III. Cardiac Support Devices Flashcards
3 different implantable devices
- Implantable Permanent Pacemaker
- Implantable Cardioverter Defibrillator
- Intra-aortic Balloon Pump
Implantable Permanent Pacemaker is for
Treatment of ____
bradycardia
Implantable Cardioverter Defibrillator
is for treatment of ____.
tachycardia and fibrillation
Intra-aortic balloon pump is for treatment of
____.
Left ventricular support
PM of today
____ lead placement
Transvenous
Goals of pacemakers today
A satisfactory heart rate to maintain effective cardiac output
A chrono-tropic physiological response
Atrio-ventricular synchronization
Inter-ventricular and intra-ventricular synchronization
Treat or prevent arrhythmias
routes of temporary pacing
transvenous, transcutaneous/transthoracicesophageal
NOT trans-arterial
indications for temporary pacing
Unstable Brady-dysrhythmias
Atria-ventricular heart block
Unstable tachydys-rhythmias
temporary pacing
Endpoint is reached after:
a resolution of reversible problem or permanent pacemaker implantation.
Indications for Permanent Pacemaker
- Sick sinus syndrome
- Tachy-brady syndrome
- Symptomatic sinus bradycardia
- A-fib with slow ventricular response
- 3rd degree heart block
- Chronotropic incompetence (Inability to increase heart rate to match exercise)
Permanent Pacemaker Indications
Non-indications
- Syncope of undetermined etiology
- Asymptomatic sinus bradycardia
- Asymptomatic 1° & 2° Mobitz Type 1 AV Block
- Reversible AV block
- Long QT syndrome or Torsades de pointes due to a reversible cause
Computerized device taht regulates the timing and sequence of one’s heartbeat
pacemaker
Pacemaker Basics
Detect the ____ activity (sense)
intrinsic
pacemaker system components
- pulse generator
- lead/s (encased in silicone)
- Programmer
benefits of lithium-diode battery (power source)
- 5-15 yr life
- voltage decrease gradually
- sudden failure UNLIKELY
battery placement
under submuscular plane of the pectoralis major
computer component of PM?
pulse generator
3 functions of PM circuitry
- time
- sensing
- output
pacemaker sizes pic
today we use <30cc
Leads placed via central access & fixed to ____.
endocardium of RV or RA
Distal attachment methods:
Active fixation → metal screw-in
Passive fixation → rubber fins/wingtips or tines
Pacing Leads Variety Pic
____ fixation has porous carbon for improved contact and decreased pacing thresholds.
passive
Pacemaker Implant Pic
3 locations of PM access
- R/L subclavian vein
- cephalic vein
Pacing & Depolarization of Myocardial Tissue
The myocardium must be ____ (not in refractory period)
excitable
Pacing & Depolarization of Myocardial Tissue
The stimulus current density (current per cross-sectional area) must:
1. Must be sufficiently ____
2. Sufficient ____
3. Lead in good position & with ____ with myocardium
high
duration
sufficient contact
Pacing & Depolarization of Myocardial Tissue
The pacemaker-generated impulse then relies on the ____ properties of the cardiac specialized conduction & myocardial tissue for depolarization of the entire heart (aka: ____)
intrinsic
AKA: “capture”
Sensing
Sensing is the detection of ____.
real or spontaneous cardiac depolarization
Factors that affect sensing:
- Electrode size
- Configuration of electrode
- Position of the lead tip within the heart and contact to the myocardium
- Programmed sensitivity level
Types of Pacemakers
Unipolar vs. Bipolar vs. Multipolar
Single vs. Dual Chamber vs. Multisite
Asynchronous vs. Synchronous
Programmable vs. Non-programmable
Polarity of the Pacemaker System
Unipolar → ____
Bipolar → ____
Multipolar → ____
Unipolar →** highest sensitivity for sensing**
Bipolar →** improved rejection for more reliable sensing**
Multipolar → special purpose leads
Quadripolar → Targeted cardiac resynchronization.
