TAVR procedure

# Overview
Several specific tasks should be considered by the Heart Valve Team before the actual procedure is performed. Valve choice, access choice, location of procedure, type of anesthesia and anticipated complications are important preprocedural parts. Important procedure parts include: anesthesia administration, vascular access and closure, pre-valve implant , valve delivery and
deployment and post-deployment valve assessments.

# TAVR procedure
The following table describes the TAVR procedure checklist.
Abbreviations:
AR: aortic regurgitation; AVR: aortic valve replacement; BAV: balloon aortic valvuloplasty; PA: pulmonary artery; TEE: transesophageal echocardiography

## Preprocedural Planning
Heart Valve Team must decide and plan for valve selection, access choice and location of procedure.

### Valve Choice
Valve selection is dependent on 2 major factors,
- Which type of valve should be considered (balloon expandable or self expanding) based on anatomical reasons
- Available valve sizes.
There currently are 2 TAVR valves commercially available in the United States:
- The balloon-expandable Sapien family of transcatheter heart valves (Edwards Lifesciences) made of bovine pericardium mounted in a cylindrical, relatively short cobaltchromium stent.
- The self-expanding CoreValve (Medtronic) family of transcatheter heart valves, which are made of porcine pericardium mounted in a taller, nitinol stent with an adaptive shape and supra-annular design.
Randomized clinical trials showed similar 1-year mortality, strokes, and re-admissions due to heart failure with either valve.
Important factors that must be considered in valve selection:
- Annulus dimensions and geometry
- Native valve and aortic root/LV outflow tract anatomy
- Coronary height
- Amount and distribution of calcification
Self expanding valves are preferred over balloon expandable in the following circumstances:
- Patients with heavy calcification of the aortic annulus/LV outflow tract with an attendant risk of rupture
- Extremely oval-shaped annulus or for transfemoral access when femoral artery diameter is between 5.0 and 5.5 mm.
Balloon expanding valves are preferred over self expandable in this situations:
- Dilated ascending (>43 mm) aorta
- Severely angulated aorta (aortoventricular angle >70 degrees, particularly for transfemoral access).
- A balloon-expandable valve is the only option in patients needing a transapical approach (e.g., those with a significant aortic calcification and peripheral vascular disease).
Several other valve designs and platforms are currently under investigation, and valve teams of the future will need to have a sound understanding of their relative merits and disadvantages for treating specific subsets of patients with AS.

### Access Choice
The patients atherosclerotic load and location, arterial size and tortuosity, and presence of mural thrombus are important factors in access selection.
When possible, transfemoral access is the preferred TAVR delivery route.

### Location of the Procedure
Optimal equipment requirements include a state of the art, large field of view fluoroscopic imaging system with a fixed overhead or floor mounted system that has positioning capability rather than a portable C-arm system. other equipment that are required in the TAVR center include: 3D echocardiography, MDCT, CMR, full catheterization laboratory hemodynamic capability, cardiopulmonary bypass machines and related ancillary supplies, with an inventory of interventional cardiology equipment for balloon aortic valvuloplasty, coronary balloons, stents, and 0.014-inch wires if coronary occlusion occurs as a complication of device deployment.
The procedure location should also be fully capable of providing anesthesia services, including advanced airway management, general anesthesia, full hemodynamic monitoring, and administration of vasoactive agents into the central circulation. 
In addition to the interventional cardiologist, cardiothoracic surgeon, and cardiovascular anesthesiologist, other personnel required during the TAVR procedure include a cardiovascular
imaging specialist, cardiac perfusionists, and other personnel trained in hemodynamic monitoring and able to rapidly deal with procedural complications.

### Anesthetic Considerations
Procedural complications, including hemodynamic collapse are common among patients undergoing TAVR. Preventing prolonged hypotension is a key goal during this procedure. Predictive factors for higher risk patients for intraprocedural instability include:
Depressed EF, elevated pulmonary pressures, significant mitral or tricuspid regurgitation, incomplete revascularization, collateral-dependent coronary and cerebral circulation, chronic lung disease, heart failure, and acute/chronic kidney disease.
TAVR is evolving from a procedure done routinely under general anesthesia with invasive central monitoring, a pulmonary artery catheter and transesophageal echocardiography to one that can safely be performed with conscious sedation and minimal instrumentation. Recent surveys showed better outcomes with conscious sedation than general anesthesia.
Now, it is recommended that TAVR procedures under conscious sedation should be performed in highly experienced centers, and not as an initial starting strategy for a TAVR program, and only using the transfemoral approach.
Conscious sedation is best avoided in patients requiring TEE guidance during valve deployment and in those with borderline vascular access, cognitive or language barriers, an inability to stay still or lie flat, chronic pain, morbid obesity, or other issues.

