Brockenbrough-Allen Needle

*FOR VETERINARY USE ONLY*

Figure One:

Indications: any procedure that requires access to the left heart, including:

• Mitral valve interventions (balloon valvuloplasty, valve repair/replacement)

• Electrophysiologic study/treatment of left atrial arrhythmias

• Left atrial decompression

The Brockenbrough-Allen needle may be used to perform transseptal puncture from the cranial or caudal approach; the cranial approach is better described in small animal medicine.

Cranial approach:

The patient is positioned in lateral position. The external jugular vein is catheterized according to standard procedure and the caudal vena cava is accessed utilizing a 6F or 7F sheath. The needle is sized to allow passage through a dilator or catheter with a minimal internal diameter of 0.038”. A 45 cm long sheath is recommended to allow appropriate needle extrusion. Once the sheath is in place in the caudal cava, the dilator is removed and both sheath and dilator are flushed. The needle is passed through the dilator external to the patient until extrusion is visualized. At that time, the needle may be reshaped according to the operator’s preference to enhance engagement with the fossa ovalis. The needle is withdrawn into the dilator until the tip is no longer extruding from the dilator, and the stylet is removed. This may be difficult if excessive/acute reshaping has been performed.The needle is flushed following stylet removal. The needle/dilator is then inserted into the sheath, with the arrow at the base of the needle pointed dorsally. The weight of the needle/dilator is supported by a second operator during passage through the hub of the sheath. The dilator/needle is advanced to the tip of the sheath in the caudal vena cava (take care not to advance the dilator beyond the sheath, as inadvertent puncture may occur). Free rotation of the dilator/needle is allowed during passage, and will naturally become dorsally oriented (the arrow at the base of the needle will point away from the operator). The sheath is then withdrawn until the dilator/needle are fully extruded. The sheath/dilator/needle assembly are then retracted cranially under fluoroscopic guidance. Once at the level of the caudal border of the cardiac silhouette on lateral projection, the assembly is rotated away from the operator (clockwise). The remainder of the procedure is best guided by 3D-transesophageal echocardiography (TEE). See Figure 3. Deformation of the caudal interatrial septum should be visualized on TEE during retraction. Rotation of the assembly should continue until the assembly is at the desired level of fossa ovalis puncture (dorso-ventral location) and should be performed during retraction to avoid excessive force on the septum. Retraction should continue until the fossa ovalis is engaged at the desired cranio-caudal location. The assembly can be held for a few cardiac cycles to assess if spontaneous puncture occurs. If not, slight caudal force may be applied while monitoring for caudal displacement of the assembly (“sliding”). If the assembly remains in the desired location of puncture but puncture does not occur, the needle may be advanced under fluoroscopic guidance (1-3 mm of extrusion is sufficient, overextrusion may split the dilator). Confirmation of atrial septal puncture is usually evident via microbubbles on TEE. If not visualized, a small bolus of saline may be given through the needle. Once puncture is confirmed, the needle is held in place as the dilator is advanced into the LA. Once LA puncture is confirmed, the needle is held in place and the dilator is advanced over the needle. Caution is needed while advancing the dilator to avoid exerting excessive pressure on the caudal/lateral walls of the LA. Once the dilator is within the LA, the sheath is advanced over the dilator and the dilator/needle are removed. This process should be performed deliberately to avoid air embolism and inadvertent movements that may displace the sheath.

Once the needle and dilator are removed, the sheath is aspirated to remove air bubbles and flushed carefully to avoid air embolism.We then administer unfractionated heparin at an empiric dose of 100 U/kg IV unless pericardial effusion has occurred due to non-target puncture.

If the assembly does not easily pass through the septum, it is usually due to caudal displacement (“sliding”) of the assembly along the IAS. There are a number of methods to address this problem. The first and typically most successful is to reshape the needle to achieve better contact with the interatrial septum. This usually means forming a secondary or tertiary bend proximal to the initial bend(s). If contact is adequate but crossing does not occur even with needle extrusion, electrification of the needle may be utilized to facilitate crossing. A bovie (unipolar, 50W cutting mode) is applied to the needle when the needle tip is slightly (1 mm) extruded from the dilator.This is nearly always effective in crossing the thickened septum. If still unable to cross, the stylet may be used to “fixate” the needle into the septum; the needle may then be able to advance over the stylet into the LA.Alternatively, a safe-sept guidewirea may be passed through the needle into the LA, which has a needle-like tip that takes a J-shape as it passes into the LA. Finally, the stiff end of an 0.014” guidewire may be passed through the needle. Typically, however, septal crossing can be accomplished by reshaping the needle and other methods are not required.

Caudal approach:

The femoral vein is catheterized in the standard manner and the cranial vena cava is accessed with a 0.035” guidewire. A 6F or 7F 45 cm sheath with a dilator of 0.038” minimum internal diameter is advanced over the wire into the cranial vena cava and the guidewire is removed.The dilator is flushed with saline.The needle is then advanced through the dilator; the stylet is removed prior to extrusion from the tip of the dilator, and the needle is flushed. The needle is then advanced to the tip of the dilator, and the assembly is then withdrawn into the right atrium with clockwise rotation to engage the fossa ovalis.The assembly will “fall off” the intervenous tubercle, which is typically immediately cranial to the fossa ovalis – confirmation of positioning should be obtained on TEE. If the site is adequate, slight cranial pressure can be applied to determine if crossing can occur. If the dilator does not puncture the septum, the needle may be advanced in order to puncture the septum. Once LA puncture is confirmed, the needle is held in place and the dilator is advanced over the needle. Caution is needed while advancing the dilator to avoid exerting excessive pressure on the caudal/lateral walls of the LA. Once the dilator is within the LA, the sheath is advanced over the dilator and the dilator/needle are removed. This process should be performed deliberately to avoid air embolism and inadvertent movements that may displace the sheath. Once the needle and dilator are removed, the sheath is aspirated to remove air bubbles and flushed carefully to avoid air embolism. We then administer unfractionated heparin at an empiric dose of 100 U/kg IV unless pericardial effusion has occurred due to non-target puncture.

Reference

Allen J, Phipps K, Barrett K. Three-dimensional transesophageal echocardiography guided transseptal puncture in dogs. J Vet Cardiol 2024; 51, 64-71.

a) Safe-sept guidewire, Oscor Inc, Palm Harbor FL, USA.

Figure 3:

A biplane transesophageal echocardiographic image of the interatrial septum. Note the left-hand image provides guidance on the dorsal/ventral position of the assembly and the right-hand image provides guidance on the craniocaudal position of the assembly.