Unipolar Pacemaker Circuit
Larger “antenna” for sensing → Bigger signals, but more ____
interference
Unipolar Pacemaker Circuit
Large circuit (____ cm) b/t single electrode at distal end of lead and the pulse generator
± 40-60cm
Unipolar Pacemaker Circuit
____ unipolar → cases where AV conduction is likely to return.
____ unipolar → normal AV conduction w/ SA node disorder.
Ventricular
Right atrium
Unipolar Pacemaker Circuit
Advantages:
High sensitivity for sensing
Large pacemaker spikes on ECG (easy interpretation)
Unipolar Pacemaker Circuit
Disadvantages:
Extracardiac stimulation possible (pectoral pocket muscle)
Sensing of extracardiac signals (i.e. detecting ventricular depolarization from atrial lead)
Non-physiological interference
Bipolar Pacemaker Circuit
Short circuit (____mm) between 2 electrodes at the distal end of the lead
± 10-15
Bipolar Pacemaker Circuit
Advantages:
Improved rejection of extra-cardiac and/or non-physiologic stimulation = More reliable sensing
Bipolar Pacemaker Circuit
Disadvantages:
Small pacemaker spikes (difficult interpretation of pacemaker ECG)
____ pacing (i.e. AAI)
Limited indications in pts. with SSS and intact conduction system or for anti-tachycardia purposes
Single chamber atrial
Single chamber ventricular pacing (i.e. VVI):
Less expensive; non-physiological loss of AV synchrony; loss of around ____% CO
25
Single Chamber Pacemakers
Preferred only in chronic atrial fibrillation and heart block, or those with very limited activity
Single chamber ventricular pacing (i.e. VVI):
Single chamber ventricular pacing (i.e. VVI):
____% incidence of pacemaker syndrome
15
“Sequential” pacemaker = electrodes in RA and RV → allows AV synchrony
Dual Chamber Pacemakers
Allows physiological variability of pacing rate
Dual Chamber Pacemakers
Dual Chamber Pacemakers
Advantages:
Increase/decrease of the cardiac output
Improved ____
No ____ syndrome [TQ]
Increase
Quality of Life
Pacemaker
Dual Chamber Pacemakers
Disadvantages:
Expensive & complex
V-V dys-synchrony possible
Inter-channel interferences possible
Multi-site Pacemakers: Dual Site Atrial Pacing
Leads placed at:
Atrial leads ____, other in the ____
Ventricular lead in the ____ at the apex or outflow tract.
RA appendage
coronary sinus
RV
Biventricular pacemakers
Leads placed at: ____, ____, ____
RA, RV, & LV
Biventricular pacemakers
Useful in the management of patients with heart failure who have evidence of ____ & ____
abnormal intraventricular conduction (i.e. LBBB)
V-V dys-synchrony.
Fixed Rate (Asynchronous) Modes:
AOO →
VOO →
DOO →
Fixed rate atrial pacing (asynchronous)
Fixed rate ventricular pacing (asynchronous)
Fixed rate AV sequential pacing (asynchronous to intrinsic rhythm)
Fixed Rate (Asynchronous) Modes
T/F: Impulse produced at a set rate with no relation to patients intrinsic cardiac activity.
true
Synchronous Pacing
Can mimic ____ pattern of the heart
intrinsic electrical activity
Pacemaker Codes & Modes
1st letter →
chamber Paced
Pacemaker Codes & Modes
2nd letter →
chamber Sensed
Pacemaker Codes & Modes
3rd letter →
Response to chamber sensed
Pacemaker Codes & Modes
4th letter →
Programmable features
Pacemaker Codes & Modes
5th letter →
Anti-tachycardia response
Pacemaker Codes & Modes Table Pic
Response to sensing options (3)
I (inhibited) → Withhold a pacemaker output in response to a sensed event.
T (triggered) → Produces output spikes coincident with the sensed signal.
