Transcript Surgical diathermy and pacemakers - The American Association for

Pacemaker
Supparerk Prichayudh M.D
Normal EKG
P wave = atrial depolarization
QRS wave = ventricular depolarization
T wave = ventricular repolarization
Outline
1.
2.
3.
4.
5.
6.
Indications
Types
Modes of pacemaker
Temporary pacemaker
Problems with pacemakers
Surgical diathermy and pacemakers
Indications
Indication: Symptomatic bradycardia
• Sinus node dysfunction
• 3° and advanced 2° AV block
• Bradycardia associated with AMI
Prophylactic Implant
• Patients with LBBB requiring Swan-Ganz
catheter placement
• Cardioversion in the setting of SSS
• New BBB in the setting of acute endocarditis
• Peri-operatively
Sick Sinus Syndrome
ACLS:
First-Degree Atrio-Ventricular (AV) Block
. P wave precedes every QRS complex
. PR interval > . second and constant
Atrial rate = ventricular rate
4. Asymptomatic, requires no Rx.
ACLS:
Second-Degree Atrio-Ventricular ( AV) Block
Mobitz type I (Wenckebach)
1 . P P in t e r v a l ( a t r ia l r a t e ) is
co n st an t
2 . P R in t e r v a l is g r a d u a lly
p r o lo n g e d  A V b lo c k ( n o
v e n t r ic u la r r e sp o n se )
ACLS:
Second-Degree Atrio-Ventricular ( AV) Block
Mobitz type II
1 . P P in t e r v a l ( a t r ia l r a t e ) is
c o n st a n t , fo llo w e d b y Q R S.
2 . S u d d e n ly , A V b lo c k o c c u r s ( n o
v e n t r ic u la r r e sp o n se a f t e r P
w ave).
ACLS:
Third-Degree Atrio-Ventricular ( AV) Block
1 . N o t r a n s m is s io n o f e le c t r ic a l a c t iv it y f r o m
a t r iu m ( P w a v e ) t o v e n t r ic le ( Q R S ) .
2 . V e n t r ic u la r c o n t r a c t io n = e ct o p ic b e a t .
3 . P P in t e r v a l ( a t r ia l r a t e ) is c o n s t a n t a n d > R R
in t e r v a l ( v e n t r ic u la r r a t e ) , P R in t e r v a l is
v a r y in g .
Types
1. Temporary
2. Permanent
Permanent pacemaker
Box = pulse generator
Pacemaker Leads
• Pacemaker leads are the conduits from the
generator to the myocardium. Most leads are
implanted transvenously.
• Wiring systems
– Unipolar
• One electrode on the heart (-)
• Signals return through body fluid and tissue to the
pacemaker (+)
– Bipolar
• Two electrodes on the heart (- & +)
• Signals return to the ring electrode (+) above the lead
(-) tip
UNIPOLAR AND BIPOLAR PACING
Modes of pacemaker
NASPE-BPEG Generic Five-Position Code
Position
I
II
III
IV
V
Parameter
measured
Chamber(s)
paced
Chamber(s)
sensed
Response to
sensing
Rate modulation
Anti-tachyarrhythmia
function
Possible
values
O = None
O = None
O = None
O = None
O = None
A = Atrium
A = Atrium
I = Inhibited
R = Rate
modulation on
P = Pace
V = Ventricle
V = Ventricle
T = Triggered
S = Shock
D = Dual (A +
V)
D = Dual (A +
V)
D = Dual (I +
T)
D = Dual
NASPE, North American Society of Pacing and Electrophysiology; BPEG, British Pacing and Electrophysiology Group
• First letter: Chamber Paced
•
•
•
•
V- Ventricle
A- Atrium
D- Dual (A & V)
O- None
• Second letter: Chamber Sensed
•
•
•
•
V- Ventricle
A- Atrium
D- Dual (A & V)
O- None
• Third letter: Sensed Response
•
•
•
•
T- Triggers Pacing
I- Inhibits Pacing (demand)
D- Dual (synchronous)
O- None (asynchronous)
Chamber Paced
– Atrial pacing
• Intact AV conduction system required
– Ventricular pacing
• Loss of atrial kick
– Atrial/Ventricular pacing
• Natural pacing
• Atrial-ventricular synchrony
Commonly used modes
•
•
•
•
•
AAI - atrial demand pacing
VVI - ventricular demand pacing
DDD – Dual chamber pacemaker
AOO - atrial asynchronous pacing
VOO - ventricular asynchronous pacing
ventricular asynchronous pacing
VOO
Indications
Temporary mode some-times used during surgery to
prevent interference from electrocautery
ventricular demand pacing
VVI
Indications
The combination of AV block and chronic atrial
arrhythmias (particularly atrial fibrillation).
