Equipment

Figure 9.1 shows the transseptal sheath with a curved dilator and a long hollow needle that are used to cross the atrial septum. The transseptal sheath is frequently 7 F or 8 F, often with a side arm that facilitates hemodynamic assessment of multiple sites with a single transseptal access (e.g., end-hole measurement for LV; side-arm port for LA pressure). The curved dilator and transseptal sheath assembly accepts a 0.032-inch guidewire that is passed from the femoral vein into the superior vena cava (SVC). The modified transseptal needle has a 21-gauge needle tip to reduce the hazard of accidental puncture of the aorta or atrial wall. Several different shapes and sizes of the transseptal needle curve are available, with the appropriate selection depending on the patient’s specific anatomy ( Fig. 9.2 ). The transseptal needle system is gently curved and attached to a pressure transducer with a rotating adapter for free movement of the long needle as it travels in the venous system through the catheter and for its manipulation toward the atrial septum.

For insertion of the curved transseptal catheter (A) from the femoral vein into the right atrium (RA), the straight stylet (B) is used. The modified transseptal needle (C) has a 21-gauge needle tip to reduce hazard from accidental puncture of the aorta or atrial wall, and the catheter (E) has side holes (to enhance injection of contrast medium) and a tapered tip to facilitate entry into the femoral vein and traversal of the atrial septum. (D) Detail of transseptal needle tip.

(From Ross J, Jr. Transseptal left heart catheterization a 50-year odyssey. J Am Coll Cardiol. 2008;51:2107-2115.)

(A) Transseptal catheter assembly. The distance between the transseptal needle and dilator hub (arrow) is set so that the needle lies just inside the dilator. (B) Frames of left ventricular (LV) cineangiogram using transseptal sheath and Berman catheter in LV. Left, Systolic frame; right, diastolic frame. Note ring of prosthetic aortic valve.

( Fig. 9.2 A from Weiner RI, Maranhao V. Development and application of transseptal left heart catheterization. Cathet Cardiovasc Diagn. 1988;15:112-120.)

Procedural steps

Transseptal catheterization can be performed using fluoroscopy alone, although adjunctive imaging with either transesophageal or intracardiac echocardiography has been increasingly used to facilitate safety and accuracy of the puncture site. Such accuracy is mandated for certain interventional procedures (e.g., MitraClip, Watchman) and can increase the success of other percutaneous therapies (e.g., posterior puncture for medial paravalvular defect closure). Fusion imaging with overlay from computed tomography (CT) has also been described for transseptal catheterization (see Fusion Imaging to Facilitate Cardiac Catheterization). The following steps describe the procedure when relying on fluoroscopy alone, with additional comments for incorporating adjunctive echocardiography.

• 1.
  

  The transseptal catheter must be measured against the transseptal needle to identify the position at which the needle extends outside the catheter ( Fig. 9.3 ). This measurement is made before inserting the catheter-needle assembly. The operator places the catheter over the needle, notes at which point the needle leaves the catheter end, and marks this distance with the right thumb. The right thumb position is used to keep the needle inside the catheter and protect from inadvertent needle damage.

  
  

  
  

  
  

  

  
  

  
  

  The transseptal arrow is oriented approximately 45 degrees posteriorly. FII, Frontal image intensifier; LII, lateral image intensifier.

  
  

  (From Weiner RI, Maranhao V. Development and application of transseptal left heart catheterization. Cathet Cardiovasc Diagn. 1988;15:112-120.)

  
  
  
  
• 2.
  

  To mark the aortic valve level as an anatomic reference point, place a pigtail catheter in the sinus of Valsalva at the aortic valve. For patients with an aortic valve prosthesis visible on fluoroscopy or when echocardiography is used, a pigtail catheter is not needed. In all cases, monitor the aortic or systemic arterial pressure during transseptal puncture.

  
  
• 3.
  

  Use fluoroscopy to determine landmarks for puncture. Figure 9.4 shows a right anterior oblique (RAO) projection, at which a horizontal line is drawn from the lower end of the pigtail catheter that intersects with the vertical line of the RA border. The fossa ovale is typically 1 cm below this line at its midpoint. If a left anterior oblique (LAO) projection is available, the operator can help to ensure a posterior orientation of the needle trajectory. In this view, the location of the fossa ovale is typically one-half to two-thirds of the distance from the aorta to the posterior wall of the LA ( Fig. 9.5 ).

