Introduction
Definition of hybrid coronary revascularization
Hybrid coronary revascularization (HCR) is a developing method of treatment of multivessel coronary artery disease (MVD) [1]. It can be defined as a combination of coronary artery bypass grafting (CABG) surgery with use of a main mammary artery to the left anterior descending artery (LAD) [2] and a percutaneous coronary intervention (PCI) focused approach to the remaining arteries [1].
The aim is to combine the advantages of both procedures with simultaneous minimization of related risks [3, 4].
This approach is particularly useful to patients with a need of individualized treatment with consideration of patients’ anatomy and condition [5], showing the best results in simple coronary anatomies due to the challenges in stent placement in convoluted arteries [3].
Typically, classic CABG is reserved for complex lesions in coronary arteries or left main (LM) disease, while PCI is used for less complicated cases [5].
Ongoing technological advancements and precise strategies are expected to further enhance the efficacy and accessibility of HCR. A particular example of this is the use of robotic surgery and 3D imaging, which entails a number of benefits related to improved surgical outcomes and benefits for the patient, mainly lower blood loss and trauma, as well as a shortened hospital stay [5].
Types of hybrid coronary revascularization
Based on the patient’s clinical diagnosis and the number of vessels requiring intervention, two main types of HCR may be distinguished.
The first type of procedure involves a single PCI intervention and a single coronary artery bypass graft. This is the least complicated method.
The second type of hybrid approach implies that the patient may undergo CABG with a combination of more than one vessel and a single PCI, or vice versa. This strategy is referred to as advanced HCR [2].
The hybrid procedure sequence
The main idea of the hybrid revascularization procedure is to combine CABG and PCI. Depending on the clinical situation, the two procedures can be performed simultaneously or at a certain time interval.
The most important principle in the hybrid approach is to treat the primary cause of ischemia. Revascularization of the LAD should take place first in the case of significant stenosis of the proximal part of the vessel, and then PCI can be considered. A patient with a subtotal occlusion of the right coronary artery (RCA) should undergo PCI prior to surgical revascularization of the LAD, particularly in cases involving chronic occlusion and collateral circulation [2].
Two staging protocols can be distinguished.
The first of them, called one-step or simultaneous HCR, involves performing LAD surgery followed by PCI. It is worth noting that in the case of a simultaneous procedure, the team has the opportunity to assess the left internal mammary artery-left anterior descending (LIMA-LAD) graft through the use of angiography and the patient undergoes only one procedure, which shortens the hospital stay. However, one needs to keep in mind the extremely significant point of dual antiplatelet therapy associated with the PCI procedure, which greatly increases the patient’s risk of bleeding. In addition, the simultaneous performance of the aforementioned procedure requires the unit to perform the procedure in the hybrid room [2, 4].
The next type of hybrid procedure is called two-step HCR. In this case, the patient can undergo CABG followed by PCI, or vice versa. The more common approach involves performing CABG first. These procedures take place on different days – the next day, after a few weeks, or occasionally 1 to 2 months later. Consequently, a patient may undergo complete revascularization during the same hospitalization or may be referred for planned admission to the invasive cardiology department after discharge. In such cases, the exact timing must consider balancing between higher bleeding complication risk (in cases of early post-surgical PCI) and postponing non-LAD revascularization (PCI in a few days-months following surgical treatment).
When CABG is performed first, it allows for angiographic evaluation of the LIMA-LAD graft, followed by stent implantation in the remaining diseased segments. This approach enables the safe administration of dual antiplatelet therapy (DAPT) without the risk of mediastinal bleeding. It also undoubtedly reduces the risk of myocardial ischemia during the PCI procedure [2, 4].
The use of PCI before CABG is usually reserved for patients with a diagnosis of ACS that is localized non-LAD (CABG first of non-LAD lesions can be treated with PCI that is unsuccessful or complicated). However, this option carries a number of potential obstacles, such as complex antiplatelet therapy, which significantly increases the risk of bleeding and stent thrombosis. In addition, it is an option that prevents us from performing follow-up angiography of the LIMA-LAD graft [4, 6] (Table I).
Table I
Hybrid procedure: simultaneous versus staged procedures
In the HCR procedure, the LIMA-LAD graft can be performed using one of the following methods: a minimally invasive, sternum-sparing approach; an open sternotomy; or robotic-assisted endoscopic surgery. The sternum-sparing technique, also known as minimally invasive direct coronary artery bypass (MIDCAB), involves LIMA mobilization through a small anterior or lateral thoracotomy incision, with the anastomosis to the LAD performed manually on the beating heart [7].
