Discussion
The main findings in the current study were as follows: (a) LA strain
parameters were significantly reduced in both AL-CA and HHD group; (b)
Patients with AL-CA had reduced LASr and LASct compared with those with
HHD, and (c) LAScd and SD-TPS were similar between AL-CA and HHD group.
In the current study, we showed lower IVS and LVPW thickness than that
in previous studies9,10,19. It suggests that patients
enrolled in the current study had less severe disease progression than
those in previous studies. Similar to the previous study, all LA strain
parameters were severely impaired in AL-CA and HHD
group9. LA strain has recently emerged as a powerful
assessment in evaluation of left ventricular diastolic
dysfunction20.Our previous study showed that LASr was
an independent predictor of elevated left ventricular end-diastolic
pressure21. In the current study, higher E/e′ values
correlated with decreased LASr in AL-CA group and HHD group, which
suggesting a decreased diastolic function. Gan et al. demonstrated that
LA remodeling reflected by larger LAVI had an incremental negative
association with LASr in patients without prior cardiac
disease22. In the current study, LA stain parameters
negatively correlated with LAVI in patients with AL-CA and patients with
HHD, which was consistent with prior study22.
Compared with those with HHD, patients with AL-CA had significantly
lower LASr and LASct in the current study. Karen et al. also showed a
significant reduction of LASr and LASct in patients with AL-CA compared
with those with HHD 9. In AL-CA group, amyloid
infiltration into the LA wall may lead to a marked functional
deterioration of this thin-walled and very vulnerable structure, and
that these alterations may lead to a significant decrease in LA
reservoir and pump function. In the current study, higher LA strain
values consisted with lower left ventricular thickness than that in
previous studies9,10,19.
Notably, the difference in LAScd between AL-CA group and HHD group was
not significant in the current study. Kotaro et al. also showed that
conduit function of LA was not impaired in all the three aetiologies of
CA10. A possible mechanism is that LA volume changes
(conduit function) may be a compensatory mechanism when LA reservoir and
pump function are impaired.
LA structural and functional
remodeling are associated with AF23,24. Kawakami et
al. showed that SD-TPS is an independent predictor of new-onset atrial
fibrillation (AF) and correlated with LASr18. In order
to assess LA strain parameters properly, we excluded patients with AF.
Both AL-CA group and HHD group had increased SD-TPS. However, the
difference was not significant between the two groups. We hypothesized
that the risk of AF was no increased in the early stage of amyloid
infiltration, although reservoir and pump function of LA were severely
impaired.
Study limitations
There are several limitations to the current study. First, patients with
AF were excluded. Typical of AF is LA remodeling. Reactive deposition of
collagen fibers in the interstitium causes massive fibrosis, and an
inverse relationship exists between the grade of fibrosis and LA
strain25,26. As a case-control study, the duration of
AF was not available. As a result, LA strain in CA patients with AF
should be investigated separately. Second, a specific software for
evaluating LA strain by speckle-tracking is not yet available.
Therefore, we analyzed LA strain using software for evaluating the left
ventricle. Third, this is a single-centered study enrolling AL-CA and
HHD patients. Therefore, our findings warrant further confirmation from
different centers and in different cardiac amyloidosis populations.