QRS Duration
Sixty-five percent of patients in this study had documented QRS
durations before and after implantation. The average increase in QRS was
37.48 ms with a standard deviation of 38.00 ms. The greatest increase in
QRS duration was 103 ms. The greatest decrease in QRS duration was 38
ms, which may be explained by conduction system pacing. The data did not
implicate an implantation location that was associated with
significantly less QRS duration lengthening. The pre-implantation and
post-implantation QRS duration correlation coefficient for the entire
dataset regardless of implantation location was 0.02, and correlation
coefficients were similar when individual implantation location groups
were assessed. This demonstrates that, although there is typically an
increase in QRS duration after pacing is initiated, it is not possible
to predict prior to implantation which patients will have significant
increases in QRS duration.