Aortic valve disease is one of the most common valvular disorders in the United States and worldwide. Transcatheter management of these defects is an emerging market as it provides a noninvasive approach to the treatment of these valvular diseases. Several transcatheter procedures have been developed in recent years for aortic valve disease. The first human case of TAVR was performed in 2002 by Crib and colleagues for severe aortic valve disease.  Unfortunately, they performed the procedure by using an anterograde, transvenous approach it came with many pitfalls.  Not long after, in an attempt to improve procedural outcome, Webb and colleagues performed the procedure using what they reported to be a safer transfemoral arterial approach.  Following this was the development of the transapical approach done by Lichenstein and colleagues.  They later studied the clinical and hemodynamic outcomes for patients who underwent valve-in-valve aortic valve implantation of an Edwards balloon-expandable valve through the transapical approach in a landmark study published in the Journal of Thoracic and Cardiovascular Surgery. In 2016, a new, innovative transcervical approach was described by Dapunt and colleagues.  Landmark trials including Partner 1, 2, Source, France, Canadian, and UK registry have outlined the benefits TAVR compared to conventional surgical intervention with favorable results. This chapter will describe in detail the anatomy of the aortic valve, indications, contraindications, complications, and techniques used for percutaneous transcatheter management of aortic valve disease.
The aortic valve is located between the left ventricle and aortic root. It is a semilunar valve meaning it is consists of three cusps that open and close. The function of the aortic valve just like any other valve in the body is to prevent backward blood flow. Any disruption in this function can lead to a leaky valve. Leaky valves, called regurgitation or insufficiency, result in backward flow and backup of blood in the pulmonary vasculature. Abnormalities that prevent a valve opening results in higher pressures across the valve and result in turbulent blood flow. Individual variations of these aortic valve abnormalities are approved for transcatheter management.
Current guidelines TAVR is approved for the following two directions:
The future of TAVR is on the horizon. As more studies are undertaken on off label uses of TAVR the indications for TAVR will broaden. For example, a study done by Abdelghani showed mixed aortic valve disease (MAVD; severe stenosis+moderate-severe regurgitation) had similar outcome results compared to pure or predominant aortic stenosis (PAS).  Furthermore, there is a current debate, on whether TAVR or surgical aortic valve replacement (SAVR) should be done in the intermediate and low-risk patient populations. Currently, guidelines recommend SAVR for these two populations if the patient is a surgical candidate. However, several studies are now being conducted to challenge this recommendation.
There are several contraindications to the use of TAVR. It is not recommended for any patient with a life expectancy under 12 months. Other contraindications include the absence of a heart team on site, no cardiothoracic surgery on site, a patient with a severely debilitated mental state such as dementia. Other factors for consideration would include a myocardial infarction less than one month before, a severe pulmonary disease, such as pulmonary hypertension with right ventricular dysfunction, severely depressed left ventricular function less than 20% ejection fraction, abnormal size of native aortic annulus less than 18 or larger than 25 mm. Also, the presence of an intracardiac mass, thrombus or vegetation, intracardiac anatomy preventing successful catheterization, or severe mitral regurgitation or insufficiency should be considered. In addition, patients unable to tolerate anticoagulation, stroke/TIA within six months of procedure, patients requiring emergent surgical intervention, patients on dialysis, those with elevated serum creatinine higher than 3 mg/dL, congenital bicuspid, unicuspid, or noncalcified aortic valve, hypertrophic cardiomyopathy (HCOM), significant aortic disease, or the presence of mixed aortic valve disease. The last of which is currently being debated. 
The TAVR/TAVI procedure requires the following for completion: new transcatheter artificial valve, an introducer sheath, guide-wire, balloon-tipped catheter, delivery catheter, fluoroscopy, echocardiogram, and compression device.
The personnel required for safe and accurate transcatheter management of aortic valve disease include an interventional cardiologist trained in transcatheter management of aortic valve, a structural heart specialist, cardiac certified nurse, cardiac surgical technician and even a cardiothoracic surgeon trained in valve replacement surgery.
