L'amylose cardiaque à transthyrétine

Abstract

Transthyretin (TTR) cardiac amyloidosis results from the dissociation of the tetrameric, liver-synthetized transport protein, either because of a mutation (hereditary CA), or spontaneously due to ageing (wild type CA). Monomers self-associate into amyloid fibrils within the myocardium, causing heart failure, arrhythmias and conduction defects. This overlooked disease must be recognized in case of unexplained increased thickness of the myocardium, particularly in subjects of African descent, in patients with heart failure and preserved ejection fraction, and in those with aortic stenosis. Some extra-cardiac symptoms must also be considered as red flags: carpal tunnel syndrome, lumbar canal stenosis, recent deafness, peripheral neuropathy, or dysautonomia. Medical assessment includes an electrocardiogram, biological assessment including troponin, natriuretic peptide and monoclonal protein assay, echocardiography with 2-D strain study, MRI and bone scintigraphy. Once the diagnosis established, cardiologic management must avoid beta-blockers and other rate-slowing drugs, which are deleterious in restrictive cardiomyopathy, and restrain the use of renin-angiotensin system inhibitors, of little use and often poorly tolerated. Congestion must be treated with diuretics. Anticoagulants are often necessary due to the risk of arrhythmias and stroke. Pacemaker or defibrillator implantation should be determined in patients with high risk of sudden death. Until now, etiologic treatments were liver and/or heart transplantation in some rare cases. Tafamidis, a TTR stabilizer has recently been approved, and new therapeutic approaches targeting TTR at the transcriptional level are under investigation.