Clin. Cardiol. 12, 412-414 (1989)
Runaway Pacemaker: A Still Existing Complication and Therapeutic
Guidelines
H.
MICKLEY,
M.D., c. ANDERSEN,
M.D., L.HEDEMANNNIELSEN,
M.D.
Departments of Cardiology B and Clinical Physiology, University Hospital, Odense, Denmark
Summary: Runaway pacemaker is a rare, but still existing potential lethal complication in permanent pacemakers. Within 4 % years, we saw two cases of runaway
pacemaker in patients with multiprogrammable, VVI
pacemakers (Siemens-Elema, Model 668). In both cases
a pacemaker-induced ventricular tachycardia (rate 240260 beatdmin) was documented. One patient died. Runaway pacemakers must be exchanged as soon as possible.
Until this can be accomplished, different emergency
maneuvers should be tried. As documented in the cases
presented, placing a magnet over the pacemaker may result
in a lower, more physiological pacing rate. Reprogramming the pulse generator to a lower output or the use of
external chest wall overdrive stimulation may also be successful, but these procedures require the presence of an
adequate escape rhythm. If this is not the case or the former maneuvers have failed, an external pacemaker may
be connected to the permanent pacing lead. Thereafter,
the lead can be safely cut. As an alternative, a temporary
transvenous pacing lead may be established prior to disconnecting the permanent pacing lead.
Key words: pacemaker failure, runaway pacemaker
Introduction
In a runaway pacemaker the pacing rate is inappropriately high due to battery failure or malfunction. In older
Address for reprints:
Hans Mickley, M.D.
Depanment of Cardiology B
University Hospital
DK-5000 Odense C, Denmark
Received: December 24, 1988
Accepted: April 1, 1989
permanent pacemakers pacing rates from 100 to 2 100/min
have been described,'-3 and the result may be a
pacemaker-induced tachycardia. Despite improved
safeguards in design and evolution of protection or security circuits in modem pacemakers, the runaway phenomenon has not been eliminated. As the mortality rate of a
runaway pacemaker-induced ventricular tachycardia is
30-40%,2-5
knowledge of this rare, but still existing complication should be widespread and immediate therapeutic guidelines are needed in order to improve the poor
prognosis.
Case Report 1
In 1979 an 81-year-old woman suffering from seconddegree sinoatrial block had a VVI pacemaker implanted.
As the patient had syncope and battery depletion was approaching, the pulse generator was exchanged in May
1982 with a Siemens-Elema multiprogrammable VVI
pacemaker, Model 668. Lead measurements revealed a
chronic stimulation threshold at 3.4 V (pulse duration 0.5
ms) and the resistance was 522Cl. Because of the rather
high stimulation threshold, output was programmed to 10
V. At follow up in August 1982, the rate was 70/min,
stimulation threshold 3.1 V (pulse duration 0.72 ms), and
output unchanged at 10 V. In December 1982, the patient was brought to the emergency room with clinical
cardiac arrest. The ECG showed an irregular pacing rate
of 210-240/min with 1: 1 ventricular capture (Fig. 1, top).
DC defibrillation with 300 J did not affect the tachycardia.
When a magnet was placed over the battery, the pacing
rate fell to 70/min (Fig. 1, bottom), however resuscitation failed, mainly due to cerebral anoxia. Measurement
of the pacemaker unit following postmortem explantation
revealed an amplitude of 1.4-2.0 V and a runaway rate
of 220-300/min, when connected to a load of 500 Q.
Case Report 2
In December 1981, a 63-year-old man suffering from
sinus node dysfunction with extreme bradycardia had an
H . Mickley et a/.: Runaway pacemaker
413
Siemens3
FIG 1 (Top) ECG o n arrival showing a pacemaker-controlled
tachycardia with ventncular rate up to 210-240/min (50 mm/s). (Bottom) After placing a magnet over the pulse genelator, the pacemaker
rate declined to 701min (50 mm/s)
.-
,
~ ~# J - 2-’ ~ ” la&-*>-, ,,1
j
/11/
/,
,
,I,.