  
  

  
  

  
  

  

  
  

  
  

  The optimal location for transseptal puncture. Diagrammatic representation of the structures visualized in 40-degree right anterior oblique (RAO) projection. Limits of the atria are depicted behind the aorta. The pigtail catheter positioned in the noncoronary aortic cusp defines the posterior boundary of the aortic root. X, The point of intended atrial septal puncture.

  
  

  (From Croft CH, Lipscomb K. Modified technique of transseptal left heart catheterization. J Am Coll Cardiol. 1985;5:904-910.)

  
  

  
  

  
  

  

  
  

  
  

  (A) The pigtail marks the location of the aortic valve on anterior-posterior imaging, with the tip of the transseptal catheter inferior and medial to the aortic valve. (B) On the lateral projection, the transseptal puncture site is at approximately two-thirds of the distance from the aortic valve to the posterior wall of the left atrium (LA). (C) In the right anterior oblique (RAO) view, the transseptal dilator engages the fossa ovalis posterior to the pigtail catheter (aortic valve) but anterior to the right atrial (RA) silhouette (dashed line). TV , Tricuspid valve.

  
  

  (From Babaliaros VC, Green JT, Lerakis S, et al. Emerging applications for transseptal left heart catheterization old techniques for new procedures. J Am Coll Cardiol. 2008;51:2116-2122.)

  
  
  
  
• 4.
  

  Advance a 0.032-inch guidewire to the SVC via the right femoral vein.

  
  
• 5.
  

  Advance the transseptal catheter (and sheath) over the guidewire to the SVC. It is important to have the end of the catheter in the SVC before removing the guidewire, because this position minimizes the need for superior movement of the assembly. Withdraw the wire and then aspirate the catheter.

  
  
• 6.
  

  Advance the transseptal needle through the catheter. As the transseptal needle is passed through the transseptal catheter to the SVC, rotate it at three points along its course to facilitate movement through the pelvic vessels. The first is at the iliac crest, the second over the spine near the renal vein, and the third at the inferior junction of the cardiac silhouette. The needle should rotate freely over these three segments and slide smoothly up through the transseptal catheter. Damage to the catheter or injury to the patient can occur if the needle does not rotate freely.

  
  
• 7.
  

  Position the needle in the SVC with the needle tip kept within the catheter, whose position was previously noted by the finger separation of the hub from the sheath. Connect the needle to a pressure transducer for continuous observation of atrial pressure during septal crossing.

  
  
• 8.
  

  Withdraw the catheter and needle assembly, now held fixed together, downward (caudally) from the SVC into the RA with a clockwise rotation of the metal arrow indicator of the needle angle pointing posterior-medially between a 4 o’clock and 5 o’clock position (see Fig. 9.3 ).

  
  
• 9.
  

  On withdrawal downward into the RA, pass the catheter assembly over the aortic knob with a forward motion and, on further withdrawal, pass under the superior limbus into the fossa ovale. Slightly advance the catheter-needle assembly until making secure contact with the atrial septum. Approximately 20% of patients have a patent foramen ovale, which allows unobstructed passage of the catheter assembly into the LA without needle puncture.

  
  
• 10.
  

  After the catheter and needle assembly makes secure contact with the atrial septum, maintain firm pressure on the sheath and catheter and advance the needle into the septum while continuously monitoring pressure waveforms. When echocardiography is used, perform imaging to demonstrate indentation of the atrial septum by the needle and a posterior orientation of the assembly ( Fig. 9.6 ).

  
  

  
  

  
  

  

  
  

  
  

  (A) Two-dimensional and (B) three-dimensional echocardiography shows tenting of the atrial septum (arrow) with the catheter pointed posteriorly and away from the aortic valve. LA, Left atrium; RA, right atrium.

  
  

  (From Babaliaros VC, Green JT, Lerakis S, et al. Emerging applications for transseptal left heart catheterization old techniques for new procedures. J Am Coll Cardiol. 2008;51:2116-2122.)

