Pressure/flow dynamics
From WikiCNS
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- Cardiac output = stroke volume x heart rate
- Arterial pressure=cardiac output x systemic vascular resistance
- Preload=ventricular volume at the end of diastole measured as the ventricular filling pressure
- Starling’s law=amount of blood in the ventricle at the end of diastole that determines end diastolic pressure which in turn determines the force of myocardial contraction
- Afterload=amount of resistance generated by the impedance of the arteries, aortic diastolic pressure, aortic root filling, vascular elasticity and left ventricular size (easiest to think of in terms of resistance to left ventricle ejection)
- The Starling curve shows stroke volume on the y axis and left ventricular end diastolic pressure on the x axis; myocardial depression flattens out the slope of the curve and increased contractility raises the slope of the curve
- Flow in rigid tubes, according to Poisseuille’s equation, is proportional to the pressure difference and the radius of the tube to the fourth power and inversely proportional to the length of the tube