Transseptal Heart Catheterization Under Fluoroscopic Guidance

Transseptal puncture under fluoroscopic guidance is usually performed for PBMV and other procedures in which precise location of the transseptal puncture is not crucial. Various methods have been described. The availability of advanced imaging technologies such as transesophageal echocardiography (TEE) and intracardiac echocardiography (ICE) have made the use of fluoroscopic maneuvers (including right atrial angiography) less common. Nonetheless, because PBMV is more commonly performed in developing countries, in which cost considerations of using these technologies may be important, it is important to understand the various techniques available using fluoroscopy to obtain a successful puncture.

“Drop” into the Fossa Ovalis

A transseptal puncture begins with access into the right femoral venous system. Although transseptal puncture is possible from the left femoral vein, the angulation is generally not favorable and therefore avoided if possible. A 0.032-inch guidewire is advanced from the inferior vena cava (IVC) into the superior vena cava (SVC), and the right femoral venous sheath is exchanged for a transseptal sheath and dilator (e.g., Mullins sheath or SL-0 catheter). The transseptal sheath is advanced into the SVC. Operators may, at the same time, choose to place a pigtail catheter in the ascending aorta to demarcate the position of the aorta on fluoroscopy (Figure 4–4). This helps identify the aorta so that the operator may direct the transseptal needle away from it (appreciable primarily in the lateral fluoroscopic projection). In the meantime, the transseptal needle is flushed carefully and attached to a pressure transducer. Many operators will slowly continuously flush the needle with a saline infusion drip to prevent air from entering the system. The small saline flush that emanates from the tip of the sheath can also aid visualization if echocardiographic imaging is used. The needle is then advanced to the distal edge of the transseptal sheath, with the operator taking care to ensure that at least a distance of 1 cm is present between the needle and sheath tips. To do so, the needle is prevented from advancing forward by gripping it in the palm of the right hand while the thumb and index fingers hold the sheath and dilator system (Figure 4–5). The orientation of the needle and sheath must be maintained by matching the metal arrow on the needle’s hub to the direction of sheath’s sidearm (Figure 4–6). The operator ensures that that the needle does not slip forward inadvertently. The entire system of sheath, dilator, and needle is held as one unit and then gradually brought down to the level of the interatrial septum. This technique also maintains a constant and safe needle distance from the tip of the dilator. In a patient with normal or near normal anatomy, as the transseptal system is brought caudally (inferiorly), there is a “drop” into the fossa ovalis as the sheath cross the limbus. This is a tactile event and occasionally may also be appreciated on fluoroscopy as well.

At this point, the operator may puncture the septum by advancing the needle carefully out the end of the sheath (Figure 4–7). By applying gentle forward pressure to the needle and transseptal sheath, the needle should cross in the LA easily. In some cases, as forward pressure is applied, the needle may slide cranially, and the original puncture location may be lost. In this case, it may be necessary to remove and reshape the needle to gain more purchase on the interatrial septum. In addition, the wire mandril that comes with the Brockenbrough needle can also be used to “anchor” the needle into the septum and to assist in stabilizing the system as forward pressure is applied (Figure 4–8). As the needle crosses in the LA, the pressure transducer should show a left atrial pressure waveform. Importantly, the operator would hope not to see aortic pressure waveforms, which would indicate puncture of the aorta. The operator may also confirm that the needle is in the LA by aspirating blood backwards. Bright red blood will usually indicate that the needle is in the LA if pressure waveforms are consistent as well. An important cautionary note is to avoid flushing the catheter if it appears that the needle has crossed but there is no waveform or if the waveform is dampened. This may represent a thrombus on the needle/catheter system. Flushing into the LA may result in a stroke. Gentle aspiration to remove the thrombus may help. Lack of any pressure may also indicate that the tip of the needle is in the wall of the LA, pericardial space, or other soft-tissue structure. If there is uncertainty as to the location of the needle, the transseptal sheath should never be advanced forward, and the entire system should be withdrawn into the right atrium (RA). There are times in which the needle appears to be clearly into the LA but there is no pressure waveform. This may occur especially if there is a very floppy septum or if an interatrial septal aneurysm is present. In such situations, although it may appear that the needle is very far into the LA on fluoroscopy, it may not have crossed the floppy septum. Adequate preprocedure echocardiography would be useful to identify the presence of a floppy septum or interatrial septal aneurysm. TEE guidance in such situations would be reassuring and would enhance patient safety.

Once across the interatrial septum, the needle is often directed posteriorly so a slight counterclockwise rotation will direct the needle away from the left atrial posterior wall. The dilator and sheath are carefully advanced over the needle and then just the sheath over the dilator to ensure that the sheath is well in the LA (Figure 4–9). The dilator and needle are then removed, and the sheath aspirated and flushed carefully. If there is difficulty aspirating, the operator needs to consider the presence of thrombus or that the sheath tip is impinging on the wall of the LA. In the latter case, the sheath may be rotated either clockwise or counterclockwise to turn the sheath posteriorly or anteriorly away from the LA wall.

Depending on the procedure, a 0.035-inch stiff wire (e.g., Amplatz Super Stiff wire [St. Jude Medical, St. Paul, Minn.]) can be advanced to the LUPV and used as a rail for the delivery for equipment or devices (Figure 4–10). On occasion, a 6F or 7F multipurpose catheter may be used through the transseptal sheath to help guide the positioning of the wire in the LUPV.

Fluoroscopic Landmarks

Before the advent of TEE and ICE, fluoroscopic landmarks were exclusively used in performing a transseptal puncture. These include the use of right atrial angiography, drawing imaginary lines on fluoroscopy stop-frame images, using a pigtail catheter on the ascending aorta, and recognizing the relative positions of the tricuspid valve, coronary sinus, and aorta. Amongst the key points to note is that it is important to avoid the aorta, which is an anterior structure (Figure 4–11). The pigtail catheter helps the operator avoid the aorta. A lateral projection can also help to identify the anterior/posterior direction of the transseptal needle. These techniques remain helpful, especially if imaging is not available. However, for complex structural heart interventions such as the MitraClip and atrial septostomy, or in patients who are at very high risk for transseptal complications (such as prior mitral valve surgery with atrial septal repair), the authors believe that it is essential to have imaging with either TEE or ICE. Fluoroscopy alone would be potentially risky in patients who cannot tolerate any hemodynamic embarrassment. Fluoroscopy would also be unable to determine a precise anatomic puncture site. Of note, electrophysiologists have used additional landmarking tools for transseptal punctures. These include the use of a catheter in the coronary sinus, which delineates the margin of the left atrial free wall; and a catheter at the bundle of HIS to identify the anterior aspect of the interatrial septum. Numerous techniques for transseptal puncture using fluoroscopy alone have been well described in the literature and will not be the focus of this chapter.

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