atrial demand pacing
AAI
Indications
Sick sinus syndrome in the absence of AV node disease or
atrial fibrillation.
atrial synchronous ventricular inhibited
pacemaker
VDD
Indications
AV block with intact sinus node function (particularly
useful in congenital AV block).
Dual chamber pacemaker
DDD
Indications
1. The combination of AV block and SSS.
2. Patients with LV dysfunction and LV hypertrophy who
need coordination of atrial and ventricular
contractions to maintain adequate CO.
Temporary pacemaker
Types
– Transvenous- pacing wire via central line to
RV under X ray, usually bipolar i.e., with 2
electrodes at the end of wire
– Transthoracic (epicardial lead)  post op
pacer wires.
– Transcutaneous  one electrode over
cardiac apex, other over right scapula or
clavicle.
– Transesophageal
Transcutaneous pacemaker
Transvenous pacemaker
• Medtronic 5388 Dual
Chamber
Setting
•
Atrial and ventricular output (lowest possible)
–
Milliamperes (mA)
•
•
Typical atrial mA 5
Typical ventricular mA 8-10
• Atrial/ventricular rate
– Set at physiologic rate for individual patient
– Post open heart sugery  90/min
– AV Interval, upper rate, & PVARP automatically adjust with set
rate changes
•
Atrial and ventricular sensitivity
–
Millivolts (mV)
•
•
Typical atrial: 0.4 mV
Typical ventricular: 2.0mV
Setting (cont.)
•
AV Interval
–
Milliseconds (msec)
•
•
Time from atrial sense/pace to ventricular pace
Synonymous with “PR” interval
• Upper rate
– Automatically adjusts to 30 bpm higher than set rate
– Prevents pacemaker mediated tachycardia from unusually high atrial
rates
– Wenckebach-type rhythm results when atrial rates are sensed faster
than the set rate
• Refractory period
– PVARP: Post Ventricular Atrial Refractory Period
• Time after ventricular sensing/pacing when atrial events are ignored
Normal Pacing
• Atrial Pacing
– Atrial pacing spikes followed by P waves
Normal Pacing
• Ventricular pacing
– Ventricular pacing spikes followed by wide, bizarre QRS
complexes
Normal Pacing
• A-V Pacing
– Atrial & Ventricular pacing spikes followed by atrial &
ventricular complexes
Normal Pacing
• DDD mode of pacing
– Ventricle paced at atrial rate
Assessing Underlying Rhythm
Problems with pacemakers
Problems with pacemakers
1.
2.
3.
4.
5.
Failure to pace
Failure to capture
Failure to sense (overpacing)
Wenkebach
Pacemaker syndrome
1. Failure to Pace
Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 7th ed., 2005.
Causes:
• Oversensing
• Battery failure
• Internal insulation failure
• Conductor coil fracture
Problems with Pacemakers
Failure to Pace
Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 7th ed., 2005.
