5. Limitations
Present data was obtained from a single centre and from a limited number
of patients, so it should be regarded as a “hypothesis-generating”
study. This limited sample size also drastically reduces the power of
the study and therefore limits the reliability of the results. The
retrospective design of the study prevents making detailed analyses on
the causes of death for patients within the third PDI tertile to
ascertain whether these cases had RVF immediately before their death.
The sample size is too small to compare PDI with other established risk
predictors and risk scores, so it is unclear whether PDI offers
incremental usefulness over existing methods. While this was an
“all-comers” study, patients who were deemed to have at high risk for
RVF did not undergo LVAD implantation and that constitutes an
unavoidable “selection bias”. As aforementioned, this bias may also
explain why a low PDI failed to predict RVF, contrary to our initial
expectations. Finally, as this analysis is retrospective, not all
confounders might have been accounted for.