Define afterload (10% of mark).
Describe the factors that can affect left ventricular afterload (90% of mark).
Many definitions of afterload were accepted. The main factors affecting left ventricular
afterload are systemic vascular resistance, aortic impedance and ventricular radius. Other
factors include blood viscosity and positive intrathoracic pressure. Good answers expanded
on the points above. Candidates who failed this question did not have enough facts.
Syllabus C1c C2c
Reference: Bray 4th edition p 342-344 and p 360-361
"Many definitions of afterload were accepted" because no standard definition has been agreed upon after over a hundred years of physiologists debating each other. They all seem to agree on the sort of factors that are involved - just not on how these factors are related. The following attempt should not be viewed as a definitive expression of afterload - instead, it represents a Tetris-like attempt to stack these determinant factors together into a logical-looking rectangular array.
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