External Cardiac Pacing
Dr PG Jones
MBChB, FACEM
Emergency Medicine Specialist
Auckland And Starship Hospitals
History
• 1791 Galvani
– Frog experiments
• 1892 Duchenne
– Resuscitated child (submersion )
• One leg electrode, tapped chest with other
Zoll
• 1950’s
– 1st successful TCP and monitor
• 3cm electrode
• 120V AC for 2msec
• 1980’s
– 80cm2 electrode, 40msec pulse duration
•  stimulation threshold x 6
– More tolerable = renewed interest
• FDA approval 1982
Indications
• Symptomatic Bradycardia
– 50-100% survival to discharge rates
• AMI with certain ECG rhythms
– Mobitz type II second-degree AV block
– Third-degree heart block
– Bilateral BBB
– Newly acquired or age-indeterminate LBBB, LBBB and
LAFBa, RBBB, and LPFBa
– RBBB or LBBB and first-degree AV block
Indications
• Asystole ?
– Most studies no benefit
– Benefit shown for <5min post arrest
• 2/5 survived neurologically normal
• Tachyarrythmia
– 57-95% termination of VT
– 4-24% acceleration of VT
How To Do It
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Inform the patient
Plug in module
Attach pads
Set rate 70
Dial up mAmps
Set mode (demand
first)
• Start
• Monitor and adjust as
needed
Capture
• Feel the pulse
– mechanical capture
• 2nd monitor to determine electrical capture
– Unless monitor blanks out skeletal muscle
contraction
• Ultrasound
Not Capturing
Paced Beat
IABP
Native Beat
Current
• 65-100mA (Unstable patient)
• 50-70mA (Volunteer)
– 90% tolerate for 15min
• Pain  Current / area (up to 10cm2)
Energy
• 100mA for 20msec = 0.1J
(with normal TTR, 50 Ohm)
• Threshold for discomfort 1-2J
(Skin tingling)
• Does not damage the myocardium
Discomfort
• Skeletal muscle contraction is the cause
– Often the limiting factor
– Attempt AP placement to minimise
• Left scapula and midline chest
• Use lowest effective current
• Sedation as needed
• CPR is safe!
Muscle Contraction
Haemodynamics
• Cardiac arrest and CHB
– Comparable to transvenous pacing
• Sinus
– Reduced cardiac output
– No ‘atrial kick’ (atrial capture threshold too
high)
References
• Bocka JJ eMedicine
http://www.emedicine.com/emerg/topic699.htm
– Updated 2002 April 24, excellent summary article
• Bocka JJ Ann Emerg Med 1989 Dec; 18(12):1280-6
• Hedges JR Pacing Clin Electrophysiol 1991
Oct;14(10):1473-8
• Barthell E Ann Emerg Med 1988 Nov;17(11):1221-6
• Klumbies A Z Gesamte Inn Med 1988 Jul 1;43(13):348-52.