Introduction
Amyloidosis is a constellation of diseases characterized by misfolded proteins deposited in target organs1. Cardiac involvements were thought to be very rare previously but are now understood to be underdiagnosed2. Acquired monoclonal immunoglobulin light-chain (AL); hereditary, mutated transthyretin-related (ATTRm); and wild-type transthyretin-related (ATTRwt) are considered as three major types of cardiac amyloidosis3. Light chains cardiac amyloidosis (AL-CA) progresses much faster than other types of amyloidosis, and appropriate treatment is capable of prolonging survival time substantially1,4.
Traditionally, AL-CA can be diagnosed by pathologic confirmation of immunoglobulin light chain amyloid in extracardiac tissue and cardiac imaging consistent with cardiac amyloidosis (CA)5. Echocardiography often provides first clues to the presence of CA, and is helpful for prompting a low threshold for further multimodality assessment2,6.
Cardiac amyloid can virtually infiltrate all cardiac chambers7,8. Previous studies have shown the significant enlargement of LA and reduction of left atrial strain in CA patients9-14. Possible mechanisms include restrictive LV physiology with elevated filling pressure resulting from intramyocardial amyloid infiltration and intrinsic LA failure due to direct amyloid infiltration10. Similarly, increased LA volume is a marker of hypertensive heart disease (HHD), and significant reduction of LA strain occurs in HHD patients15. A study containing 11 AL-CA patients, 33 ATTR-CA patients, and 25 HHD patients showed that HHD group had significantly higher left atrial strain values than the amyloid cases9. However, the number of AL-CA patients in that study was small. Meanwhile, patients with atrial fibrillation (AF) had reduced left atrial strain values, which were not studied separately in that study9. The aim of this study was to evaluate the differences in left atrial strain between patients with AL-CA and those with HHD.