A hybrid therapy combines surgical therapy with endovascular intervention to achieve optimal benefits in patients with cardiovascular disease by using less invasive methods. The concept of hybrid revascularization is not new.1,2 Cardiac surgeons and interventional cardiologists have been performing hybrid procedures since the mid-1990s to lower procedure-related morbidity by combining minimally invasive cardiac surgery with percutaneous coronary techniques.1 The rationale of such a treatment modality is to attempt to reduce the procedural risk while not compromising the benefit of the treatment. First and foremost, percutaneous coronary intervention (PCI) combined with coronary artery bypass grafting (CABG) or other cardiac surgical procedures can be a feasible alternative in patients with multivessel coronary artery disease (CAD). Failure rates for safenous vein grafts (SVGs) have been reported between 1.6% and 30%, with an average rate of 20% at 1-year follow-up.3 In addition, studies have shown that in-stent restenosis rates for PCI using drug-eluting stents (DES) are ∼10% at 1-year follow-up.4,5 Therefore, DES-PCI may represent a valid alternative to SVGs in patients with lack or poor conduit, nongraftable but stentable vessels, repeat operations, and severe comorbidities. Second, by using stents instead of SVGs would reduce the number of grafts, which would be beneficial for both on-pump and off-pump procedures. In on-pump procedures, it would decrease the cardiopulmonary bypass (CPB) and ischemic times, reducing the risks associated with CPB use such as stroke, myocardial infarction, low cardiac output syndrome, and arrhythmias. In off-pump procedures, it would result in shorter operative time, less manipulation of the heart, and decreased potential for ischemia. In addition, applying minimally invasive approach to graft the left internal mammary artery (LIMA) to the left anterior descendent (LAD) artery would reduce the risk for sternal wound infection and shorten patient's recovery.
In most centers, surgical intervention and PCI are performed as a “two-staged” procedure, separated by days, weeks, or perhaps even months. In centers with a “hybrid” operating room (OR), which contains the facilities of a fully functional catheterization laboratory and a cardiovascular surgery OR, hybrid procedures are performed as a “one-stop” or combined procedure, meaning both procedures are performed in one setting. Examples of hybrid procedures include hybrid CABG/PCI, hybrid valve/PCI, hybrid endocardial and epicardial atrial fibrillation (AF) procedures, and hybrid CABG/carotid artery stenting (CAS).
The Hybrid OR
The hybrid OR combines the “tools” available traditionally only in the OR with those available traditionally only in the catheterization laboratory. Successful implementation of the hybrid OR that serves both diagnostic and treatment purposes clearly requires a team approach. Performing hybrid procedures requires the presence of staff from interventional cardiology, cardiac surgery, perfusion, cardiac anesthesiology, electrophysiology, echocardiography, and specially trained nursing/support staff. It also requires realizing, planning, and building the OR in a way that it carefully balances and takes into consideration each of the individual team's requirements. Therefore, a hybrid OR should be larger than a standard OR to allow for all necessary equipment and personnel. Expert opinion recommendations for newly built OR suggest it to be between 550 and 900 ft2.6 The floor- or ceiling-mounted C-arm capable of rotational high-quality angiography requires the floor to ceiling height to be at least 10 ft.6,7
Planning and designing of the hybrid OR should also address other important issues such as equipment location and radiation exposure. The location of equipment is crucial. Each clinical team requires a different set of equipment in the hybrid OR that can cause potential conflicts over space and alignment. This challenge can be solved by carefully planned teamwork. This would include recruiting the necessary engineering staff to plan carefully for power requirement, high-voltage alternating current, and other building infrastructure services. In addition, all the cables and wires of medical equipment should be kept off the floor to avoid tripping hazards and to assist in housekeeping. Radiation is also an important concern in the hybrid OR. Thus, in the hybrid OR, all personnel, including surgeons, need to wear lead aprons for protection from radiation during any procedure with concurrent imaging and radiation badges to gauge the amount of overall radiation exposure. Another important issue is the increased care required to adhere to hygienic requirements because of the larger size of the OR and involvement of higher number of personnel and equipment. To minimize infection risk, the hybrid ORs should be equipped with laminar airflow ceilings, and sterile techniques should be carefully maintained.
Because of the increased spatial requirements and the need for monitors, lighting, imaging systems, and operating tables that meet the requirements of all involved teams, the hybrid OR is more expensive to build than a standard OR or a catheterization laboratory. The hybrid OR is a multifunctional suite that can be used as a fully functional catheterization laboratory, as an endovascular procedure suite, as an electrophysiology suite, and as a fully equipped OR.
