Procedures in the Hybrid Operating Room

Definition of a Hybrid Operating Room

A hybrid OR combines advanced imaging capabilities with a fully functioning operating suite. This means that angiographic, fluoroscopic, and other imaging capabilities (eg, computed tomography [CT], echocardiography) are integrated into a cardiac OR.

Equipment and Layout

In addition to components of a surgical suite, the following features should be available:

• 1.

  High-quality fluoroscopy (generally with flat-panel imaging) in a lead-lined room.

• 2.

  Integration of other modalities, such as a biplane system, C-arm CT, integrated ultrasound, and electromagnetic navigation systems (optional).

• 3.

  A control area for radiologic technicians either inside or outside of the hybrid OR with a direct view to the surgical field.

• 4.

  A radiolucent, thin, nonmetallic carbon fiber operating table that can accommodate both angiography and open operations. It must also be integrated to the imaging system to avoid collisions. Because of a lack of metal parts, some operating table functions are lost, such as isolated movement of upper or lower parts of the patient's body. Nevertheless, a floating tabletop with multidirectional tilt function is needed for accurate catheter maneuvering.

• 5.

  Adequate room size (800 square feet [74.3 m ² ] to 1000 square feet or more) to accommodate the equipment required by cardiac or vascular surgeons and interventional cardiologists, as well as the anesthesia team, nursing team, perfusionist, and radiologic technicians. Careful equipment positioning is required to allow fast conversion to conventional surgery if needed.

• 6.

  Ceiling-mounted monitors placed in positions that allow all team members (surgeons, anesthesiologists, and interventionists) to visualize the images simultaneously. Images from angiography, echocardiography, and hemodynamic monitoring need to be displayed.

• 7.

  Circulating heating, ventilation, and laminar air flow to provide a smooth undisturbed air flow suitable for conventional surgical operations.

• 8.

  Adequate high-output lighting for surgical interventions.

• 9.

  Other inevitable requirements such as adequate number of power receptacles, gas and suction outlets for both the anesthesia machine and the cardiopulmonary bypass (CPB) system, and hot and cold water outlets for the CPB.

• 10.

  Equipment: high-definition displays and monitors, oxygen (O ₂ ) analyzer, suction, O ₂ supply, defibrillator/resuscitation cart, echocardiographic equipment, sonographers, anesthesia equipment, CPB equipment, syringe pumps, radiation protection (along with the imaging system), blood warmers and blood bank access, point-of-care laboratory monitoring for blood gases and coagulation parameters, and so on. Because of the life-threatening complications that may be encountered during the procedure, ready-made crash carts consisting of any equipment necessary in an emergency must be available.

• 11.

  A complete sterile environment.

Fluoroscopy

Fluoroscopy may be portable or fixed. In general, fixed systems enable higher imaging quality and less radiation exposure compared with portable systems. The fixed C-arm may be mounted on the ceiling or the floor. Ceiling-mounted systems do not occupy OR floor space, but they need higher ceilings, which affects lighting, monitor placement, and laminar air flow. While these disadvantages can be avoided using floor-mounted systems, this comes at the cost of the available floor space. The fluoroscopy operating system generates a considerable amount of heat and noise, and it is suitable to put it outside the hybrid OR.

Digital Subtraction Angiography

This technique is used to visualize the blood vessels and identify any abnormalities without interference from background structures. In TAVR, it is used for identification of the coronary arteries immediately before valve implantation.

Echocardiography

Transesophageal echocardiography (TEE) is used during TAVR preprocedure, intraprocedure, and postprocedure for diagnosis of the disease and complications. Real-time 3D TEE can be a helpful tool that facilitates maneuvering of the delivery system and proper positioning of the aortic prosthesis. Transthoracic echocardiography (TTE) may be used in interventions performed under monitored anesthetic care (MAC) in which TEE is not possible.

Patient Selection and Indications

Currently, TAVR is recommended for patients with severe symptomatic AS who are inoperable or at high risk for needing surgical AVR and have a predicted post-TAVR survival of more than 12 months. High-risk patients are generally defined as those with a Society of Thoracic Surgeons (STS) score of 10% or European System for Cardiac Operative Risk Evaluation (EuroSCORE) of 20%. According to the American Heart Association (AHA) and the American College of Cardiology (ACC), high risk is defined as an STS predicted risk of mortality (PROM) of 8% or higher; or two or more indices of frailty (moderate to severe); or up to two major organ systems compromised, not to be improved postoperatively; or possible procedure-specific impediment.

