Hybrid and Robotic-Assisted Coronary Artery Revascularization Compared to Conventional Coronary Artery Bypass Graft Revascularization-Juniper Publishers
Objectives: Data were evaluated to
compare hybrid and robotic revascularization procedures with
conventional coronary artery bypass grafting for the treatment of multi
vessel coronary artery disease.
Background: Hybrid coronary
revascularization provides an alternative approach to conventional
coronary artery bypass graft and percutaneous intervention
revascularization therapies. Data comparing the two strategies are
limited.
Methods: A retrospective evaluation
was conducted on patients who underwent coronary revascularization by
hybrid, robotic alone or conventional coronary artery bypass grafting
from 2003 through 2014 at the University of Minnesota medical center by a
single operator
Results: A total of 399 patients
were included in the comparison with 31 hybrid, 68 robotic-only and 300
conventional coronary bypass patients. Mean OR times and hospital stay
durations were decreased for hybrid and robotic-only procedures in
comparison to conventional bypass procedures. Peri-operative blood
product requirements were also decreased in the hybrid group and
robotic-only groups. Post-operative stroke events occurred in 3 patients
(1%) in the conventional bypass group, but did not occur in the hybrid
or robotic-only groups. Similarly, post-operative death occurred in 5
patients (1.7%) in the conventional bypass group, but did not occur in
the hybrid or robotic-only groups.
Conclusion: Hybrid and
robotic-assisted coronary revascularization are both effective therapies
for multi vessel coronary artery disease. The hybrid and
robotic-assisted strategies allow for minimal invasion, which translates
into shorter operative and hospital length of stay durations, decreased
blood product requirements and seemingly fewer stroke and death events.
Keywords: Minimally invasive; Off-pump; Percutaneous coronary interventionAbbreviations: HCR: Hybrid Coronary Revascularization; LAD: Left Anterior Descending Artery, LIMA: Left Internal Mammary Artery; PCI: Percutaneous Coronary Intervention; LCx: Left Circumflex; RCA: Right Coronary Arteries; CABG: Coronary Artery Bypass Grafting; CAD: Coronary Artery Disease; STS: Society of Thoracic Surgeons
Introduction
Hybrid coronary revascularization (HCR) is a
technique used to minimize patient invasion while obtaining excellent
restoration of blood flow to the myocardium. The procedure involves a
robotic take-down of the left internal mammary artery (LIMA) for
revascularization of the left anterior descending artery (LAD) by a
small lateral thoracotomy and percutaneous coronary intervention (PCI)
for significant lesions in the left circumflex (LCx) and right coronary
(RCA) arteries. Robotic coronary artery bypass grafting (CABG) is a
technique that has traditionally only been an option for high-risk
patients with comorbidities that prohibited a conventional median
sternotomy approach. The improvement in off-pump techniques and
reduction in peri-procedural complications compared to on-pump
procedures has broadened the use of robotic and minimally invasive
procedures to now include patients with all risk profiles [1].
Previous studies have examined the utilization of
hybrid procedures for coronary artery revascularization and have shown
this approach to be a feasible option [2]. Hybrid revascularization
patients have similar or fewer post-operative
complications when compared to conventional CABG patients
[3,4] as well as shorter durations of intubation, intensive care
unit and hospital stays [3,5-7]. Patients undergoing HCR have
similar 30-day MACE rates of around 1% and three year survival
of approximately 94% [8]. This study was performed to compare
hybrid, robotic-assisted alone (i.e., without PCI as in hybrid
procedures) and conventional CABG at a single center to further
evaluate the use of hybrid and robotic-assisted procedures in
revascularization and to provide additional data to help expand
the number of observations in this growing field.
Methods
Data from patients undergoing surgical revascularization by
a single operator from September 2, 2003 through December
18, 2014 at the University of Minnesota medical center were
collected from the electronic medical record. Revascularization
procedures were categorized as hybrid procedures if a minimally
invasive LIMA to LAD bypass was performed and additional
coronary artery stenoses were treated with PCI either during the
same hospitalization or within a reasonably soon time period.
In addition to hybrid and conventional CABG revascularization
procedures, data regarding robotic-only revascularization
procedures (not associated with additional PCI or vein grafts)
were also collected. The hybrid population was designated as
Group A, the robotic-only population was designated as Group B
and the conventional CABG population was designated as Group
C.
