DISCUSSION
HCR has not, as yet, become widely employed as a mainstream option for
treating coronary artery disease, particularly for those patients who
have more than just an isolated LAD lesion. Published data on HCR is
relatively limited, with the majority of studies thus far being
primarily single-center, non-randomized reports, incorporating only
small to moderate patient numbers, with few exceptions (18, 19). At
present, no randomized trials specifically compare HCR with CABG. To the
best of our knowledge, there is only one other study to analyze
propensity-matched data, comparing HCR to both CABG and multi-vessel PCI
in patients with TVD (20). However, our study is thus far the only
propensity-matched study comparing long-term clinical endpoints for all
three revascularization methods.
For patients undergoing HCR, we prefer a MIDCAB-first approach, followed
by interval PCI, typically within 4 to 6 weeks of surgery. This allows
the surgical revascularization to be performed without concern for
potential bleeding that may be associated with the dual antiplatelet
therapy that is mandatory after PCI with DES. We have, nevertheless,
previously described our satisfactory experience with MIDCAB in patients
taking dual antiplatelet agents (21), results that have not necessarily
been consistent amongst all surgical groups (22). More importantly,
however, the MIDCAB-first approach allows the patency of the LIMA to LAD
bypass graft to be interrogated during the subsequent PCI procedure.
A PCI-first HCR strategy was pursued in those patients who presented
with a coronary syndrome in which the culprit lesion was deemed to be
within one of the non-LAD vessels, or in those individuals in whom the
angiographic severity and clinical import of at least one of the non-LAD
stenoses was thought to be greater than that of the disease within the
LAD itself. For these patients, subsequent LIMA to LAD grafting was
undertaken on uninterrupted dual antiplatelet therapy.
Of the 100 patients in our final study population who underwent HCR, 72
had MIDCAB followed by PCI, whereas the remaining 28 had PCI prior to
MIDCAB. We did not perform any cases of simultaneous MIDCAB and PCI,
although this approach has been adopted by other investigators (23, 24).
None of our MIDCAB patients required intraoperative conversion to
sternotomy.
The primary end-point of our study, all-cause mortality at 8 years, was
not significantly different across the three revascularization cohorts.
Freedom from MACE at 8 years was also comparable between patient groups.
However, despite having a higher SYNTAX score at baseline, those
patients that underwent HCR ended up with a lower residual SYNTAX score
did those who had multi-vessel PCI, reflective of a significant
difference in the completeness of revascularization achieved. By
contrast, HCR patients had similar residual SYNTAX scores to those
patients managed by traditional CABG. Our data also shows that early
complications from HCR were infrequent. The HCR cohort did benefit from
a shorter length of hospital stay than did the CABG group.
The mean baseline SYNTAX score in our HCR cohort was 28.9 ± 10.6. In the
SYNTAX trial, patients with TVD with similar, intermediate, SYNTAX
scores demonstrated no significant difference in the incidence of MACE
at 12 months, when the PCI group was compared to CABG (1). When this
group was of patients was followed for 5 years, MACE rates were indeed
found to be higher in the PCI cohort, but there was no significant
mortality difference between treatment groups (25). Similarly, in
diabetic patients with intermediate SYNTAX scores, the FREEDOM trial
found that the composite end-point of death, MI and stroke at 5 years
favored CABG over PCI, again with no significant mortality difference
identified (2). These results suggest that, in the TVD patient
population with intermediate SYNTAX scores, although mid-term survival
is comparable across treatment arms, morbidity may be higher after PCI,
particularly with respect to the increased incidence of repeat
revascularization and new myocardial infarction. We suggest that it may
be this group of patients that may be ideally suited to benefit from
HCR.
The longer-term overall mortality rates in our patient groups were
slightly lower than that observed in comparable individuals in some of
the larger trials. It is our hypothesis that these low mortality rates
are attributable, at least in part, to the low residual SYNTAX scores
that were able to be achieved in each patient group, regardless of the
technique of revascularization. There is good data to support the
assertion that the completeness of revascularization (as quantified by
the residual SYNTAX score) is a predictor of short-to-medium term MACE
in patients with multi-vessel coronary artery disease undergoing PCI or
CABG (26 – 28). Our group has previously reported that a low residual
SYNTAX score after HCR was associated with 8-year survival that was not
significantly different than that seen after traditional CABG in
patients with double-vessel coronary disease (29). Our current results
suggest that HCR is also associated with favorable long-term results in
patients with TVD, provided that the operators can achieve a low
residual SYTNAX score.
This study is also one of the first thus far to demonstrate that HCR may
be considered a reasonable method of revascularization in TVD patients
with left main-stem involvement. Of the 24 patients with left main
coronary disease who underwent HCR, there was only 1 death (4.2%) at
long-term follow up.
Sixteen patients who underwent HCR required repeat revascularization by
8-year follow-up. Of these, only 6 (37.5%) actually required a ‘target
vessel revascularization’. The remaining 10 patients (62.5%) all
required intervention for de-novo lesions. In those 6 HCR
individuals that required target vessel revascularization, 3 procedures
were performed due to problems with the LIMA to LAD graft, whereas 3
interventions were undertaken in non-LAD vessels. The incidence of
target vessel revascularization was not significantly different between
the HCR, CABG and multi-vessel PCI groups; in the CABG population, 2
patients required a re-intervention for the LIMA to LAD graft.