D (dual) → I and/or T
4th - Programmable Options
O (none) → not programmable
P (simple programmable) → limited to 3 or fewer programmable parameters
M (multiprogrammable) → device can be programmed in more than 3 parameters
Rate, sensing, output, refractory periods, mode, hysteresis
C (communicating) → capable of transmitting or receiving data for informational or programming purposes.
R (rate responsive) → device is capable of a rate responsive function
Most bradycardia devices are what (4th) programmable option
O (none)
5th — Anti-tachycardia Responses (4)
O (none) → Not activated
P (paced) → pace the patient out of tachycardia
S (shocks) → deliver a defibrillating shock
D (dual) → paced and shocks (MOST ICDs)
- Fixed rate ventricular pacing (no sensing or response)
- Asynchronous pacing
- Indications:
Temporary mode sometimes used during surgery to prevent interference from electrocautery. - Monitor for R on T with ESU diathermy → torsades de pointes
VOO
- Ventricular pacing and sensing
If no intrinsic electrical impulse sensed → paced at a pre-set rate
If intrinsic electrical impulse sensed → pacing inhibited - Asynchronous pacing
- Indications: Combination of high grade AV block and chronic atrial arrhythmias (particularly A-fib)
- VVIR = as above but adds rate-adaptive mechanism for exercise
VVI
- Paces + Senses both atrium and ventricle
- If no intrinsic electrical impulse sensed → triggers pacing (EKG – 2 spikes)
- If intrinsic electrical impulse sensed → pacing inhibited
- AV Synchronicity maintained (“Sequential”)
DDD
DDD
Indications:
Combination of AV block and SSS
Pts. w/ LV dysfunction and LV hypertrophy who need coordination of A & V contraction to maintain adequate CO
DDD
adds rate-adaptive mechanism for exercise
DDDR
Atrium paced, Atrium sensed, & will inhibit if intrinsic electrical impulse
AV Synchrony maintained
AAI
AAI
Indications
Sick sinus syndrome in the absence of AV node dz. or A-fib.
Failure to Capture
Ventricular Pacemaker
Rate responsive pacing is influenced by what three variables
- activity sensors (accelerometers)
- Motion
- Ventilation
Pacemaker complications apperent on EKG:
- Failure to Output
- Failure to Capture
- Sensing Abnormalities
what is occuring?
failure to sense
what is occuring
Pacemaker Syndrome
Low CO and heart failure like manifestations that happens in about 15% of pts with VVI or VOO pacemakers as a result of _____.
loss of AV synchrony.
pacemaker syndrome
Atria contract against closed valves = ____ waves
(cannon A waves)
Pacemaker Syndrome
Symptoms:
Vertigo/Syncope (worsens with exercise)
Unusual fatigue
HoTN
Cyanosis
Jugular vein distention
Oliguria
Dyspnea/SOB
Altered mental status
Pacemaker Syndrome
Treatment:
establish normal AV synchrony
Pacemaker Syndrome EKG Pic
- Designed to treat a cardiac tachydysrhythmia
- Performs cardioversion/defibrillation
- ATP (antitachycardia pacing)
- Some have pacemaker function (combo devices)
Automatic Implantable Cardio-Defibrillator (AICD or ICD)
Biventricular pacemakers that are combined with an implantable cardioverter defibrillator (ICD) do not tend to last as long — ____ years
about two to four years.
AICD Functions
Antitachycardia Pacing
Cardioversion
Defibrillation
Bradycardia Pacing
- Generally used in patient’s who experienced a previous cardiac arrest
- Patients with undetermined origin of, or continued, VT or VF despite medical interventions
AICD
Antitachycardia Pacing Pic
ICD Cardioversion Pic
ICD Defibrillation Pic
____ delivers an asynchronous shock of energy.
Defibrillation
____ delivers a reduced shock of energy in synchrony with QRS complex.
Cardioversion
What type of PM shock is delivered if patient is in V-Fib?
