Apical sparing and clinical parameters in patients with histologically confirmed transthyretin amyloidosis

Abstract State of research Wild-type transthyretin amyloidosis (wtATTR) is a multisystemic disease characterized by deposition of amyloid fibrils in the interstitium. Cardiac involvement is usually associated with an unfavorable prognosis. The echocardiographic phenomenon of "apical sparing" shows a high sensitivity and specificity for the diagnosis of cardiac amyloidosis. It is assumed that less amyloid is deposited in the apical region of the heart than in the basal region, but this has not yet been clearly demonstrated. The clinical, histological and prognostic difference between patient groups with and without apical sparing is currently the subject of scientific debate. Aims and methods To investigate the differences between patients with and without apical sparing, 55 patients with ATTR amyloidosis were analyzed (apical sparing n=39; no apical sparing n=16). Inclusion criteria included histologically confirmed TTR amyloidosis based on left ventricular myocardial biopsy. Results Patients with apical sparing showed a significantly higher amyloid content in the myocardial biopsies (p=0.0123) compared to the group without apical sparing, matching higher Perugini scores (p=0.0001), greater septal thickness (p=0.0224), increased NT-proBNP (p=0.0001) and troponin values (p<0.0001) as well as a reduced global longitudinal strain (GLS, p=0.0084). There were no significant differences between the two groups with regard to age (p=0.6750), ejection fraction (EF, p=0.6640), posterior wall thickness (p=0.2371), LVEDD (p=0.7369) and serum free kappa and lambda light chain concentrations (p=0.1877, p=0.0639, respectively). Conclusion The presence of apical sparing on echocardiography is associated with a significantly higher amyloid load in the left ventricular myocardium, which is associated with an increased Perugini score and increased cardiac markers as extent of amyloidosis progression. The occurrence of apical sparing therefore seems to indicate an advanced ATTR stage and could be used for risk stratification and therapy modification in the future. Further studies are required to investigate in detail the prognostic relevance of the apical sparing phenomenon in cardiac amyloidosis.