12

Patients should have cardiac imaging prior to the procedure, generally with transthoracic ECG, or with TEE if there is any risk of LA thrombus. Patients may also have had cardiac CT or MRI performed, depending upon the ablation procedure being performed. Any of these allow for the evaluation of the LA size and the IAS for abnormalities such as aneurysm (Figures 12.1 and 12.2; Videos 12.1 and 12.2) or lipomatous hypertrophy (Figure 12.3; Video 12.3), which can make transseptal puncture more challenging. If the patient has previously had a transseptal puncture performed, resultant scarring can also make crossing the septum more difficult. Prior surgical or percutaneous repair of an atrial septal defect (ASD) or PFO can also make transseptal puncture difficult or even impossible, depending on the materials used for the repair.

In addition, the patient’s anticoagulation status should be assessed prior to transseptal puncture. We routinely perform transseptal punctures for the ablation of AF in patients with therapeutic INR values; however, we avoid doing the procedure if the INR is greater than 3.

Table 12.1 provides a description of the required equipment and personnel that should be available in order to perform a transseptal puncture.

Access is first obtained with short sheaths in the femoral veins. If 2 transseptal punctures are planned, 2 8-Fr short sheaths are place in the right femoral veins, to be exchanged later for the transseptal sheaths. Additional diagnostic catheters are useful to denote fluoroscopic landmarks, and we routinely place a CS catheter through the left femoral vein. The course taken by the CS catheter helps to define the patient’s cardiac rotation, and the site of transseptal puncture is superior and slightly posterior to the CS ostium in the RAO projection. The course of the transseptal sheath should be roughly parallel to the CS, and the CS catheter can define the LA border in the LAO projection (Figure 12.4) and thus indicate how far the dilator should be advanced into the LA after crossing the septum.

Baseline Imaging Prior to Transseptal Puncture

Transseptal puncture can be performed with fluoroscopic guidance alone, but the use of ICE has been shown to reduce the incidence of complications.1–3 We routinely use ICE guidance for transseptal punctures, and a second operator is usually present to steer the ICE catheter and assist with the sheath exchanges during the procedure.

A 9-Fr sheath is placed in the left femoral vein through which an 8-Fr ICE catheter is advanced. We use a phased-array catheter with a frequency range of 5.0 to 10.0 MHz, with a tip deflectable in 160° in anterior/posterior and left/right directions (ACUSON AcuNAV Catheter, Siemens Medical Solutions USA, Inc., Malvern, PA). This catheter allows for real-time 2D intracardiac imaging, as well as color Doppler, continuous, and pulse-wave Doppler. The ICE catheter is advanced into the heart and baseline images are obtained. From the RA, the IAS is imaged to determine the location and anatomy of the fossa ovalis. Slight posteroflexion of the ICE catheter is often helpful in bringing the fossa into view. By rotating the ICE catheter clockwise, the LA can be imaged to identify the LA appendage, the left and right pulmonary veins, and the aorta. Typically the ostium of the left pulmonary veins provides a target toward which the transseptal puncture will be oriented; however, for transseptal ventricular ablation or for balloon-based ablation of AF, a more anterior transseptal target may be helpful. The pericardial space is imaged as well, first from the RA, then from within the RV, to enable better analysis of the pericardium inferior and posterior to the LV (Figure 12.5; Video 12.4). These baseline images allow for rapid identification of a pericardial effusion should it develop after a transseptal puncture or later in the ablation procedure (Figure 12.6; Video 12.5). To image the LV and its pericardial space from the RV, the ICE probe is rotated until the tricuspid valve is imaged. The catheter is anteflexed while keeping the tricuspid valve in view until the RV apex is seen and then advanced through the tricuspid valve into the mid RV. The anteflexion is released, leaving the catheter tip in the proximal RV outflow tract. From this position, the RV free wall and anterior pericardial space is imaged. The catheter is rotated clockwise, allowing imaging of the interventricular septum, and, with further rotation, the LV and its adjacent pericardial space. The ICE catheter is then withdrawn back into the RA in preparation for the transseptal puncture.

Anticoagulation Prior to the Transseptal Puncture

Next the stylet is removed from the transseptal needle, which is then connected to a flush line with a pressure transducer. The needle is flushed rapidly during insertion into the dilator (to avoid introducing bubbles) and is advanced into the dilator under fluoroscopic guidance until the tip is just inside the end of the dilator, when the hub of the needle is one to two fingers’ breadths from the hub of the sheath. The base of the needle has a flat metal hub with an arrow that points in the direction of the curvature of the needle. As the needle is advanced into the dilator, the arrow is gently aligned with the side port on the sheath to ensure that the curvature of the needle and sheath are oriented in the same direction once the needle is fully inserted (Figure 12.7). RA pressure is recorded through the transducer on the needle at this point, and the scale is set to 20 to 40 mmHg in preparation for measurement of the LA pressure (if the tip of the dilator is against the vessel wall, RA pressure may not be seen until the dilator is being withdrawn into the RA).

With the left hand on the dilator and sheath and the right hand on the needle to maintain needle position just inside the dilator, the assembly is withdrawn as one under fluoroscopic guidance. The assembly is withdrawn primarily under the LAO view ( Video 12.6), and by turning the assembly to about a 4 o’clock position, the curve of the needle and sheath is oriented in a left posterior direction. The second operator adjusts the ICE image to keep the IAS and fossa ovalis in view. As the assembly is withdrawn under fluoroscopy, the tip can be seen to have two distinct “jumps” to the left. The first corresponds to the tip dropping from the SVC into the RA, and the second corresponds to the tip dropping over the superior limbus into the fossa ovalis ( Videos 12.7 and 12.8). ICE imaging at this point is used to confirm that the tip is in contact with the IAS in the center of the fossa ovalis—the assembly can be withdrawn a little more if need be to ensure that it is at the correct height ( Videos 12.9 and 12.10), after which gentle forward pressure on the entire assembly is applied to ensure tenting of the septum. The ICE probe is rotated slightly clockwise and counterclockwise to ensure that the tip is visualized and that it is oriented toward the left pulmonary veins (Figure 12.8; Video 12.11). On fluoroscopy, this correlates with a course parallel to the CS catheter (away from the imager in an RAO view). We feel that this is the perfect positioning for transseptal puncture. More anterior positions are either dangerous (aortic perforation) or result in subsequent difficulty delivering catheters to posterior targets such as the pulmonary veins. More posterior positions are dangerous as there is less room in the atrium, increasing the risk of posterior wall perforation. If the dilator tip is visualized in too anterior a view on ICE—such as toward the LA appendage, mitral valve, or even the ascending aorta ( Video 12.12)—the assembly is rotated clockwise to a more posterior orientation. Similarly, if the dilator tip is visualized in too posterior a view on ICE—toward the posterior LA wall ( Video 12.13) or right pulmonary veins—the assembly is rotated counterclockwise to bring it more anterior.

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