Concept of Physiologic Pacing
Thoughtful and meticulous placement of the RV lead is of paramount importance for long-term successful pacing. Gone are the days where passive leads were just floated to the RV apex. With active fixation leads the implanter has more options for more physiologic and safe lead placement.
RV apical pacing produces a left bundle branch type conduction pattern in the ventricles and leads to delayed activation of LV compared to RV. When a similar LBBB occurs in native conduction system in patient with pre-existing LV failure, it was shown that LV systolic function improves by pacing both ventricles together as done in CRT – therefore the assumption is that by creating an LBBB activation pattern by RV apical pacing, we are causing an iatrogenic dyssynchrony which leads to LV dysfunction
RV Septal Pacing
Another option is to pace both ventricles using different leads at the same time. At the moment this is reserved for cardiac re-synchronization therapy in patients with pre-existing stage C LV failure as the implantation of the LV pacing lead has its own plethora of issues. Please remember that in this discussion we are dealing with patients with normal LV function and our aim is to prevent LV failure in the very long term and not to improve pre-existing LV failure. Standard pacing in patient with pre-existing LV failure has a complex decision making process and if there is a anticipation of more than 40% requirement of ventricular pacing, the current consensus is to implant a BiV device.
How about evidence for physiologic pacing ? Sadly the state of evidence for long term benefits of septal pacing is equivocal – even in 2019 – because all the attention is going towards direct his bundle pacing
But – It’s a pleasure to see a narrow complex paced rhythm rather than a wide complex paced rhythm. Narrower the QRS, happier the me !
Personally, the biggest benefit I see from septal pacing is the relative safety and ease of lead extraction. More and more young patients are undergoing device implantations and the indications for lead extraction in later years is rising. Lead extraction it self is seeing major progress but undoubtedly a septal lead is less of a risk than a apical lead to extract
The second reason – a properly placed septal lead has virtually no risk of leading to a tamponade. I have seen many cases of pericaridal effusions following apical placement of leads and septal pacing is definitely safe in this aspect