Limitations
It should be noted that our findings, based on a subanalysis of the
MADIT-CRT trial, should be considered as hypothesis generating since
other unmeasured variables in the MADIT CRT data set may have further
contributed to the observed outcomes. Accordingly, the present findings
need to be further validated in prospective studies that will be
appropriately design to identify LBBB patients who may derive benefit
vs. harm from CRT implantation. At present, we believe that our data can
be used to enhance decision support in this high-risk and understudied
population. Furthermore, the current analysis utilizes patient data from
MADIT-CRT cohort, with specific enrollment selection criteria. Thus, the
findings of the present study are applicable only to patients with mild
heart failure symptoms enrolled in the trial.