When you are growing up and your parents tell you that recreational drugs are bad (and rightly so), but then you become a teenager and you question this, maybe even do your own research (what a night that was!) and you become more informed…
In the same way, Pacemaker Technicians are currently brought up accepting two things.
2. This can be avoided by Septal Lead Pacing.
RV Apex Pacing
When the right Ventricular Apex is paced
the electrical signal moves through a large portion of the Right Ventricle first before moving across and initiating a contraction in the Left Ventricle. Therefor the right heart starts to contract before the left heart giving rise to a twisting of the heart and an asynchronous (not synchronised) heart beat. If this continues for a prolonged period of time, the differing strains on the heart can lead to remodelling and in turn are said to increase the chance of Atrial Fibrillation
and Heart Failure
The short answer is Yes, the long answer is YEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEES!
So here we have 6 reasonably large scale studies, the general consensus of which is that RV Apex Pacing increases the incidence of Atrial Fibrillation and Heart Failure.
Perspective – from my previous posts on RV Apex Pacing being linked to AF and HF. I realise that this is worrying for some patients. As a caveat I want to just point out a few things. Firstly not everyone who is paced in the RV Apex ends up with AF and Heart Failure – it just increases the risk. Secondly, RV Apex Pacing is often a lot better than the alternative – which will severely impact on someones quality of life. My post on Heart Failure will help put that in perspective too…
SO RV APEX PACING IS GREAT – but not perfect.
RV Septal Pacing
The idea behind RV Septal Pacing
, His Bundle Pacing or Right Ventricular Outflow Tract Pacing is simple. By starting the pacing stimulation near/at the His Bundle you induce a more natural heart beat. A more natural heart beat
will be without mechanical changes in the contraction of the heart and in turn should avoid remodelling of the heart that leads to Atrial Fibrillation and Heart Failure
Why a more natural heart beat? well the pacing stimulus activates very little Right Ventricle before the His Bundle is captured. This instigates a rapid signal down the septum and into the Pirkinje Fibres. This is the pathway a natural heart beat
This time the right Ventricle and Left Ventricle contract simultaneously.
42 Patients were enrolled in a study that investigated this theory and seemingly confirmed that RV septal pacing showed the advantages of shorter contraction time, less ventricular asynchrony, better mechanical performance in comparison with apical pacing. Yu CC, et al. Septal pacing preserving better left ventricular mechanical performance and contractile synchronism than apical pacing in patients implanted with an atrioventricular sequential dual chamber pacemaker. Int J Cardiol . 2007;118:97.
SO, the theory is all there as of yet there is not an abundance of studies…
Lets scan over some….
12 Patients who had Permanent AF and Dilated Cardiomyopathy (an enlarged Left Ventricular Cavity) were paced directly in the HIS Bundle (DHBP) – this showed an improvement in Cardiac Function and the Cardiomyopathy. Deshmukh P, et al. Permanent, direct His-bundle pacing: a novel approach to cardiac pacing in patients with normal His-Purkinje activation. Circulation . 2000;101:869
A Meta analysis of 9 studies (217 Patients in all) found that Right Ventricular Outflow Tract Pacing has a moderate but statistically significant haemodynamic improvement (more efficient heart beat) when pacing in the outflow tract compared to the RV Apex. de Cock CC , et al. Comparison of the haemodynamic effects of right ventricular outflow-tract pacing with right ventricular apex pacing: a quantitative review. Europace . 2003;5:275.
A study of 150 patients that looked into RV Apex pacing and RV Outflow Tract Pacing, found that RV outflow tract pacing appears to improve medium and long term survival in those with over 70% pacing burden. The study concluded that further investigation was required because of the small sample size. Vanerio G, et al. Medium- and long-term survival after pacemaker implant: Improved survival with right ventricular outflow tract pacing. J Interv Card Electrophysiol . 2008;21:195.
28 Patients were also enrolled into a study comparing Septal Pacing and Apex Pacing in THE SAME Patients. The study found that Left Ventricular Ejection Fraction was maintained during RV Septal pacing but deteriorated during RV Apex pacing. Victor F, et al. A randomized comparison of permanent septal versus apical right ventricular pacing: short-term results. J Cardiovasc Electrophysiol . 2006;17:238.
Another 12 Person study found that direct His bundle pacing is superior to RV Apex Pacing in reducing mitral regurgitation and left ventricular dyssynchrony. Zanon F, et al. Direct His bundle pacing preserves coronary perfusion compared with right ventricular apical pacing: a prospective, cross-over mid-term study. Europace . 2008;10:580.
This is all looking pretty straightforward – they may need more numbers in the studies but they certainly seem to be pointing in the right direction.
However there are contrasting studies….
One such study found that after 18 months of pacing either the Apex or the Septum in 98 Patients – there was no significant difference in three markers of heart failure (Exercise capacity, Left Ventricular Ejection Fraction and BNP levels). Kypta A, et al. Long-term outcomes in patients with atrioventricular block undergoing septal ventricular lead implantation compared with standard apical pacing. Europace . 2008;10:574.
In conclusion it does seem to look promising for Septal Lead positions but there really is a need for larger numbers and longer term studies before we can be sure. Also consider is a septal lead more likely to move?
Would I want a septal lead – YES but not because I am convinced it is markedly better physiologically… but because it sure doesn’t seem to be worse than RV Apex Pacing – so why not.
Moving forward, what is the answer…?
Well it may be Septal pacing… other areas look into just LV Pacing. I am inclined to predict a gradual increase in Biventricular Pacing in those that do not have pre-existing heart failure – but will have a high lifetime pacing burden. But thats my opinion and until today I had always thought Septal Pacing was the answer 🙂
Further explanation around these topics and more is available in the book Pacemakers Made Easy by Carl Robinson.
Time to tow my dads car to the garage!!
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Thanks for Reading
Image courtesy of ddpavumba, / FreeDigitalPhotos.net