulation during exercise leading to hyperventilation is the main determinant of ventilatory inefficiency in hereditary transthyretin cardiac amyloidosis patients. This novel finding helps to better understand the mechanism of exercise intolerance in these patients where physiological limitation may be related to both heart dysfunction and abnormal pulmonary response.

The Silent Period for Small Fiber Sensory Neuropathy Assessment in a Mixed Cohort of Transthyretin-Mediated Amyloidosis

Background: Transthyretin-mediated amyloidosis (ATTR) is a rare multisystemic disease involving the peripheral nervous system and heart. Autonomic and small fiber involvement is one of the hallmarks of ATTR, and many tools have been proposed to assess this aspect. Aim: The aim of this study was to investigate cutaneous and mixed nerve silent periods (CSP and MnSP) as instruments for small fiber assessment. Methods: A total of 21 ATTR patients, 20 healthy controls, and 18 asymptomatic carriers underwent a sensory conduction study from the right sural and non-dominant ulnar nerves. A motor conduction study from the right deep peroneal and non-dominant ulnar nerves, with their F waves, CSPs, and MnSPs, was performed. Results: The amplitudes of the sural and ulnar sensory nerves and of the peroneal and ulnar motor nerves were reduced in ATTR patients compared to the other groups. F waves from the ulnar and peroneal nerves showed no differences between the three groups. The CSP and MnSP latency, but not amplitude, were increased in both the ulnar and peroneal nerves of ATTR patients. Conclusions: ATTR patients showed axonal involvement of large sensory and motor nerve fibers and demyelinating features of small sensory fibers.

Prevalence and Clinical Outcomes of Transthyretin Amyloidosis: A Systematic Review and Meta-analysis

BACKGROUND

Systematic evidence on the prevalence and clinical outcome of transthyretin amyloidosis (ATTR) is missing. We explored: a) the prevalence of cardiac amyloidosis in various patient subgroups, b) survival estimates for ATTR subtypes and c) the effects of novel therapeutics on the natural course of disease.

METHODS

A systematic review of literature published in Medline before 31/12/2021 was performed for the prevalence of cardiac amyloidosis & all-cause mortality of ATTR patients. Extracted data included sample size, age, sex, and all-cause mortality at 1, 2 and 5-years. Subgroup analyses were performed for ATTR subtype i.e., wild type ATTR (wtATTR) vs. hereditary ATTR (htATTR), htATTR genotypes and treatment subgroups.

RESULTS

We identified a total of 62 studies (n=277,882 individuals) reporting the prevalence of cardiac amyloidosis, which was high among patients with a hypertrophic cardiomyopathy phenotype, HFpEF, and elderly with aortic stenosis. Data on ATTR mortality were extracted from 95 studies (n=18,238 ATTR patients). Patients with wtATTR were older (p=7x10^-10 ) and more frequently male (p=5x10^-20 ) vs. htATTR. The 2-year survival of ATTR was 73.3% (95%CI 71.6-76.2); for non-subtyped ATTR 70.4% (95%CI 66.9-73.9), for wtATTR (76.0%, 95%CI: 73.0-78.9) and for htATTR (77.2%, 95%CI: 74.0-80.4); in meta-regression analysis wtATTR was associated with higher survival after adjusting for confounders. There was an interaction between survival and htATTR genotypes (p=10^-15 , Val30Met having the lowest and Val122Ile/Thr60Ala the highest mortality). ATTR 2-year survival was higher on tafamidis/patisiran compared to natural disease course (79.9%, 95%CI: 74.4-85.3 vs. 72.4%, 95%CI 69.8-74.9, p<0.05).

CONCLUSIONS

We report the prevalence of ATTR in various population subgroups and provide survival estimates for the natural course of disease and the effects of novel therapeutics. Important gaps in worldwide epidemiology research in ATTR were identified. This article is protected by copyright. All rights reserved.

