Atrial Lead Implantation

We prefer dual chamber pacing for all valid indications but AAIR pacing remains a not so infrequently used option in our setup.

RV pacing provides life sustaining rhythm support and is the most critical lead of a pacing system. However more and more patients are getting paced for non-life threatening yet highly symptomatic sinus node dysfunction. Therefore functional pacing and maintenance of physiologic cardiac activation is a prime concern when pacing for sinus dysfunction. To enable such, atrial pacing has evolved to be an integral component of pacing for sinus node dysfunction.

As long-term RV pacing has been proven to be deleterious, it became unwise to pace the RV when the problem is in the sinus node. Therefore initial attempts to avoid RV pacing  was to pace only the atrium provided the AV nodal function was acceptable. This was the AAI mode. [ Atrial demand pacing]. Subsequent development of advanced sensor technology enabled physiologic rate adaptation mimicking natural sinus node activity and AAI became AAIR [ Rate adaptive Atrial Demand Pacing]. Atrial only pacing was possible only if the AV node was normal – otherwise had to pace the ventricle. On the west side of the Atlantic, the skepticism for atrial only pacing was high and this accelerated the development of dual chamber pacing systems which would pace both chambers based on the underlying pathology and rhythm.

Regardless of the above, dual chamber systems are still very expensive compared to single chamber systems (and there is a unresolved issue of risk of heart failure with pure sinus node dysfunction). Therefore in cost-constrained developing country environments such as ours, we still attempt AAIR pacing if feasible. Usually these patients are young patients with only sinus node dysfunction and have had a non – invasive workup to assess AV nodal function before pacing AAI. An intra-operative testing of AV nodal function determines the final mode of pacing (our protocol is given in the section on Atrial Lead Implantation)

With regard to the site of pacing, right atrial appendage (RAA) is the location of choice – mainly because its an easily accessible and stable place. We avoid the lateral atrial wall because of phrenic nerve capture and the inter-atrial septum is only very rarely used for pacing because almost always, a good site in the RAA can be found.

1. Kenneth A. Ellenbogen –  Clinical Cardiac Pacing, Defibrillation, and Resynchronization Therapy 4e.
   • Chapter 10 : Clinical Trials of Atrial and Ventricular Pacing Modes by Carsten W. Israel
2. Fred M. Kusumoto – Cardiac Pacing for the Clinician 2e. –
   • Chapter 9  : Sinus Node Dysfunction  by Irene H. Stevenson, Paul B. Sparks, and Jonathan M. Kalman
     
   • Chapter 10 : Acquired Atrioventricular Block  by S. Serge Barold and Bengt Herweg

• Have vascular access : Either the only sheath (for AAIR) or second sheath for a dual system
• If dual – ventricle lead in place and finalized
• Insert atrial lead and park in right atrium (as described for the ventricular lead)
• Change the straight stylet with a appropriate J curved stylet
• Negotiate the distal curved end of the lead to the Right Atrial Appendage under fluroscopic guidance
• Check parameters and deploy active fix screw
• Exchange stylet to a straight one and anchor the lead at the pocket after removing the sheath.

Firstly, the lead has to be parked in the RA. If the system is going to be only AAIR then, the existing sheath can be used to insert the lead as described here for ventricular pacing.  If it is a dual chamber system, an additional sheath has be in place as described here via an additional guide-wire as described here.

One potential place where brisk forcible insertion might cause problems is the SVC free wall: If the sheath is too much in, the tip will lie against the free wall of the SVC and the lead coming out of it will impinge on the wall creating a resistance. Therefore it is imperative that fluroscopic screening is done at the slightest resistance without pushing the lead blindly. If impinging, the whole sheath should be slightly withdrawn and the lead marched forward with about inch of stylet pulled out to make it floppy and fall down

Each lead is accompanied by a one or two pre-formed J shaped stylets – these vary in size and stiffness. Therefore if a lead refuses to move into the appendage, a stylet with a smaller curve can be tried.

If one appreciates the shape of the lead which is given by the stylet) it can be easily figured out why it is dangerous to pull the stylet fast : It can lead to a lead out-migration through the appendage roof. If pulled fast, the J stylet tip provides force at the lead tip forcing it cranially against the appendage roof. Since the screw is already deployed, it gets further wedged in the muscle wall and if the site of anchoring has a thin wall, the deployed screw length is sufficient to reach out of the myocardium into the pericardium. The potential serious complication is bleeding to the pericardial space – but the usual symptom is central pricking sharp chest pain. Author has seen three such cases where symptoms rapidly resolved after re-positioning the atrial lead.

If the pacing is for pure sinus node dysfunction, AAIR pacing can be considered (although dual chamber pacing is preferred). To pace in AAIR, one has to be absolutely sure that there is no current AV nodal disease. We assess this in two ways – Non invasively with Holter and Exercise testing and invasively during implantation of device. If holter and exercise ECG shows only evidence of sinus node dysfunction, we plan for an AAIR system and do intra-operative reconfirmation of AV nodal function. The intra-operative method is described below.