Baseline transesophageal echocardiogram (TEE) or cardiac computed tomography angiography (CCTA) is important to exclude pre-existing LAA thrombus and assess for suitability for LAA closure, especially for sizing and device selection. TEE is the conventional standard pre-procedural imaging and multiple views should be evaluated, including a complete sweep from 0 to 180° for complete evaluation of the LAA, and with multiple measurements taken at 30° intervals. In particular, baseline measurements at both short-axis (30–60°) and long-axis (120–150°) of the landing zone and orifice are important. The LAA measurements are usually wider at the long-axis (which corresponds to the caudal projection on fluoroscopy), compared to the short-axis (corresponds to the RAO cranial view). For ACP, the LAA orifice represents the line from the pulmonary vein ridge to the atrial-side of the circumflex artery (echocardiographic LAA ostium) (Fig. 12.4). The landing zone is measured at 10 mm within the orifice at an angle that is perpendicular to the axis of the neck (proximal segment of the LAA). The depth of the LAA is measured from the orifice to the back wall of the appendage along the axis of the neck. For the Amulet device, the landing zone is ~12 mm (12–15 mm) from the orifice, due to the wider lobe dimensions (Table 12.1).

Pre-procedural cardiac CT angiography (CCTA) is also useful to examine LAA anatomy and dimension, given the superior spatial resolution and three-dimensional portrayal of cardiac structures. Moreover, CCTA is good for ruling out LAA thrombi, especially when double-contrast injection, delayed imaging, dual-energy, and prone positioning are employed (negative predictive value 100 %) [13]. Patients also need not be fasting prior to CCTA and saline infusion is typically administered before scans, which provides more accurate measurements at euvolemic states. Thus, CCTA may be a non-invasive alternative to TEE in experienced CCTA centers and is increasingly routinely performed prior to LAA closures. We routinely perform baseline CCTA for all LAA cases, which help strategize device selection and approach to closure (see Chap. 8).

Procedural TEE is the routine standard in the majority of centers and is usually accompanied by general anaesthesia. There are a few centers adept with and use procedural intracardiac echocardiography (ICE) to guide LAA closure, avoiding the need for general anaesthesia. However, obtaining adequate ICE LAA images can be challenging, and operators may overcome this problem by advancing the ICE probe into the left atrium through another transseptal puncture (see Chap. 7). Although very limited centers rely on fluoroscopy alone during LAA closure, this approach is not generally advised.

Venous access is preferred through the right femoral vein for easier and more direct transseptal access. The subcutaneous tissue at the access site should be well-separated and dilated with scalpel and forcep to ease advancement of large 13–14 Fr sheaths. Manual compression, “figure-of-8” suture, and pre-closing with 6 Fr Perclose are various approaches used for venous hemostasis.

The optimal location for transseptal puncture for LAA closure is inferior and posterior at the fossa ovalis. This position is well-visualized with the bicaval and short-axis TEE view, respectively (Fig. 12.5). ICE is a good alternative to guide transseptal puncture. The patent foramen ovale should not be used for sheath access as the resulting transseptal angle is not optimal for co-axial approach to the LAA. Instead, it is advised to perform a separate transseptal puncture inferoposteriorly to provide a more direct vector orientation to access the LAA, which arises anteriorly and superiorly. Intravenous heparin is administered before or immediately following transseptal puncture to maintain ACT >250 s. Adequate mean left atrial pressure (>12 mmHg) should be attained with fluid bolus for accurate LAA measurements.

Following transseptal access, a 5F marker pigtail is advanced into the LAA and cineangiograms are taken in multiple projections to ascertain the LAA anatomy and measurements (Fig. 12.6). Baseline CCTA can help predict the best fluoroscopic angles during the procedure. For ACP, we usually start with right anterior oblique (RAO) 30° cranial 10°, RAO 30° cranial 30°, and anteroposterior (PA) caudal 20–30° projections. Both fluoroscopic landing zone and orifice diameters are measured as per the TEE described above. The typical implant view used for the ACP device is RAO 30° cranial 10°, which is best to visualize the proximal LAA and orifice.

To cross the interatrial septum with the delivery sheath safely, we typically advance a long (260 cm) J-tipped stiff 0.035″ wire (e.g. Amplatz Super Stiff™ J-tip 3 mm curve) into the left upper pulmonary vein (LUPV) as a rail support. The appropriately sized TorqueVue 45 × 45 delivery sheath is then advanced to the LUPV ostium over the stiff wire. The delivery sheath should be gently rotated during advancement to achieve coaxial approach when crossing the interatrial septum. The TorqueVue sheath tip is advanced to the LUPV orifice over the stiff J-wire, and the dilator and wire are removed and de-aired carefully. The sheath is then withdrawn slightly and counterclocked to fall into the LAA ostium. Alternatively, a J-wire or pigtail may be used to engage the LAA to minimize traumatizing the thin left atrium.

ACP/Amulet sizing is based on the widest diameter of the landing zone measured on fluoroscopy or TEE. An accepted recommendation is to upsize the device by 3–5 mm for ACP and 2–4 mm for Amulet according to the widest landing zone diameter (Table 12.2). This degree of oversizing improves stability of the device. In addition, oversizing and achieving adequate lobe compression may improve the seal of the device and potentially lower the chance of residual leak into the LAA as we have shown on CCTA follow-up [14]. However, dramatic oversizing should probably be avoided, especially in the case of very elliptical landing zones (where the widest diameter is >6 mm larger than the narrowest diameter) where the tendency is to upsize according to the widest diameter. This may lead to dramatic oversizing of the narrowest dimension, which often results in the lobe being extruded out of the LAA.