Diagnostic and prognostic value of subcutaneous tissue biopsy in patients with cardiac amyloidosis

Cardiac involvement in systemic amyloidosis causes detrimental prognosis; therefore, early detection and classification are important to develop appropriate therapeutic strategies. Subcutaneous tissue biopsy is a useful screening procedure for systemic amyloidosis; however, its diagnostic and prognostic value in patients with cardiac amyloidosis remains elusive. Thus, we investigated the value of subcutaneous tissue biopsy in cardiac amyloidosis. In 22 patients with cardiac amyloidosis, we retrospectively analyzed 14 consecutive patients with cardiac amyloidosis who underwent subcutaneous tissue biopsy. Amyloid deposition was observed in 11 patients (79%). Histopathologic analysis demonstrated that acquired monoclonal immunoglobulin light-chain amyloidosis could be predicted when the degree of amyloid deposition was greater in blood vessels than adipose tissue compared to senile systemic amyloidosis and familial amyloidosis (60% vs 0%, p = 0.03). During the follow-up period (median 297 days, range 3 to 761), 7 patients (5 with monoclonal immunoglobulin light-chain amyloidosis and 2 with senile systemic amyloidosis) died or were admitted to the hospital because of worsening heart failure. Of them, 6 patients (86%) were positive for amyloid deposition in blood vessels in subcutaneous tissue biopsy. Incidence of death and composite outcome including heart failure hospitalization and death was significantly higher in patients positive for amyloid deposition in blood vessels than in those without (p = 0.03, p = 0.006, respectively). These results suggest that amyloid subtype could be diagnosed by assessing the degree of amyloid deposition in blood vessels and adipose tissue in subcutaneous tissue biopsy samples from patients with cardiac amyloidosis. Amyloid deposition in blood vessels suggests poor prognosis of these patients.