Although right ventricular (RV) apical pacing is an established practice since the first pacemaker implant in early sixties, recent studies have highlighted its deleterious effects. This has led to a concept of ‘minimizing RV pacing’ to prevent long term negative effects of RV pacing. New features have been added to pacemaker models to achieve this aim. This article looks at negative effects of RV pacing and how to minimize it.

1. IS RIGHT VENTRICULAR PACING A BOON OR A CURSE?

2. Review Article
Cardiac pacing has come a long way since the first
implant almost 50 years ago. Not only has there been
advancement in the hardware and techniques of
implantation, but also there has been a change in the
concept of cardiac pacing. Traditionally endocardial
ventricular leads are placed in the right ventricular (RV)
apex. From being one of the most innovative inventions in
modern medicine, questions have been raised on the
detrimental effects of RV pacing after over four decades of
successful pacing.
Cardiac pacing continues to be the only effective and
established treatment of choice for patients with sick sinus
syndrome (SSS) and atrioventricular (AV) conduction
blocks. Although the earliest pacemaker was a single
chamber ventricular pacemaker, 1980’s saw the advent of
dual chamber pacemaker and the term ‘physiological
pacing’ was coined. In contrast to single chamber
ventricular (VVI) pacemaker, dual chamber ‘physiological
pace-makers’ maintain atrio-ventricular timing and
synchrony mimicking normal sequence of atrial and
ventricular contractions. This in return results in better
hemodynamics and better quality of life. A number of
publications followed documenting the relative advantage
of dual chamber pacing in respect to better clinical
outcomes, fewer episodes of atrial fibrillation, lesser
strokes, better hemodynamics and better quality of life. For
the next 20 years dual chamber pacing remained the
preferred mode of pacing for patients of SSS and AV
blocks as endorsed in the American and European
guidelines.
Although a number of studies reported less favourable
outcomes of VVI pacing in patients with sick sinus
syndrome compared to AAI pacing [1], it is only in the
recent past that questions have been raised in clinical
IS RIGHT VENTRICULAR PACING A BOON ORACURSE?
Rajnish Sardana
Senior Consultant Cardiologist and Electrophysiology, Indraprastha Apollo Hospitals, Sarita Vihar, New Delhi 110 0176, India.
E-mail: sardana_r@hotmail.com
Although right ventricular (RV) apical pacing is an established practice since the first pacemaker implant in
early sixties, recent studies have highlighted its deleterious effects. This has led to a concept of ‘minimizing RV
pacing’ to prevent long term negative effects of RV pacing. New features have been added to pacemaker
models to achieve this aim. This article looks at negative effects of RV pacing and how to minimize it.
Key word: Right ventricular pacing.
studies about the detrimental effects of RV apical pacing.
In a sub study of MOST [2] (mode selection trial) trial,
in patients with sinus node dysfunction it was
demonstrated that there was a strong association between
RV pacing and risk of heart failure hospitalizations as
well as atrial fibrillation (AF) episodes in both the
‘physiological dual chamber’ pacing and single chamber
VVI pacing. It also demonstrated that higher percentage
of pacing (>40% in DDDR & >80% in VVIR) was
associated with higher incidence of heart failure
hospitalisations and atrial fibrillation.
The ‘Dual chamber pacing or ventricular backup
pacing in patients with an implantable defibrillator’
(DAVID) [3] trial demonstrated that in patients with
LVEF <40% and no indication of pacing, patients with
dual chamber ICD compared to single chamber ICD, had
higher incidence of combined end-point of
hospitalization for CHF and death and was linked to
unnecessary RV pacing. The Multicenter Automatic
Defibrillator Implantation Trial II (MADIT II) [4] also
showed that patients with dual chamber ICD’s had higher
heart failure admissions and hypothesized to be related to
higher percentage of right ventricular pacing.
PATHOPHYSIOLOGY OF DETRIMENTAL
EFFECTS OF RV APICAL PACING
These clinical trials brought to light the evidence
highlighting the negative effects of RV apical pacing. It
was hypothesized to be due to abnormal electrical and
mechanical activation pattern (Dyssynchrony) of the
ventricles, as during RV apical pacing the electrical wave
front propagates through the cardiac muscle, which is
much slower conducting, instead of his-purkinje system
and is from apex to base rather than base to apex of
Apollo Medicine, Vol. 8, No. 3, September 2011 198

