Transthyretin Amyloidosis in Patients with Carpal Tunnel Syndrome
Carpal tunnel syndrome is considered a warning sign for cardiac amyloidosis. Amyloid deposits are often found in the tenosynovial material removed during surgery. However, the prevalence of concomitant cardiomyopathy is not yet fully understood. Japanese researchers from Kumamoto University recently focused on the relationship between carpal tunnel syndrome and cardiac amyloidosis in their newly published prospective study.
Warning Signs of Cardiac Amyloidosis
The development of transthyretin cardiomyopathy is usually indicated by the concurrence of several typical signs, also known as red flags. These are manifestations of the accumulation of transthyretin deposits, which appear years before cardiac symptoms emerge. Among the non-cardiac red flags are, for example, bilateral rupture of the biceps tendon, lumbar spinal stenosis, or carpal tunnel syndrome.1
Approximately 30–50% of individuals with wild-type transthyretin cardiomyopathy (wtATTR-CM, formerly known as senile cardiac amyloidosis) have a history of carpal tunnel syndrome that precedes the diagnosis of cardiac disease by 5–10 years. According to literature, amyloid deposits are found in the tenosynovium removed during carpal tunnel surgery in about one-third of cases (10–37%).2
Available data suggest that patients with carpal tunnel syndrome who have amyloid deposits in the removed tenosynovium represent a high-risk population for cardiac amyloidosis. The authors of the presented analysis focused on the prevalence of cardiomyopathy in this population.
Study Methodology
The prospective study was conducted at Kumamoto University between June 2019 and February 2023. A total of 700 patients with confirmed carpal tunnel syndrome who underwent surgery participated. Samples of removed tenosynovium were analyzed using Congo red staining, and if amyloid deposits were confirmed, the patient was offered cardiomyopathy screening. This included ECG, echocardiography, and evaluation of biomarkers – cardiac troponin (hs-cTnT), natriuretic peptide (BNP or NT-proBNP), estimation of glomerular filtration rate (eGFR), and serum light chain levels (FLC).
Patients with an interventricular septum thickness ≥ 14 mm (or within the 12–14 mm range with concurrently elevated hs-cTnT levels ≥ 14 ng/l) were recommended for scintigraphy with 99mTc-labeled pyrophosphate. The diagnosis of ATTR-CM was considered confirmed in the presence of TTR deposits in the removed tenosynovium (and absence of monoclonal protein) and a positive scintigraphy result.
Results
Amyloid deposits were found in 261 out of 700 evaluated patients after carpal tunnel surgery. These patients were significantly older (average age 71 years) compared to those with a negative finding (average age 60 years; p < 0.001) and were predominantly male (61% of positive samples in the male population, 24% in females).
A total of 120 patients agreed to cardiomyopathy screening, with TTR deposits confirmed in 116 of them (4 samples were unassessable). Elevated hs-cTnT levels were observed in 30% of patients. An interventricular septum thickness ≥ 12 mm was seen in 17 patients (14%), with 5 of them having a thickness ≥ 14 mm.
A total of 14 patients were referred for scintigraphic examination based on echocardiography and biomarker levels. One patient refused the examination, and another underwent MRI with contrast instead due to a high suspicion of hypertrophic cardiomyopathy, which was confirmed. Among the 12 patients who underwent scintigraphy, wtATTR-CM was diagnosed in 6 of them. One patient was diagnosed with heart failure class II according to NYHA criteria and commenced therapy with furosemide and tafamidis. The other participants showed no signs of heart failure and will continue to be monitored.
Conclusion
The prevalence of cardiac amyloidosis in this analysis was 5% (9% in the male population) among patients with amyloid deposits in the tenosynovium removed during carpal tunnel surgery. In the subgroup of patients who additionally had hypertrophic left ventricular wall and elevated hs-cTnT levels, the prevalence of cardiac amyloidosis reached 50%.
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Sources:
1. Garcia-Pavia P., Rapezzi C., Adler Y. et al. Diagnosis and treatment of cardiac amyloidosis: a position statement of the ESC Working Group on Myocardial and Pericardial Diseases. Eur Heart J 2021; 42 (16): 1554–1568, doi: 10.1093/eurheartj/ehab072.
2. Takashio S., Kato T., Tashima H. et al. Prevalence of cardiac amyloidosis in patients undergoing carpal tunnel release with amyloid deposition. Circ J 2023; 87 (8): 1047–1055, doi: 10.1253/circj.CJ-23-0223.
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