Assessment and Management of Older Patients With Transthyretin Amyloidosis Cardiomyopathy: Geriatric Cardiology, Frailty Assessment and Beyond

Transthyretin amyloidosis cardiomyopathy (ATTR-CM) is commonly diagnosed in older adults, in particular the wild-type (ATTRwt), which is regarded as an age-related disease. With an aging population and improved diagnostic techniques, the prevalence and incidence of ATTR-CM will continue to increase. With increased availability of mortality reducing ATTR-CM therapies, patients are living longer. The predominant clinical manifestation of ATTR-CM is heart failure, while other cardiovascular manifestations include arrhythmia and aortic stenosis. Given their older age at diagnosis, patients often present with multiple age-related comorbidities, some of which can be exacerbated by ATTR, including neurologic, musculoskeletal, and gastrointestinal problems. Considerations related to older patient care, such as frailty, cognitive decline, polypharmacy, falls/mobility, functional capacity, caregiver support, living environment, quality of life and establishing goals of care are particularly important for many patients with ATTR-CM. Furthermore, the high cost ATTR treatments has increased interest in establishing improved predictors of response to therapy, with assessment of frailty emerging as a potentially important determinant. Multidisciplinary care inclusive of collaboration with geriatric and elder care medicine specialists, and others such as neurology, orthopedic surgery, electrophysiology and transcatheter aortic valve replacement clinics, is now an important component of ATTR-CM management. This review will examine current aspects of the management of older ATTR-CM patients, including shared care with multiple medical specialists, the emerging importance of frailty assessment and other considerations for using ATTR therapies.

Frailty in Wild-Type Transthyretin Cardiac Amyloidosis: The Tip of the Iceberg

ATTRwt-CA occurs in elderly patients and leads to severe heart failure. The disease mechanism involves cardiac and extracardiac infiltration by amyloid fibrils. The objectives of this study are to describe the frailty phenotype in patients with ATTRwt-CA and to assess the associations between frailty parameters, the severity of cardiac involvement, and the course of amyloid disease. We used multidimensional geriatric tools to prospectively assess frailty in patients with ATTRwt-CA consulting (in 2018-2019) in the French National Reference Center for Cardiac Amyloidosis. We included 36 patients (35 males; median age: 82 years (76-86). A third of the patients were categorized as NYHA class III or IV, and 39% had an LVEF below 45%. The median serum NTproBNP was 3188 (1341-8883) pg/mL. The median duration of amyloidosis was 146 months (73-216). The frequency of frailty was 50% and 33% according to the physical frailty phenotype and the Short Emergency Geriatric Assessment questionnaire, respectively. Frailty affected a large number of domains, namely autonomy (69%), balance (58%), muscle weakness (74%), malnutrition (39%), dysexecutive syndrome (72%), and depression (49%). The severity of CA was significantly associated with many frailty parameters independently of age. Balance disorders and poor mobility were also significantly associated with a longer course of amyloid disease. Frailty is frequent in patients with ATTRwt-CA. Some frailty parameters were significantly associated with a longer course of amyloid disease and CA severity. Taking into account frailty in the assessment and management of ATTRwt should improve patients' quality of life.

Prevalence and prognostic value of autonomic neuropathy assessed by Sudoscan® in transthyretin wild-type cardiac amyloidosis

Aims

The prevalence of autonomic neuropathy (AN) is high in patients with hereditary transthyretin amyloidosis but remains unknown in transthyretin wild‐type cardiac amyloidosis (ATTRwt‐CA). This study aimed to determine the prevalence of AN in patients with ATTRwt‐CA using Sudoscan®, a non‐invasive method used to provide evidence of AN in clinical practice and based on measurement of electrochemical skin conductance at the hands and feet (fESC).

Methods and results

A series of 62 non‐diabetic patients with ATTRwt‐CA was prospectively included over 2 years and compared with healthy elderly subjects, matched by age, gender, and body mass index. The presence of AN was defined as electrochemical skin conductance at the hands <60 μS and/or fESC <70 μS, and conductances were analysed according to clinical, biological, and echocardiographic data. Mean fESC was significantly lower in patients with ATTRwt‐CA compared with elderly controls: 68.3 (64.1–72.5) vs. 76.9 (75.6–78.1) μS (P < 0.0001), respectively. Prevalence of fESC <70 μS was higher in ATTRwt‐CA patients than in controls: 48.4% vs. 19.9%, P < 0.05. Univariate analysis showed that fESC, N‐terminal pro‐B‐type natriuretic peptide, creatinine plasma levels, and echocardiographic global longitudinal strain were associated with decompensated cardiac failure and death. Multivariate analysis revealed that fESC was an independent prognostic factor, and Kaplan–Meier estimator evidenced a greater occurrence of cardiac decompensation and death in patients with fESC <70 μS, P = 0.046.

Conclusions

Reduced fESC was observed in almost 50% of patients with ATTRwt‐CA and was associated with a worse prognosis. Sudoscan® could easily be used to screen ATTRwt‐CA patients for the presence of AN and identify patients at higher risk for a poor outcome.