Discussion
In this study, we performed DSE in patients with severe AR and reduced
LVEF (pre-operative LVEF < 50%), for whom surgery was
indicated. We found that patients with pre-operative LVEF of> 45% exhibited a significant increase in LVEF;
however, patients with pre-operative LVEF of <45% showed no
change in LVEF. When we examined the results of DSE performed in
patients with pre-operative LVEF of <45%, ΔLVEF of ≥6% (with
CR) during DSE was related to an improvement in post-operative LVEF.
Previous studies have shown that the long-term outcomes after AVR in
patients with a low pre-operative LVEF are
poor.15-17 Patients
with reduced LVEF are often considered at very high risk of AVR, and
some are denied surgery because they are thought to be at an
irreversible worsening stage. However, a recent study revealed that a
low pre-operative LVEF for AVR was associated with lower mortality than
medical therapy.6 The
post-operative echocardiographic parameters (LVDd, LVDs and LVEF) are
important predictors of long-term cardiac
death.7 In addition,
some studies have shown that pre-operative LVEF does not correlate with
the post-operative LVEF. Even when the pre-operative LVEF is depressed,
the LVEF of some patients recovered after surgery and the long-term
prognosis after AVR is not affected by pre-operative LV
dysfunction.18
19 Therefore, it is clinically important
to assess the viability and to identify the predictors of post-operative
LV remodeling in patients with reduced pre-operative LVEF.
Some studies have focused on the effect of pre-operative status on
recovery of LV function. Cho et al. demonstrated that an LVDs index of
<35.3 mm/m2 and an LVDd index of
<44.2 mm/m2 were associated with normalised
LVEF (LVEF > 50%) in 79 patients with severe AR who
underwent AVR. However, in this study, 62 out of 79 patients had
pre-operative LVEF of
>50%.20Furthermore, as for stress echocardiography for AR, CR by exercise
echocardiography has been shown to be a prognostic value for
post-operative LV function and clinical outcome in asymptomatic or
mildly symptomatic patients with severe AR and preserved LVEF at
rest.21 This exercise
stress echocardiography also included patients with preserved LVEF.
There are few studies regarding the predictions for post-operative LV
remodeling that focus on patients with reduced pre-operative LVEF.
DSE is an established tool for detecting myocardial
viability8 in various
diseases, including chronic heart failure or aortic
stenosis.9-11 However,
there are few reports about DSE in patients with severe AR. Tam et al.
studied 16 patients who underwent elective surgery for AR and had
echocardiograms obtained at baseline and with 7.5 µg/kg/min
dobutamine.22 This
study included patients with preserved or reduced LVEF; however, the
authors concluded that LVEF during DSE was highly predictive of
post-operative LVEF. DSE may therefore have a role in predicting the
clinical outcomes of patients following AVR for AR. Marcia et al.
performed DSE (20 µg/kg/min) in 24 patients with AR and preserved LVEF
(mean LVEF, 62.3%).23However, they found that the percentage increase in LVEF under DSE did
not predict the need for surgery and/or death. Unlike our study, this
study included patients with preserved LVEF. Therefore, DSE may be
better at identifying patients who already require surgery and are at a
more advanced stage than asymptomatic or minimally symptomatic patients.
These findings support our results that DSE may be a helpful tool for
predicting post-operative reverse remodeling in patients with severe AR
and, particularly, more progressive, decreased LVEF.
Our study is one of the few to investigate the usefulness of DSE in
patients with severe AR and reduced LVEF and to show cut-off values for
contractile reserve for the improvement of post-operative LVEF.