What changes in ECG leads may indicate a myocardial infarction?

Elevated ST segments on an electrocardiogram (ECG) are a critical indicator of myocardial infarction (MI). When a particular area of the heart muscle experiences hypoxia or necrosis due to insufficient blood flow, it leads to changes in the electrical activity observed in an ECG. Specifically, this results in an upward shift of the ST segment from the baseline. This elevation suggests that there is a significant injury to the heart muscle, typically due to acute ischemia caused by a blockage in one or more coronary arteries.

In the context of the options provided, increased heart rate may be seen in various conditions but is not specific to myocardial infarction. Inverted P waves can indicate atrial activity issues but don’t directly correlate with ischemic changes. Additionally, decreased QRS amplitude can occur due to various factors, such as pericardial effusion or obesity, but it is not a direct indicator of myocardial infarction. Thus, elevated ST segments stand out as the definitive sign signaling that myocardial tissue is under distress or has been damaged.