The open sternotomy off-pump approach, also known as off-pump coronary artery bypass (OPCAB), was developed to avoid the complications of cardiopulmonary bypass, using the same LIMA mobilization through a limited sternotomy [8–10].
The robotic-assisted endoscopic method is carried out through three port accesses in the left chest. Using the Da Vinci surgical platform, the LIMA can be harvested in a skeletonized or pedicled fashion, followed by a micro-thoracotomy (3 to 5 cm) over the LAD, where the anastomosis is performed similarly to the MIDCAB technique on the beating heart. A similar effect may be achieved using endoscopic vision and a harmonic scalpel for left internal mammary artery harvest, which is known as endoscopic atraumatic coronary artery bypass grafting (EACAB) or video-assisted MIDCAB. An even less invasive approach is the beating heart totally endoscopic coronary artery bypass, which involves LIMA mobilization and LAD arteriotomy and anastomosis performed with the robot. Surgery with cardiopulmonary support is no longer part of modern HCR protocols [11–13].
Indications for hybrid coronary revascularization
In a situation where we are considering eligibility of a patient for a hybrid procedure, the final decision should be made by the interdisciplinary Heart Team, especially bearing in mind ischemic heart disease.
According to the current guidelines, management by a Heart Team consisting of a cardiac surgeon, interventional and non-interventional cardiologist, as well as an anesthesiologist, is a Class I recommendation [2].
The Heart Team’s task is to decide which way the patient should undergo the procedure, PCI or perhaps CABG first.
The following patient profiles may be considered eligible for HCR intervention:
Chronic coronary syndrome caused by significant anatomical changes in the proximal LAD and concomitant stenotic lesions in other vessels.
Chronic coronary syndromes due to a single distal lesion, which include main left bifurcation or trifurcation.
Patients with CAD and valve pathology referred to the PCI, transcatheter or minimally invasive intervention.
Low to moderate SYNTAX scores (generally < 22–32), supporting the feasibility of PCI in selected vessels.
Clinical conditions that increase the risk of wound infection or poor healing after conventional CABG, such as:
Factors limiting the feasibility of standard surgical revascularization, including:
History of prior chest surgery (e.g., previous sternotomy).
Severe obesity or moderate to severe chronic obstructive pulmonary disease (COPD) requiring single-lung ventilation.
Contraindications to multivessel bypass grafting, for example:
Acute myocardial infarction with a non-LAD culprit lesion, combined with significant LAD stenosis requiring revascularization.
Patient preference for minimally invasive procedures to avoid full sternotomy [2, 14].
Based on studies and literature, it can be concluded that a candidate who fits the above criteria is a person who has complex coronary artery disease that involves LAD changes and/or a minimum of one coronary vessel suitable for PCI [4].
Outcomes after hybrid coronary revascularization
Assessment of safety, effectiveness, and long-term outcomes of hybrid coronary revascularization
Although the primary aim of any revascularization method is to achieve freedom from long-term mortality and adverse cardiac events, various strategies should also focus on minimally invasive methods that promote quicker recovery, avoid sternal cuts, eliminate aortic manipulation, and avoid cardiopulmonary bypass to reduce complications. As a result, a combined approach that leverages the advantages of both techniques, rather than treating them as separate options, could be beneficial for patients with MVD. This approach seeks to reduce immediate risks and invasiveness while optimizing long-term outcomes [1–3, 15, 16].
The assessment of safety, efficacy, and long-term outcomes of HCR has advanced significantly in recent years. However, substantial limitations and knowledge gaps persist, underscoring the need for further research to inform future guidelines. Key areas for investigation include evaluating the impact of guideline-directed medical therapy, clarifying the effects of revascularization on cardiovascular and non-cardiovascular mortality, comparing the outcomes of PCI and CABG, and exploring the safety and effectiveness of hybrid revascularization involving minimally invasive surgery for the left anterior descending artery [17].
Although the concept is appealing, hybrid revascularization procedures are performed at a very low rate, accounting for approximately 0.1% of surgical revascularizations. This low adoption rate highlights the insufficient sample sizes available for robust clinical and observational studies. The ESC/EACTS Guidelines on myocardial revascularization recommend hybrid procedures for specific patient subgroups treated in specialized centers, assigning HCR a Class IIb recommendation [2, 18].
