Corresponding Author:
Prof GD Angelini, MD,MCh,FRCS, FMedSci
British Heart Foundation Professor of Cardiac Surgery,
Bristol Heart Institute
Bristol Royal Infirmary,
Upper Maudlin Street BS2 8HW
Bristol, UK
G.D.Angelini@bristol.ac.uk
Conflict of Interest : none
Funding: This work was supported by the British Heart
Foundation and the NIHR Biomedical Research Centre at University
Hospitals Bristol and Weston NHS Foundation Trust and the University of
Bristol.
Key words : Hybrid coronary revascularization, OPCAB, Totally
endoscopic CABG
Hybrid coronary revascularization (HCR) consists of left internal
thoracic artery (LITA) graft to the left anterior descending (LAD)
artery and transcatheter revascularization of the non-LAD stenosis in
specific settings to achieve complete coronary revascularization.
Technique to perform the LITA to LAD graft has ranged from median
sternotomy with cardiopulmonary bypass to robotically assisted totally
endoscopic coronary bypass surgery using beating heart
revascularization. Torregrossa et al in this study on HCR, harvested the
LITA robotically and performed the LITA to LAD anastomosis through a
mini thoracotomy without using cardiopulmonary bypass(1). They have also
compared this technique of HCR with conventional on-pump coronary artery
bypass grafting (CABG) and off-pump bypass grafting (OPCAB). The authors
have shown excellent outcomes with all the three techniques. In this
study, HCR led to reduced post-operative bleeding, need for blood
transfusion and re-exploration for bleeding as well as reduced incidence
of atrial fibrillation. This resulted in shorter lengths of intensive
care unit (ICU) and hospital stays. The long-term survival was similar
to conventional on-pump CABG and OPCAB. In order to balance the baseline
differences that existed between the groups compared, the authors used
Inverse probability of treatment weighting (IPTW) which is another
strength of the paper and makes the conclusions drawn more reliable.
The reduction in post-operative blood loss along with reduced blood
transfusion requirements is one of the most consistent advantages
reported and has been confirmed in several meta-analyses.(2–6) Equally,
most of the studies have also confirmed that compared with other
techniques of revascularization, HCR is associated with similar 30-day
mortality. (2–6) The evidence on reduction in rates of atrial
fibrillation (AF) is not very strong with other studies and
meta-analysis reporting no difference in AF rates between HCR and other
techniques of revascularization.(4,7) The shorter ICU and overall
hospital length of stay reported in this study is also supported by
several other studies. (3–6) However, the definition of what
constitutes operative time and hospital length of stay needs further
discussion. HCR consists of two distinct procedures – CABG and PCI. In
large number of patients HCR is carried out as a staged procedure during
two separate admission and the hospital length of stay should include
combined duration of stay for both the interventions. Similarly, the
operative time of HCR, unless carried out as a single stage procedure,
should include the time for both the surgical and transcatheter
component. Regardless, most of the studies have shown that the operating
time with HCR is significantly longer irrespective of whether they are
robotically assisted or not. (7,8)
HCR constitutes a very wide range of approaches and the methodology of
studies on HCR, need to provide more granularity. Whether the HCR was a
single or two-staged procedure, whether PCI preceded CABG or vice-versa,
the duration between the two procedures, any complications during
waiting for the second intervention, and whether it was planned or
unplanned must all be reported to make a more comprehensive and accurate
comparison. The importance of this granularity cannot be over emphasized
as, in the absence of data regarding both the components of HCR, it is
difficult to draw reliable inferences both from scientific as well as
resource utilization perspectives.
Robotically enhanced HCR is a niche area of coronary revascularization
that requires the highest degree of technical expertise. Unlike PCI
alone, it accomplishes revascularization of the LAD with the best graft,
the LITA and thus provides the best of both worlds. The technique needs
to be evaluated most importantly from a clinical outcome perspective but
also from the economic perspective as well as the patient’s perspective.
