Abstract 4363543: Phenotypic Evolution of Early to Late Cardiac Amyloidosis with Serial Cardiac Magnetic Resonance

Introduction: Cardiac amyloidosis (CA) is an infiltrative cardiomyopathy associated with significant morbidity and mortality. The natural history and optimal surveillance strategies for at-risk patients are incompletely defined. We present a patient with initially mild, non-specific cardiac magnetic resonance (CMR) abnormalities who then developed dramatic phenotypic expression of CA on CMR five years later. Methods: Retrospective review of the patient's clinical course was conducted using the electronic health record. Case Presentation: A 54-year-old White male with refractory atrial fibrillation after ablation underwent CMR for preoperative planning prior to mini Maze and left atrial appendage ligation. CMR showed subtle late gadolinium enhancement (LGE) of the basal inferoseptum with normal left ventricular (LV) cavity size, wall thickness, and mildly reduced LV ejection fraction (56%). He re-presented five years later with heart failure symptoms and palpitations. Transthoracic echocardiography measured the LV ejection fraction to be reduced at 45% with restrictive filling characteristics. Repeat CMR was performed and demonstrated findings consistent with CA: wall thickening (maximum 2 cm), diffusely elevated native T1 values, abnormal gadolinium kinetics, and widespread subendocardial LGE. Technetium pyrophosphate scan showed tracer uptake in the ventricular myocardium. Genetic testing did not identify any pathogenic mutations, and serum and urine testing did not identify a monoclonal dyscrasia. The patient was diagnosed with wild type transthyretin CA and started on acoramidis. Discussion: Timely diagnosis of CA is crucial, as therapies are more effective early in disease. Advanced imaging such as CMR can evaluate for CA or phenotypic mimics. However, if an initial study is negative despite clinical suspicion, optimal timing for repeat testing is uncertain due to limited understanding of early CA progression. Risk stratification scores such as Mayo ATTR-CM and AMYloidosis Index (AMYLI) scores have been described as screening tools for CA. Our patient had a Mayo score of 4 (screened out) and AMYLI score of 4.3 (not screened out), highlighting the clinical suspicion that can persist despite non-diagnostic testing. Conclusions: This case illustrates that the “warranty period” of a CMR that does not show clear signs of CA despite reasonably high clinical suspicion may be under 5 years. Further investigations are necessary to define progression and screening intervals.