Left ventricular transthyretin amyloid load and apical sparing in patients with newly confirmed transthyretin amyloid cardiomyopathy.

AIMS: Transthyretin amyloid cardiomyopathy (ATTR-CM) is marked by deposition of transthyretin amyloid in the myocardium. Patients present with symptoms of heart failure, left ventricular (LV) hypertrophy, diastolic dysfunction, and arrhythmias. Echocardiographic apical sparing, quantified via the relative apical sparing (RELAPS) pattern, is a hallmark imaging feature but its histopathological and clinical implications remain uncertain. This study investigated the association between apical sparing, myocardial amyloid load, and clinical phenotypes in newly diagnosed ATTR-CM. METHODS AND RESULTS: We prospectively enrolled 61 patients undergoing LV endomyocardial biopsy for suspected amyloidosis between May 2022 and May 2024. After histological confirmation, 56 patients with wild-type ATTR-CM were included. LV amyloid load was quantified from Congo red-stained endomyocardial biopsies. Echocardiographic parameters including global longitudinal strain (GLS) and RELAPS were assessed peri-interventionally. Clinical, laboratory, and imaging features were compared between patients with and without RELAPS. Patients with RELAPS had significantly higher LV amyloid load than those without. RELAPS was associated with elevated N-terminal pro-B-type natriuretic peptide levels, higher Perugini scores, lower GLS and atrial strain. No differences between patients with and without RELAPS were found regarding age or wall thickness. RELAPS correlated with markers of disease severity and atrial remodelling. The Perugini scores failed to distinguish intermediate levels of myocardial amyloid content in 71.1% of cases. CONCLUSIONS: Apical sparing reflects advanced myocardial involvement in ATTR-CM and correlates with increased amyloid load and biomarkers in a large endomyocardial biopsy collective. RELAPS, together with histological amyloid quantification, offers valuable insights for risk stratification and may guide therapeutic intervention in this progressive disease.