Limitations
This was a retrospective study that involved a small sample size, which
might have led to a statistical bias. Controlled studies are required to
confirm the effects of CRT upgrades in patients with CS. There was a
possibility that the differences in the baseline characteristics in each
group (gender and LA diameter) affected the incidence of composite
outcomes after the CRT upgrade. In general, women tend to have a better
CRT response and clinical outcome than men.17, 18Although more female patients were included in group 1, the
echocardiographic response in group 1 was the worst. Therefore, we
considered that the good long-term prognosis despite the lack of a high
echocardiographic response in group 1 was influenced by the
corticosteroid therapy. Although we could not determine the outcome of
the CRT upgrade in patients with CS in this study, further studies are
warranted to evaluate the outcome of a CRT upgrade.