ICD Defibrillation,
Once out of V-Fib, PM will pace asynchronously (VVI mode) until the device is reset by healthcare provider
A magnet placed over the pacemaker does what?
- converts to asynchronous mode (will not sense/defibrillate/cardiovert)
If a magnet is placed over the heart, and the PM is disabled, what function does the PM retain?
ability to pace
A procedure above what level should present some concern for PM interference?
umbilicus
Using a magnet to disable the PM is appropriate for a/an ____ procedure.
emergent
if procedure is non-emergent, a rep will disable in pre-op
What is convenient about using Neo in conjuction with PM patients?
No reflex bradycardia
Steps to take if patient with AICD codes:
1. Start CPR & Defibrillate
T/F: If pt with AICD codes, removing the magnet is a reliable method of defibrillating patient.
FALSE
magnet ‘likely’ deprogrammed AICD, now requires provider to reset
Person giving CPR may feel slight buzz if AICD functions
A 30-joule intra-cardiac shock is ____ j on skin
<2 J
Coding pt with AICD
Change paddle placement if unsuccessful attempt:
Try ____ paddle placement if Anterior-Lateral unsuccessful.
Anterior-Posterior
External defibrillation will/will not not harm AICD
will not
A counterpulsation system that is used to give temporary support to the LV by mechanically displacing the blood w/i the aorta.
Intra Aortic Balloon Pump (IABP)
one of the most common modalities of augmenting circulatory support
How does the IABP work?
It optimally times inflation and deflation contractions of the heart
What are the advantages of using a IABP?
- ↓LV systolic work, LVEDP & Wall Tension
- ↓O2 consumption
- ↑CO, Pefusion, CPP (Coronaries)
What patients most often require a IABP?
HF and/or cardiogenic shock
IABP Placement
A flexible catheter with long balloon mounted on the end → inserted via ____ → placed in ____
femoral artery
descending aorta
IABP
Balloon is inflated to displace blood in ____(“counter pulsation”)
When inflated, balloon blocks ____
aorta
85-90% of aorta.
IABP
Sudden inflation = moves blood ____ and ____ to balloon (inc. pressure).
superiorly
inferiorly
IABP
when does the IABP balloon inflate?
immediately after aortic valve closure (during diastole)
after LV contraction ejected blood through aortic valve into aorta; but heart is weak and is unable to contract hard enough to circulate blood effetively. That is why the balloon pump then inflates, forcing blood superiorly, into coronary arteries, and inferiorly to distal organs.
IABP
What is caused by balloon inflation?
- ↑ aortic pressure
- ↑ Coronary Perfusion Pressure & BF
- ↑ Systemic Perfusion Pressure
- ↑ O2 supply to both the coronary and peripheral tissue
- ↑ Baroreceptor Response
- ↓ Sympathetic Function = ↓HR, ↓SVR, ↑LV Function
The balloon remains inflated throughout the entirety of what part of cardiac cycle?
diastole
IABP
Triggered to deflate during:
opening of the aortic valve (onset of systole)
to allow blood volume to enter aorta, so that it may be soon pumped out
IABP
Deflation creates a “____” in the aorta (↓volume and ↓pressure) = reduced impedance to ____.
potential space
LV ejection
IABP
What are the cardiac effects of deflating balloon?
- ↓afterload → ↓ myocardial oxygen consumption (MVO2)
- ↓peak systolic pressure → ↓LV work.
- ↑CO
- ↑EF & forward flow
(Normal EF = 50-70%)
IABP Hemodynamic Effects Table Picture
Indications for IABP
- Refractory unstable angina (despite maximal medical management)
- Persistent myocardial ischemia
- Cardiogenic shock
- Acute mitral regurgitation
- Perioperative treatment of complications due to myocardial infarction
- Failed PTCA (Percutaneous transluminal coronary angioplasty)
- As a bridge to cardiac transplantation
(15-30% of end-stage cardiomyopathy pts. awaiting transplantation need mechanical support.) - During or after cardiac surgery
(Cardiac failure / weaning from CPB)
IABP
Contraindications
- Severe aortic insufficiency
- Aortic aneurysm
- Aortic dissection
- Limb ischemia
- Thromboembolism
- Uncontrolled sepsis
- Severe PVD
- End-stage heart dz. with no anticipation of recovery.
