Discussion
We presented a retrospective analysis of the differences in neurological
outcomes related to the clamping approach (single vs double SAC
and DAC respectively) of the aorta when performing CABG in a low to
moderate risk population. A single, experienced surgeon performed all
the procedures. A total of 5 patients (2%) had stroke with no
significant clinical sequalae, probably because of the limited
interested cerebral anatomical area. We could not be able to find any
significant difference in the stroke rate between the SAC and DAC group.
Classically, many risks factors have been linked to stroke following
CABG. First, the use of CPB has been advocated to be related with a
certain risk of neurocognitive sequelae linked with inflammatory
response and microembolism [4-9, 24].
In our series, all patients underwent on-pump CABG, even if in the
literature there is still an on-going debate between the usefulness of
on-pump versus off-pump coronary artery bypass (OPCAB) surgery.
Prospective studies like ROOBY trial showed better results in term of
myocardial infarction (lower rate in on-pump CABG) and better rate of
venous graft patency at 1 year, along with better Fitz-Gibbon grade, for
on-pump CABG [25]. While other studies such as the SMART trial
[26] highlighted no significant differences between the two
techniques in term of mortality, myocardial infarction, stroke and
recurrent angina or readmission for cardiac or non-cardiac events.
Regarding neurological outcomes, The ROOBY trial [25] showed a
better scoring in the clock-drawing test in the off-pump group.
Therefore, there must be other variables linked to peri-operative stroke
following CABG. Indeed, cannulation itself (including type of cannula),
cross-clamping and, more widely, aortic manipulation, are \soutshowed
suspected to be linked with neurocognitive impairment [12-14].
The debate regarding the best strategy for proximal anastomosis (SAC vs
DAC) is still on-going. Chu D. et al.[27] performed a retrospective
study on 1819 patients without finding any difference in terms of
neurological events between SAC and DAC patients. Araque JC et
al.[20] had the same results on a bigger cohort of patients and,
moreover, at the univariate and multivariate analysis the degree of
aortic manipulation was not associated with post-operative stroke .
Their results were confirmed by a large, retrospective study on patients
recruited from the Society of Thoracic Surgery database; no differences
between SAC and DAC were found regarding neurological events and
mortality [28].
On the other hand, several authors have showed conflicting results.
Remarkably, Hammon et al.[18] prospectively analyzed 237 high risk
patients undergoing OPCABG vs. CABG with single vs multiple clamp
technique and failed to find an improve outcome in term of
neuropsychological deficit in the OPCAB group. More frequent
neuro-psychological deficits were found in the DAC group. Instead,
patients undergoing CABG with single clamping had better outcome,
suggesting that the mild hypothermia during CPB may allow a
neuro-protective environment [29].
In our cohort none of the techniques used showed to be superior in term
of stroke incidence over the other. As each technique has its own
surgical advantages and disadvantages (for instance, more space to
perform proximal anastomosis in SAC and direct evaluation of graft’s
length in DAC) the surgeon should choose the technique most appropriate
to a specific situation, given the fact that good clinical outcomes and
low complication rates could be achieved with both techniques. However,
according to the existing evidences, the presence of aortic atheromas,
fibrosis or frail tissue push the operator to reduce aortic manipulation
to reduce the risk of local or distal problems, and thus a SAC strategy
could be preferred over DAC. OPCABG and use of double mammary graft or Y
configuration could be advocated in the case of porcelain aorta to avoid
excessive aortic manipulation.
On this regard an interesting aspect, as reported by Hammon et
al.[18], is that neuropsychological deficits, even if absent and
even not radiologically detectable early after operation, can appear
over a period of six months from the index procedure, suggesting that a
closer neurological follow-up should be taken into consideration in
high-risk patients to better estimate the real neurological outcome .
Our study offers a very long follow-up, reaching up to 14 years. In the
SAC group, 1 (0.9%) patient had stroke during follow up, while in the
DAC group nobody had neurological events. Therefore, it is realistic to
assume that most of the strokes after CABG happen in the early
post-operative period, and that the risks related to aortic manipulation
decrease in the long-term period.
Finally, it is interesting to notice that after 10 years the SAC group
had a significant lower freedom from MACCE, often related to the
progression of the vasculopathy. Indeed, patients in the SAC group had a
5-times higher risk of MACCE than patients in the DAC group during
long-term follow-up.
This result further underlines that an accurate analysis of the aorta at
the time of surgery may reveal many pathological changes that put the
patients at risk, immediately and during follow-up. Therefore, besides
pre-operative imaging exams and anamnesis, a in-depth analysis of the
features and consistency of the aorta at the time of surgery is crucial
to decide if a DAC or a SAC is the best strategy. It is possible to
assume that our patients in the SAC group had a worse vascular tissue
already at time of CABG, and this would explain the higher incidence of
MACCE at follow up. Hence, patients who have a worse aortic tissue
should be kept in a strict long-term follow up (up to 10 years) for
MACCE.