Damy, Thibaud

Abstract Cardiac amyloidosis is a serious and progressive infiltrative disease that is caused by the deposition of amyloid fibrils at the cardiac level. It can be due to rare genetic variants in the hereditary forms or as a consequence of acquired conditions. Thanks to advances in imaging techniques and the possibility of achieving a non-invasive diagnosis, we now know that cardiac amyloidosis is a more frequent disease than traditionally considered. In this position paper the Working Group on Myocardial and Pericardial Disease proposes an invasive and non-invasive definition of cardiac amyloidosis, addresses clinical scenarios and situations to suspect the condition and proposes a diagnostic algorithm to aid diagnosis. Furthermore, we also review how to monitor and treat cardiac amyloidosis, in an attempt to bridge the gap between the latest advances in the field and clinical practice.

Introduction: Tafamidis meglumine, available as 20 mg capsules, is approved in >40 countries for use in early stage, symptomatic transthyretin amyloidosis with polyneuropathy. It is also approved in a growing number of countries as an 80 mg daily dose (4 x 20 mg capsules) and as tafamidis free acid 61 mg (a single dose bioequivalent to tafamidis meglumine 80 mg) for the treatment of transthyretin amyloid cardiomyopathy (ATTR-CM). As some patients receiving tafamidis meglumine 20 mg may benefit from transition to tafamidis free acid 61 mg, we assessed the hypothesis that this transition is not associated with any new safety concerns. Methods: In the Tafamidis in Transthyretin Cardiomyopathy Clinical Trial (ATTR-ACT) patients with ATTR-CM were treated with tafamidis meglumine 20 mg, 80 mg, or placebo for up to 30 months. Patients completing the trial could enroll in a long-term extension study (LTE) with placebo-treated patients randomized to tafamidis meglumine 20 mg or 80 mg. All patients in the LTE were later transitioned to tafamidis free acid 61 mg. Adverse events (AEs) emerging during the LTE were assessed in patients treated with tafamidis meglumine 20 mg in the LTE who transitioned to tafamidis free acid 61 mg (median exposure 19.8 months). AEs were compared with those emerging during ATTR-ACT in patients treated with tafamidis meglumine 20 mg (median exposure 29.7 months). Results: The 87 patients treated with tafamidis meglumine 20 mg in the LTE who transitioned to tafamidis free acid 61 mg had a similar incidence of the most common AEs by system organ class, and of specific AEs, as those treated with tafamidis meglumine 20 mg in ATTR-ACT (see Table ). The safety profile of tafamidis meglumine 20 mg was previously shown to be similar to placebo. Conclusions: While the duration of exposure to tafamidis free acid 61 mg was shorter than for tafamidis meglumine 20 mg, these data demonstrate that the transition to tafamidis free acid 61 mg is not associated with any new safety concerns.

Cardiomyopathy is a manifestation of transthyretin amyloidosis (ATTR), which is an underrecognized systemic disease whereby the transthyretin protein misfolds to form fibrils that deposit in various tissues and organs. ATTR amyloidosis is debilitating and associated with poor life expectancy, especially in those with cardiac dysfunction, but a variety of treatment options have recently become available. Considered a rare disease, ATTR amyloidosis may be more prevalent than thought, particularly in older persons. Diagnosis is often delayed because of a lack of disease awareness and the heterogeneity of symptoms at presentation. Given the recent availability of effective treatments, early recognition and diagnosis are especially critical because treatment is likely more effective earlier in the disease course. The Amyloidosis Research Consortium recently convened a group of experts in ATTR amyloidosis who, through an iterative process, agreed on best practices for suspicion, diagnosis, and characterization of disease. This review describes these consensus recommendations for ATTR associated with cardiomyopathy as a resource to aid cardiologists and others in the recognition and diagnosis of ATTR associated with cardiomyopathy. Included in this review is an overview of red flag signs and symptoms and a recommended diagnostic approach, including testing for monoclonal protein, scintigraphy, or biopsy and, if ATTR associated with cardiomyopathy is identified, TTR genotyping.

Background: Hereditary transthyretin-mediated (hATTR) amyloidosis is a rapidly progressive, multisystem disease that presents with cardiomyopathy or polyneuropathy. The APOLLO study assessed the efficacy and tolerability of patisiran in patients with hATTR amyloidosis. The effects of patisiran on cardiac structure and function in a prespecified subpopulation of patients with evidence of cardiac amyloid involvement at baseline were assessed. Methods: APOLLO was an international, randomized, double-blind, placebo-controlled phase 3 trial in patients with hATTR amyloidosis. Patients were randomized 2:1 to receive 0.3 mg/kg patisiran or placebo via intravenous infusion once every 3 weeks for 18 months. The prespecified cardiac subpopulation comprised patients with a baseline left ventricular wall thickness ≥13 mm and no history of hypertension or aortic valve disease. Prespecified exploratory cardiac end points included mean left ventricular wall thickness, global longitudinal strain, and N -terminal prohormone of brain natriuretic peptide. Cardiac parameters in the overall APOLLO patient population were also evaluated. A composite end point of cardiac hospitalizations and all-cause mortality was assessed in a post hoc analysis. Results: In the cardiac subpopulation (n=126; 56% of total population), patisiran reduced mean left ventricular wall thickness (least-squares mean difference ± SEM: –0.9±0.4 mm, P =0.017), interventricular septal wall thickness, posterior wall thickness, and relative wall thickness at month 18 compared with placebo. Patisiran also led to increased end-diastolic volume (8.3±3.9 mL, P =0.036), decreased global longitudinal strain (–1.4±0.6%, P =0.015), and increased cardiac output (0.38±0.19 L/min, P =0.044) compared with placebo at month 18. Patisiran lowered N -terminal prohormone of brain natriuretic peptide at 9 and 18 months (at 18 months, ratio of fold-change patisiran/placebo 0.45, P <0.001). A consistent effect on N -terminal prohormone of brain natriuretic peptide at 18 months was observed in the overall APOLLO patient population (n=225). Median follow-up duration was 18.7 months. The exposure-adjusted rates of cardiac hospitalizations and all-cause death were 18.7 and 10.1 per 100 patient-years in the placebo and patisiran groups, respectively (Andersen–Gill hazard ratio, 0.54; 95% CI, 0.28–1.01). Conclusions: Patisiran decreased mean left ventricular wall thickness, global longitudinal strain, N -terminal prohormone of brain natriuretic peptide, and adverse cardiac outcomes compared with placebo at month 18, suggesting that patisiran may halt or reverse the progression of the cardiac manifestations of hATTR amyloidosis. Clinical Trial Registration: URL: https://www.clinicaltrials.gov . Unique identifier: NCT01960348.