Abstract Body (Do not enter title and authors here): Introduction: Hypertrophic cardiomyopathy (HCM) and cardiac amyloidosis (CA) have similar features on transthoracic echocardiography (TTE) which may make the two difficult to distinguish. However, it is recognized that CA presents at an older age compared to HCM. Our aim was to determine optimal TTE parameters for differentiating HCM from CA and the incremental value of age at the time of diagnosis for differentiation of these two disorders.

Methods: Patients with CA (N=121) and HCM (N=227)—diagnosed in accordance with guidelines—who underwent TTE were retrospectively identified. TTE parameters—including left ventricular global longitudinal strain (LVGLS), apical sparing ratio (ASR), AMYLoidosis Index (AMYLI), relative wall thickness (RWT) and ejection fraction to strain ratio (EFSR)—were calculated using artificial intelligence software (US2.AI) and validated by a level III echocardiography reader. Univariate and multivariable logistic regressions were used to compare TTE parameters between CA and HCM patients. Receiver operating characteristic curve (ROC) analysis was conducted to determine performance of echo parameters in distinguishing CA and HCM.

Findings: CA patients were older compared to HCM (Figure 1A). With respect to TTE parameters, CA was associated with lower magnitude of LVGLS and higher value of ASR, AMYLI, and EFSR. LVGLS (AUC 0.865, 95% CI 0.81-0.91) outperformed AMYLI, RWT, and EFSR for differentiation of HCM from CA (Figure 1B). For all five TTE parameters, age provided incremental predictive value for LVGLS (p<0.001), ASR (p<0.001), AMYLI (p=0.007), RWT (p<0.001), and EFSR (p<0.001), Figure 2A-C). LVGLS <-15.8% was 85% sensitive and 79% specific for CA.

Conclusion: LVGLS is an optimal echo parameter for differentiating CA from HCM, outperforming all other traditional CA diagnostic markers. Age provides incremental diagnostic value in the differentiation of these two groups with TTE.