IABP Components Picture
list IABP 2 major components
- Double-Lumen catheter w/ balloon
- Console w/ pump to drive the balloon
size of IABP catheter
7.5-9.5 Fr
IABP
IABP balloon capacity
30-60 mL
how is the IABP sized?
based on pt height
How many lumens does the catheter have?
2
- gas exchange (blowing up balloon)
- monitoring central aortic pressure
2 different gases used to inflate balloon
- helium
- CO2
Helium vs CO2
Pros & Cons
Helium:
- lower density, inflates/deflates faster
- risk of air embolism if balloon rupture
CO2:
- Safer, dissolves into blood quickly
- slower balloon response
What does radio opaque marker on IABP allow for?
placement confirmation on X-ray
The end of the balloon should be just distal to the takeoff of the ____.
left subclavian artery.
Tip approximately 1-2cm below the origin of the left subclavian artery and above the renal arteries.
Position should be confirmed by ____ or ____.
fluoroscopy
chest x-ray
Should be visible in the 2nd or 3rd intercostal space
Event the pump uses to identify the onset of cardiac cycle (systole)
Trigger
most common modality used as trigger for IABP
ECG
On ECG:
Inflation occurs at ____.
Deflation occurs at ____.
Inflation: end of T-wave
Deflation: beginning of R-wave
If arterial pressure waveform is used as IABP trigger,
Inflation occurs at: ____
Deflation occurs at: ____
Inflation: dicrotic notch
Deflation: systolic upstroke
What modality is used by IABP during CPB or VFib?
intrinsic set rate
(1:1 - 1:8)
every beat or every 8th beat
Normal augmented A-line Waveform with IABP
Will MAP decrease or increase with a IABP?
Increase
Although systolic pressures decrease slightly, diastolic pressure increases significantly.
Diastolic augmentation should be lower/higher than systolic.
higher
Early Inflation (before dicrotic notch)
…if balloon inflates too soon, interrupting the end of systole
- Increase work of heart (at end systole)
- Aortic Regurgitation (inflation will cause backflow of blood into LV)
- 2nd worst
Late Inflation (after dicrotic notch)
- Heart is not getting enough help during diastole
- decreased Coronary Perfusion
- NOT making heart work, just less effective
Early Deflation
…while heart is still in diastole
- some help with coronary perfusion, just not optimal
- not making the heart work harder
Late Deflation
- WORST
- balloon obstructing systole
- Significantly Increases work of heart
IABP Complications
-
Limb ischemia
(Thrombosis, Emboli) -
Local vascular injury
(Bleeding at insertion site, Groin hematoma, False aneurysm) - Aortic perforation and/or dissection
- Malpositioning causing cerebral, renal, or bowel compromise
- Neurologic complications including paraplegia
- **Heparin induced thrombocytopenia
- Balloon rupture → gas embolus
Infection**
Weaning from IABP
- Timing of weaning
(Patient should be stable for 24-48 hours) - Decreasing inotropic support
- Decrease augmentation slowly
- Decreasing pump ratio
(From 1:1 to 1:2 or 1:3) - Monitor patient closely
(If patient becomes unstable, weaning should be immediately discontinued)
Final Points IABP
The primary goal of IABP treatment is to increase ____ and decrease ____.
myocardial O2 supply
myocardial O2 demand
Final Points IABP
Decreased urine output after insertion may occur because of balloon positioning obstructing ____.
renal artery
Hemolysis from mechanical damage to RBCs can reduce Hct by up to ____%
5%
IABP is ___-genic → always anticoagulant the pt.
thrombo
Final Points IABP
T/F: Never switch the balloon off while in use
True