  
  
  
  
• 11.
  

  Clockwise rotation of the entire assembly leads to posterior positioning of the needle on the atrial septum and counterclockwise rotation will move it anteriorly. The atrial septum courses anteriorly from inferior to superior. Thus, movement of the assembly to a superior position will also result in slight anterior positioning and inferior movements will result in relatively posterior positioning.

  
  
• 12.
  

  Observe the LA pressure waveforms to note entry of the needle into the LA. If the operator is in doubt about the location of the needle tip, aspirate blood to determine oxygen saturation (which should be arterial) or inject a small amount of contrast material under fluoroscopy. After confirming the proper positioning of the needle in the LA, advance it slightly and advance the catheter over the needle with a counterclockwise rotation of the needle, which permits the transseptal catheter to turn anteriorly toward the mitral valve. The operator can give small amounts of contrast during manipulation across the septum to help avoid injury of the posterior or superior walls of the atrium.

  
  
• 13.
  

  The operator can advance the sheath over the transseptal catheter. This advancement can be performed with or without removal of the needle, by fixing the catheter. During the advancement of the sheath, the relatively abrupt transition between the catheter and sheath can cause the assembly to be pushed off the atrial septum back into the RA with loss of transseptal access. To help minimize this error, use gentle forward pressure taking care to avoid inadvertent forward movement of the assembly. This forward pressure can be applied after withdrawing the needle and reinserting a preshaped guidewire (e.g., Inoue wire).

  
  
• 14.
  

  To access the LV, insert a guidewire into the transseptal catheter or sheath and advance across the mitral valve and into the LV. Do not turn the sheath without a wire or dilator in place, because it is thin-walled and easily kinked. Pass a balloon catheter (filled with carbon dioxide to minimize risk in the event of balloon rupture) through the transseptal sheath and float the catheter into the LV. The operator can transduce the balloon catheter for ventricular pressure or use it as a rail for passing the transseptal catheter into the LV.

  
  
• 15.
  

  The timing of heparin administration is at the preference of the operator. Some operators prefer administering prior to transseptal puncture, others prefer after. Regardless, full heparinization (100U/kg IV) should occur once transseptal access has been successfully obtained.

The fossa ovale is located in the middle third of the atrial septum and is concave toward the LA in a normal heart. Valvular disease may significantly alter the location of the fossa ovale. In aortic valve disease, a dilated ascending aorta may displace the fossa superiorly and anteriorly. In mitral valve disease, the LA usually enlarges posteriorly and inferiorly and displaces the fossa ovale inferiorly. In severe mitral disease, the fossa may become everted and displaced into the lower third of the septum. This makes the fossa difficult to locate on catheter descent and transseptal puncture technique must be modified accordingly. In general, left atrial enlargement leads to horizontal displacement, which usually requires a shallow needle trajectory (∼50 degrees). Right atrial enlargement leads to vertical displacement, which requires a more aggressive needle shape (∼70 to 90 degrees).

In some patients, the atrial septum can be thickened and difficult to cross with the transseptal needle or catheter assembly. A transseptal method using radiofrequency energy to ablate the atrial septum has been developed. A needle, which is fully insulated excepted for the 21-gauge tip, is connected to a generator that creates monopolar output to deliver 10 W of energy for 2 seconds (Baylis Medical Company, Quebec, Canada). Comparing the radiofrequency method with conventional transseptal needle techniques, a randomized trial showed a shorter time to transseptal puncture (2.3 min vs. 7.3 min) and a higher rate of success (100% vs. 72.2%) with radiofrequency.

When there is concern about the forward pressure needed to advance a transseptal needle or catheter assembly, the atrial septum can be initially crossed with a low-profile guidewire. In this technique, the catheter assembly and needle is used to indent the septum, followed by advancement of a 135-cm long 0.014-inch diameter nitinol wire (SafeSept, Pressure Products, San Pedro, CA). The tip of this wire is sharp to allow relatively easy passage across the septum; once across, the preshaped configuration helps to prevent inadvertent injury from forward advancement of the catheter assembly into the LA.