**2.7 Hybrid surgery for rhythm disturbances**

The combination of the surgical epicardial approach with the interventional endocardial approach for the treatment of rhythm disturbances in particular atrial fibrillation offers theoretically advantages over conventional endocardial or epicardial therapy alone. First reports emphasized the potential benefit. Krul and coworkers from Amsterdam (Krul et al., 2011) reported on 31 patients with atrial fibrillation (AF); thereof 13 with persistent and two with permanent AF. A minimally-invasive approach combining thoracoscopic pulmonary vein isolation (PVI) and ganglionated plexus (GP) ablation with intraoperative electrophysiological confirmation of PVI was performed in order to decrease recurrences of AF during follow-up. Results at one year follow-up were very encouraging, with 86% of the patients without recurrence of AF. A hybrid approach for drug-refractory ventricular tachycardia was described by Michowitz (Michowitz et al., 2010). Fourteen 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 cathlabs. DynaCT angiographic 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.

### **2.8 Other applications outside cardiovascular therapy**

Hybrid operating rooms outside cardiovascular therapies are currently more and more used in neurosurgery, traumatology, orthopedics, urology, and general surgery. Interdisciplinary usage may be considered.

The need for hybrid operating theatres is not restricted to cardiac surgery. Vascular surgeons and neurosurgeons have equally developed hybrid procedures necessitating angiography systems in the OR. Furthermore, hybrid operating rooms are already in use by abdominal surgeons, traumatologists, orthopedic surgeons, and even urologists. Imaging needs, hygienic requirements, and room set up - particularly for neurosurgery - may be considerably different. Other surgical disciplines may want to introduce navigation systems, magnetic resonance imaging, endoscopy, biplane angiography systems, or a lateral position of anesthesia equipment. However, the hybrid operating rooms are more commonly shared with interventionalists including cardiologists, interventional radiologists,

The Hybrid Operating Room 79

higher x-ray doses than standard fluoroscopy. Thus, data acquisition is not recommended as

Data acquisition can be combined with specific imaging protocols, for example, to enhance blood vessels while removing background structures (see section 3.3) or to acquire 3D

Over the past three decades, digital subtraction angiography (DSA) has become a wellestablished 2D imaging technique for the visualization of blood vessels in the human body (Katzen, 1995). With this technique, a sequence of 2D digital X-ray projection images is acquired to show the passage of an injected contrast agent through the vessels of interest. Background structures are largely removed by subtracting an image acquired prior to injection (usually called the mask image) from the live images (often referred to as contrast images). It is obvious that in the resulting subtraction images, background structures are completely removed only if these structures are exactly aligned and have equal grey-level distributions (see Fig. 2b). Therefore, various motion correction algorithms are applied to

Fig. 2b. 2D digital subtraction angiography shows the difference between an initial fluoroscopic acquisition and a fluoroscopic acquisition after injecting contrast agent. Thus, the vessels are clearly depicted in these images. Other remaining structures (white next to black structures) caused by motion, are considered artefacts, and can be partly compensated

DSA is clinically used for diagnostic and therapeutic applications of vessel visualization throughout the entire body. During complex interventional procedures, DSA is often combined with so-called *road mapping*. In this mode, a DSA sequence is performed and the frame with maximum vessel opacification is identified, which becomes the road map mask. The road map mask is subtracted from subsequent live fluoroscopic images to produce realtime subtracted fluoroscopic images overlaid on a static image of the vasculature. Road mapping is useful for the placement of catheters and wires in complex and small vasculature, because fluoroscopy alone may not adequately show the vessels and may not visualize small wires in the distracting underlying tissue. It is also possible to combine the road mapping feature with a feature called image fade, which allows the user to manually

long as fluoroscopy is sufficient or the images do not need to be stored.

images (see section 3.5).

**3.3 Digital subtraction angiography** 

reduce such artifacts in the image.

by modern angiography devices.

adjust the brightness of the static vessel road-map overlay.

electrophysiologists, neuroradiologists, and pediatric cardiologists. Their specific needs have to be carefully considered and weighted when planning the hybrid theatre.
