Cardiac amyloidosis: state-of-the-art review

Abstract

Cardiac amyloidosis (CA) is caused by deposition of amyloid fibrils in the myocardium and has two main subtypes, transthyretin cardiac amyloidosis (ATTR) and immunoglobulin light chain cardiac amyloidosis (AL). ATTR is further differentiated into wild-type (wtATTR) and hereditary (hATTR), depending on the absence or presence of mutation in the transthyretin gene. The increased recognition of disease with the improvement in diagnostic armamentarium and serendipitous advancements in the therapeutic landscape have changed the status of CA from being a rare and untreatable disease to being a not-so-rare and treatable disease. Both ATTR and AL have certain clinical aspects that can provide early clues for the disease. While electrocardiography followed by echocardiography and subsequently cardiac magnetic resonance can raise suspicion for CA, the definitive diagnosis of ATTR is non-invasively established by bone scintigraphy while that of AL always needs histological confirmation. Severity of CA can be gauged by serum biomarker-based staging of both ATTR and AL. ATTR therapies work by silencing or stabilizing TTR or by degrading amyloid fibrils, while AL is managed with anti-plasma cell therapies and autologous stem cell transplant.

Figure 1

Pathobiology of the two most common types of cardiac amyloidosis.

Figure 2

Spectrum of phenotypic expression for common transthyretin mutations.

Figure 3

Sites involved in systemic amyloidosis in the body.

Figure 4

Semiquantitative method of visual grading of tracer uptake in ^99mTc-pyrophosphate scintigraphy.

Figure 5

Summary of key points in the management of congestive heart failure and arrhythmias in cardiac amyloidosis.

Figure 6

Mechanisms of amyloid-specific therapies for transthyretin cardiac amyloidosis.