Results of hybrid coronary revascularization versus PCI
Multiple studies have found no statistically significant differences between HCR and PCI at 30 days in terms of mortality, myocardial infarction, stroke, target vessel revascularization (TVR), or major adverse cardiac and cerebrovascular events (MACCE) [3, 19, 20]. Puskas et al. observed a non-significant difference favoring HCR at 18 months [20].
Lowenstern et al. reported that patients undergoing hybrid coronary revascularization experienced notably higher unadjusted in-hospital mortality compared to those treated with multivessel PCI. No significant difference in unadjusted mortality was observed between hybrid revascularization patients who underwent PCI before CABG and those who had PCI after CABG. However, hybrid coronary revascularization patients were more prone to non-fatal adverse events following PCI than patients treated with multivessel PCI. Among hybrid revascularization cases, individuals who underwent PCI followed by CABG were at a higher risk of periprocedural myocardial infarction, heart failure, and bleeding compared to those who had CABG before PCI [19].
Hybrid revascularization patients also had significantly longer hospital stays, with 85.9% remaining hospitalized for four or more days after the cardiac catheterization procedure. At discharge, patients treated with hybrid CABG/PCI were less likely to return home compared to those who underwent multivessel PCI. Among hybrid revascularization patients, those who had PCI before CABG experienced longer hospital stays but had similar rates of discharge home as those who underwent PCI after CABG [19].
The groups differed significantly from each other; patients undergoing HCR were generally younger and less likely to have a history of prior myocardial infarction (MI) or prior PCI compared to those treated with multivessel PCI. HCR patients were also more frequently admitted with acute coronary syndrome, presented with cardiogenic shock at the time of the PCI procedure, and had a greater need for intra-aortic balloon pump support [19].
Coronary angiography revealed that HCR patients were more likely to have significant left main or proximal left anterior descending artery lesions compared to multivessel PCI patients. The median number of lesions treated with PCI was lower in the HCR group. Additionally, lesions in HCR patients were longer and more likely to be high-risk/type C lesions. At discharge, patients treated with HCR were less likely to be prescribed a P2Y12 inhibitor compared to those treated with multivessel PCI [19].
Both the Ganyukov et al. and Lowenstern et al. studies reported a significant reduction in hospital stays and major bleeding events in the PCI group [19, 21].
However, it must be underlined that essential observation should be focused on long-term follow-up. Further, the minimally invasive nature of HCR, its avoidance of aortic-coronary bypass grafting, and the reduced need for aortic manipulation suggest that this procedure carries a low risk of perioperative stroke. Supporting this view, a meta-analysis by Zhao et al. demonstrated that off-pump CABG without aortic manipulation was the most effective approach in reducing stroke risk compared to conventional on-pump CABG [1, 3, 19].
Many scientists were waiting for the results of the prospective Hybrid Trial and hoped that it would clearly demonstrate the superiority of HCR over PCI by analyzing the composite outcome of major adverse cardiac and cerebrovascular events (MACCE) in a substantial cohort multivessel patients. Regrettably, the ‘Hybrid Coronary Revascularization Trial’ was terminated prematurely after enrolling only 200 patients due to slow recruitment [2, 22] (Table II).
Table II
Studies comparing HCR with PCI and/or CABG
Results of hybrid coronary revascularization versus CABG
Many studies and meta-analyses have demonstrated that the length of hospital stay (LOS) is shorter for HCR [23–26]. The studies have shown that 30-day mortality rates for HCR and CABG are comparable, regardless of the surgical technique used [23, 26–28]. Moreover, the risk of perioperative blood transfusions was noticeable lower for HCR compared to CABG, as demonstrated in meta-analyses and single-center studies [23, 27, 29, 30]. The HCR group experienced a higher rate of revascularization during the perioperative phase [31].
HCR appears to outperform surgery in terms of ventilation time and is not inferior to CABG regarding the incidence of postoperative atrial fibrillation, renal complications, myocardial infarction, or stroke. No sex-based differences were present. HCR is safer in older patients. Compared to CABG, HCR is associated with a lower risk of reoperation and postoperative infections [15, 16, 23, 27].
Assessing long-term outcomes is more challenging due to limited and heterogeneous evidence. Most studies had a follow-up period restricted to 5 years. Mortality during follow-up has been shown to be comparable between HCR and CABG, as demonstrated by several meta-analyses and prospective studies. Under similar constraints, the incidence of MACCE did not differ significantly between surgery and HCR. The long-term efficacy of HCR needs to be validated in well-designed studies [15, 16, 23, 27–30].