Causes:
• Crosstalk (V oversensing when A paced)
Oversensing
• Pacing does not occur when intrinsic rhythm is
inadequate
Oversensing
• Causes
– Pacemaker inhibited due to sensing of “P” waves
& “QRS” complexes that do not exist
– Pacemaker too sensitive
– Possible wire fracture, loose contact
– Pacemaker failure
• Danger - heart block, asystole
Oversensing
• Solution
–
–
–
–
–
–
–
–
View rhythm in different leads
Change electrodes
Check connections
Decrease pacemaker sensitivity (↑mV)
Change cables, battery, pacemaker
Reverse polarity
Check electrolytes
Unipolar pacing with subcutaneous “ground wire”
Reversing polarity
• Changing polarity
– Requires bipolar wiring system
– Reverses current flow
– Switch wires at pacing wire/bridging cable
interface
2. Failure to Capture
• Atrial non-capture
– Atrial pacing spikes are not followed by P waves
Failure to Capture
• Ventricular non-capture
– Ventricular pacing spikes are not followed by QRS
complexes
Failure to Capture
• Causes
–
–
–
–
Insufficient energy delivered by pacer
Low pacemaker battery
Dislodged, loose, fibrotic, or fractured electrode
Electrolyte abnormalities
• Acidosis
• Hypoxemia
• Hypokalemia
• Danger - poor cardiac output
Failure to Capture
• Solutions
– View rhythm in different leads
– Change electrodes
– Check connections
– Increase pacer output (↑mA)
– Change battery, cables, pacer
– Reverse polarity
3. Failure to Sense (overpacing)
• Atrial undersensing
– Atrial pacing spikes occur regardless of P waves
– Pacemaker is not “seeing” intrinsic activity
Failure to Sense
• Ventricular undersensing
– Ventricular pacing spikes occur regardless of QRS
complexes
– Pacemaker is not “seeing” intrinsic activity
Competition
– Pacemaker & patient’s intrinsic rate are similar
– Unrelated pacer spikes to P wave, QRS complex
– Fusion beats
Failure to Sense
• Causes
– Pacemaker not sensitive enough to patient’s
intrinsic electrical activity (mV)
– Insufficient myocardial voltage
– Dislodged, loose, fibrotic, or fractured
electrode
– Electrolyte abnormalities
– Low battery
– Malfunction of pacemaker or bridging cable
Failure to Sense
• Danger – potential (low) for paced ventricular beat
to land on T wave (R on T)  VF!!
Failure to Sense
• Solution
–
–
–
–
–
–
–
–
View rhythm in different leads
Change electrodes
Check connections
Increase pacemaker’s sensitivity (↓mV)
Change cables, battery, pacemaker
Reverse polarity
Check electrolytes
Unipolar pacing with subcutaneous “ground wire”
4. Wenckebach
• Assessment
– Appears similar to 2nd degree heart block
– Occurs with intrinsic tachycardia
Wenckebach
• Causes
– DDD mode safety feature
– Prevents rapid ventricular pacing impulse in
response to rapid atrial rate
•
•
•
•
Sinus tachycardia
Atrial fibrillation, flutter
Prevents pacer-mediated tachycardia
Upper rate limit may be inappropriate
Wenckebach
• Solution
– Treat cause of tachycardia
•
•
•
•
Fever: Cooling
Atrial tachycardia: Anti-arrhythmic
Pain: Analgesic
Hypovolemia: Fluid bolus
– Adjust pacemaker upper rate limit as appropriate
5. Pacemaker syndrome
• Ventricular pacing  sacrifice the atrial
contribution to ventricular output
– Loss of AV synchrony  Atrium contracts against
closed TV,MV  ↓ CO, ↑ JVD
– Retrograde ventriculoatrial (VA) conduction 
inverted P, ↑ PR, AV dissociation
– Absence of rate response to physiologic need
• 14-57% in VVI
• Patients with intact VA conduction are at
greater risk
• Rx
– VVI  Add A-lead, ↓ Rate
– Other  interrogation and reprogramming to fix
loss of AV synchrony
Surgical diathermy and pacemakers
• Ventricular fibrillation – most common if
pacemaker unit is older type
• Inhibition of demand function- sensing
may be triggered, with resultant chamber
inhibition or arrhythmias induced
• Unpredictable setting of programmable
types
• Asystole
• Unit failure
Recommendations
• Place indifferent electrode on same side as operation & as far
from pacemaker unit as possible
• Limit use of diathermy
• Use lowest current setting possible
• Use bipolar diathermy
• Careful monitoring of pulse, pulse oximetry & arterial
pressure
• Transcutaneous pacing should be available
• Isoprenaline should be available
• Interrogation before Sx
• Magnet
– Reset PM to asynchronous
– Inactivate defribillation feature in AICD
Post operative care
• Full telemetric check
• Reprogramming back to original setting
THANK YOU