Hybrid cardiac surgery

A hybrid cardiac surgical procedure in a narrow sense is defined as a procedure that combines a conventional surgical part (including a skin incision) with an interventional part, using some sort of catheter-based procedure guided by fluoroscopy (or other, e.g. CT or MRI) imaging in a hybrid OR without interruption. A wider definition includes a clinically connected succession of a catheter intervention and a surgical procedure with a time gap.

Hybrid revascularization approach
Surgical bypass grafting and percutaneous coronary artery revascularization are traditionally considered isolated options. A simultaneous hybrid approach may allow an opportunity to match the best strategy for a particular anatomic lesion. Revascularization of the left anterior descending artery with the left internal mammary artery is by far the best treatment option in terms of long term results. Integrating this therapy with percutaneous coronary angioplasty (hybrid procedure) offers multi-vessel revascularization through a mini-thoracotomy. Particularly in high risk patients, morbidity and mortality decreases in comparison to conventional surgery. A study from FuWai Hospital in Beijing reports on 104 patients with multivessel coronary artery disease who were compared with the same sized group of patients undergoing off pump surgery using propensity score matching. The patients treated with the hybrid approach had a significantly shorter intensive care unit stay and intubation time and experienced less complications in terms of bleeding and transfusions needs. At a median follow up of 18 months, patients undergoing the hybrid procedure also had a significantly higher freedom from major adverse cardiac or cerebrovascular events (99% vs. 90.4%; p = 0.03). The hybrid procedure was also less costly than an exclusively percutaneous strategy.

Completion angiography
For a patient who underwent coronary artery bypass grafting, coronary imaging (completion angiography) for the routine evaluation of the bypass grafts is reasonable, as the one-year re-occlusion rate is at 20%. Thereby, defected implantations may be detected. In a study designed and published by the Vanderbilt Heart and Vascular Institute, routine intraoperative completion angiography performed in a fully functional hybrid operating room detected important defects in 97 of 796 (12% of the grafts) venous coronary artery bypass grafts in 366 adult patients (14% of the patients) with complex coronary artery disease. Their findings in completion angiography at the end of the operation included suboptimal anatomies, poor positioning of the venous bypass graft, and bypasses to not diseased vessels. Consequently, these defects, which usually would be detected at follow-up, could be rectified immediately, through traditional surgical revision or percutaneous coronary interventions, resulting in optimal bypass outcomes.

Pediatric cardiac surgery
For congenital cardiac malformations, even though surgery remains the treatment of choice, interventional cardiology approaches are increasingly being used. However, such percutaneous approaches can be challenging or even impossible because of difficult and complex anatomies (such as double-outlet right ventricle, or transposition of the great arteries, acute turns or kinks in the pulmonary arteries of tetralogy of Fallot patients) and patient characteristics/ complications (low weight, poor vascular access, induced rhythm disturbances, hemodynamic compromise). Nevertheless, surgery has its limitations, so that combining interventions and surgery into a single therapeutic procedure potentially leads to reduction of complexity, cardiopulmonary bypass time, risk, and to improved outcomes. Another important concept in hybrid procedures is completion angiography, as described above, which in the case of congenital heart disease surgery may detect residual structural lesions, thus reduce postoperative complications. Again, 3D imaging using rotational angiography should be the concept of choice. Completion angiography in a hybrid OR may even induce a reduction of contrast media and ionizing radiation dose applied to the patient, as it reduces the need for post-operative examination. Further dose reduction can be achieved with a combination of intraoperative rotational angiography and intraoperative MRI, when both a fixed C-arm and a MRI system are available in the surgical theatre, and MRI adds functional information.

Transcatheter aortic valve implantations (TAVI)
The conventional approach for treatment of aortic valve stenosis is surgical replacement of the aortic valve. This procedure has excellent outcomes particularly in younger patients at relatively low-risk and will remain the gold standard for aortic valve replacement in the upcoming years. However, TAVI (transcatheter aortic valve implantation) has emerged as a valid alternative for patients in whom conventional surgical techniques are considered too invasive and risky. The Partner trial using the Edwards Sapien valve demonstrated that patients with severe aortic stenosis, who are not eligible for conventional aortic valve replacement because of too high risk, benefit significantly from TAVI in comparison to standard therapy including valvuloplasty at one year in terms of survival (Cohort B, ). In addition, 700 enrolled very high risk patients undergoing TAVI for severe aortic stenosis had comparable mortality rates to those receiving conventional aortic valve replacements at one year (Cohort A, 25% vs. 26%). The transfemoral approach was used on approximately two-thirds of TAVI patients, while the transapical approach was used in the remaining third, unlike Cohort B where only the transfemoral approach was used.

