Basal-to-Apical Longitudinal Strain Similar in Several Types of Cardiac Amyloidosis

New evidence suggests that basal-to-apical longitudinal strain (LS) abnormalities are similar in several types of cardiac amyloidosis (CA) and that apical LS is an independent predictor of major adverse cardiac events (MACE).

In a study involving 79 patients with CA, researchers found that mean LS and number of segments with late gadolinium enhancement (LGE) were similar in light-chain amyloidosis (AL; n=26), hereditary transthyretin amyloidosis (M-TTR; n=36), and wild-type transthyretin amyloidosis (WT-TTR; n=17), with a mean LS of -10 ± 4%. LS also correlated with LGE and amyloid burden (r=0.72). In addition, native hearts of 3 patients who received transplants were subjected to histological examination.

Echocardiography was performed at baseline and cardiac magnetic resonance imaging (MRI) was performed within 5 days. Occurrence of MACE (eg, death, heart transplantation, or new-onset heart failure) was the composite primary end point.

With the exception of age, there were no major clinical differences across the 3 types of amyloidosis (AL=64 ± 13; M-TTR=69 ± 10; WT-TTR=84 ± 7; P<.001). Preserved ejection fraction (left ventricular ejection fraction [LVEF] >50%) was seen in 59.5% of patients, and ischemic and increased filling pressure myocardial biomarkers (eg, troponin and NT-proBNP) were increased similarly in all 3 CA groups.

Researchers noted that the global LS-interventricular septum thickness (IVST) slope coefficient of the regression line appeared to be greater in the AL group compared with the other 2 CA groups. This suggests that LV contractility impairment may be worse in AL than in M-TTR or WT-TTR. “Myocardial deformation analysis showed a basal-to-apical gradient,” they wrote. “However, 52% of patients overall did not exhibit apical sparing (apical LS / [basal LS+mid-cavity LS] <1).”

During a median follow-up of 11 months, at least one MACE occurred in 36 (46%) patients. In the first 6 months, 19 (26%) patients experienced a first MACE—8 died and 11 had acute heart failure. Causes of death included cardiac arrest (2 patients) pulmonary embolism (1 patient), and refractory heart failure (5 patients).

In their examination of explanted hearts, researchers discovered more abundant amyloid deposits in the basal and mid-cavity sections as well as “a strong negative correlation between the amyloid burden measured by histopathology and segmental LV-LS in all 3 types of amyloidosis.” Researchers noted that further investigations using explanted hearts are needed to confirm this data, given that the histopathological examination was limited to 3 patients.

“Our study provides information on the usefulness of speckle-tracking echocardiography and MRI in the 3 main types of CA and suggests hypotheses regarding the pathophysiology of amyloidosis-induced LV dysfunction,” the researchers wrote. “LV-LS impairment reflected the amyloid burden and LGE during cardiac MRI was associated with LV-LS impairment. Apical LS, NT-proBNP, and NYHA [New York Heart Association] functional class independently predicted the occurrence of MACE.”

They concluded by urging future studies to evaluate new imaging techniques in order to “identify and validate specific diagnostic markers.”

Reference

Ternacle J, Bodez D, Guellich A, et al. Causes and consequences of longitudinal left ventricular dysfunction assessed by 2D-strain echocardiography in patients with cardiac amyloidosis. JACC Cardiovasc Imag. 2016. doi:10.1016/j.jcmg.2015.05.014.