Do you know what ischemic heart disease is caused by unstable medium and small bloodvessells? How serious is ?

This ischemic heart disease is not cause by the major arteries of the heart, but rather by the medium and small blood vessels that seemingly the deprived heart muscle causes ultimately a serious blockage of oxygen rich blood.

Ischemic heart disease is usually caused by blockages and/or spasms of coronary arteries, the tiny vessels that surround the heart muscle and supply it with oxygenated blood. It is a serious condition because failure of these arteries to supply oxygen can lead to necrosis (tissue death) which is myocardial infarction (heart attack).

Sudden Cardiac Arest (SCA) is the same i think. ischemic heart disease鈥擜 serious problem caused by inadequate circulation of blood to the heart muscle. Blood flow to the heart is blocked by obstructions of heart arteries by cholesterol deposits. Ischemic heart disease is the underlying disorder for sudden episodes such as heart attack and sudden death as well as the chronic condition of angina pectoris. Ischemic heart disease is also called coronary artery disease or coronary heart disease.
http://www.acc.org/media/patient/chd/isc...
Please see the webpages on Ischemic cardimyopathy and Heart disease & stroke. Due to this type of heart disease, the pumping capasity of the blood by the heart is affected. Even though coronary arteries (left & right) are very small, it is considered as very important arteries. "Coronary" is derived from the Latin word "corona" which means "crown".
You have to change your life style in order to prevent a second attack.
http://www.nlm.nih.gov/medlineplus/ency/...
http://news.bbc.co.uk/hi/english/static/...
Most ischemic heart disease is caused by occlusion in the epicardial vessels, but small capillaries can get occluded as well. Is this what you are thinking of?