Prospective screening of Afro-Caribbean heart failure patients to determine the prevalence of cardiac transthyretin (ATTR) amyloidosis

Abstract

Purpose: 4% of African Americans possess the transthyretin (TTR) V122I polymorphism, which is associated with late onset cardiac amyloidosis. However, the incidence of clinically significant disease is not known and the diagnosis is readily missed due to clues on echocardiography being attributed to hypertensive heart disease, along with the misconception that the ECG always demonstrates low voltage complexes in amyloidosis. We previously demonstrated that 10% of Afro-Caribbean patients attending a heart failure clinic in South London have ATTR V122I cardiac amyloidosis, and we report here a simple diagnostic algorithm that we applied to an Afro-Caribbean patient population at another large tertiary cardiac centre in London. Methods: We prospectively reviewed the echocardiograms of Afro-Caribbean patients with non-ischaemic cardiomyopathy over a 6 month period. Patients with increased ventricular wall thickness (>12 mm) and no clinical diagnosis of hypertrophic cardiomyopathy were referred for cardiovascular magnetic resonance (CMR) and 99mTc-DPD scintigraphy. Patients in whom cardiac imaging suggested amyloidosis were further investigated at the National Amyloidosis Centre. Results: 49 Afro-Caribbean patients presented during the screening period, 11 of whom (22%) met the criteria for further investigation (median age 67 (55-77); 72% males). DPD scintigraphy was performed in all 11 patients and CMR in the 6 patients without a contraindication. A diagnosis of amyloidosis was made in 3 patients (27% of those referred for specialist review and 6% of the total number screened), two of whom had the TTR V122I variant and one had wild-type ATTR amyloidosis. Conclusions: Cardiac amyloidosis is an important cause of heart failure in the elderly Afro-Caribbean population and the diagnosis should be considered when echocardiography suggests LVH. DPD and CMR imaging are valuable diagnostic tools. Several specific therapies for ATTR amyloidosis are currently in clinical development, underscoring the need for accurate diagnosis.