a lot of research indicate that chronically high blood levels of glucose cause dilated cardiomyopathy by direct toxic effect of sugar on the heart muscle. poor controlled diabetes is associated with small blood vessel disease called (microangiopathy) in which the structure of such vessels(some of which have the duty of supplying food and oxygen to the heart muscle) their structure is damaged making them less able to deliver oxygen and nutrients and making them more susceptible to clogging (atherosclerosis) diabetes especially type 2 is now considered as a part of a spectrum of abnormalities in metabolism associated with middle age known as(metabolic syndrome), diabetes makes more sugar available for storing as fat because this high blood glucose level is not being burned by insulin,this fat is associated with blood clogging(atherosclerosis) which ultimately causes heart attacks . diabetes also effects the kidneys in the long run(also mainly through toxic effect of glucose on structural protiens , and through affecting the small vessels of the kidney) kidney failure leads to increased risk of heart disease.