2.2.2: Mechanical and Circulatory Assist Devices Flashcards
What are the 5 major stages of the cardiac cycle?
- late diastole / ventricular filling
- the AV valve and mitral valves are open
- blood enters into RA from VC
- blood enters into LA from PV - atrial systole
- isovolumetric ventricular contraction
- the amount of blood in the ventricles remains the same
- Tricuspid valve, pulmonary (semilunar) valve, aortic (semilunar) valve, and mitral valve are all closed
- pressure in ventricles increases significantly
- “lub” sound - ventricular ejection
- semi-lunar valve opens
- pulmonary valve opens - isovolumetric ventricular relaxation
- pressure in ventricles drops significantly
- semilunar valves close
- “dub” sound
- AV valve opens up (ventricular pressure drops below atrial pressure)
What are the valves doing and what is the heart doing during late diastole / ventricular filling
- the semilunar valves are closed
- the AV valves are open
- the heart is relaxed
What is happening during atrial systole?
- the atria contract
- AV valves are open
what happens during isovolumetric ventricular contraction
-ventricles contract
- all valves in the heart are closed
what happens during ventricular ejection?
- semilunar valves open
- AV valves are shut
- blood flows out of the ventricles
what happens during isovolumetric ventricular relaxation?
- all valves are closed
- ventricles stop contracting and begin to relax
What is preload?
the amount of stretch on the ventricles prior to contraction
- starling’s law
-
What is afterload?
the resistance to ventricular ejection
- the mass of blood that must be moved
What is aortic end diastolic pressure (AEDP)?
the pressure that the left ventricle must push against in order to open the aortic valve and generate blood flow
what are the 4 measurements of cardiac performance?
- cardiac output
- cardiac index
- fick principle
- systemic vascular resistance
What is the equation for CI
SV x HR / BSA
What are the three components of the A&P of a failing heart?
- left ventricular failure
- hypervolemia
- tissue hypoxia
What is the value range for systemic vascular resistance (SVR)?
800-1200
What is the definition of SVR?
The resistance to blood flow from all of the systemic vasculature excluding the pulmonary vasculature.
What will happen to the SVR when there is vasoconstriction?
The SVR will go up
What will happen to the SVR when there is vasodilation?
The SVR will go down
What does hypertrophy of the mycoardium lead to?
stiffness of the ventricle and decreased ability to relax during diastole
When does the balloon pump inflate and when does it deflate?
Inflation during diastole and deflation during systole
What is the primary benefit of an IABP?
that it corrects supply vs demand mismatch
What does inflation of the IABP do to the supply?
increased supply
What does deflation of the IABP do to the demand?
decreased demand
What is the range for a typical IABP catheter?
25-50 mL
What are the hemodynamic effects of an IABP?
- increases diastolic arterial pressure
- increases coronary blood flow
- increases CO, EF, and forward flow
- increases cerebral and renal blood flow
- increases systemic perfusion
- increases coronary and systemic oxygen supply
- increases hemodynamic pulse rate
- decreases systolic arterial pressure
- decreases afterload
- decreases LV wall tension
- decreases preload congestion
- decreases heart rate
What is the placement for an IABP?
1-2 cm below the subclavian artery,
proximal to the renal and mesenteric arteries
What percentage of the aorta foes the balloon occlude when properly placed? Why doesn’t it fully occlude?
80-90%
full occlusion will damage the walls of the aorta and cause hemolysis
How far inferior to the aortic arch should be tip of the IAB be?
2-3 cm
What are the absolute contraindications for IABP?
- severe aortic valve insufficiency
- dissecting aortic aneurysm
How often should the hematocrit of a patient with an IABP be monitored?
daily
What does apparent rust in the IABP tubing mean ?
it means the balloon may have burst or torn and there is blood in the tubing
Where would limb ischemia occur in the case of an IABP?
In the leg it is put in or in the left arm (because the balloon could advance and block blood flow)
What are the risk factors for limb ischemia with an IABP?
- female
- diabetic
- peripheral vascular disease
CSM should be checked ___ min after IABP insertion and every ___ hours after
30, 2
What should you do if the IABP machine has failed?
inflate and deflate the balloon every 5-10 minutes by hand using the syringe and stopcock filled with 40-60cc air or helium
Approximately how many mLs of helium are pumped into the IAB
35-40 mL
When the IAB is inflated, which way is blood pushed?
superiorly and inferiorly
- superior blood is pushed into the coronary arteries, increasing perfusion to the myocardium and the brain
- inferior blood is forced into distal organs
What are the goals of IAB inflation?
- increase coronary perfusion pressure
- increase systemic perfusion pressure
- increase peripheral oxygen supply
- decreases SVR
- decreases HR
When the IAB deflates, pressure in the aorta rapidly decreases. What does this do to afterload?
reduces afterload
What are the goals of IAB deflation?