To put this approach into practice, a hybrid OR is strongly recommended by a number of professional associations, including the European Society of Cardiology, the European Association of Cardio-thoracic Surgery, the German Society of Cardiology, and the German Society of Cardiac, Thoracic and Vascular Surgery.

In terms of necessary devices, currently two valves, the Corevalve (Medtronic, Minneapolis, MN) and the Sapien valve (Edwards, Irvine, CA) have been granted CE mark in 2007 and are successfully being implanted. Several newer generation valves aim to improve the results by more sophisticated designs to decrease the common current TAVI complications of aortic regurgitation, misplacement, and heart block.

Advanced image guidance by dedicated 2D and 3D applications (e.g. syngo Aortic Valve guide, Siemens; Heart Navigator, Philips; CTHV, Paieon) may further simplify navigation and deployment of the devices. Some of the new TAVI valves (e.g. Symetis Accurate, Jena Valve, Embracer, Medtronic) have dedicated mechanisms to anchor in the sinuses, thus are designed to align with the patient anatomy. Therefore, anatomically correct rotation of the valve within the aortic annulus is needed to optimally deploy the devices. 3D imaging may prove highly valuable to understand the correct relationships between the valve and the annulus.

Mitral valve repair
The repair of a defected mitral valve is a potential future hybrid procedure, that is still dependent on approval of the necessary devices by the U.S. Food and Drug Administration. Some of these devices also will most likely be used for procedures performed in regular cath labs. Further prostheses for mitral und tricuspid valve replacement are under development and certainly will be available within the next years. Complex hybrid procedures may arise where the various parts of the mitral valve apparatus (e.g. chordae, leaflet and ring) are repaired on a beating heart in combination with purely interventional techniques (e.g. MitralClip). From an imaging modality perspective, fluoroscopy will most likely be combined with 2D and 3D ultrasound and a fusion of these modalities may become helpful. The reason is that the metal devices are optimally imaged without artifacts by fluoroscopy whereas the valve itself is better evaluated with ultrasound. As an alternative to transesophageal echocardiography, the use of intracardiac 2D and 3D echo may prove useful because it would allow avoiding general anesthesia in selected patients.

Thoracic endovascular aortic repair (TEVAR)
For aneurysms of the thoracic aorta, thoracic endovascular aortic repair (TEVAR) has become a valid alternative to open repair. This method may even be applied to pathologies of the aortic arch and the distal descending aorta. A common complication of EVAR are endoleaks. These may be missed by 2D angiographic evaluation. Rotational angiography, providing CT-like 3D imaging with the angiographic C-arm enables the surgeon to diagnose this complication intraoperatively and correct it right away. This has been demonstrated in a study by the University of London: In 5 of 80 patients undergoing EVAR, endoleaks that were not visible in 2D angiography could be detected by intra-operative rotational angiography. In addition, conventional CT evaluations before discharge did not reveal any endoleak which was not previously seen in 3D rotational angiography. In addition, the environment of the hybrid operating room allowed for immediate treatment of the endoleaks, if required. In the near future, off the shelf fenestrated aortic stents will become available for the treatment of extensive aortic disease. These fenestrated stents have to be rotated in the aorta, such that the fenestrations cover the branches of the aorta. For these highly complex procedures, 3D imaging in a hybrid operating room may be extremely helpful for the navigation of wires and devices.

Surgery for rhythm disturbances
With regards to rhythm disturbances, in particular atrial fibrillation (AF), a hybrid procedure involves the combination of the surgical epicardial approach with the interventional endocardial approach. The advantages of such a combined approach have been reported by first studies, in one of them 31 AF patients were treated, therof 13 with persistent and two with permanent AF using a minimally-invasive approach combining thoracoscopic pulmonary vein isolation (PVI) and ganglionated plexus (GP) ablation with intraoperative electrophysiological confirmation of PVI in order to decrease recurrences of AF during follow-up. At one year follow-up, an encouraging 86% of the patients were without reoccurrence with AF. There are not only first results available for atrial fibrillation, but also for treating drug-refractory ventricular tachycardia. In one study, 14 patients (most of them after previous cardiac surgery) underwent surgical ablation with an epicardial approach with concomitant electrophysiological mapping. The authors conclude that the surgical access with subxiphoid window and limited anterior thoracotomy in the electrophysiology lab is feasible and safe. Pacemakers and implantable cardioverter defibrillators (ICD), particularly bi-ventricular systems, may be optimally implanted in a hybrid OR environment, because the hybrid operating theatre offers the required superior angulation and imaging capabilities in comparison to mobile C-Arms, and the higher hygienic standards compared to cath labs. Rotational angiography (3D imaging) may prove useful for imaging the venous system of the heart. The coronary sinus can be depicted in 3D and than be overlaid over the fluoroscopy image to better guide placement of the left ventricular lead.