Indications for HCR included favorable LIMA and LAD
anatomic locations for a robotic approach as well as additional
coronary artery disease (CAD) lesions deemed treatable by
PCI. Patients were selected for a HCR approach based on
comorbidities, prior surgical complications, and projected poor
wound healing and patient preference. The decision to proceed
with HCR was made after careful consideration of other options
including conventional CABG by the surgeon, interventional
cardiologist, referring physician and patient. Contraindications
to HCR included diffuse CAD that was not amenable to PCI
and inability to undergo a robotic harvest of the LIMA. Factors
limiting robotic harvesting of the LIMA included body habitus,
unstable CAD and severe pulmonary disease that would be
unlikely to tolerate single-lung ventilation.
The minimally invasive bypass method involved a robotic
LIMA harvest followed by a small anterior or lateral thoracotomy.
The da Vinci Surgical System (Intuitive Surgical Incorporation,
Sunnyvale, California) was used for LIMA harvest, to access
the pericardium and to identify the optimal LAD graft site. A
small anterior thoracotomy incision of 5 cm is then made for
grafting of the LIMA to the LAD. Exposure of the LAD graft site
is obtained with a soft tissue retractor and the LIMA to LAD
anastomosis is completed with an 8-0 polypropylene suture.
The procedures were performed without need for rib spreading or cardiopulmonary bypass. The PCI portion was generally
performed after the robotic bypass to limit bleeding risk given
the requirement of dual anti-platelet therapy following PCI.
Timing of robotic and PCI procedures were determined by
acuity, disease severity, patient comorbidities (e.g., staged PCI
to limit risk of contrast induced nephropathy) and availabilities
of the patient and procedural teams. Drug eluting stents were
implanted unless a contraindication for longer term dual antiplatelet
therapy existed.
Peri-operative hospital requirements and complications
were the outcomes evaluated for this study. Hospital
requirements included OR time, intubation time, ICU time
and hospital duration. Complications included post-operative
cerebrovascular accidents, atrial fibrillation, bleeding requiring
a blood transfusion, death and readmission within 30 days. The
robotic revascularization group was separated into HCR and
robotic-only revascularization groups. The robotic-only group
refers to patients that only underwent revascularization with a
LIMA to LAD graft by robotic LIMA harvest and did not have vein
grafts or PCI. Statistical analyses were conducted using SAS 9.3
(SAS Institute Inc. Cary, NC, USA.). Differences in the distribution
of baseline characteristics and outcomes between groups were
assessed using chi-square tests for categorical variables and
t-tests for continuous variables. Given the exploratory nature of
this analysis, if the expected cell count for any chi-squared test
was below 5, Fisher’s exact test was used in lieu of a chi-squared
test.
The study included a total of 399 patients with 31 hybrids,
68 robotic-only and 300 conventional CABG revascularization
strategies. Baseline characteristics were generally similar
between groups and are displayed in (Table 1). The PCI portion
was completed after the robotic CABG portion in all but three
cases, occurred during the robotic CABG hospitalization in 18
patients and was performed an average of within 38 days of
the robotic procedure. The mean age, gender distribution (male
68% to 73%) mean BMI values were similar across groups.
Risk factors of diabetes, hyperlipidemia, hypertension, family
history and tobacco use were similar. Pre-operative medication
regimens were similar for aspirin, beta blocker, angiotensin
converting enzyme inhibitor/angiotensin receptor blocker and
lipid-lowering therapy. A greater proportion of patients with
prior coronary bypass revascularization were identified in
the conventional bypass group. The hybrid patient group was
composed of patients with single-vessel disease (3%), twovessel
disease (45%) and three-vessel disease (52%); whereas,
the conventional bypass group had patients with single-vessel
disease (4%), two-vessel disease (18%) and three-vessel disease
(78%). Average surgical mortality risks, based on Society of
Thoracic Surgeons (STS) Adult Cardiac Surgery Risk Calculator
estimates, were similar across groups with 2.2% to 2.8% risk
estimates.
Table 1: Baseline Patient Characteristics for
Hybrid, Robotic-Only, Hybrid/Robotic Combined and Conventional Coronary
Revascularization.
Note that “n” refers to the number of patients. P-values marked with (†)
indicate rank-sum test was used for data comparison. P-values marked
with (‡) indicate that Fisher’s exact test was used for data comparison.
Values listed following a “±” are standard deviation values. Single
values
listed in parentheses represent the percentage of patients within each
category.