The POLMIDES study compared two-stage HCR with CABG and demonstrated a comparable rate of repeat revascularization between the two groups [14]. This contrasts with the findings of other studies, where repeat revascularization was predominantly associated with HCR [16, 23, 26, 28].
Di Bacco et al. reported a higher incidence of MACCE in the HCR group, primarily driven by an increased need for repeat revascularization of the target vessel, while no difference was observed between the groups in the occurrence of early acute myocardial infarction [26] (Table II).
Based on the mentioned studies, it can be concluded that HCR is a viable option for patients with multivessel coronary artery disease and is not inferior to CABG. It offers a lower risk of complications in the immediate postoperative period. However, all these studies primarily included short-term follow-up periods, which is why the outcomes do not differ significantly during this early observation phase. Patients eligible for HCR are typically at higher risk and have a lower expected survival rate, as Heart Teams often designate patients ineligible for classic CABG to minimally invasive hybrid revascularization.
Result of hybrid coronary revascularization versus OPCAB
The authors of many papers have compared HCR with OPCAB in patients with left main disease and found that HCR was associated with lower rates of blood transfusion and new-onset atrial fibrillation, and reduced need for mechanical ventilation, chest tube drainage, and intensive care unit (ICU) stay in propensity-matched patients undergoing single-stage HCR compared to OPCAB, with similar MACCE rates between the two groups. They noted non-significantly lower long-term mortality and reported a 46% reduction in troponin I release following HCR, indicating less myocardial injury compared to OPCAB [10, 30, 32, 33].
Torregrossa et al. compared fully robotic HCR with OPCAB and found no significant differences in operative mortality during the immediate postoperative period. However, HCR was associated with lower blood transfusion rates and shorter hospital stays. Over a mean follow-up period, there were no significant differences between the groups in terms of overall survival, confidence intervals, myocardial infarction, stroke, target vessel revascularization, angina, or major adverse cardiac and cerebrovascular events [13].
In subsequent research conducted by these authors, a group of women underwent robotic-assisted or conventional OPCAB. During the intraoperative period, women undergoing robotic-assisted OPCAB had longer operative times, higher rates of extubation in the operating room, and lower rates of blood transfusion. Postoperatively, they experienced reduced rates of new-onset atrial fibrillation, fewer blood transfusions, and shorter ICU and hospital stays. No significant differences were observed in operative mortality rates between the groups [12] (Table II).
Results of hybrid coronary revascularization versus coronary artery bypass grafting versus percutaneous cardiovascular intervention
Randomized controlled trials (RCTs) comparing HCR with CABG have generally been small-scale studies, and the only RCT to date comparing HCR with multivessel PCI was prematurely halted due to slow patient recruitment [16, 28]. Currently, there is only one randomized study directly comparing HCR with both CABG and PCI, by Ganyukov et al. In this report, hospital stay length, use of hospital rehabilitation, and duration of sick leave were longer for patients undergoing surgical procedures (CABG or HCR), with hospitalization and institutional rehabilitation duration being similar between the CABG and HCR groups. The highest rate of MACCE at 30 days was observed in the CABG group, primarily due to myocardial infarction. Bleeding occurred most frequently in patients undergoing CABG. There were no differences in the primary endpoint between patients with two-vessel disease and those with more than two-vessel disease. All three treatment methods showed similar freedom from MACCE at 12 months. The overall rate of TVR at 12 months was numerically more favorable for CABG [21]. Additionally, a recent meta-analysis of 119 studies with a maximum follow-up of 1 year found no significant differences among the three treatment approaches [1].
It was observed that patients who were not discharged with a P2Y12 inhibitor had a higher incidence of ACS, diabetes, and dialysis. Additionally, patients discharged without a P2Y12 inhibitor were similarly less likely to be discharged with aspirin and statin therapy [19].
Song et al. from Beijing presented a comparison of patients with similar characteristics who underwent one-stage HCR (LIMA-LAD through mini-sternotomy plus DES for lesions other than LAD) versus isolated CABG via sternotomy and multivessel PCI. After 3 years of follow-up, the cumulative MACCE rate was significantly lower in both the hybrid and CABG groups. Notably, the MACCE rate in patients with a high SYNTAX score was significantly lower after HCR than after PCI, but similar to that observed for CABG [4, 30] (Table II).
In conclusion, the optimal treatment choice remains unclear, highlighting the need for future prospective randomized trials to directly compare HCR with both CABG and PCI.
