OBJECTIVES : Transthyretin amyloid cardiomyopathy (ATTR-CM) is a rare and fatal disease caused by deposition of transthyretin amyloid fibrils in the heart. The prevalence of ATTR-CM is largely unknown due to fragmented knowledge of the disease, underdiagnosing and limitations of current diagnostic methods. This study aims to estimate the age and sex specific prevalence and study the epidemiology of ATTR-CM in Sweden.

METHODS : This was a retrospective, observational study which utilized data extracted from nation-wide Swedish administrative health registers covering the years 1998 to 2018. ATTR-CM patients were identified between 2008 and 2018 using diagnosis of amyloidosis in combination with either heart failure or cardiomyopathy. The years 1998 -2008 were used as look-back period. Patients with light chain amyloidosis (AL), Multiple Myeloma (MM) and previous heart, liver or stem cell transplants were excluded.

RESULTS : In the process of patient identification, 497 patients were excluded due to AL, MM or transplants. A remaining total of 994 diagnosed ATTR-CM patients were identified over the study period. Between 2008-2013, an average of 79 patients were identified per year, between 2014-2018 this number rose to 104 patients per year. The average age at identification increased from 70 to 76 years between 2008 and 2018. During the study period the estimated prevalence of ATTR-CM cases increased from 1.04/100,000 in 2008 to 4.99/100,000 in 2018. In 2018, the majority of diagnosed ATTR-CM patients was male (75%) and above age 75 (52%).

CONCLUSIONS : This is the first Nordic Study estimating the prevalence of ATTR-CM using a national dataset over a period of 11 years. The prevalence and average age over time likely reflect increased awareness and the adaption of non- invasive imaging modalities in recent years. The estimated prevalence in 2018 is still well below the threshold of 50/100,000 used by the European Medicines Agency for orphan designation.