Study limitations
One of the limitatations, which may have influenced study results, is
that patient number was low and the etiology of low ejection fraction
was both ischemic and dialted cardiomyopathy, furthermore were dont have
only patients with LBBB but we also have patients with RBBB and LBBB
type interventricular conduction delay. All of these may have an
influence on the improvement of mitral regurgitaiton after CRT
implantation. Another limitation was follow up period restricted to
three months, as this period is not adequate to predict improvement
either in LVEF or in mitral regurgitation. In three months follow up, no
marked change was found in LVEF and volumes but in the long term,
improvement in these parameters associated with left ventricle reverse
remodelling, may decrease the degree of MR. For its evaluation, long
term follow up will be more appropriate.
In addition, although the severity of mitral regurgitation was evaluated
with transthoracic echocardiography at the third month follow up , as
the patients did not undergo control TEE examination, the parameters of
mitral valve, which are evaluated with TEE, improving and influencing
the response to treatment of mitral regurgitataion, could not be
determined.