Preoperative transthoracic echocardiography (TTE) and transesophageal echocardiography (TEE) are used to assess the anatomy and severity of aortic valve (AV) disease, size AV annulus, diameter of the ascending aorta, structural and functional assessment of the other valves, and assessment of left and right ventricular function as well as regional wall motion abnormalities.  Sometimes 3-dimensional echocardiograms or cardiac CT are done to provide more detail regarding the structure of the aortic valve. Laboratory workup should include an assessment of the baseline kidney function, liver function, hemoglobin, glucose, and type and cross-match. A pulmonary function test, chest radiograph, and arterial blood gas analysis should be performed in patients with known or suspected pulmonary disease. A detailed airway evaluation is crucial to assess if the patient will tolerate general anesthesia and to avoid preventable complications. A thorough review of the patient's preoperative medications should also be done.
The patient is instructed to continue medications as they would for any other surgical procedure. Aspirin and clopidogrel may be already part of a patient’s list of drugs, or they may be newly administered before the procedure. Aspirin in a dose of 75 to 300 mg should be delivered before the procedure if there are no contraindications to the use. Inform the patient that they will be on Aspirin indefinitely.  Currently, there are no strict guidelines regarding the need and duration of an antiplatelet medication regimen. Thus, different regimens vary regarding the use of clopidogrel, which is given as a bolus of 75 to 300 mg preoperatively and is continued for three to six months after the procedure. On the day of the operation, approximately one hour before the procedure, pretreatment with intravenous antibiotics should be administered. There are no guidelines for post-operative antibiotic therapy, but some reports in the literature report prophylactic antibiotics for three to seven days following the procedure.
Several approaches have been developed including a transeptal approach , transfemoral arterial approach , trans-aortic approach , trans-apical approach , and transcervical approach . The transfemoral approach is the most commonly used TAVR/TAVI approach worldwide. The transfemoral approach starts with obtaining femoral artery access using an introducer sheath. A guide-wire is then threaded through the sheath up through the ascending then descending aorta, and into the left heart. Next, a balloon-tipped catheter is passed over the guide-wire and positioned at the site of the aortic valve. The balloon is inflated to open the narrowed aortic opening. The balloon catheter is then deflated are removed from the guide-wire. The new artificial aortic valve is crimped onto a delivery catheter which makes the valve small enough to be transported through sheath and vasculature to the heart. Using fluoroscopy, the delivery catheter attached to the new valve is threaded over the guide-wire and positioned at the site of the old calcified aortic valve. The balloon on the delivery catheter is inflated to expand the new valve inside the diseased valve replacing it. The balloon is then deflated, and the delivery catheter along with the guide-wire is then removed. An intraoperative echocardiogram is done before closure. If the position of the valve is determined to be ideal, then the sheath is removed, and a compression device is placed to prevent hemorrhage or hematoma formation.
According to Smith and Colleagues in their study on transcatheter versus surgical aortic-valve replacement in high-risk patients revealed that vascular complications, followed by arrhythmia, then stroke , then by death, and finally by major hemorrhage were all possible complications of TAVR/TAVI.  A less common complication included a coronary artery obstruction. According to a study done by Ribeiro, they showed the risk of coronary artery obstruction to be four times higher in patients following valve-in-valve TAVR.  Other documented complications include worsening aortic stenosis or regurgitation, mispositioning of the valve, device embolus, kidney disease or myocardial infarction. Partner 2 Trial results showed a significantly higher rate of kidney disease with the use of TAVR versus SAVR. 
The advent of the transcatheter approach in managing aortic valve disease was a monumental turning point in the field of cardiology. Once where the only option was death or invasive surgical procedure with a high complication risk, now stands a plethora of opportunities for growth. Transcatheter management of aortic valve disease has changed the game. This minimally invasive procedure provides treatment to a large sector of patients who once were offered only offered medical supervision because of being a nonsurgical candidate. The development and progress of the transcatheter therapy for aortic valve disease have come so far, and one is only to predict that there is so much more to come in the future.
Percutaneous transcatheter management of aortic valve disease requires a skilled interprofessional team of healthcare professionals that includes a cardiac nurse, laboratory technologists, a pharmacist and some physicians in different specialties. Without proper pre-operative, intra-operative, and post-operative management life-threatening complications can and will occur. Therefore, it is imperative that the interprofessional team works as a unit with reliable communication to optimize patient-centered care. From the moment an aortic valve defect is identified, the discovering clinician has a responsibility to coordinate care including the following:
The management of aortic valve disease is a dynamic, ever-changing field. New technology comes up every day. It is crucial for the team to be up-to-date with the new upcoming technology and guidelines.
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