Outcomes of hospital care durations are listed in (Table 2)
and displayed in (Figure 1). Mean OR times for hybrid, roboticonly
and conventional bypass groups were 400 min, 385 min
and 434 min, respectively. Mean ICU stays were 60 hours for
hybrid, 46 hours for robotic-only and 64 hours for conventional
bypass patients. Mean peri-operative intubation times were 12.9
hrs (771 min) in hybrid, 16.7 hrs (1,002 min) in robotic-only and 27.2 hrs (1,629 min) in conventional bypass patients. Mean
lengths of hospital stays were 8 days in hybrid, 8 days in roboticonly
and 9 days in conventional bypass patients.
Outcomes of in-hospital complications are listed in (Table
2) and displayed in (Figure 2). Peri-operative blood product
requirements were increased in the conventional bypass group with approximately 75% of patients in the conventional bypass
group requiring a blood transfusion compared to 45% of hybrid
and 32% of robotic-only groups. Peri-operative atrial fibrillation
occurred in 19% of hybrid, 18% of robotic-only and 25% of
conventional bypass patients. Post-operative stroke events
occurred in 1.0% of the conventional bypass group, but did
not occur in the hybrid or robotic-only groups. Similarly, postoperative
death occurred in 1.7% of the conventional bypass
group, but did not occur in the hybrid or robotic-only groups.
Re-admission rates within 30 days from the date of surgery were
26% in the hybrid group, 22% in the robotic-only group and
17% in the conventional bypass group.
Discussion
The results of this study confirm that hybrid and roboticonly
procedures provide an excellent option for coronary
revascularization. The data reflect outcomes of a single operator
so there are no possibilities for inter-operator variability.
Hybrid and robotic revascularization procedures are associated
with shorter durations of OR time, ventilator management,
ICU care and overall hospital length of stay as well as fewer
requirements for blood transfusions. Previous studies have
also identified substantially shorter durations of OR time,
ventilator management, ICU care and overall hospital length of
stay for hybrid procedures in comparison to conventional CABG
procedures [6,7,9]. Although most patients undergo LIMA to
LAD revascularization prior to PCI, as was the case in this study,
the sequence of revascularization has been shown to have no
impact on outcomes [10]. However, performing the PCI before
or at the same time of robotically assisted revascularization did
relate to shorter durations of ICU and hospital lengths of stay
compared to a surgery-first approach [10].
The hybrid and robotic-only groups were found to have lower
rates of peri-operative blood transfusions as well as fewer stroke
and death events, but myocardial infarction events occurred
more frequently in the hybrid group. Although there were no
CVA or death events in the hybrid and robotic-only groups, the
lack of events possibly reflects the relatively smaller number of
patients available for evaluation, but may also be related to the
avoidance of both aortic cross clamping as well as the heart-lung
machine. There was a trend toward greater prevalence of PAD
in the hybrid and robotic-only groups, but, even though PAD is
a predictor of poor operative outcomes, the hybrid and roboticonly
groups had no CVA or death and generally had better
outcomes. The improved outcomes identified in the hybrid and
robotic-only combined group may relate to the decreased use of
intravenous nitroglycerin during the surgical procedure as this
may result in decreased blood pressure variability.
Prior studies have found no difference in rates of in-hospital
CVA or death between hybrid and conventional CABG groups
with both CVA and death rates less than 1%; however, there is a trend of fewer events in the hybrid group [3,7-9,11]. Overall
in-hospital MACE rates have been similar between hybrid and
conventional CABG groups [7-9] with the exception of one study
that found higher MACE rates in the conventional CABG group [3].
This study identified higher rates of peri-operative myocardial
infarction in the hybrid group in comparison to both the roboticonly
and conventional bypass groups. Peri-operative myocardial
infarction with resultant Q wave development complicates up to
10% of conventional bypass operations [12,13]. Peri-procedural
myocardial infarction as defined by a biomarker increase
greater than three times the upper limit of normal complicates
approximately 22% of PCI procedures [14].
Patients with complex CAD and low to intermediate surgical
risk assessments based on SYNTAX (score < 33) and Euro Score
(score < 6) have been shown to have similar 30 day rates of MACE,
changes in renal function and bleeding events between hybrid
and conventional CABG groups [15]. Longer-term monitoring
has shown similar results at 3 years with similar MACE rates in
low, intermediate and high-risk groups, based on SYNTAX and
Euro Score estimates [16]. Revascularization is one endpoint
that has been identified in some, but not all studies, to occur
more frequently in the hybrid and robotic-only revascularization
groups [6-9]. Although our data do not specifically evaluate
outcomes of HCR in high risk patients, individuals in this group
are seemingly good candidates for HCR as the LIMA bypass is
utilized, but the stress of sternotomy, aortic cross-clamping and
bypass pump administration is avoided.
