Cardiovascular [Cardiac Output] Flashcards
Equation for cardiac output
CO = HR x SV
What is cardiac output? What is the average?
The volume of blood ejected into the aorta per minute.
4-7L per min
What Is cardiac reserve?
Difference between resting and max - how much storage the heart has
What is stroke volume?
The volume ejected by the left ventricle in one cardiac cycle
What are the two mechanisms behind which stroke volume is regulated?
Intrinsic regulation of F of contraction: stretch at end of diastole.
Extrinsic: activity of autonomic system + hormones
What is preload?
The tension developed in myocardial fibres due to a rise in pressure from blood returning to the ventricle in diastole. MMHg
What is afterload?
The work the heart has to do to pump blood out. Arterial pressure. MMHg
What is frank-starling law of the heart?
More in = more out
LV + RV balanced.
More stretched = more force
What percentage of blood is pumped out in the ejection fraction? How is heart failure related to this? 3 symptoms
60-70%.
Heart failure is only 25% which leads to breathlessness and pulmonary conjestion. Increased HR.
What is stroke work? Equation and explanation
W = change in P x change in V
Work is given by area of P V curve for contraction.
What happens from point A to B of the pressure-volume curve?
Mitral valve opens at ~20 P.
V increase from 40 to 120mL.
Mitral valve closes
What happens from point B to C of the pressure-volume curve?
Mitral valve closes. P increases from <20 to 80. V stays at 120. Aortic valve opens so that Pv > Paorta Diastolic
What happens from point C to D in the pressure-volume curve?
Aortic valve opens so that Pv > P aorta.
V drops and P increases from 80 to 120.
Ejection to systolic (max).
Aortic valve closes and P drops. V = 40 again.
What happens from point D to A in the pressure-volume curve?
Aortic valve closes.
P drops from 120 to <20 but V stays 40.
Rheumatic fever how caused?
Valves leaky to blood coming back in. Loop gets smaller causing heart failure.
