minniedog,

Hardening of the vessels are not the same as hardening of the blood vessels.

The blood vessels of the heart can get hardened due to deposition of plaques along the arteries. These plaques are mainly made up of cholesterol and other fats. The condition is known as atherosclerosis. As the plaques build up they cause the arteries to become narrow and harder decreasing blood flow to the muscles. When the blood supply to aparticulr muascle completley stops, the muscle dies off causing a heart attack.

The heart muscles may become hard in conditions like amyloidosis and sarcoidosis in which the muslces beocme hard and inelastic. The heart fails to fill properly with blood and to pump out the blood again to the body. The condition is known as restrictive cardiomyopathy.

You can read about restrictive cardiomyopathy here:

- http://www.nlm.nih.gov/MEDLINEPLUS/ency/article/000189.htm

I hope this helps.

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