Diagnosis of wild‐type transthyretin amyloid cardiomyopathy in Japan: red‐flag symptom clusters and diagnostic algorithm

Wild‐type transthyretin amyloid cardiomyopathy (ATTRwt‐CM) is caused by the deposition of wild‐type transthyretin (TTR) amyloid fibrils in the heart. The age at diagnosis of ATTRwt‐CM is reported to be approximately 70–80 years, and patients commonly present with non‐disease‐specific cardiac abnormalities, such as heart failure with preserved ejection fraction and diastolic dysfunction. The disease can be fatal if left untreated, with an approximate survival of 3–5 years from diagnosis. An oral TTR stabilizer, tafamidis, has enabled early intervention for the treatment of ATTRwt‐CM. However, awareness of ATTRwt‐CM remains low, and misdiagnosis and a delay in diagnosis are common. This review discusses the epidemiology, characteristics, treatment strategy, and red‐flag symptoms and signs of ATTRwt‐CM based on the published literature, as well as recent advances in diagnostic modalities that enable early and accurate diagnosis of the disease. We also discuss an algorithm for early and accurate diagnosis of ATTRwt‐CM in daily clinical practice. In our diagnostic algorithm, a suspected diagnosis of ATTRwt‐CM should be triggered by unexplained left ventricular hypertrophy (LVH), which is LVH that cannot be explained by an increased afterload due to hypertension or valvular disease. In addition, heart failure symptoms, laboratory test results (N‐terminal pro‐B‐type natriuretic peptide, high‐sensitivity troponin T, or high‐sensitivity troponin I), electrocardiogram and imaging (echocardiogram or cardiac magnetic resonance) data, age (≥60 years), and medical history suggestive of ATTRwt‐CM (e.g. carpal tunnel syndrome) should be examined. Detailed examinations using bone scintigraphy and monoclonal protein detection tests followed by tissue biopsy, amyloid typing, and TTR genetic testing are warranted for a definite diagnosis of ATTRwt‐CM.