At the Vanderbilt Heart and Vascular Institute, we have built a hybrid OR/catheterization laboratory in 2005 (Fig. 1). Close and ongoing collaboration between several clinical teams, such as cardiology, cardiac surgery, cardiac anesthesia, imaging, hospital administration, and optimal geographic and financial arrangements have resulted in a successful hybrid program. To optimize the working environment, we have also united the cardiology and cardiac surgery intensive care units, colocated the cardiology and cardiac surgery offices, and joined cardiology and cardiac surgery conferences. The leading role in implementation of hybrid concept and creating an ideal working environment has been efficiently performed by our guiding coalition that consists of the chief of cardiology, the chief of cardiac surgery, the chief of catheterization laboratory, and the chief of cardiac anesthesia.
In our hybrid OR, we are currently using the hybrid approach to perform combined CABG and PCI, combined minimally invasive valve surgery and PCI, and combined minimally invasive coronary artery bypass (MIDCAB) and PCI. Studying of clinical outcomes of hybrid procedures is ongoing, and our preliminary results have been good.8–11 We believe that the hybrid strategy significantly increases diagnostic and treatment options available to the surgeons and interventionalists for patients with complex cardiac disease.
Hybrid Coronary Artery Revascularization
Hybrid coronary revascularization combines the advantages of traditional coronary surgery with the advantages of PCI. Hybrid coronary revascularization was introduced in 1996 when six patients underwent MIDCAB of the LIMA-to-LAD combined with PCI/stents to non-LAD lesions.1 Further development of CABG techniques performed on the beating heart challenged the hybrid concept, and by the end of the decade, off-pump CABG had become an established technique worldwide that superseded hybrid revascularization because of the lower reintervention rates observed after multivessel CABG than after multivessel PCI.12 Thus, it had been reported by several randomized clinical trials that despite the similar short- and long-term survival after CABG versus PCI,13 the repeat revascularization rate at 1-year follow-up was 3.8% for CABG versus 26.5% for PCI and at 5-year follow-up was 9.8% for CABG and 40.1% for PCI with bare metal stents (BMS).13 However, hybrid coronary artery revascularization has recently gained renewed popularity because of the success of DES at reducing reintervention rates compared BMS.14,15 The LIMA-to-LAD bypass graft is the single most important surgical technique to improve long-term survival, freedom from angina, and quality of life in patients with CAD.16 After MIDCAB of the LIMA-to-LAD, the patency rates have been reported between 92% and 99%3,17,18 and between 95% and 98%19,20 at 5 and 10 years, respectively. Non-LAD lesions are treated with SVGs. Failure rates for SVGs have been reported between 1.6% and 30%, with an average rate of 20% at 1 year of follow-up, with increase of up to 40% to 50% at 10 to 15 years of follow-up.14,19,20 Studies have been shown that PCI may have equal or even better results in non-LAD coronary arteries. It has been reported that target lesion revascularization for BMS-PCI of right coronary artery or left circumflex artery is 18.1% at 9-month follow-up21 and 21.4% versus 7.7% for DES-PCI at 5-year follow-up.22 At 12 months, in-stent restenosis rates for non-LAD lesions are reported to be 13% for DES and 39% for BMS.23 Therefore, it is reasonable to hypothesize that PCI using DES is a better treatment for non-LAD lesions than SVG.
Although 10 years ago hybrid revascularization was considered an option only for high-risk patients, it is hypothesized that this approach may now provide superior results in achievement of complete long-term revascularization, minimize procedural risk, and become a better alternative for multivessel disease involving the LAD by enabling combination of the LIMA-to-LAD graft with DES-PCI to other vessels. PCI may also be a better alternative to SVG grafts in cases of lack or poor quality of the conduit, nongraftable but stentable vessels, repeat operations in which PCI is preferable to avoid full cardiac dissection, or in patients with severe comorbidities (organ dysfunctions, recent myocardial infarction, and severe atherosclerotic aortic disease).
