Figure 7-1 shows the curved long catheter (Fig. 7-1, A) and long hollow needle (Fig. 7-1, C) used to cross the atrial septum. A long sheath with an extending curved obturator that accepts a 0.032-inch guidewire has now replaced the straight stylet that was used for insertion of the curved transseptal catheter from the femoral vein into the right atrium. The modified transseptal needle has a 21-gauge needle tip to reduce hazard from accidental puncture of the aorta or atrial wall, and the catheter 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. Detail of transseptal needle tip is shown in Figure 7-1, D. Several methods exist to cross the atrial septum. Intracardiac echocardiography is popular among electrophysiologists to guide their approach. Using angiographic landmarks alone is commonly used by seasoned operators and is described here. The transseptal Mullen’s catheter and sheath system or Brockenbrough catheter with large or small curves are the catheter systems most commonly used (Fig. 7-2). The transseptal needle system is gently curved and attached to a pressure transducer with a rotating adaptor for free movement of the long needle within the catheter as it travels up to the heart.

Figure 7-1 The straight stylet (B) is used for insertion of the curved transseptal catheter (A) from the femoral vein into the right atrium. 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.

(Reprinted from Brockenbrough et al in Ross J: J Am Coll Cardiol 51:2107-2115, 2008.)

Figure 7-2 A, Transseptal catheter assembly. The distance between the transseptal needle and the dilator hub (arrow) is noted so that the needle lies just inside the dilator. B, Frames of left ventricular cine angiogram using transseptal sheath and Berman catheter in left ventricle. Top, Systolic frame; bottom, diastolic frame. Note ring of prosthetic aortic valve.

(A from Weiner RI, Maranhao V: Cathet Cardiovasc Diagn 15:112, 1988.)

Steps to perform transseptal catheterization are as follows

(Note for imaging- Views of the initial placement of pigtail, guidewires, and transseptal system are obtained in the AP projection. To estimate anterior or posterior placement of catheter in the atrial septum, RAO angulation is used. Transseptal puncture is performed in the AP projection to see needle entry in atrium.):

1. A pigtail catheter is placed in the aortic sinus of Valsalva just above the valve for anatomic reference and measurement of aortic pressure.

2. A 0.032- to 0.035-inch J-tipped guidewire is advanced to the superior vena cava (SVC) via the right femoral vein.

3. The transseptal catheter (and sheath) is advanced over the guidewire to the SVC.

4. The wire is withdrawn. The catheter is flushed. The transseptal needle is advanced through the catheter, permitting free rotation of the needle. The needle is positioned in the SVC with the metal arrow indicator pointing to the 12 o’clock position. The needle tip is kept within the catheter (previously checking this distance by finger separation of hub from sheath). The needle is connected to a pressure transducer for continuous observation of atrial pressure during septal crossing.

5. The catheter and needle assembly, now held fixed together, is withdrawn downward (caudally) from the SVC into the right atrium with a clockwise rotation of the needle angle indicator pointing posteriorly between 3 and 5 o’clock position (Fig. 7-3).

6. On withdrawal downward into the right atrium, the catheter assembly passes over the aortic knob with a forward motion, and on further withdrawal passes under the aortic indentation into the fossa ovale. Slight advancement of the catheter needle assembly is made until secure contact with the atrial septum. Approximately 15% to 20% of patients have a patent foramen ovale, which allows unobstructed passage of the catheter assembly into the left atrium without needle puncture.

7. The positioning technique described by Croft and others is used to precisely localize the point of puncture on the interatrial septum (Fig. 7-4). This technique uses the right anterior oblique angulation. Using the lower edge of the pigtail catheter within the sinus of Valsalva and right atrial (RA) posterior wall, a horizontal line is drawn from the lower end of the pigtail catheter intersecting with the vertical line of the RA border. The operator moves the needle to 1 cm below the line. The needle tip should bisect this line at the midpoint. This point usually is centered within the fossa ovale.

8. After the catheter and needle assembly makes secure contact with the interatrial septum, the operator maintains firm pressure on the sheath and catheter and advances the needle into the septum while continuously monitoring pressure waveforms. Observing the left atrial pressure waveforms signifies entry of the needle into the left atrium. If the operator is in doubt about the location of the needle tip, blood may be aspirated for determination of oxygen saturation (which should be arterial) or a small amount of contrast material may be injected under fluoroscopy. After the operator confirms the proper positioning of the needle in the left atrium, it is advanced slightly and the catheter is advanced over the needle with a counterclockwise rotation of the needle, which permits the transseptal catheter to turn anteriorly into the mitral valve orifice area. The needle is withdrawn, and the transseptal catheter is carefully aspirated and connected to pressure. (Caution: Left-sided injections of thrombus or bubbles can enter the systemic circulation.) After reinserting the J-tipped guidewire, the catheter and sheath can be safely advanced farther. After the transseptal catheter is positioned in the left atrium, the sheath can be advanced over the catheter into the left atrium. A small amount of contrast material may be injected to identify catheter position and to avoid advancing the catheter into pulmonary veins.

9. To access the left ventricle, a guidewire is inserted into the transseptal catheter or sheath and advanced across the mitral valve and into the left ventricle. In some cases, a balloon catheter can be passed through the transseptal sheath and floated into the left ventricle. The catheter (or sheath) is advanced over the guidewire or balloon catheter into the left ventricle.

Figure 7-3 Transseptal arrow is oriented approximately 45 degrees posteriorly. FII, Frontal image intensifier; LII, lateral image intensifier.

(From Weiner RI, Maranhao V: Cathet Cardiovasc Diagn 15:112, 1988.)

Figure 7-4 The optimal spot for transseptal puncture. Diagrammatic representation of the structures visualized in 40 degrees right anterior oblique projection. The 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. The point of intended atrial septal puncture is delineated by X.

(From Croft CH, Lipscomb K: J Am Coll Cardiol 5:904-910, 1985.)

Preparatory Notes

1. The transseptal catheter must be measured against the transseptal needle to identify the position at which the needle extends outside the catheter (Fig. 7-2). This measurement is done on the back table before insertion of the catheter-needle assembly. The operator places the catheter over the needle, notes at what point the needle leaves the catheter end, and marks this distance with a fingertip. Keeping the needle inside the catheter protects the wall of the atrium from inadvertent needle damage.

2. As the transseptal needle is passed through the transseptal catheter to the SVC, it is rotated at three points along its course. The first is the iliac crest, the second is over the spine near the renal vein, and the third is 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.

3. If necessary, left ventriculography through the transseptal catheter can be performed at low volume (<20 ml) and moderate flow rates (<10 ml/sec) because of the end-hole configuration of the catheter. A small test injection of contrast medium should be performed to avoid catheter malposition. Perforation of the left ventricle with end-hole catheters has been reported. It is preferable to exchange the transseptal catheter for a pigtail catheter or use a Berman catheter through the Mullin sheath.

4. The fossa ovale is located in the middle third of the atrial septum and is concave toward the left atrium in a normal heart. Valvular disease may significantly alter the location of the fossa ovale. In aortic valve disease the dilated ascending aorta may displace the fossa superiorly and anteriorly. In mitral valve disease, the left atrium 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 the transseptal puncture technique must be modified accordingly.

5. Heparin (40 U/kg IV) should be given once the transseptal access has been successfully obtained.