What does myocardial ischemia look like on an ECG?

As a medical professional with expertise in cardiology, I can provide you with an overview of what myocardial ischemia typically looks like on an ECG. Myocardial ischemia occurs when there is a lack of blood flow to the heart muscle, which can lead to chest pain or angina. On an ECG, the signs of myocardial ischemia can vary depending on the severity and duration of the ischemic episode. Here are some key features to look for: 1. ST Segment Depression: This is one of the most common signs of myocardial ischemia. The ST segment should be relatively flat and isoelectric. Depression of the ST segment indicates that the heart muscle is experiencing a lack of oxygen. 2. T Wave Inversions: Deep and symmetrical T wave inversions, particularly in leads facing the area of ischemia, can also be a sign of ischemia. 3. Pathological Q Waves: In the case of a more severe and prolonged ischemic event, such as a myocardial infarction (MI), pathological Q waves may appear. These are broad and unusually deep Q waves that suggest tissue death. 4. ST Segment Elevation: While this is more characteristic of an acute MI, ST segment elevation can also be seen in certain types of ischemia, particularly when there is a complete blockage of a coronary artery. 5. Tachycardia or Bradycardia: Changes in heart rate can also be seen with ischemia, with some patients experiencing an increased heart rate (tachycardia), while others may have a slower heart rate (bradycardia). It's important to note that the ECG changes in myocardial ischemia are not always straightforward and can be influenced by various factors, including the patient's underlying heart condition, the presence of other medical conditions, and the medications the patient is taking. Therefore, a thorough clinical assessment is necessary to interpret ECG findings accurately.

Acute myocardial infarction (MI) affects both ventricular depolarization (appearance of pathological Q waves) and repolarization (ST-T wave changes). Specific manifestations depend on whether the lesion is subendocardial or transmural in location. The ECG sign of subendocardial ischemia is ST segment depression (A).