In the minimally invasive approach to LIMA-to-LAD grafting, the LIMA is harvested through a small left anterior thoracotomy incision or lower hemisternotomy. The LIMA-to-LAD bypass is crafted through this limited incision on the beating heart. Improvements in technology and operative techniques have enabled performing of robot-assisted, totally endoscopic, closed-chest CABG surgery of the LIMA-to-LAD with the use of fine instruments and peripheral institution of CPB. Totally endoscopic CABG (TECAB) of the LIMA-to-LAD was introduced in 1999,2 and in 2000, the first TECAB of the LIMA-to-LAD was combined with PCI of the left circumflex system.24 This technique is technically demanding and requires a surgeon to work with endoscopic instruments and to become familiar with camera-assisted visualization, and therefore, there is steep learning curve. For the above reasons, it is not widely performed. It is still not clear whether TECAB provides superior outcomes compared with conventional CABG. However, it is hypothesized that reported TECAB outcomes reflect early experience typically associated with new techniques and can be improved by further progress in anastomotic technology, endoscopic stabilization, and target vessel identification systems.25
Coronary bypass surgery may be performed before or after PCI. There are benefits and drawbacks for both these approaches. Advantages of a PCI-first approach include assurance that PCI was successful, thereby circumventing the need for further multivessel bypass. Performing surgery under Clopidogrel, performing the PCI without the protection of LIMA-to-LAD, and performing LIMA-to-LAD bypass without following completion angiography are the main disadvantages of this approach. CABG-first approach avoids bleeding-related complications caused by the use of Clopidogrel, provides a protected environment with the LIMA-to-LAD graft, and allows assessment of the patency of the LIMA-to-LAD graft. The major disadvantage is that in case of PCI failure, a second high-risk operation needs to be performed. The rate of emergent CABG after failed PCI is reported to be low (<1%).26
Simultaneous or “one-stop” hybrid procedures avoid the need for two separate procedures, two teams, two costs, and longer hospital stay. This requires hybrid suite and close collaboration between cardiac surgeons and interventional cardiologists. We believe that one-stop hybrid coronary revascularization procedure is a superior approach compared with two-staged hybrid procedures because it allows for excellent monitoring, diagnosis, and resolution of complications in one setting. The use of Clopidogrel and unknown response of DES to heparin reversal with protamine are the major concerns of this approach.
From April 2005 to July 2007, we have performed 112 one-stop hybrid procedures in our hybrid OR. Of these 112 one-stop hybrid CABG/PCI patients, median age was 63 (range, 32–89) years, 67 patients (60%) underwent “planned” hybrid procedure based on preoperative assessment, whereas 45 patients (40%) underwent open-chest PCI (“unplanned” hybrid) based on intraoperative angiography findings.8 The indications for planned hybrid were attempt to minimize surgical risk (32 of 67 patients; 48%), ungraftable vessels but favorable PCI lesion (29 of 67 patients; 43%), poor conduits (3 of 67 patients; 4.5%), and stenting of left subclavian artery to use the LIMA as a conduit (3 of 67 patients; 4.5%). The indications for unplanned PCI at the time of the surgery were mostly graft defects identified at routine completion coronary angiography (43 of 45 patients; 95%).8
The observed operative mortality was 2.6% (3 of 112). Ten (3%) patients underwent reoperation for bleeding. To minimize the risk of bleeding-related complications caused by Clopidogrel, we have adopted a strategy of giving 300 mg of Clopidogrel per mouth immediately before entering the OR. In unplanned hybrid patients, the 300 mg Clopidogrel is given through the nasogastric tube at the time the decision for open-chest PCI was made. All hybrid patients received 75 mg of Clopidogrel per day for >6 months. All patients received daily 325 mg of aspirin after the surgery. To date, there is no standard protocol for the administration of antiplatelet agents for hybrid procedures. To minimize the risk of bleeding, some authors have given the first dose of Clopidogrel at arrival in the intensive care unit.27 More studies are needed to better understand the interaction and effect of Clopidogrel and the effect of the CPB on such patients. In our experience, by administering a reduced loading dose of Clopidogrel, we have not observed a significantly increased rate of bleeding complications in hybrid coronary artery revascularization patients.
Although bleeding is a major concern of hybrid coronary procedures, acute stent thrombosis is a dreadful complication. In our series,8 1 of 112 (1%) patients developed acute in-stent thrombosis after off-pump coronary bypass surgery and died. The patient developed acute left main stent thrombosis after heparin reversal with protamine. More studies are needed to determine the implications of on-pump coronary bypass surgery versus off-pump and need of more intense antiplatelet strategies and individual patient response to Clopidogrel.
