Heart is also an organ and requires blood for its own functioning, Coronary arteries supply blood to different portions of heart. Cardiac muscles rythmically contract and relax causing the pumping action. When arteries supplying blood to heart itself get clogged due to atherosclerosis, heart muscles do not recieve adequate blood and together with it oxygen, thus causing undue fatigue of the muscles- this condition is termed as Coronary Artery Disease, when this happens for a long time the muscles may get permanently damage and may not work efficiently leading to 'Heart failure'.

While walking, lifting weight, climbing, upstairs, while thinking, under any emotional stress or even after eating the requirement of oxygenated blood increases and heart has to pump more, in order to do this 'extra' work heart muscles themselves require 'extra' blood, when they do not get that - pain or heaviness in chest is felt, initially it may be relieved with rest but as blockages increase it may require medication for relief. Such pain or discomfort is called 'Angina' . Important thing is that in diabetics with autonomic neuropathy this pain may not be percieved (silent Angina)and the person would continue to overburden the fatigued heart.

If any such symptoms are noted 2 tabs of Sorbitrate ( Isosorbide dinitrate ) should immediately be kept under the tongue as they dilate the blood vessels of heart and allow more blood to flow to heart.

Poorly controlled Diabetes with persistently high blood glucose levels cause damage to the muscles of heart. They slowly loose their functional capability and are not able to pump the required amount of Blood leading to a condition called heart failure.

As the muscles of heart contract they push out the blood from the respective chamber, when they relax that chamber again gets filled with blood. In diabetics the characterstic failure is that of the relaxing muscles,the chambers of heart do not get filled up sufficiently and hence do not pump sufficient blood. Damage to the muscles may be compounded by coronary artery disease which may further decrease their fuctioning.

The functioning capacity of heart is assessed by Echocardiography, a non invasive technique similar to ultrasound.