The HCR strategy provides mortality benefits from
both a LIMA to LAD bypass as well as achieving complete
revascularization of non-LAD arteries with drug-eluting
stents. The survival benefit associated with a LIMA to LAD
bypass in comparison to vein grafts and stenting has been
demonstrated [17-20]. Complete revascularization has also
been shown to have a mortality benefit compared to incomplete
revascularization over a period of monitoring up to 10 years [21-
25]. Under reasonable circumstances of anatomy and viability,
complete revascularization provides benefits over incomplete
revascularization and should be the goal when applicable.
Maintenance of revascularization patency has been an issue
with both vein graft and stent therapies. Vein graft failure (>70%
of grafts occluded) occurs in about 10-45% of conventional
CABG patients at one year and around 50% of vein grafts are
occluded at 10 years [26-28]. In contrast, in-stent restenosis
requiring revascularization occurs in approximately 25% of
bare-metal and 5-10% of drug-eluting stents at 5 years [29-
31]. The combined benefits of mortality reduction with LIMA to
LAD bypass grafting and non-LAD revascularization patency of
stenting make a HCR a favorable approach.
Conventional CABG procedures are traditionally performed
on an arrested heart with use of a temporary bypass pump for circulatory support (on-pump). Minimally invasive CABG
procedures, including robotic-assisted CABG, are often
performed on a beating heart without need for additional
circulatory support (off-pump). The LIMA graft patency at one
year was found to be significantly less in the off-pump group
with patency rates of 88.7% in off-pump and 93.4% in on-pump
groups [32]. Although the LIMA patency rate was found to be
decreased with off-pump procedures, a separate meta-analysis
found lower rates of post-operative stroke and no change in
mortality or myocardial infarction at 30 days [33].
Lastly, minimally invasive procedures utilized for harvesting
the LIMA and for anastomosis of the LIMA to the LAD are not
universally practiced and their success, like all procedures,
depends on the proficiency of the operator. Rates of conversion
from a robotically-assisted procedure to an open-chest
procedure were studied and found to substantially decrease
as robotic experience increased from a conversion rate of 28%
in the first 25 patients to 4% after completion of 75 patients
[34]. Significant decreases in operative time and hospital length
of stay durations also correlated with increasing experience
[34]. Although successful completion of the intended robotic
procedure and overall efficiency improved with experience,
patient safety was not compromised during the learning period
as mortality remained unchanged. Limitations of the study
included the small number of hybrid patients and the lack of
detailed follow up beyond the initial hospitalization. This was a
retrospective cohort analysis that lacks the obvious benefits of
prospective randomized trial. Patients were selected to undergo
HCR based on comorbidities, prior surgical complications;
projected poor wound healing and patient preference so a
selection bias is possible.
Conclusion
Hybrid coronary revascularization procedures provide
complete revascularization with utilization of optimal LIMA
to LAD bypass grafting with percutaneous intervention of
the LCx and RCA vessels. Robotic bypass grafting allows for
minimal invasion and requires shorter durations of ventilation
management, ICU stay and length of hospitalization as well as
fewer peri-operative blood transfusion requirements. Emergent
robotic bypass grafting is possible, but more commonly
completed by conventional bypass grafting. The finding that
operating room time and surgery time (i.e., skin incision time)
were both shorter in the hybrid/robotic group is notable as
these data are for a single skilled surgeon. Increased successful
extubation within the operating room and decreased blood
product requirements in the hybrid/robotic group are also
important findings. Although the numbers of stroke and death
events were too small for statistical analyses, there were
no stroke or death events in the hybrid and robotic bypass
groups. Patients with multi vessel CAD should be considered
for revascularization with a HCR procedure. We suggest that patients with non-emergent coronary heart disease who have
less than severe lung disease and pulmonary hypertension
with LIMA anatomy that is favorable for harvest by a lateral
incision are ideal candidates for HCR and will benefit from this
revascularization method.
Author Contributions
Dr. Drexel wrote the manuscript with help from Drs. Das and
Liao and Samit Roy and all were involved with some aspect of
procedural completion, data collection and analysis. All authors
have reviewed and approved of this paper.
Conflict of Interest
Dr. Drexel: none. Samit Roy: none. Dr. Das: none. Dr. Liao: none.
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