Study Limitations
Our study has several limitations. First, there were no specific
recommendations for MPP programming and were left to the physician’s
discretion. Second, an important limitation of the study was the number
of patients involved and the length of the follow-up that limits the
identification of additional potential advantages of MPP further than 6
months. Third, the main limitation of the study, inherent to any
registry, is the absence of a randomized comparator group of
conventional biventricular pacing. Consequently, it cannot be concluded
the superiority of any strategy for CRT. However, the better clinical
outcomes observed in the group of patients treated with MPP merits to be
analysed in future trials. Fourth, it was observed a benefit when
programming MPP with the widest pacing electrodes. However, we did not
address the percentage of cases in which it is possible to program MPP
following this strategy. In our study, it was selected in 31% of
patients, value similar to that observed in the MORE CRT MPP study
(29%) or in the MPP IDE study (23%). We do not know if this
programming was not possible in the remaining cases and factors as
phrenic stimulation or unacceptable pacing thresholds limited the
selection of the widest electrodes for MPP. If we accept that MPP could
improve the results of CRT only when the selected pacing poles are
enough separated it will be desirable to define the percentage of cases
in which this is possible. Finally, we did not address the impact of MPP
over device battery longevity that is an important issue when
considering early activation of MPP.