Cardio-Physio-Cardiac cycle and coronary circulation Flashcards
What process allows for the heart valves to open?
Pressure changes, higher pressure moves to lower pressure area
What is the normal cardiac output?
5 L/min
Formula for cardiac output?
Cardiac Output = Stroke Volume x HR
or
the volume ejected per minute (mL/min)
Stroke volume?
Volume ejected in one beat (mL)
What is the formula for mean arterial pressure?
Pa = Mean arterial pressure (mm Hg)
Pa = Cardiac output x TPR (total peripheral resistance)
Total peripheral resistance units?
mm Hg/mL/min
Fick’s principle
The pulmonary vein will always be the larger number. Pulmonary arterial blood is another way of saying systemic vein or venous blood.
Diagram of the cardiac cycle
What does isovolumetric mean?
no change in volume
examples: contracting but blood not yet moving through valves
or
ventricular diastole, resting and filling up with blood
The Wiggers Diagram
The venous return should/should not equal the cardiac output?
Should
Why is the heart known as a dual pump?
Left to systemic circulation and right to pulmonary circulation. Atria contract simultaneously and ventricles contract simultaneously.
What is the dicrotic notch (insinsura) in the Wiggers Diagram?
There is a small pressure pulse into the aorta
What is the formula for mean arterial pressure (MAP)?
MAP = [(2 x DBP) + SBP]/3
How to calculate pulse pressure?
SBP-DBP
Aortic stenosis (narrowing of valve) creates a large between the aorta and the left ventricle during ejection.
pressure gradient
Aortic valve incompetence is commonly associated with wide/shallow pulse pressures?
wide, also with an early diastolic decrescendo murmur
this is when there is diastolic leakage from the aorta to the LV
Aortic pressure falls to a lower value because of the leakage, causing the PP to be wider
What is another name for left atrial pressure (LAP)?
Pulmonary Capillary Wedge Pressure (PCWP)
Pulmonary artery wedge pressure is similar to left atrial pressure as it measures the pressure right up until the point the pulmonary artery leaves the heart (it is not realistic to measure pulse pressure in the left atrium as you would have to go through the lung)
Jugular venous pulse is synonomous with?
pressure in the right atrium as they are very close to and drain into the right atrium
Which jugular venous pulse wave is caused by atrial contraction?
a wave -normally, it increases 4-6 mmHg during atrial contraction
Which is the jugular venous pulse wave that occurs when the ventricles begin to contract and is caused partly by slight backflow of blood into the atria at the onset of ventricular contraction but mainly by bulging of A-V valves backward toward atria due to increasing pressure in ventricles?
c wave
When does the jugular venous pressure v wave typically occur?
toward the end of ventricular contraction resulting from slow flow of blood into the atria from veins while AV valves closed during ventricular contraction
What pathology results in larger than normal jugular venous pulse pressure a waves?
tricuspid stenosis -blood can’t get through valve as well and blood reflects back into atria causing peak
What pathology results in absent jugular venous pulse pressure a waves?
atrial fibrillation - the atria aren’t contracting very well, hence the absent jugular venous pulse pressure wave
Which pathology results in large jugular venous pulse pressure v waves?
tricuspid regurgitation - the tricuspid valve isn’t closing well and blood pushed backwards into artia (close to jugulars) during ventricular contraction
Review diagram
Review the diagram
What is the end diastolic volume?
maximum volume of the heart, right before contraction
What is the difference between the end diastolic volume and the end systolic volume?
stroke volume
What is the formula for ejection fraction and what is it?
Fraction of blood ejected from the heart with respect to the EDV
stroke volume/ EDV
What does this pressure-volume loop indicate?
increased preload
What does the following pressure-volume loop indicate?
increased afterload
What does the following pressure-volume loop indicate?
increased contractility
What does the area of the PV loop indicate?
Stroke work
blood flow is autoregulatory.
Coronary (having to do with its sensitivity to metabolites and self regulating)
Coronary blood flow is extremely sensitive to ?
hypoxia
What is the metabolite involved in control of coronary blood flow if the vessels sense hypoxia?
adenosine (vasodilator)
:opens up coronary vessels to allow more blood flow
What is the least important mechanism of coronary blood flow control and the most important mechanism of coronary blood flow control?
least= sympathetic control
most = local metabolic control (adenosine)
Does mechanical compression during systole of the heart affect coronary blood flow?
Yes. During systole the vessels are compressed and flow decreases.
Blood flow through the coronary arteries is greatest during systole/diastole?
Diastole, because the vessels are not compressed.
Why is prolonged increased heart rate detrimental for the heart?
Diastole is shortened, which means less coronary flow to the heart itself, which could cause the heart to fail.
Which type of muscle fibers have a higher density of capillaries? skeletal or cardiac
cardiac - cardiac muscle fibers have a higher demand for O2
Pulmonary arterial content is similar to:
venous blood
