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Aims Differentiating cardiac amyloidosis (CA) subtypes is important considering the significantly different therapies for transthyretin (ATTR)-CA and light chain (AL)-CA. Therefore, an echocardiographic method to distinguish ATTR-CA from AL-CA would provide significant value. We assessed a novel echocardiographic pixel intensity method to quantify myocardial calcification to differentiate ATTR-CA from phenocopies of CA and from AL-CA, specifically. Methods and results 167 patients with ATTR-CA (n = 53), AL-CA (n = 32), hypertrophic cardiomyopathy (n = 37), and advanced chronic kidney disease (n = 45) were retrospectively evaluated. The septal reflectivity ratio (SRR) was measured as the average pixel intensity of the visible anterior septal wall divided by the average pixel intensity of the visible posterior lateral wall. SRR and other myocardial strain-based echocardiographic measures were evaluated with receiver operator characteristic analysis to evaluate accuracy in distinguishing ATTR-CA from AL-CA and other forms of left ventricular hypertrophy. Mean SRR was significantly higher in the ATTR-CA cohort compared to the other cohorts (P < 0.001). SRR demonstrated the largest area under the curve (AUC) (0.91, P < 0.001) for distinguishing ATTR from all other cohorts and specifically for distinguishing ATTR-CA from AL-CA (AUC = 0.90, P < 0.001, specificity 96%, and sensitivity 63%). There was excellent inter- and intra-operator reproducibility with an ICC of 0.91 (P < 0.001) and 0.89 (P < 0.001), respectively. Conclusion The SRR is a reproducible and robust parameter for differentiating ATTR-CA from other phenocopies of CA and specifically ATTR-CA from AL-CA. [ABSTRACT FROM AUTHOR]

Aims: Differentiating cardiac amyloidosis (CA) subtypes is important considering the significantly different therapies for transthyretin (ATTR)-CA and light chain (AL)-CA. Therefore, an echocardiographic method to distinguish ATTR-CA from AL-CA would provide significant value. We assessed a novel echocardiographic pixel intensity method to quantify myocardial calcification to differentiate ATTR-CA from phenocopies of CA and from AL-CA, specifically., Methods and Results: 167 patients with ATTR-CA (n = 53), AL-CA (n = 32), hypertrophic cardiomyopathy (n = 37), and advanced chronic kidney disease (n = 45) were retrospectively evaluated. The septal reflectivity ratio (SRR) was measured as the average pixel intensity of the visible anterior septal wall divided by the average pixel intensity of the visible posterior lateral wall. SRR and other myocardial strain-based echocardiographic measures were evaluated with receiver operator characteristic analysis to evaluate accuracy in distinguishing ATTR-CA from AL-CA and other forms of left ventricular hypertrophy. Mean SRR was significantly higher in the ATTR-CA cohort compared to the other cohorts (P < 0.001). SRR demonstrated the largest area under the curve (AUC) (0.91, P < 0.001) for distinguishing ATTR from all other cohorts and specifically for distinguishing ATTR-CA from AL-CA (AUC = 0.90, P < 0.001, specificity 96%, and sensitivity 63%). There was excellent inter- and intra-operator reproducibility with an ICC of 0.91 (P < 0.001) and 0.89 (P < 0.001), respectively., Conclusion: The SRR is a reproducible and robust parameter for differentiating ATTR-CA from other phenocopies of CA and specifically ATTR-CA from AL-CA., Competing Interests: Conflict of interests: V.A. discloses speaking honoraria from Abbott Laboratories. A.N. discloses speaking honoraria from Abbott Laboratories and Edwards Lifesciences. J.T. discloses consulting roles with Abbott Laboratories, Caption Health, GE Health care, and egnite. R.W. discloses consulting role with Ionetix Corporation. R.W. assisted in the approval of final manuscript. S.S. discloses speaking, advising, or consulting roles with American Medical Association, Aria CV, Inc., Axon Therapies Inc., Bayer AG, Boehringer Ingelheim, Boehringer Ingelheim GmbH, Boston Scientific Corporation (includes Guidant Corporation), Edwards Lifesciences, LLC, Heart Failure Society of America, Inc. (HFSA), IMARA Inc., Impulse Dynamics, Ionis Pharmaceuticals, Inc., Kikaku International (USA) Corporation, Merck Sharp & Dohme Corporation, Novartis, Novo Nordisk A/S, Pri-Med Institute, LLC, Regeneron Pharmaceuticals, Inc., Rivus Pharmaceuticals, Roche Diagnostics Corporation, Shifamed LLC, Tenaya Therapeutics, The Lynx Group (TLG), Total CME, (© The Author(s) 2024. Published by Oxford University Press on behalf of the European Society of Cardiology. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)