Conclusions
MV surgery, including MVr, has continued to evolve over the past several
decades[1,17]. MVr is widely accepted as both preferable and
superior to replacement when the repair is expected to feasible,
durable, and associated with a low morbidity and mortality[18]. In
our recently published series of 446 patients undergoing MVr, survival
was excellent at 97%, 96%, 95%, and 94% at 1,3, 5, and 10 years, and
the cumulative incidence of progression of mitral regurgitation (MR)
with mortality as a competing risk was 4.7%, 10.5%, 21.1%, and 35.8%
at 1, 3, 5, and 10 years[14]. Other contemporary studies have also
demonstrated excellent survival and low rates of MR recurrence,
suggesting that in the era of evolving technologies, the excellent
results obtained with surgical MVr should not be forgotten[19-21].
The optimal approach to the MV remains debatable. Minimally invasive
approaches to the MV were developed, and continue to be developed and
improved, with the hope of decreasing the morbidity and mortality
associated with a standard sternotomy approach. While there are strong
proponents of the minimally invasive approach, demonstrating a clear
benefit over standard sternotomy has been difficult. Results of
comparative studies are often contradictory, however, several studies
suggest a minimally invasive approach can be associated with less blood
product use, equivalent or shorter lengths of stay, decreased hospital
readmissions, and equivalent perioperative morbidity and
mortality[5-7,9-12]. The long-term benefits of minimally invasive MV
approach when compared to a sternotomy approach are even less clear with
far fewer studies with a comparator group and long-term outcomes. This
is made more difficult by the lack of randomized controlled trials, and
given lack of surgeon equipoise, the unlikelihood that an appropriately
designed trial will be conducted.
The present study used a propensity score model to compare long term
survival, need of mitral reoperation, and progression of mitral
regurgitation with two surgical approaches to MVr, the standard
sternotomy, and our preferred minimally invasive approach, the small
right anterior thoracotomy. The principle findings of our study were
that overall survival was at least equivalent between groups, and there
were no differences in the need for MV reoperation or progression of
mitral regurgitation over time between groups.
Overall survival was excellent with both surgical approaches, and is
comparable to other reports[5,6,9,10,12]. Perioperative mortality
was 1.5% in the sternotomy group and 0.4% in the small right anterior
thoracotomy group, and 10-year survival was 91.4% in the sternotomy
group and 97.0% in the small right anterior thoracotomy group. After
propensity adjustment on baseline factors predictive of operative
approach, there was a protective benefit for the small right anterior
thoracotomy approach, which was independent of the type of MVr (HR 0.32,
95% CI 0.13-0.82, p=0.018). This protective benefit, while
statistically significant, should be viewed with caution and should not
be interpreted to suggest that a right anterior thoracotomy approach is
superior to a standard sternotomy approach.
One should carefully interpret these results within the context of this
study. The higher mortality rates in the sternotomy group likely
reflects their sicker nature and inclusion of those needing coronary
revascularization, despite risk adjustment. This is seen in our
sensitivity analysis with lessening of survival “benefit” with removal
of coronary revascularization patients indicating, albeit a good
logistic model, all bias was not removed. However, the analysis does
strongly support equivalent long-term survival between these two
operative approaches. Patient selection (body habitus, anatomy, etc)
partially accounts for our excellent minimally invasive results, for
which we offer no apologies.
Our rates of MV reoperation and progression of MR over time are somewhat
difficult to interpret in the context of the literature as we
appropriately included death as a competing outcome. That said, the
important finding here is that after risk adjustment for differences in
selection of operative approach, there does not seem to be any more or
less need for MV reoperation or progression of MR in either group.
There are numerous limitations to this study, some of which are
discussed above. This was a retrospective cohort study from a single
center and has the inherent limitations of this type of analysis.
Selection to a surgical approach was not randomized and was highly
biased based on preoperative characteristics. While we have attempted to
adjust for these baseline differences with our statistical modeling,
inherently not all bias is removed.
In conclusion, MVr via a small right anterior thoracotomy incision in
select patients can be performed with surgical results and survival that
are equivalent to the sternotomy approach. Growing evidence supports the
safety and durability of less invasive MVr, making it the preferred
approach of many experienced MV surgeons.