Surgical treatment for patients with combined cardiac valve disease and CAD has traditionally involved valve and concomitant CABG surgery performed through a median sternotomy. However, in certain high-risk patients, comorbidities may preclude this combined surgical approach. For example, in patients with poor conduit quality, poor coronary target vessel quality, and low ejection fraction and in patients undergoing reoperative cardiac surgery, the risks of combined valve surgery and CABG may be prohibitive. Therefore, a less invasive surgical technique, in which valve surgery would be combined with PCI, may prove to be a feasible alternative in such selected patients. Combined PCI and valve surgery have already been shown to improve outcomes in patients with complex coronary and valve disease who present with acute coronary syndrome.11
Several retrospective, single-center studies have consistently reported reduced postoperative pain, faster recovery, less usage of autologous blood, and superior cosmetic results after aortic and mitral valve minimally invasive procedures,9,28–31 which resulted in increased frequency of combined PCI and valve surgical procedures.9,11,32 However, there have been no large randomized trials to prove the benefit of minimally invasive valve surgery.
The main reason this approach can be advantageous in certain high-risk patients is because it simplifies the operation by combining two lower risk procedures (minimally invasive valve surgery and PCI), thereby circumventing the risks of a more invasive and high-risk procedure.
Patients with poor conduit and target vessel quality for CABG may prove to benefit from this hybrid approach. Poor vein graft quality and poor target vessel quality are the reasons for the failure rate of vein grafts at 1 year, which can be as high as 30%.33 In such selected patients, a combined valve and PCI procedure may prove to be a superior alternative to standard CABG and valve surgery.
Patients with valve disease and CAD who present with acute coronary syndrome or poor ventricular function (left ventricular ejection fraction [LVEF] ≤35%) may also serve to benefit from this procedure. Such high-risk patients may often not have the capacity to tolerate the extensive operative and CPB times that combined valve and CABG surgery may entail. A hybrid approach could convert such a high-risk scenario into an isolated valve operation by enabling PCI of the culprit lesion and surgical correction of the valve pathology. This could serve to shorten and simplify the operation and lower the risk of mortality, which can be crucial in such high-risk cases.
This technique can also be valuable in patients requiring valve surgery who have undergone cardiac surgery in the past. This is particularly true in patients with a patent LIMA-to-LAD graft as resternotomy poses an increased risk because of the high mortality rate associated with injury to the LIMA graft.34,35 In addition, in patients with previous aortic valve surgery who are undergoing redo mitral valve surgery, the exposure of the mitral valve through conventional sternotomy may be extremely poor because the heart is fixed anteriorly, whereas a right thoracotomy approach offers a superior exposure.
Thirty-nine consecutive patients with combined coronary and mitral valve disease, median age of 70 (range, 44–85) years, have undergone a PCI and minimally invasive mitral valve surgery through a 5-cm right mini-thoracotomy without aortic cross-clamping in our hybrid OR between March 2006 and June 2009. The patients were relatively at high risk. Five patients (13%) presented with acute coronary syndrome, 19 of 39 (49%) were in congestive heart failure, 16 of 39 (41%) underwent urgent or emergent surgery, and 16 of 39 (41%) had previous heart surgery. Thirty patients (77%) underwent a one-staged procedure with initial PCI followed by valve surgery in the hybrid OR. Nine patients (23%) underwent a two-staged procedure because this was felt to be in the best interests of the patients. In these patients, PCI was performed 1 to 4 days before the surgical procedure. According to the Society of Thoracic Surgeons risk stratification algorithm, the mean predicted mortality for conventional valve and CABG surgery for this cohort of patients was 14.1% ± 9.5%, whereas the observed in-hospital mortality was only 2.6% (1 of 39). Hence, in our experience, this hybrid approach resulted in a significantly lower observed mortality than predicted by the conventional method. Overall, from what we have observed at our institution, we believe that the benefits of this technique far outweigh the risks for selected patients, and we have been pleased with the results.