Antiplatelet treatment
The requirement for antiplatelet therapy may raise the risk of bleeding following CABG. Conversely, the procoagulant effects of surgical trauma and/or the need for shortened or reduced antiplatelet therapy may increase the risk of stent thrombosis. This could counterbalance the long-term benefits of complete revascularization, which is typically achieved through the hybrid approach. Recent guidelines and advancements in drug-eluting stent technologies suggest that many patients may benefit from a shorter duration of DAPT, depending on their specific anatomical and clinical characteristics. This facilitates improved selection of HCR candidates and more effective planning of the interventional steps’ staging strategy [34, 35].
For patients with high-risk coronary anatomy requiring CABG within 4–6 weeks after PCI, specific therapy is recommended. In such cases, a less aggressive DAPT regimen is initiated on the day of PCI by adding a 600 mg loading dose of clopidogrel to aspirin therapy, followed by a standard dose up to the day of surgery. Alternatively, clopidogrel may be replaced with intravenous heparinization within 48 hours of surgery to minimize bleeding risks. DAPT should be resumed postoperatively as soon as feasible and continued until the prescribed duration is completed, considering the patient’s bleeding risk. Even in patients with high bleeding risks or those requiring anticoagulation for conditions such as atrial fibrillation or recurrent thromboembolism, international guidelines recommend a very short DAPT period after coronary stenting [2, 34, 36].
In patients presenting with acute coronary syndrome (ACS), primary PCI is performed first on the culprit lesion, particularly if non-LAD vessels are involved. In this context, DAPT is typically administered for at least four weeks, after which CABG can be safely conducted under single antiplatelet therapy. DAPT is initiated on the day of the PCI with a 600 mg loading dose of clopidogrel. For ACS patients with a low bleeding risk, a more intensive approach is recommended, using ticagrelor or prasugrel as soon as possible after PCI. These medications are discontinued before CABG or removed intraoperatively and are reintroduced postoperatively at the earliest opportunity, continuing for 12 months thereafter. For patients with chronic coronary disease, the antiplatelet regimen may be limited to aspirin monotherapy after surgery [2, 37, 38].
However, DAPT is recommended in specific situations, such as for patients with severe diffuse CAD or those undergoing coronary artery endarterectomy. Furthermore, the 2024 EACTS guidelines on perioperative medication in cardiac surgery provide a Class IIb recommendation for the use of DAPT in CABG patients at higher ischemic risk, including those undergoing coronary endarterectomy or off-pump surgery. The decision to administer DAPT should be tailored to each patient, considering their specific characteristics, the reason for surgery, and balancing the potential antithrombotic benefits with the bleeding risks [35].
Advantages and disadvantages of hybrid revascularization
Compared to traditional CABG, hybrid revascularization offers faster recovery times, reduced risks of neurological complications, bleeding, and infections, and shorter mechanical ventilation duration and hospital stays; avoids sternal incisions, aortic manipulation, and cardiopulmonary bypass; achieves improved patency rates for LAD lesions treated with LIMA over DES and better outcomes for non-LAD lesions treated with modern DES versus SVGs; and potentially provides superior long-term event-free survival compared to multivessel PCI or standard CABG [4].
Hybrid revascularization is unsuitable for emergency procedures, involves a longer recovery period compared to PCI alone, is not applicable for patients without LM or LAD disease, is more technically demanding than traditional CABG or multivessel PCI, and requires specialized, costly resources such as hybrid operating rooms and robotic surgical systems, resulting in overall in-hospital costs likely exceeding those of PCI or CABG alone [4].
Conclusions
Hybrid coronary revascularization (HCR) may reduce in-hospital complications and length of stay, as well as improve patient satisfaction compared to traditional CABG, while maintaining the benefits of LIMA and replacing SVGs with DES. This suggests the potential value of HCR. Ongoing advancements in advanced hybrid revascularization techniques, such as the use of multiple internal mammary arterial grafts performed entirely endoscopically, show great promise. However, minimally invasive surgical techniques come with their own learning curve. The success of HCR, and optimizing revascularization for patients with complex CAD, relies on strong collaboration among general cardiologists, interventional cardiologists, and cardiac surgeons within a formal Heart Team. Despite the apparent advantages of combining the benefits of both CABG and PCI, the safety, efficacy, and cost-effectiveness of HCR must be validated in well-designed randomized trials, particularly considering the higher initial costs of performing two procedures compared to a single multivessel PCI or CABG.
