Week 2 Flashcards
two components of the heart
- Electrical is heart rate
- Mechanical is stroke volume
Calculating cardiac output
- One way is to look at stroke volume and heart rate.
- increases in stroke volume or heart rate allows for an increase in cardiac output
What things can regulate stroke volume
Preload, afterload, and contractility
Preload
- what does it deal with?
- what dertermines it?
- It has to deal with stretch and is your end diastolic volume (EDV)
- Venous return
- this is volume
Afterload
- what is it?
- It’s the pressure that the heart/or chamber has to pump against in order to allow blood to move from one area to the next
- Afterload is PRESSURE
Contractility
- what is it
- hat effects it?
- How hard the heart pumps
- calcium cycling to allow for the force of contraction, independent of EDV
Cardiac cycle
- what does blood enter?
- what does blood come back through?
- flow
- arteries
- veins
- right atrium –> right ventricle –> pulmonary arteries –> pulmonary capillaries –> pulmonary veins –> left atria –> left ventricle –> aorta
how do we get blood to move from one area to the next?
High pressure to low pressure
Flow
change in pressure/resistance
Right side of heart CO
(mean pulmonary arterial pressure − left atrial pressure) / (pulmonary vascular resistance)
Left side of heart CO
(mean arterial pressure − right atrial pressure) / (systemic vascular resistance)
Wiggers diagram
- left atrial pressure
- left ventricle pressure
- aortic pressure
isovolumic contraction
- what is happening
- why?
- The valves are closed, the volume is constant but the pressure is increased
- the pressure needs to exceed the pressure of where the blood needs to go– in left ventricle it needs to increase to greater than pressure in aorta
as the blood is flowing out of the ventricle, what’s going to happen to the pressure in the ventricle compared to that of the aorta
- the pressure will decrease and then the aortic valve will close
isovolumic relaxation
- what is happening
- why?
- reducing pressure in comparison to the atria, because the atria has lower pressure.
- in order to have ventricular filling, the atria need to be a greater pressure than that of the ventricles.
Stroke volume
- the amount of blood ejected in one pump
- SV = EDV - ESV
Ejection fraction
- what is it?
- formula
- normal
- EF for heart failure
- tells you about the efficiency of the pump, the function of the ventricles
- EF = SV/EDV
- Normal ejection fraction is 50-60%
- Ejection fraction of 20% indicates heart failure and that your ventricles aren’t pumping as efficiently as they should
ECG correlation; what does it correspond to with electrical and mechnical function of heart
- P wave
- QRS complex
- T wave
- P wave: correlates in response to atrial depolarization, which correlates in response to atrial contraction
- QRS complex: ventricular depolarization; it’s seen right in front of ventricular contraction
- T wave: Ventricular repolarization is right before ventricular relaxation
Heart Sounds
- S1: Corresponds to mitral valve and tricuspid valve closing
- S2: Corresponds to the aortic and pulmonic valve closing
Identify and explain the cause of the splitting of S2
- During inspiration you have an increase in the intrathoracic pressure, and there’s more volume of blood in the pulmonary vessel, and so your diastolic pressure back to the right side of the heart is altered and your pulmonic valve shuts a little later than your aortic valve, and the reason your aortic valve shuts a little quicker is because there’s less filling and less venous return, so the cycle is a little quicker and so the valve will close a little quicker than the pulmonic valve
Varying widening of S2
- cause? dx?
- how?
- Delayed closure of pulmonic valve
- Pulmonic valve stenosis
- RBBB: You have slow conduction on right side of heart, which delays that closure of pulmonic valve
- Pulmonary hypertension: Right ventricle has to try and exceed pulmonic artery
Fixed splitting of S2
- causes, how?
- Atrial septal defects can cause this: There is shunting of blood from the left to the right side of the heart, and you’re changing those volumes
Paradoxical splitting
- what happens
- causes
- There’s delayed closure of aortic valve
- LBBB and Aortic stenosis
S4
- cause
- why?
- Left ventricle stiffening
- When the atria is pumping into a stiff LV, the contraction of the atria actually causes an S4 sound