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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 28, No 2, March/April 2017
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AFRICA
haemodynamic sequelae of right ventricular-only pacing.
Symptoms range from fatigability to syncope and occur during
ventricular pacing. Postulated mechanisms include loss of
AV synchrony, vasodepressor reflexes, and retrograde atrial
activation. One of the ways to avoid pacemaker syndrome is
maintenance of AV synchrony with a dual-chamber pacemaker
with atrial tracking.
The overall incidence of pacemaker syndrome is unclear,
with different studies reporting different results. In the Mode
Selection Trial (MOST), pacemaker syndrome incidence was
approximately 18%.
6
According to Ausubel and Furman, the
estimated incidence of pacemaker syndrome ranged from seven
to 20%.
7
The aetiology of pacemaker syndrome is poorly understood,
but several risk factors are associated with its development:
•
Low intrinsic rate and high ventricular pacing rate, as noted in
our patient, results in high percentage of ventricular pacing,
therefore more AV dyssynchrony, and this may also explain
the development of left ventricular systolic dysfunction.
•
Intact ventricular–atrial (VA) conduction poses a greater risk
for the development of pacemaker syndrome.
•
Patients with non-compliant ventricles, such as in dias-
tolic dysfunction, heart failure, hypertrophic cardiomyopa-
thy, among others, are particularly sensitive to loss of atrial
contribution to ventricular filling.
8
•
Ventricular pacing leads to decreased cardiac output, with the
resultant increase in left atrial pressure and left ventricular
filling pressure.
5
A major cause of AV dyssynchrony is VA conduction.
Retrograde conduction leads to non-physiological timing of
atrial contraction in relation to ventricular contraction. It
should, however, be noted that many conditions other than VA
conduction promote AV dyssynchrony.
Conventional non-physiological right ventricular pacing has
deleterious effects on left ventricular systolic function.
2
Yu
et
al.
reported that conventional right ventricular apical pacing
resulted in adverse left ventricular remodelling and therefore a
reduction in LVEF in patients with normal systolic function.
3
From the MOST and DAVID trials,
4
it has become clear
that a high amount of right ventricular apical pacing may be
associated with a worse clinical outcome, including worsening
left ventricular systolic function, new-onset congestive cardiac
failure, as well as tachyarrhythmias, such as atrial fibrillation.
Unfortunately, it remains unclear as to the exact amount of right
ventricular apical pacing that negatively affects cardiac function.
Conclusion
This case demonstrated that switching of atrial and ventricular
leads at the pacemaker header resulted in pacemaker syndrome
in a patient with a dual-chamber permanent pacemaker. The
syndrome was due to incorrectly connected leads, resulting in
ventricular paced atrial sensed (VP-AS), essentially producing
the VVI pacing with retrograde conduction and loss of AV
synchrony. This case also illustrates the possibility of right
ventricular pacing-induced left ventricular dysfunction and
highlights the need to maintain a high level of concentration
during device implantation.
References
1.
Hamdi A, Jastrzebski M, Hawas JM. A dual chamber pacemaker leads
switch at the header – An electrocardiographical and clinical picture, a
case report.
J Sulaimani Med Coll
2013;
3
(2): 131.
2.
Tops LF, Schalij MJ, Bax JJ. The effects of right ventricular apical
pacing on ventricular function and dyssynchrony: implications for
therapy.
J Am Coll Cardiol
2009;
54
(9): 764–776.
3.
Yu C-M, Chen JY-S, Zhang Q,
et al
. Biventricular pacing in patients
with bradycardia and normal ejection fraction.
N Engl J Med
2009;
361
: 2123–2134.
4.
Wilkoff BL, Cook JR, Epstein AE,
et al.
Dual-chamber pacing or
ventricular backup pacing in patients with an implantable defibrillator:
the Dual Chamber and VVI Implantable Defibrillator (DAVID) trial.
J
Am Med Assoc
2002;
288
: 3115–3123.
5.
Pacemaker syndrome, Medscape Reference.
http://emedicine.medscape.com/article/159706-overview.
6.
Link MS, Hellkamp AS, Estes NAM,
et al
. High incidence of pace-
maker syndrome in patients with sinus node dysfunction treated with
ventricular-based pacing in the Mode Selection Trial (MOST).
J Am
Coll Cardiol
2004;
43
(11): 2066–2071.
7.
Ausubel K, Furman A. The pacemaker syndrome.
Ann Intern Med
1985;
103
(3): 420–429.
8.
Pacemaker syndrome, Cardiology.
http://cardiologyheartt.blogspot.
com/2014/01/pacemaker-syndrome.html.