From an economic perspective, studies attempting the cost-benefit
assessment have shown considerable variations based on the surgical
access or utilization of robotic assistance. Two studies with similar
design where HCR was carried out as a single stage procedure using
mini-thoracotomy for a LITA to LAD anastomosis reported a
non-significant increase in costs associated with HCR when compared to
conventional OPCAB. (9,10) However, it has to be noted that none of
these studies utilized robotically assisted LITA harvesting. Another
study which compared HCR without robotically assisted LITA harvest, but
used mini-sternotomy rather than mini-thoracotomy reported a
significantly increase in costs involved with HCR.(7) Studies reporting
cost-comparison in studies similar to that of Torregrossa et al , where
LITA was harvested with robotic assistance and the anastomosis performed
through a mini-thoracotomy, have shown that irrespective of whether HCR
was performed as a one-stage single day procedure or on two separate
days during the same admission the costs were found to be significantly
higher. (7,11) This is not surprising at all, as both the fixed and
variable costs with the robotic systems are bound to be higher.
From the patient’s perspective, assessments are generally done based on
pain scores, quality of life and markers of functional recovery like the
ability to return to work. While one study showed that the pain scores
after robotically assisted HCR were surprisingly similar with OPCAB (8)
the duration for pain to completely subside has been reported to be
significantly shorter with HCR.(9) Overall satisfaction scores and the
odds of returning to work within the first month were also significantly
higher after HCR.(8,9,12). The average time for returning to complete
normal activity has been reported to be shorter by roughly three weeks
after HCR. (8)
Clinical outcomes constitute the most important aspect of comparison for
any intervention and is evaluated by feasibility and safety of the
procedure in the short term as well as longer term outcomes. The safety
and feasibility of HCR has now been well established through different
studies and several meta-analyses. Two randomized controlled studies
have been published comparing HCR with CABG. The 5-year report of the
HYBRID (Hybrid Revascularization for Multivessel Coronary Artery
Disease) trial has been published recently reported similar all-cause
mortality, myocardial infarction(MI), repeat revascularization, stroke,
and major adverse cardiac and cerebrovascular events(MACCE) between HCR
and CABG.(13) Interestingly while the RCT confirmed clinical equipoise
it also failed to show any differences in terms of reduced blood
transfusion requirements, or length of stay between HCR and CABG. (14)
Whether this represents a “true lack” of difference between the
techniques or is an effect of “trial settings” which are often
different from real life selection criteria remains unclear. Another
RCT, the Hybrid coronary REvascularization Versus Stenting or Surgery
(HREVS), that randomized patients to HCR, CABG and multivessel PCI also
confirmed clinical equivalence among the three techniques with respect
to all-cause mortality, rates of MI, stroke, MACCE rates and
re-interventions at 3-year follow-up. However, once again, the trial
showed no difference between HCR and CABG in terms of length of
stay.(15)
Besides, both these RCTs have brought out an important issue, which is
the conversion rate among patients designated to undergo HCR. In the
HYBRID trial, only 93.9% patients in the HCR group received HCR. Six
(6.1%) required a sternotomy and in 2(2.04%) had failed PCI.(14)
Nearly 1 in 10(9.8%) patients randomized to the HCR arm of the HREVS
trial were converted to CABG. (15)This is an important observation that
further highlights that fact that while robotically assisted HCR may
have good results in experienced hands it may have a long learning
curve, that limits its uptake. Besides, it also suggests that in
observational institutional studies the patients who got converted to
alternative techniques may not have been included in the reported
series.
The need for specialized operative infrastructure and specialized hybrid
suites has been an important deterrent for robotically assisted HCR.
Robotically assisted HCR is appealing as far as patient satisfaction are
concerned, however, the reported advantage of reduced requirement for
blood transfusion and shorter hospital length of stay are now being
challenged by RCTs. This in turn negates the economic benefit argument
with HCR even further. The conversion rates associated with HCR brings
the issue of expertise into the discussion as well and may further deter
uptake of robotically assisted HCR. In the absence of overwhelming
superiority of HCR, it is unlikely that robotically assisted HCR will be
practiced by surgeons widely and it is very likely to be confined to
certain centers of excellence.