- decreases afterload
- decreases oxygen consumption of the left ventricle
- decreases assisted peak systolic pressure
What does the IABP use to know when to inflate and deflate?
it uses the central aortic pressure waveform and the EKG to identify the dichrotic notch
What can a pacer spike do to an IABP?
it can result in loss of capture, which may result in loss of balloon deflation during systole
- the pump may continue to follow the pacing rate rather than the ventricular contraction rate
During cardiac arrest, the IABP must be taken out of ____ mode and placed into ___ mode
EKG, pressure
What are the four types of timing errors that can occur with an IABP?
- early inflation
- late inflation
- early deflation
- late deflation
When does the IAB inflate in early deflation?
prior to the dichrotic notch
What physiologic effect can early inflation of the IAB have?
- increase in aortic pressure causing regurgitation of blood into the left ventricle
What are the clinical implications of late IABP inflation?
- decreased perfusion pressure
- decreased volume to the coronary arteries
What will the assisted end-diastolic wave look like in early deflation of the IABP?
it may be equal or less than the unassisted aortic end-diastolic pressure
What will the end-diastolic wave look like in late deflation of the IABP?
it may be equal or greater than the unassisted aortic end-diastolic pressure
What are the physiologic effects of late IABP deflation?
- there is no afterload reduction now… now there is a blockage
- increased MVO2 consumption
- balloon may impede left ventricular ejection and increase afterload
- potential reduction in cardiac output
What can cause a low plateau pressure on IABP?
- low balloon volume
- too small of a balloon
- balloon placement too low in the aorta
What can cause balloon pressure waveform artifact on IABP?
- balloon still in sheath
- suture too tight
- partial kink
- slow helium speed
- tortous vessels
What can cause an elevated baseline on IABP waveform?
- kinked catheter
- partially wrapped balloon
- balloon in sheath
- overfill
- balloon too low in aorta
- balloon too large
What can cause the baseline to be below zero on IABP waveform?
- blood in tubing
-leak in tubing - kinked catheter
- ectopy
What can cause a square or rounded plateau on IABP waveform?
- high pressures
- partially wrapped balloon
- balloon in sheath
- too large of balloon
- inaccurate balloon placement
Transvenous pacing serves as a bridge to:
permanent cardiac pacemaker implantation
If the HR is greater than what the pacer is set at, the sensitivity is too ____ (high/low)
low (failure to sense)
If the HR is less than what the pacer is set at, the sensitivity is too ____ (high/low)
high (failure to pace)
ECMO can assume up to ___% of cardiac output
75
Which vessels are the cannulae placed into in ECMO?
internal jugular and carotid artery
What are the absolute contraindications of ECMO?
- unable to systemically anticoagulate the patient
- terminal disease with short survival
- underlying moderate to severe chronic lung disease
- advanced multiple organ failure syndrome
- unresponsive septic shock
- uncontrolled metabolic acidosis
- central nervous system injury
What medication is contraindicated for patients on ECMO and why?
Protamine, it can cause serious circuit-related thrombosis
What type of patient is a TAH designed for?
patients waiting for a heart transplant who do not respond to other treatments and who are at risk for imminent death from non-reversible bi-ventricular failure
What is a VAD and what does it do?
ventricular assist device, can replace the LV, RV, or both (BIVAD)
It decreases the workload of the heart while maintaining adequate flow and blood pressure
Is bleeding from VAD surgery common? what % of patients experience it?
very common, 30-50%
What do VADs depend on to function?
VADs are preload dependent, they need the preload
they are afterload sensitive
What are three major concerns to be aware of with a VAD patient?
- bleeding
- clotting
- infection
What is suckdown in a VAD patient and why does it happen?
suckdown is LV collapse due to hypovolemia or VAD overdrive- happens when the preload isn’t there
What is a sign that suckdown is occurring
you can hear knocking/grinding sounds when auscultating the device
hypotension
PVCs/vtach
RV failure
Are all VAD patients pulseless?
No, it is not uncommon for a VAD patient to have a carotid pulse
Besides blood pressure (which can be inaccurate in a VAD patient) what other measurement is important?
MAP
When should a VAD patient be defibrillated or cardioverted?
when they are unstable
sometimes VAD patients have an apparent life-threatening arrhythmia, but that is normal for them
When should CPR be initiated on a VAD patient
per medical control or if instructed by someone at the VAD center
What is the first line therapy in an unstable VAD patient and why?
volume resuscitation because all VADs are preload dependent
Can VAD patients receive nitro?
no, silly goose
Which VAD device unloads blood from the left ventircle and expels it into the ascending aorta?
the Impella
What type of device is the intra-aortic balloon pump?
a volume displacement device
What is the primary benefit of a balloon pump?
it corrects the supply vs. demand mismatch
What are the contraindications to impella use?
- mural thrombus in LV
- mechanical aortic valve or heart constrictive device
- aortic valve stenosis/calcification
- moderate to severe aortic insufficiency
- severe PAD that precludes placement
What triggers the IABP balloon?
- EKG
- pressure
- pacer spike
When does the IABP deflate?
at the r wave
What mode should the IABP be put into if the pt goes into arrest?
art line or pressure mode
