Mechanical Circulatory Devices Flashcards
To better understand and operate Mechanical Circulatory Devices. Including: Itra-aortic Balloon Pump (IABP) Transvenous Pacing (TVP) Extracorporeal Membrane Oxygenation (ECMO) Total Artificial Heart (TAH) Left or Right Ventricular Assist Device (LVAD or RVAD)
What are the 5 major stages of a Cardiac Cycle?
- Late Diastole (Ventricular Filling)
- Atrial Systole (Atrial Contraction)
- Isovolumetric Ventricular Contraction (Electrical stimulation causing the ventricals to tense up but not contract)
- Ventricular Ejection (Ventricular Contraction)
- Isovolumic Ventricular Relaxation (Return to Diastole)
What are the 2 Semilunar Valves?
and
When do they close in the Cardiac Cycle?
The 2 Semilunar Valves are the Pulmonary Valve and Aortic Valve.
They Close during Late Diastole when the ventricals are filling. The three flap valve helps prevent blood from retrograding back into the ventricals.
What happens to the heart at each point of the ECG?
P Wave?
R Wave?
T Wave?
At the P Wave the Atrium are Depolarizing
At the R Wave the Ventricals are Depolarizing
At the T Wave the Ventricals are Reploarizing
What is Preload?
and
How can we measure Preload?
Preload - is the amount of stretch on the ventricular myocardium prior to contraction.
Preload is often referred to as the “filling pressure” and is Pre-Systole.
We can measure preload by monitoring wedge pressures.
What is Afterload?
Afterload is the resistance the Ventricals must overcome to circulate blood.
The more mass against the ventricals the more inertia that must be generated, to overcome it. Therefore increasing pressure within the ventricals and decreasing cardiac output.
What are the four measurements of cardiac performance and what are their formulas?
-
Cardiac Output (CO)
- Stroke Volume (SV) x HR
-
Cardiac Index (CI)
- (SV x HR) / BSA
-
Fick Principle
- Requires Invasive monitoring
-
Systemic Vascular Resistance (SVR) (Afterload)
- (MAP - CVP) / CO
What is Ejection Fraction?
and
What is the Normal EF range %?
Ejection Fraction (EF) is the amount of blood pumped out of the left ventricle during each cycle.
Normal EF is 55 - 75%
EF of 40 - 50% indicates damage to the myocardium
EF < 40 % indicates heart failure
EF = (SV / EDV) x 100%
What is Systemic Vascular Resistance (SVR)?
and
What is another term for SVR?
Systemic Vascular Resistance (SVR) is the resistance to blood flow offered by all of the systemic vasculature excluding the pulmonary vasculature.
Another term for SVR is Afterload
- SVR = (MAP - CVP) / CO*
What are the three phases of Heart Failure?
and
What ultimately does Heart Failure lead to?
The Three Stages of Heart Failure are:
- Vasoconstriction
- Hypervolemia
- Tissue Hypoxia
Ultimately leading to Cardiogenic Shock
What causes Hypertrophy?
and
What does Hypertrophy do to the myocardium?
Hypertrophy is caused by the heart muscle fibers increasing in size to improve contractility due to increase afterload pressure.
Hypertrophy leads to stiffness of the ventricle and decreased ability to relax during diastole. Overall increasing the O2 demand of the heart muscle therefore requiring the heart to beat faster to meet the demands.
What type of device is the Intra-Aortic Balloon Pump (IABP)?
The IABP is a Volume Displacement Device
When does the IABP inflate and deflate?
and
What is the primary benefit to IABP?
IABP inflates - during diastole - increased supply
IABP deflates - during systole - decreased demand
The Primary Benefit to IABP is it corrects the supply versus demand mismatch.
- Increases Coronary Perfusion
- Decreases Afterload
True or False
Myocardial oxygen demand is all about “supply and demand”
True
Where is the IABP placed?
1 -2 cm below the subclavian artery
In the aortic arch the arteries are B L S
- Brachial Cephalic
- Left Common Carotid
- Subclavian Artery
How much of the aorta with the balloon occulude when it is placed correctly?
80 - 90%
What are the absolute contraindications for IABP placement?
- Aortic Valve Insufficiency
- Dissecting Aortic Aneurysm
What are the side effects of IABP’s?
1) Thrombocytopenia (low platelet count)
2) Infection
3) Compartment Syndrome
4) Heavy Bleeding from the insertion site
5) Tearing or bursting balloon
6) Immobility of the balloon
What occurs when the balloon tears or bursts?
May allow blood into the tubing (appears like flakes of rust)
After insertion how often should peripehral pulses be checked?
Distal pulses, color, temperature, and capillary refill should be checked 30 mins after insertion, and then every 2 hours afterwards.
What should be done with an IABP machine fails?
1) Immediately notify the physican
2) Inflate and deflate the balloon every 5- 10 minutes by hand using a syringe and stopcock filled with 40 - 60cc of air or helium
What happenswhen the IABP balloon inflates and deflates?
Inflates - blood is pushed superiorly into the coronary arteries increasing myocardial perfusion, and inferiorly into the distal organs
- Increases Coronary perfusion pressure
- Increases systemic perfusion pressure
- Increases peripheral oxygen supply
- Indirectly decreases SVR
- Decreases HR
Deflates - allows blood to continue to cycle through and be circulated through body
- Decreases afterload
- Decrease oxygen consumption of the left ventricle
- Decrease assisted peak systolic pressure
What are the Trigger events?
1) EKG “R” Wave (EKG)
2) Arterial Waveform (Pressure)
3) Pacer Spike (Pace)
Prefered methog is EKG to identify the dicrotic notch (aortic valve closure)
The balloon should be deflated before the full onset of systole
What should be done with a patient who has a IABP and goes into cardiac arrest?
the IABP must be placed in pressure mode not EKG mode (no EKG or poor EKG)
- The pressure of the CPR will trigger the IABP
How much helium is rapid pumped in and out of the balloon?
35 - 40 cc
Helium is used because if the ballon bursts the Helium quickly dissociates out of the vasculature, and does not cause any gas concerns such as PE.
What is Transvenous Pacing (TVP)?
Short-term treatment for patients with bradyarrythmias that do not respond to transcutaneous pacing or pharmacoligical therapy.
- temporary before pacemaker is placed
What is Extracoporeal Membrane Oxygenation (ECMO)?
Temporary heart lung bypass
- can assume up to 75% of cardiac output
What are the two types of ECMO?
- Veno-arterial (VA) - Bypass the lungs and the heart (out arteries and in veins)
- Bad lungs and heart
- Veno-venous (VV) - Bypass lungs and heart circulates blood (out veins and in veins)
- Bad lungs good heart
What does it mean if the tubes start to vibrate?
Turbulet flows from hypovolemia (needs more fluid)
Describe the Total Artificial Heart (TAH)?
Consist of two artificial ventricles, each made of a semi-rigid polyurethane housing with four flexible diaphragms separating blood chamber from the air chamber.
What are they different types of VAD’s?
LVAD- Left Ventricular Assist Device
RVAD - RIght Ventricular Assist Device
BIVAD - Bilateral Ventricular Assist Device
VADS decrease the workload of the heart while maintaing adequate flow and blood pressure
What are the 2 VAD modes?
Fixed Mode - A set rate the pump will beat regardless of other conditions
Auto Mode - THis mode is only seen in volume displacement pumps
What is the first line of therapy in an unstable VAD patient?
Volume Resuscitation
