Vol 41 # 3 September 2009 - Kma.org.kw

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External Non-Invasive Cardiac Pacemaker: Evaluation of Usefulness, Function and Capture...
September 2009
PATIENTS AND METHODS
Study patients:
Initially we enrolled 162 patients with
symptomatic bradycardia or asystolic cardiac
arrest but only 140 patients (124 male and 16
female) with a mean age of 55.3 ± 6.4 years were
included in the study. Twenty-two patients were
excluded due to incomplete data. All patients were
admitted in the coronary care unit (CCU) of the
department of medicine with hemodynamically
significant bradyarrhythmias between January 1997
and September 2004. All patients were evaluated
clinically by looking at history, physical examination,
12-leads ECG, chest X-ray, routine laboratory
investigations and echocardiography and Doppler
study. Thirty- eight patients had type 2 diabetes
mellitus but no patient had ketoacidosis. Twentythree
patients had history of chronic obstructive
pulmonary disease (COPD). Twenty-six patients
had history of coronary artery bypass graft (CABG)
surgery with post-sternotomy scar. The study was
approved by the hospital ethical committee.
Methods:
We trained all CCU nursing staff to perform
transcutaneous pacing in one to two-hour classes.
Informed consent was obtained from patients for
insertion of intravenous temporary pacemaker (ITP)
if necessary.
Pacing devices:
Three different new pacemaker devices were used
in the study and all were devices of the modified
version which was introduced in 1983 [8] .
1. CardioMaster device in 48 patients
2. CardioLife device in 40 patients
3. CardioServe device in 52 patients
The NTP consists of an electric cardiac pacemaker
combined with a cardiac monitor and a paper
recorder. The pacemaker monitor senses voltage
changes of appropriate amplitude and slew rate
from cardiac depolarizations or pacemaker stimuli.
It provides audible and visual signals of such events
with oscilloscopic and paper recordings, displays
their rate and rings an alarm if selected limits are
exceeded. The pacemaker functions in the demand
mode (VVI), emitting stimuli that are synchronized
to the sensed electrical signals at escape rates up to
180 beats/minute and an amplitude upto 140 mA.
Large stimulating electrodes of high impedance
are placed on the apex and at right upper border
of the sternum and monitor leads are attached. The
pacemaker output is lowered to zero and the power is
turned on. The pacemaker amplitude is then increased
until a stimulated QRS-T response follows the artifact
immediately and suppresses any intrinsic complex
that might fall in its refractory period (Fig. 1). The
Fig. 1: Bradycardiac patient with signs of hypoperfusion. The
demand pacemaker (VVI) was attached to the patient and the
current was raised until capture.
stimulus amplitude is kept just above this stimulation
threshold. In emergency situations, stimulation may
be started within seconds.
Treatment protocol:
Asystolic cardiac arrest patients: Asystole is
defined as the absence of electrical activity greater
than 1 mm (calibrated to 10 mm per millivolt) for at
least 15 seconds [10] . Cardiopulmonary resuscitation
was started immediately with endotracheal
intubation by an anesthetist followed by placing of
transcutaneous NTP leads and adjusting the current
for capturing the heart myocardium.
Symptomatic bradycardia patients: Patients with
hemodynamically significant sinus bradycardia,
complete heart block with idioventricular rhythm and
escape junctional rhythm were indicated for NTP.
Evaluation of pacemaker capture:
1. Carotid pulse rate and volume: by palpating right
or left common carotid artery in the neck between
medial border of the sternomastoid muscle and the
trachea
2. Blood pressure response: non-invasive
measurement of BP by an electronic device
3. Monitor rhythm: as detected on cardiac monitor
screen display
4. Echocardiogram: transthoracic parasternal long
and short axis views were obtained to detect
presence or absence of myocardial wall motion
as an indication of proper electrical capture of the
NTP stimulation
Collection of data and clinical outcomes:
1. Variables related to the emergency device such as
type of external pacemaker, current (mA), pulse
duration (msec) and pacing electric capture
2. Variables related to the hemodynamically significant
bradycardia patients such as etiology, diagnosis