An EKG/ECG that finds dead tissue of undetermined age in the inferior heart wall is called an "inferior infarct, age undetermined." An infarct is heart tissue that dies from a heart attack, which electrocardiograms, or EKG/ECG, detect because the dead muscle no longer contracts, according to WebMD and the American Heart Association.
The muscles in the heart need oxygen to survive, just like any other muscle, according to the American Heart Association. When the heart muscle is starved of oxygen for too long, the tissue dies. This process usually begins with the build up of fats and cholesterol (plaque), in the coronary arteries that deliver blood to the heart muscle. Eventually, part of this plaque accumulation breaks off and a blood clot forms around it. If this clot creates a blockage, or ischemia, in a coronary artery, then it can prevent blood from flowing to part of the heart, causing that part to die.
The buildup of plaque in the coronary arteries happens slowly and often without any direct warning signs, but when plaque breaks off, it can quickly lead to an ischemia, as the American Heart Association reports. However, not all ischemia lead to heart attacks. Some ischemia are dislodged before they cause permanent damage, reports WebMD. This results in chest pain called angina, which serves to warn patients of plaque buildup and serious heart attack risk.