Atrial fibrillation increases risk of blood clots, heart failure and stroke. Left atrial occlusion devices such as the Watchman minimize this risk and alleviate the need for oral anticoagulants. The role of TEE includes verifying a clean LAA prior to implantation, identifying LAA shape and dimensions, assisting with trans-septal puncture and verifying final position of the Watchman. In this TEE view the LAA is obviously not "clean" with a nasty little thrombus present.
An essential "first view" is to rule out thrombus prior to implant of the LAA occlusion device. The LAA view is found by pulling back from ME AV SAX to ascending aorta, omniplane 30-40 degrees, then rotating the probe
Pulse wave Doppler has high utility in determining whether flow exists in the left atrial appendage (LAA) in patients with suspected thrombus. The LAA is a small discrete structure that is difficult to acquire a volume for but PW Doppler is excellent in this regard. In addition color flow Doppler offers qualitative assessment of flow in the appendage.
The LAA begins with an orifice that is typically ovoid and thus has a major and a minor orifice diameter. or this reason four planes are measured to create a 3D perspective, starting at 0 degrees.
The LAA landing zone is measured from the top of the mitral valve annulus or circumflex coronary artery to a point 2cm below the tip of the left upper pulmonary vein. Depth is measured from the plane of the LAA orifice to the LAA apex.
Multiple echocardiographic measurements in multiple views are made in addition to fluoroscopic evaluations. Measurement of the landing zone (neck) for the Watchman device are from the inferior part of the LAA at the level of the circumflex and posterior mitral valve to a point 1 to 2 cm distal to the LUPV (ligament of Marshall).
All measurements needed to characterize the LAA before closure should be performed at the end of diastole. A LAA width of 17-31 mm is required for the Watchman. LAA orifice diameter that is either too small (< 16.8 mm) or too large (30.4 mm) are exclusion criteria as Watchman sizes are 21, 24, 27, 30, 33. Also LAA lobe depth that is too shallow, a large atrial septal aneurysm or significant mitral stenosis are also exclusion criteria.
Biplane fluoroscopic guidance is used in conjunction with biplane TEE for trans-septal puncture. TS puncture site is inferior and posterior to have good alignment with LAA. A transseptal needle catheter (Baylis) and dilator are passed through the inferior vena cava into the right atrium and temporarily placed in the superior vena cava.
The delivery catheter and needle (Baylis) s advanced against the interatrial septum to tent the interatrial septum at the appropriate location. Tenting of the interatrial septum can then be used to confirm the puncture location before final advancement of the needle. Misadventures include aortic puncture (see "complications" below...).
Fluoroscopy and TEE are essential in guiding the proper location of septal puncture/tenting and identification of fossa ovalis or PFO.
The device is verified fluoroscopically in conjunction with TEE using the PASS protocol. With the PASS, the shoulder of the Watchman (POSITION) should not protrude more than 50% over the orifice of the LAA. The tug test (ANCHOR) tests the obvious. The Watchman should be compressed to shoulder to shoulder 8-20% during systole (SIZE), while the SEAL is assessed with contrast.
Use of TEE, Color and Pulse Wave Doppler
The LAA ostium lies superior to the mitral valve and anteriorly to the left-sided pulmonary veins. A device placed in the LAA can theoretically compress the LUPV or alter the MV apparatus (posterior leaflet compression). Pulmonary vein flow should both be evaluated by color flow and pulse wave Doppler. Color-flow Doppler with a low Nyquist limit should be used to assess for peri-device leakage and persistence of communication between the LA and LAA
Tamponade is the most important (and common) complication (2-5%), usually as a result of an incorrect TS puncture or manipulation of catheters, guidewires, or devices in the LA or the LAA. Treatment depends on severity, based on RA bounce and width of effusion.
Color Doppler is applied to the interatrial septum to assess the degree of procedurally related ASD at the site of transseptal puncture. An ASD of 10 mm is unusual and may require percutaneous ASD closure.
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