Limitations
This is a single-center study of MS patients obtained from a database
review. The reliability of results from linear regression modeling in
this study is diminished by the study design. Due to the small sample
size, we had to use stratification to control for confounding and could
account for the effect of diastolic dysfunction on the echocardiographic
characteristics. There are significant differences in the demographic
profile of the two groups. DMS group had a high frequency of chronic
kidney disease and ESRD. We excluded patients with ESRD and hyperdynamic
LV from analysis to minimize confounding.
Our study utilized the continuity equation method as an independent
standard. The continuity equation valve area in the DMS population was
comparable to that of 3-Dimensional MVA in one
study.10 The retrospective nature of our study
prevented us from using an alternative imaging modality to corroborate
these findings, which is a significant limitation.
In the presence of significant MR and aortic regurgitation, our results
may not be applicable. Therefore, DMSI should be avoided in the
assessment of stenosis severity if there is more than mild MR or AR.
Also, VTI can show beat-to-beat variability with irregular heart rhythm.
Thus, in the setting of cardiac arrhythmia, DMSI can only be reliable if
the average of multiple VTI values is used.
Our study included a limited number of DMS patients with AF. Therefore,
our results may not accurately capture the impact of AF on TMPG and
transmitral flow, both of which were shown to be affected by AF in RMS
patients.25 Given the retrospective nature of the
data, the ROC curves shown are the best-case scenario and that
association strength may be variable in a larger cohort of patients.
Also, there is a lack of validation of these cutoff values.
The presence of at least mild MS on the official echocardiography report
was an eligibility criterion for our study. Moreover, some interpreters
may avoid calling MS in the setting of MAC since these patients usually
have normal-appearing leaflet excursion on 2D echocardiography.
Therefore, our subjects might not represent the full spectrum of DMS. It
is also a limitation that men were underrepresented in our DMS and RMS
groups.