Vessel changes in relation to modification of the cardiac mass. A) atrophic heart with acquired serpentoid form of extramural vessels due to cardiac mass reduction, and minor intramural vascularity. The contrary is seen in cardiac hypertrophy (B) in which the extramural arteries increase in length and diameter (but not in number) to adapt themselves to the greater myocardial mass. Similarly, the same enlargement is seen in the intramural branches. Cor pulmonale, in which condition the right ventricle may become greater than the left one, is an extreme example of adaptation of extramural (C) and intramural, including collaterals (D). No histologic evidence exists of new vessel formation. The cardiac vein show a similar behaviour.