Hybrid Endocardial and Epicardial AF Procedures
Different management strategies in AF have been recently debated because of significant increase in knowledge of potential AF mechanisms in different patient populations and the impact of pharmacologic and nonpharmacologic therapies to treat these mechanisms. The predominant therapies for patients with AF in its paroxysmal, persistent, and permanent form are still medical therapy and electrical cardioversion. However, different medical treatment strategies have had limited success in sinus restoration. Catheter-based and surgical ablation techniques achieved higher rates of freedom from AF.36 Therefore, all cardiac surgery patients presenting with AF should undergo a more complete operation that corrects not only the structural heart disease (CABG and valve surgery) but also AF simultaneously. Current approaches include a traditional Maze procedure (multiple left and right atrial incisions placed to isolate triggers and interrupt multiple re-entrant circuits),37 an ablation-assisted complete Maze procedure (using various energy sources such as radiofrequency, cryothermia, laser, microwave, and a high-intensity ultrasonography to create scars without cutting the tissue),38 various endocardial and epicardial left atrial lesion sets (most include pulmonary vein isolation, excision of left atrial appendage, and linear left atrial connecting lesions),38 and the beating heart approach (usually includes pulmonary vein isolation with or without ablation lines).39 For lone AF, indications are not as clear. Generally, symptomatic patients with medically refractory AF should be considered for intervention. Catheter-based procedures are used more often for lone AF. Surgical procedures are indicated for symptomatic patients with medically refractory AF who prefer surgical approach, in whom catheter ablation has failed or who are not candidates for catheter-based approach.40 Current approaches for lone AF include beating heart right-sided thoracoscopic pulmonary vein isolation with multiple ablation technologies (microwave, laser, and radiofrequency),41,42 an arrested right-sided thoracotomy (cryothermia and radiofrequency),43 and bilateral mini-thoracotomies.44 All ablation technologies that use various energy sources destroy tissue by either heating or cooling but leave the anatomic structure intact. Over time, the destroyed tissues turn into scar. The introduction of these new ablation technologies during past 10 years determined the progress of AF management by eliminating major difficulty of traditional Maze procedure such as sewing together the remaining atrial tissue and therefore reducing the risk of bleeding from the suture lines. However, the ability to create a transmural, full-thickness scar lesion varies and thus, the efficacy of these procedures varies as well. A partial thickness lesion leaves an area of viable tissue (conduction), which may cause recurrence of AF.
The ablation-assisted surgical approaches have the advantages of being faster than the catheter-based and provide access to the entire atrial epicardium of a beating heart. However, some lesions (eg, the lesion to the mitral annulus) are more easily created by percutaneous approach and that is why the hybrid-maze procedure has been developed and used by several groups. Currently, this procedure is performed in a staged fashion combining the mini-thoracoscopic surgical epicardial approach with percutaneous endocardial catheter-based ablation.45 Ideally, this procedure would be done in a specially designed hybrid suite combining both OR and electrophysiology laboratory.45 Future success in treatment of AF will depend on better understanding of the mechanisms of AF, further development of less invasive techniques, and improvement of epicardial and endocardial ablation technologies to create transmural lesions.
Management of patients with severe carotid artery stenosis and CAD remains controversial. High rates of operative mortality and myocardial infarction are observed after simultaneous carotid endarterectomy (CEA)/CABG or staged CEA followed by CABG, and high rates of stroke are reported for staged CABG followed by CEA procedure.46 Carotid artery stenting (CAS) with cerebral embolic protection has emerged as an alternative to CEA for high-risk patients.47,48 Thus, the hybrid-staged and simultaneous CABG/CAS approach has been recently proposed.49 Several investigators compared major clinical outcomes (in-hospital stroke and death rates) in patients undergoing CABG/CEA versus CABG/CAS and reported lower incidence of postoperative stroke.50 In-hospital mortality was similar in both groups.50 Other investigators have reported a significant reduction of mortality and morbidity after simultaneous CABG/CAS in high-risk patients.50 Thus, CAS may provide a safer carotid revascularization option for patients who require concomitant CABG. However, large randomized studies are needed to evaluate the potential clinical applicability of the hybrid CABG/CAS as an alternative to the current treatment strategies.
The ability to offer less invasive treatments and more options for cardiovascular patients is directly linked to the ability to collaborate among cardiac surgeons, interventional cardiologists, electrophysiologists, vascular surgeons, and interventional radiologists. The hybrid suite offers the ideal platform for these new approaches in which it is possible to combine all the tools available to different specialists.
Further progress of hybrid strategies will depend on technological advancements, improved percutaneous and minimally invasive techniques and skills, and the availability of a hybrid suite. However, the key requirement for successful implementation of this multidisciplinary strategy is ongoing close collaboration between cardiologists and cardiac surgeons.51,52 As with any advancing technology, the learning curve required to achieve good clinical proficiency and results with this relatively new treatment modality can only be adequately assessed by long-term study of the clinical outcomes. The initial results for hybrid strategies seem to be promising. However, long-term follow-up and prospective, randomized, multicenter trials will be required to adequately assess the extent of this benefit.
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