Right Ventricular Strain Improves the Echocardiographic Diagnosis and Risk Stratification of Transthyretin Cardiac Amyloidosis Among Other Phenotypes of Left Ventricular Hypertrophy

Aims: Cardiac amyloidosis is a diffuse disease affecting all cardiac chambers. The value of right ventricular free-wall strain is uncertain as an echocardiographic red flag. We hypothesized that right ventricular free-wall strain is of added value for diagnostic and prognostic purposes in patients with transthyretin cardiac amyloidosis (ATTR-CA). Method: A diagnosis of ATTR-CA required positive Tc-99m pyrophosphate scintigraphy and negative serum clonal dyscrasia. Patients with left ventricular (LV) hypertrophy (LVH; interventricular septal thickness >= 1.2 cm) by echocardiography and negative pyrophosphate scintigraphy served as controls after exclusion of amyloid light-chain cardiac amyloidosis. Longitudinal strain was computed with speckle-tracking echocardiography. Results: We studied 108 subjects with ATTR-CA and 106 controls with LVH, retrospectively. Right ventricular free-wall strain was independently associated with the diagnosis of ATTR-CA after adjusting for classical echocardiographic parameters, namely, relative apical sparing (RAS), e', and E/e'. Right ventricular free-wall strain >= -16% was incremental to LV RAS in the overall group and in the subgroup without extreme wall thickness (<= 1.4 cm; Harrell's C, net reclassification improvement = 0.213, P < .001; and net reclassification improvement = 0.463, P = .015, respectively). Major adverse cardiovascular and cerebrovascular events (heart failure hospitalization, stroke, death) occurred in 47 ATTR-CA patients, during follow-up (median, 38; range, 6-60 months). Right ventricular free-wall strain >=-16% was associated with 3-fold increased risk of MACCE in ATTR-CA patients independently of age, comorbidities, B-type natriuretic peptide, and tafamidis treatment. Right ventricular free-wall strain was additive to LV ejection fraction for risk stratification (chi square = 10.2; P = .017). Conclusions: Right ventricular free-wall strain >-16% has incremental value to LV RAS for the differential diagnosis of ATTR-CA among LVH phenotypes and is associated with poor prognosis.