Assembliy and Insertion of Peel-Away Sheaths for Cardiac Pacing
Insertion of Sheath(S)
Peel-away Sheath : A revolution in venous access for pacing
Peel-away sheaths revolutionized insertion of leads after punctured access. A fact that made cut-down essential in the past was the lack of suitable removal sheath. Peel-away sheaths facilitated venous access via seldinger technique and helped popularize punctured venous access for pacing.
Once the guide-wire is in place (venous system), the sheath is glided along the guide wire into the vein. Before doing so, the sheath system must be checked and flushed. The system consists of a central dilator (which gives strength and stability to create a path out of soft tissue) and surrounding peel-away soft sheath. The dilator should be partially taken out and re-fitted to ensure that they are not stuck and the sheath should be flushed with heparinized saline before insertion. For standard bradycardia pacing, the dilator size is 7 French and for ICD leads it is 9 French.
In pacing, sheath insertion should be undertaken only after the ensuring that the guide-wire is in the venous system (Subclavian vein – SVC – RA – IVC). Sheaths should never be passed if there is a doubt as to where the wire is.
Insertion of Peel-away Sheath
Before inserting the sheath, one must ensure that the guidewire is at the floor of the pocket – i.e. its is seen to emerge from the pocket floor muscle. If it is not, the future sheath entry point and subsequent lead entry point would be more superficial and this may cause the lead to erode to the surface much later on. The best way is to dissect tissues surround the guidewire and take it down to the pocket floor (see video below) before inserting the sheath.
Upon sliding the sheath, one encounters two steps of resistance. The initial one occurs when the dilator enters the deep pocket tissues and the second one when the sheath attempts to slide along within these tissues and cross the medial border of the rib . In a vast majority of patients, these resistances are overcome with minimal force and the whole sheath assembly passes through without an issue. However rarely one might find that significant force is necessary for pushing the sheath – even if the dilator managed to pass in. In such situation forcible sliding of the sheath might damage it and render it useless not to mention potential vascular trauma – therefore the whole sheath -dilator system should be withdrawn and a slightly larger dilator alone should be passed along the wire to create a potential tract. If the original size was 7 Fr, one may try advancing a 8 Fr or 9Fr dilator only along the wire to create a track. This dilator should be completely sent in and taken out leaving a potential track along with the guide-wire. Now the original sheath -dilator assembly is advanced utilizing the space created by the larger dilator. If the advancement was difficult and force was used, carefully inspect the sheath end to exclude damage – the sheath should smoothly taper over the dilator. If there sheath edge is damaged, it would be extremely difficult to advance the sheath and therefore a new one must be used.
Video : Insertion of Sheath (single chamber system) – Note that you feel a distinctive “give-away” when the sheath enters the vessel and crosses the medial border of the first rib. Its a good practice to check wire mobility by gently tugging the wire after the “give-away” to ensure that the wire is not trapped by kinking. Use of excessive force may tear the vessel, kink the guide-wire or damage sheath if there is no space. If space is inadequate, take out sheath and insert the dilator only to create a track. Ideally another dilator of a slightly larger diameter (e.g if the sheath was 7 Fr, an 8 Fr or 9 Fr dilator) should be used to create this track. A kinked guidewire is a nightmare for subsequent sheath insertion.
If you find it difficult to send even a large dilator, then its best to abandon the puncture and do a fresh puncture slightly lateral to the existing guide-wire as your original puncture may have been too medial causing bony impingement. The first guide-wire will serve as a guide and therefore it should be removed only after the new guide-wire has been inserted correctly.
Sheaths should never be sent in with brute force as a vascular tear can have catastrophic consequences. Further, difficult sheath insertion means a tight space and that translates into lead friction which may create problems for the lead in the future.
For multi-lead systems, sequential sheaths for separate leads are inserted only after completion of previous lead. It’s dangerous (air embolism from a displaced dilator) and impractical (having multiple sheaths jutting from the pocket) to insert all sheaths at once. To avoid insulation damage to the first lead when inserting the second sheath, one must ensure that adequate spacing between the punctures when placing guide-wires in the beginning ( see here for techniques getting multiples wires in)
Video : Insertion of Second Sheath in multi-lead configuration. Note that the second sheath glides adjacent to the previously inserted lead and therefore current sheath insertion must be gentle. If you apply brute force and there is lack of space, the previous lead might get a insulation breach by friction.