Transcatheter aortic valve implantation (TAVI)
Transcatheter aortic valve implantation or replacement (TAVI/TAVR) is a technique to replace the aortic valve through a transvascular or transapical approach. Compared to traditional open aortic valve replacement with sternotomy and a heart-lung bypass machine, the TAVI technique is less invasive and can be performed on the beating heart. Thus, this technique may be beneficial for patients with symptomatic aortic stenosis and a high-risk for perioperative complications.
Pre-operative assessment before TAVI includes several tests and imaging examinations that are performed to evaluate the current vascular status, potential anatomic problems (e.g. severe iliac calcifications) and best surgical approach.
Ultrasound allows for dynamic analysis of the heart function and assessment of aortic stenosis and measurement of aortic annulus and left ventricular outflow tract. It also allows for evaluation of the other cardiac valves although aortic stenosis remains the main indication for valve replacement. Trans-esophageal echocardiography may be performed instead of trans-thoracic echocardiography for a better visualisation of the cardiac valves.
Recent innovations have lead to automated analysis of cardiac CT data for preprocedural planning of TAVI. The aortic annulus and left ventricular outflow tract (LVOT) can be accurately measured to select a fitting aortic valve replacement 3. When using retrospectively ECG-gated protocols, cardiac volumetry and function can also be assessed. It is crucial to measure the distance between the coronary ostia and the aortic annulus to allow for safe placement of the valve replacement (usually greater than 10 mm). Furthermore, CT angiography of the abdominal aorta and ilio-femoral vessels is performed for preprocedural planning.
Currently, there are three main access routes for TAVI. Individual selection of an access is based on patient anatomy, cardiac anatomy and cardiovascular disease.
This is the most widely used technique for TAVI. A small incision is made in the groin and a catheter is placed in the femoral artery and used to deliver the folded aortic valve replacement.
A small transthoracical incision is made to allow for visualization of the cardiac apex. This antegrade approach may be a viable option for patients with significant vascular calcifications and due to the direct access significantly reduce vascular injury during TAVI.
This technique is a surgical option in patients with severe peripheral vascular disease.
Although TAVI is a less-invasive technique with a reduced periprocedural risk for the patient compared to traditional open heart surgery, several complications may occur 2.
The valve replacement may be malpositioned, dislocate, block the coronary ostia, or limit the mitral valve mobility.
An important complication that can be assessed during the procedure, or with CT and echocardiography postoperatively, is paravalvular aortic regurgitation (PAR) / paravalvular leak. This complication occurs when the aortic valve implant is not in complete apposition with the annular wall, allowing blood to leak around the prosthesis. A decreased survival rate has been reported, depending on the degree of PAR, and even mild PAR has been associated with late mortality 4. A combination of CT and echocardiography are needed for the anatomic and functional confirmation of PAR, respectively. Cardiac MR is a promising way to unite these functions, but requires more validation before it can be used routinely 4.
Any cardiovascular intervention can result in aortic dissection, bleeding, cardiac tamponade, delayed wound healing, infection, myocardial infarction, stroke or other vascular complications. Obviously, vascular injuries are more likely when selecting a transvascular approach for TAVI. However, the tendency for selecting a reduced sheath size has led to a decrease in vascular complications.
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