Mechanical Circulatory Devices

Question 1

What are the 5 major stages of a Cardiac Cycle?

Answer 1

1. Late Diastole (Ventricular Filling)
2. Atrial Systole (Atrial Contraction)
3. Isovolumetric Ventricular Contraction (Electrical stimulation causing the ventricals to tense up but not contract)
4. Ventricular Ejection (Ventricular Contraction)
5. Isovolumic Ventricular Relaxation (Return to Diastole)

Question 2

What are the 2 Semilunar Valves?

and

When do they close in the Cardiac Cycle?

Answer 2

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.

Question 3

What happens to the heart at each point of the ECG?

P Wave?

R Wave?

T Wave?

Answer 3

At the P Wave the Atrium are Depolarizing

At the R Wave the Ventricals are Depolarizing

At the T Wave the Ventricals are Reploarizing

Question 4

What is Preload?

and

How can we measure Preload?

Answer 4

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.

Question 5

What is Afterload?

Answer 5

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.

Question 6

What are the four measurements of cardiac performance and what are their formulas?

Answer 6

1. Cardiac Output (CO)
   
   1. Stroke Volume (SV) x HR
2. Cardiac Index (CI)
   
   1. (SV x HR) / BSA
3. Fick Principle
   
   1. Requires Invasive monitoring
4. Systemic Vascular Resistance (SVR) (Afterload)
   
   1. (MAP - CVP) / CO

Question 7

What is Ejection Fraction?

and

What is the Normal EF range %?

Answer 7

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%

Question 8

What is Systemic Vascular Resistance (SVR)?

and

What is another term for SVR?

Answer 8

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*

Question 9

What are the three phases of Heart Failure?

and

What ultimately does Heart Failure lead to?

Answer 9

The Three Stages of Heart Failure are:

• Vasoconstriction
• Hypervolemia
• Tissue Hypoxia

Ultimately leading to Cardiogenic Shock

Question 10

What causes Hypertrophy?

and

What does Hypertrophy do to the myocardium?

Answer 10

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.

Question 11

What type of device is the Intra-Aortic Balloon Pump (IABP)?

Answer 11

The IABP is a Volume Displacement Device

Question 12

When does the IABP inflate and deflate?

and

What is the primary benefit to IABP?

Answer 12

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

Question 13

True or False

Myocardial oxygen demand is all about “supply and demand”

Answer 13

True

Question 14

Where is the IABP placed?

Answer 14

1 -2 cm below the subclavian artery

In the aortic arch the arteries are B L S

• Brachial Cephalic
• Left Common Carotid
• Subclavian Artery

Question 15

How much of the aorta with the balloon occulude when it is placed correctly?

Answer 15

80 - 90%

Question 16

What are the absolute contraindications for IABP placement?

Answer 16

• Aortic Valve Insufficiency
• Dissecting Aortic Aneurysm

Question 17

What are the side effects of IABP’s?

Answer 17

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

Question 18

What occurs when the balloon tears or bursts?

Answer 18

May allow blood into the tubing (appears like flakes of rust)

Question 19

After insertion how often should peripehral pulses be checked?

Answer 19

Distal pulses, color, temperature, and capillary refill should be checked 30 mins after insertion, and then every 2 hours afterwards.

Question 20

What should be done with an IABP machine fails?

Answer 20

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

Question 21

What happenswhen the IABP balloon inflates and deflates?

Answer 21

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

Question 22

What are the Trigger events?

Answer 22

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

Question 23

What should be done with a patient who has a IABP and goes into cardiac arrest?

Answer 23

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

Question 24

How much helium is rapid pumped in and out of the balloon?

Answer 24

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.

Question 25

What is Transvenous Pacing (TVP)?

Answer 25

Short-term treatment for patients with bradyarrythmias that do not respond to transcutaneous pacing or pharmacoligical therapy.

• temporary before pacemaker is placed

Question 26

What is Extracoporeal Membrane Oxygenation (ECMO)?

Answer 26

Temporary heart lung bypass

• can assume up to 75% of cardiac output

Question 27

What are the two types of ECMO?

Answer 27

• 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

Question 28

What does it mean if the tubes start to vibrate?

Answer 28

Turbulet flows from hypovolemia (needs more fluid)

Question 29

Describe the Total Artificial Heart (TAH)?

Answer 29

Consist of two artificial ventricles, each made of a semi-rigid polyurethane housing with four flexible diaphragms separating blood chamber from the air chamber.

Question 30

What are they different types of VAD’s?

Answer 30

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

Question 31

What are the 2 VAD modes?

Answer 31

Fixed Mode - A set rate the pump will beat regardless of other conditions

Auto Mode - THis mode is only seen in volume displacement pumps

Question 32

What is the first line of therapy in an unstable VAD patient?

Answer 32

Volume Resuscitation