A septal myocardial infarction is a type of heart attack characterized by identifiable changes in the patient's electrocardiogram, says ECGpedia.org. The term "septal" indicates the location of the heart attack, while "age undetermined" refers to ECG findings that fail to indicate when the heart attack occurred.
A septal myocardial infarction occurs in the area of the septum, the band of tissue that separates the two sides of the heart. These infarctions occur due to narrowing of the septal branches of the left anterior descending artery, says ECGpedia.org. The corresponding changes in the patient's electrocardiogram tell the doctor where cardiac circulation is compromised; this allows the doctor to try to correct the defect and restore circulation to the heart.
Although many heart attacks cause sudden symptoms, such as chest pain, shortness of breath, nausea and dizziness, some heart attacks produce no symptoms, explains WebMD. These "silent" heart attacks often go undetected until the patient has a routine ECG. Under these circumstances, it may be impossible to determine when the heart attack occurred.
Nearly all heart attacks are the result of atherosclerosis, or narrowing of the arteries that supply blood to the heart, says WebMD. This narrowing is typically the result of calcified deposits, or plaque, within the arteries. However, the direct cause of most heart attacks is a blood clot that forms on the surface of the plaque. The clot cuts off the blood supply to a portion of the heart, depriving it of oxygen until the muscle dies.