Table 1.

Summary of commonly encountered “red flag” symptoms associated with ATTR-CM from the HIDDEN mnemonic present in each illustrative case.

“Red flag” symptoms associated with ATTR-CM	Case 1 ATTR-CM + MGUS	Case 2 AL amyloidosis	Case 3 ATTRwt-CM	Case 4 ATTRm-CM
$\text{H}$FpEF and other cardiac conditions, including atrial fibrillation, arrhythmia and atrioventricular block (10)	✓	✓	✓
$\text{I}$ntolerance to standard heart failure therapies (e.g., angiotensin converting enzyme inhibitors/angiotensin receptor blockers and beta-blockers) (19)		✓	✓
$\text{D}$iscordance of QRS voltage and left ventricular wall thickness seen on echocardiography (24, 37)	✓	✓	✓	✓
$\text{D}$iagnosis of carpal tunnel syndrome, biceps tendon rupture or lumbar spinal stenosis (38, 39)	✓	✓	✓	✓
$\text{E}$chocardiography showing increased left ventricular wall thickness and/or low-flow gradient aortic stenosis and additional echocardiography parameters# (24)	✓	✓	✓	✓
$\text{N}$ervous system—autonomic nervous system dysfunction, including gastrointestinal complaints or unexplained weight loss (40)		✓	✓	✓

^#Echocardiographic, speckle-strain and tissue doppler “red flags”: Heart failure normal or mid-range ejection fraction; increased wall thickness; left atrial enlargement; low stroke volume index; low-flow, low-gradient aortic stenosis (Stage D2); low myocardial contraction fraction; advanced diastolic dysfunction; impaired global longitudinal strain with apical sparing; low mitral annular tissue Doppler S' (average septal and lateral annulus) (24).

AL, light-chain amyloidosis; ATTR-CM, transthyretin amyloid cardiomyopathy; ATTRm-CM, hereditary (mutant) transthyretin amyloid cardiomyopathy; ATTRwt-CM, wild-type transthyretin amyloidosis cardiomyopathy; HFpEF, heart failure with preserved ejection fraction; MGUS, monoclonal gammopathy of undetermined significance; QRS, Q wave, R wave, and S wave.