Atherosclerosis - arteries are blocked by fat and cholesterol deposits, reducing blood flow.
Disease
Aneurysm - weakening of the blood vessel wall - may rupture.
Valve defects in the heart.
Varicose veins - Leaky venous valves - make veins become dilated and twisted in appearance - varicose veins (varic - swollen vein).
This is an image of the myocardium from a damaged heart.
What do you think has happened?