Management of diabetic patients with aortic intramural hematoma:
There may be more involved besides MMP9
Is intramural hematoma, in fact, an aortic dissection where the intimal
tear is not visualized by the current imaging technology? There is
certainly a divide between the east and the west regarding the
appropriate management strategy for intramural hematoma involving the
ascending aorta (IMHA). In the United states, an IMHA is mostly treated
like a Type A dissection, with urgent surgery. However, several reports
from Asian centers, such as the current series, propose an initial
medical approach constituting impulse control and serial imaging to
select patients for surgical treatment. These reports have enhanced our
understanding of high risk features surrounding IMH (pericardial
effusion, aortic diameter > 5 cm, or IMH width
> 1 cm) that will likely fail medical management and
require surgery.
In this manuscript, the authors have compared outcomes of medical
management of IMHA in patients with newly diagnosed DM to those without
DM and report a higher rate of death associated with increased MMP-9
levels in patients without DM. The authors contribute the early
mortality in the DM group to a sharp increase in the MMP9 levels due to
aggressive glycemic control in this group, often with use of insulin. It
is however, interesting to note that the only time period with
significant difference in mortality between the two groups, with higher
mortality in patients without DM is during the 3-6 month period (Figure
4D), when the MMP 9 levels patients without DM are rapidly declining,
which is not congruent with the hypothesis of the study. Further, the
only mortality in the 25-36 months is in the DM group; during this
period, the MMP9 levels in this group are significantly lower as
compared to the no DM group. Also, the authors report that 8 of 10 late
deaths occurred after ascending aortic complications (retrograde Type A
dissection or ascending aortic pseudoaneurysms) after TEVAR placement.
This is very high, likely related to placing a stent graft with the
proximal landing zone in diseased aorta, something that we try hard to
avoid while treating patients with acute Type B dissections, taking
measures (arch re-routing etc.) to ensure a proximal stent landing zone
in undissected aorta. In patients with IMHA, that is not possible due to
the hematoma extending into the ascending aorta. The outcomes in the
group of patients subjected to this approach in the current study raises
the question if these complications are treatment related, as much as
disease related.
While there remain some questions regarding the findings of the current
report, if one were to believe the conclusions of the study, an even
more interesting question comes up – how aggressively should DM be
controlled in patients with IMHA, or more broadly, with all acute aortic
syndromes? And for how long? The systemic manifestations of DM are well
known and the potential protective effect of DM for aortic disease
presents an important clinical conundrum for the clinicians providing
care for these patients; it runs counterintuitive to all we have learned
about patient care. The presence or absence of DM is an unmodifiable
risk factor, particularly when newly diagnosed in a patient presenting
with an IMHA. The only modifiable factor is how we treat it. There is an
interesting mechanism question that has not been answered by any study,
but which is suggested by the authors’ findings: Could some IMH arise
from intramural bleeding from vasa vasora, rather than from a localized
dissection not detected by imaging. If DM can affect vasa vasora so that
the microvascular anatomy of the aorta is diminished, could this result
in selection of patients with smaller IMH?
Perhaps future studies examining aortic outcomes in patients with DM and
detailed pathologic examinations, comparing patients with strict or
relaxed glycemic control will help answer some of these questions.
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Note that mortality rates of medically-treated patients in the European
and American series are higher (1-3), compared with the Asian series
(4-6).