The approach to patient selection for TAVR is optimal with a multidisciplinary team (MDT) that includes a primary cardiologist, cardiac surgeon, interventional cardiologist, echocardiographer, imaging specialists (CT or cardiac magnetic resonance [CMR]), heart failure and valve disease specialist, cardiac anesthesiologist, nurse practitioner, and cardiac rehabilitation specialists. At minimum, cardiologists, cardiac surgeons, cardiac anesthesiologists, and an imaging specialist should be involved in daily clinical practice.

The following issues must be discussed during the patient selection process:

• 1.

  Indication for aortic valve replacement (AVR), either surgical or TAVR.

• 2.

  Risk assessment and indication for TAVR.

• 3.

  Feasibility of the procedure for specific patient and choice of most proper access (eg, severe peripheral arterial disease).

• 4.

  Selection of specific valve type and size for the individual patient.

Other factors that may affect the decision-making process include availability, experience, and institutional commitment to managing very high-risk patients, technical skills, local results, referral patterns, and patient preference.

Risk Assessment and Indication for TAVR

The two most commonly used scores for risk assessment are the STS risk score and the EuroSCORE and the related logistic EuroSCORE. Five risk factors have special importance, either because of their impact on outcome or because they are not presented in risk models in spite of their prevalence. These factors are chronic kidney disease, coronary artery disease, chronic lung disease, mitral valve disease, and systolic dysfunction. Some patients are generally eligible for surgical AVR, but because of local disease abnormalities they may be scheduled for TAVR (eg, severe calcification of ascending aorta, porcelain aorta, friable aortic atheroma, and previous radiation therapy to the mediastinum). Two other factors that may affect the decision on surgery are (1) very elderly with associated comorbidities, and (2) frailty and futility.

The inclusion and exclusion criteria have been subjected to many modifications as a result of advances in technology and the specifications of next generation valves. Other clinical and anatomic contraindications also must be considered, such as valve endocarditis, elevated risk of coronary ostium obstruction (asymmetric valve calcification, short distance between annulus and coronary ostium, small aortic sinuses), and untreated coronary artery disease requiring revascularization ( Box 21.1 ).

Box 21.1

Inclusion Criteria and Contraindications for TAVR

Inclusion Criteria

• Calcific aortic valve stenosis

• Echocardiography: mean gradient >40 mm Hg or jet velocity >4.0 m/s and AVA <0.8 cm ² or indexed EOA <0.5 cm ² /m ²

• High risk for conventional AVR assessed by one cardiac interventionist and two experienced cardiothoracic surgeons

• Symptomatic

Contraindications (Candidates Will Be Excluded If Any of the Following Conditions Are Present)

• Absolute

  • Absence of a heart team and no cardiac surgery on the site

  • Appropriateness of TAVR, as an alternative to AVR, not confirmed by a heart team

• Clinical

  • Estimated life expectancy <1 year

  • Improvement of quality of life by TAVR unlikely because of comorbidities

  • Severe primary associated disease of other valves with major contribution to the patient's symptoms, which can be treated only by surgery

• Anatomic

  • Inadequate annulus size (<18 mm, >29 mm) (when using the current devices)

  • Thrombus in the left ventricle

  • Active endocarditis

  • Elevated risk of coronary ostium obstruction (asymmetric valve calcification, short distance between annulus and coronary ostium, small aortic sinuses)

  • Plaques with mobile thrombi in the ascending aorta or arch

  • For transfemoral/subclavian approach: inadequate vascular access (vessel size, calcification, tortuosity)

• Relative

  • Bicuspid or noncalcified valves

  • Untreated coronary artery disease requiring revascularization

  • Hemodynamic instability

  • LVEF <20%

  • For transapical approach: severe pulmonary disease, LV apex not accessible

  • Mixed aortic valve disease (aortic stenosis and aortic regurgitation with predominant aortic regurgitation >3+)

  • Hypertrophic cardiomyopathy

  • Severe incapacitating dementia

  • Renal insufficiency (creatinine >3.0 mg/dL) and/or end-stage renal disease requiring chronic dialysis

  • Severe pulmonary hypertension and RV dysfunction

AVA, Aortic valve area; AVR, aortic valve replacement; EOA, effective orifice area; LV, left ventricular; LVEF, left ventricular ejection fraction; RV, Right ventricle; TAVR, transcatheter aortic valve replacement.