Aortic Stenosis Microchapters
Transcatheter Aortic Valve Replacement (TAVR)
TAVR evaluation On the Web
American Roentgen Ray Society Images of TAVR evaluation
Patient evaluation for TAVR procedure is divided in to 3 steps. Preprocedure, periprocedure and postprocedure evaluation are important steps for successful procedure.
Aortic Valve Morphology
- Transthoracic Echocardiography (TTE) is performed for initial visualization of aortic valve to identify the number of leaflets; size, location, extent of calcification, leaflet motion, and a preliminary view of annular size and shape.
- If additional imaging is needed, valve anatomy and function can be evaluated by cardiac magnetic resonance imaging (CMR) or ECG-gated MDCT.
Aortic Valve Function
Doppler echocardiography is superior to other imaging modalities to evaluate Aortic valve function. AS severity should be evaluated according to the ESE/ASE Recommendations for Evaluation of Valvular Stenosis and staged according to the AHA/ACC Guideline for the Management of Patients with Valvular Heart Disease.
LV Geometry and Other Cardiac Findings
TTE also is recommended for evaluation of LV hypertrophy, chamber size, LV diastolic function, regional wall motion, and ejection fraction as well as newer measures of LV function such as global longitudinal strain. In addition, TTE is useful for assessment of aortic dilation, presence of subvalvular outflow tract obstruction, estimation of pulmonary pressures, and identification of other significant valve abnormalities.
The 3D dataset provided by MDCT are more accurate than TTE findings regarding annular size. Measurement of LV outflow tract diameter on TTE has been well validated for calculation of aortic valve area and continues to be the standard for determination of AS severity. CMR can also provide comprehensive assessment of the aortic valve, annulus, and aortic root with good correlation with MDCT. CMR can be a valuable tool in patients who cannot undergo MDCT.
Aortic Root Measurements
MDCT allows for the careful measurement of the size of the sinuses of Valsalva, the coronary ostia distance from the annulus, the size of the aorta at the sinotubular junction and 40mm above the annulus, and the extent and position of aortic calcifications.
MDCT also may be of use in identification of coronary artery and coronary bypass graft location and stenosis, evaluation of the RV to chest wall position, and identification of the aorta and LV apex to chest wall position in direct aortic approaches.
Because of high prevalence of dementia and atherosclerosis in this elderly patient population, a preprocedural work-up including carotid ultrasound and cerebrovascular MRI might be considered prior to considering or such patients for TAVR.
Because of the relatively large diameter of the delivery sheaths, appropriate vascular access imaging is critical for TAVR. It is important to evaluate the entire thoracoabdominal aorta, major thoracic arterial vasculature, carotids, and iliofemoral vasculature. MDCT is able to provide valuable dataset regarding vascular anatomy.
MDCT can assist with predicting the optimal delivery angle on fluoroscopy prior to valve deployment.
Confirmation of annular sizing
Preprocedural MDCT is the best modality to evaluate annular size. At the time of the procedure, fluoroscopy is the main imaging modality. If questions remain about the correct annular sizing, balloon inflation with contrast root injection can be performed. Also, 3D TEE is able to evaluate the annular size, at the time of the procedure.
Optimal deployment angles are obtained using fluoroscopy and root injections. Deployment is done under fluoroscopy at many institutions, although TEE is an alternative approach.
TEE and TTE are required to assess the valve in different aspects. Also, TEE can be used to assess the immediate gradient changes after valve seating. Aortic root angiography also may be used to assess for regurgitation after valve implantation. As the volume of cases performed without general anesthesia increases, there may be an expanding role for periprocedural TTE.
Immediate complications such as annular rupture resulting in pericardial effusion and tamponade can be detected by TEE, TTE, angiography, and direct hemodynamic measurements.
Long-Term Postprocedural Evaluation
Evaluate Valve Function
- Echocardiography is recommended to evaluate the valve postprocedurally to search for valvular and paravalvular leak, valve migration, complications such as annular or sinus rupture, valve thrombosis, endocarditis, paravalvular abscess, LV size, function and remodeling, and pulmonary pressures.
- MDCT can be used to evaluate valve anatomy A and to evaluate for valve thrombosis.
- CMR can also be used to quantify AR and can be complementary to TTE for the quantification of paravalvular leak.
LV Geometry and Other Cardiac Findings
TTE is used to evaluate changes in LV function after TAVR.
General contraindications for transcatheter aortic valve implant (TAVI) through every approach include:
- Aortic annulus size <18 mm or >25 mm for balloon expandable devices and <20 mm or >27 mm for self expandable devices.
- Severe mitral regurgitation.
- Presence of apical left ventricle thrombus.
- Aortic root dimension > 45 mm at the sino-tubular junction for self-expandable prostheses.
- Low position of the coronary ostia (<8 mm from the aortic annulus)
- Asymmetric heavy valvular calcification which may compress the coronary arteries during the procedure of TAVI.
- Bicuspid valves - because of the risk of incomplete placement of the prosthesis.
- Intracardiac mass
- Presence of vegetations is an absolute contraindication for TAVI.
- Severe aortic regurgitation
- Serum creatinine >3.0 mg/dL or patient on dialysis
- Left ventricular ejection fraction <20%
- Untreated coronary heart disease requiring revascularization.
- Hemodynamic instability
- Upper gastrointestinal bleed within the past 3 months.
- Cerebrovascular accident (CVA) or transient ischemic attack (TIA) within the last 6 months.
- Aortic aneurysm or severe ilio-femoral insufficiency disease
- Hypertrophic cardiomyopathy
- Bleeding disorders
- Active infective endocarditis
The transfemoral approach has a few specific contraindications which include:
- Severe tortuosity, calcification and narrowing of the iliac arteries
- Previous aorta-femoral bypass
- Abdominal aortic aneurysm
- Severe angulation of the aorta
- Severe atherosclerosis of the ascending aorta and arch of the aorta.
Contraindications for transapical approach include:
- Previous surgery to the heart
- Severe respiratory insufficiency
- Chest deformity
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