3. Review Article
199 Apollo Medicine, Vol. 8, No. 3, September 2011
ventricles. This leads to less efficient contraction of left
ventricle and now better understood since the advent of bi-
ventricular pacing.
Further evidence has been provided by animal study
documented pathological changes in the cardiac muscle
within months of pacing. In a small study on 14 patients
with congenital heart block [5], Karpawich showed that
long term RV apical pacing induced histo-pathological
changes including intracellular & mitochondrial changes,
myocardial disarray along with degenerative fibrosis in
the endomyocardial biopsy specimens.
Similarly perfusion defects, changes in LV wall
thickness and LV remodelling has been reported following
RV pacing in various studies.
CONCEPT OF MINIMIZING VENTRICULAR
PACING
Based on increasing data on detrimental effects of RV
pacing, it is now desired that effort should be made in
every patient to avoid or decrease RV pacing to the
minimum. In January 2005, AHA endorsed this by
releasing an advisory stating that “for patients who need a
dual chamber pacemaker, efforts should be made to
program the device to minimize the amount of ventricular
pacing when atrioventricular conduction is intact”.
How can this aim of avoiding or minimizing RV
pacing be achieved? The first step would be to identify
patients in whom this can be achieved, which would
include (i) patients of sinus node dysfunction with normal
AV node conduction (ii) ICD patients with no indication
of pacing and (iii) significant percentage of patients with
AV block who have intermittent conduction block. All
these patients can be either (a) implanted with pacemaker
models specially designed for the purpose e.g. MVP
model from Medtronic inc., which can switch from
AAI(R) to DDD(R) back and forth depending on AV
conduction or (b) programming the pacemaker in a way to
promote intrinsic AV conduction whenever present.
Almost all present day pacemakers have this additional
feature where the AV delay (corresponding to the PR
interval of surface ECG) is prolonged intermittently to
look for intrinsic AV conduction and if present kept at the
extended value ofAV delay. Whenever there is no intrinsic
AV conduction AV delay is returned to the nominal value.
With these tailor made programming, unnecessary RV
pacing can be reduced down to less than 10%. Clinical
benefit of minimal ventricular pacing has already been
shown in a large RCT (SAVE-PACe) [6] where in patients
with sinus node dysfunction there was 40% relative risk
reduction in development of persistentAF.
ALTERNATE SITE PACING / BIVENTRICULAR
PACING
As an alternative to RV apical pacing other site/sites
like RVOT, His bundle pacing and RV septal pacing has
been explored in clinical trials with encouraging results
but have not conclusively shown to be superior to translate
into guidelines or recommendations. However
biventricular pacing (CRT-P) has been shown to be
superior to conventional RV apical pacing and is
recommended for patients who have bradycardic
indication of pacing and LV dysfunction.
CONCLUSION
Right ventricular pacing is the established and
undisputed treatment of choice for patients with
bradycardia despite its detrimental long term effects. So
for patients who need RV pacing it could be lifesaving and
therefore ‘necessary evil’ while for those patients who
don’t need it or need it intermittently, it could be a curse.
Efforts should be made to minimize ventricular pacing
whenever possible by tailoring programming in every
patient individually by the cardiac electrophysiologist. In
selective patients alternative site pacing or bi-ventricular
pacing could be an option.
REFERENCES
1. Andersen HR, Nielsen JC, Thomsen PE, et al. Long-term
follow-up of patients from a randomised trial of atrial
versus ventricular pacing for sick-sinus syndrome:
Lancet 1997; 350: 1210-1216.
2. Lamas GA, Lee KL, Sweeney MO, et al. for the MOST
Investigators. Ventricular pacing or dual chamber pacing
for sinus node dysfunction. N Engl J Med 2002;
346:1854-1862.
3. The DAVID Trial Investigators. Dual-chamber pacing or
ventricular backup pacing in patients with an implantable
defibrillator: the Dual Chamber and VVI Implantable
Defibrillator (DAVID) trial. JAMA 2002; 288: 3115-3123.
4. Moss AJ, Zareba W, Hall WJ, et al. Prophylactic
implantation of a defibrillator in patients with myocardial
infarction and reduced ejection fraction. N Engl J Med
2002; 346: 877-883.
5. Karpawich PP, Rabah R, Haas JE. Altered cardiac
histology following apical right ventricular pacing in
patients with congenital atrioventricular block. Pacing
Clin Electrophysiol 1999; 22: 1372-1377.
6. Sweeney MO, Bank AJ, Nsah E, et al. for the Search AV
Extension and Managed Ventricular Pacing for
Promoting Atrioventricular Conduction (SAVE PACe)
Trial. Minimizing ventricular pacing to reduce atrial
fibrillation in sinus-node disease. N Engl J Med. 2007;
357(10): 36-44.

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