### Anticipated complication management
The following table summarizes the common complication for TAVR procedure and their treatment options.
Abbreviations:
AVR: aortic valve replacement; CABG: coronary artery bypass grafting; CPB: cardiopulmonary bypass; CVA: cerebrovascular accident; PCI: percutaneous coronary intervention; PPM: permanent pacemaker; SAVR: surgical aortic valve replacement; TAVR: transcatheter aortic valve replacement

## Procedural Details

### Anesthesia Administration
Typically, a temporary transvenous lead is passed through the femoral or internal jugular veins or, in the case of transapical procedures, can also be sewn directly on the epicardial surface. Arterial pressure monitoring may be done via the radial artery. At least 1 large-volume line is obtained peripherally or centrally. Immediate access to a defibrillator device
is necessary because ventricular fibrillation can occur with manipulation of catheters within the heart or with rapid ventricular pacing. Volume status needs to be supplemented carefully to prevent volume overload and hypovolemia. Inhaled nitric oxide or inhaled epoprostenol should be readily available for the treatment of severe pulmonary hypertension and right ventricular failure.
Routine surgical antibiotic prophylaxis administered prior to surgical incision or vascular access is warranted to decrease the risk of wound infection and endocarditis.

### Vascular Access
Vascular ultrasound may be needed to assess vessel wall calcification prior to puncture.
- For transfemoral access, both percutaneous and cutdown access approaches are used. Percutaneous approaches are preferred when access sites are relatively large and free of significant atherosclerotic disease and calcification, and in patients with wound healing concerns.
- For transapical cases, access is obtained via a left anterior thoracotomy, which is made after localization of the apex by fluoroscopy, TTE, and/or TEE.
- For transaortic cases, access is either through an upper partial sternotomy or a minthoracotomy at the second or third right intercostal space.

### Prevalve Implant
One of the key steps in preimplant is identifying the optimal fluoroscopic and intraprocedural views for device deployment. A pigtail catheter is typically placed in the noncoronary cusp (for self-expanding valves) and right coronary cusp (for balloon-expandable valves) and aortography is performed in a fluoroscopic view perpendicular to the native valve in order to identify the coplanar or coaxial view.
Anticoagulation therapy is usually initiated after insertion of the large sheath into the vasculature, and repeated to maintain an activated clotting time (ACT) of >250300 seconds.
Following this, the aortic valve is crossed using standard interventional techniques and a stiff wire exchange is performed, with redundancy in the LV cavity to prevent loss of position.
Prior to passage of the valve, predilation of the annulus may be required. Standard techniques of percutaneous balloon aortic valvuloplasty are employed, with rapid pacing during
inflation. Radiographic contrast opacification of the root during maximal inflation may provide useful information when the location of the coronary ostia in relation to the annulus and the
leaflet calcification or any other aortic root pathology requires further delineation. 
This is also helpful in situations where valve sizing falls between valve sizes. For example, use a 22-mm or 23-mm Edwards balloon when deciding between a 23-mm and a 26-mm transcatheter valve. If the 22-mm or 23-mm balloon reaches the hinge points and there is no significant leak around the balloon on angiography, then generally the 23-mm transcatheter valve would be selected. If the 22-mm balloon does not reach the hinge points and/or there is clear leak into the ventricle around the balloon, then the 26-mm valve would generally be implanted.

### Valve Delivery and Deployment
The transcatheter valve is positioned across the annulus in the predetermined coaxial annular plane. The optimal landing zone should be identified and will vary depending on the type of
valve.

### Post-deployment Valve Assessments
Immediately following implantation, valve position and location should be checked with echocardiography (TTE or TEE), hemodynamics, and/or aortography. A quick assessment for changes in MV or LV function and new pericardial effusion should also be routinely performed.
Post-TAVR AR must be characterized in terms of its location, severity, and cause and should integrate both central and paravalvular origins to allow for an estimate of overall volumetric impact.
Central regurgitation is generally a result of improper valve deployment or sizing. Paravalvular regurgitation is generally caused by underdeployment of the prosthesis, very low implants (e.g., below the valve skirt of the self-expanding valve), or calcific deposits, which prevent the valve unit from properly seating and sealing within the annulus. Acute leaks may respond to repeat ballooning of the valve to obtain a better seal and greater expansion of the valve.
Following TAVR deployment, the delivery system and sheath are removed. Anticoagulation is typically reversed and access site closure is performed.