.,,_
~ ,r * . , ~ y ,
FIG 2 The ECG shows a pacemaker-controlled tachycardia wlth
ventricular rate 260/min.
sources, which allows a hermetically sealed case.
Nevertheless, as documented in the present case reports,
runaway pacemaker is still a serious complication, and
the failing pacing unit must be removed as soon as possible. Unfortunately, literature gives only scant information on the emergency maneuvers which should be tried
until surgical replacement of the defective pulse generator can be done.
Treatment with antiarrhythmic agents or DC shock is
ineffecti~e.~,’
A magnet placed over the pacemaker, as
illustrated in both the cases presented, resulted in a more
physiological pacing rate. Although one of the patients
died, this 83-year-old woman had suffered from clinical
cardiac arrest for several minutes, before the magnet
maneuver was tried. Measurement of pacemaker output
after explantation revealed an amplitude which should
have been too low to stimulate the right ventricle. We have
no explanation for this phenomenon, but the DC defibrillation might have damaged the pacemaker further.’ If a
magnet fails to inhibit the pacemaker-induced
t a ~ h y c a r d i a , ~ ,other
~ - ’ ~ emergency treatment should be
tried. Reprogramming the pulse generator to lower outp ~ t , ~ .or
I l partial inhibition of the pacemaker by external
Discussion
chest wall overdrive stimulation has been s u ~ c e s s f u l . ~ ~ ~
In older pacemakers runaway used to be the result of
Both these methods require the presence of an adequate
escape rhythm which may not always be the
leakage of tissue fluid into the pulse g e n e r a t ~ r . ~ . ~ . spontaneous
~
However, the incidence of the runaway phenomenon has
c a ~ e . ~Chest
. ~ , wall
~
stimulation also demands that the
declined, and the reason for this is generally believed to
pulse generator is able to sense the external ~ t i m u l i . ~
he the incorporation of electrical safeguards built into the
If emergency intervention still is not successful, and if
newer pacemakers, added to the use of lithium power
the patient is hernodynamically unstable, the permanent
unipolar VVI pacemaker implanted. In February 1982,
because of skeletal muscular stimulation due to a defective coating, the pacemaker was replaced by a SiemensElema, multiprogrammable VVI pacemaker, Model 668.
In April 1987 the stimulation threshold was I .3 V (pulse
duration 0.74 ms). In July 1987 the patient was admitted
to the local hospital. The ECG showed a pacemakerinduced tachycardia 260/min with 1:1 ventricular capture
(Fig. 2), but the patient was conscious with blood pressure 90/60 mmHg. A magnet placed over the pulse generator immediately reduced the pacing rate to a fixed rate
at 70- 120lmin. The patient was hernodynamically stable
and was transferred to a pacemaker center, where the pacing unit was immediately replaced. The electrode had no
defects with stimulation threshold 1.9 V (pulse duration
1 .O ms), and a resistance of 815 9.Measurements of the
failing pacemaker unit after explantation revealed fixed
rate pacing at 70/min, output 4.6 V, and no runaway
phenomenon. Revision of the pacemaker by the manufacturers revealed a “leak current” of the security circuit,
and this was sufficient to induce the high pacing rate.
414
Clin. Cardiol. Vol. 12, July 1989
pacing lead should be connected to an external pacemaker, after which the lead can be safely cut.4.5.9Alternatively,
a temporary transvenous pacing system should be established prior to cutting the permanent
If equipment for transthoracic pacing is available,” this may also
be applied when disconnecting the permanent pacing system. If the patient is hemodynamically stable, pacemaker
exchange can be performed in a more ambient atmosphere,
and if the procedure is done in a sterile manner, the permanent lead may be used again for implantation of a new
permanent pacing unit.9
Recent reports illustrate that life-threatening arrhythmias
may result from therapeutic inadiation of newer multiprogrammable pacemakers which employ complementary metal oxide semiconductors (CMOS). These appear to be more Sensitive to ionizing radiation than the
bipolar semiconductors used in older pacemakers. I s
Although runaway pacemaker is a rare complication in
modern pacemakers, the phenomenon still occurs. Therefore, all physicians must be familiar with the emergency
treatment protocol to follow when confronted with this
potentially lethal complication.
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