ST segment elevation in ECG is seen in all of the following except:
**Core Concept**
ST segment elevation in an electrocardiogram (ECG) is a marker of myocardial ischemia or infarction, indicating damage to the cardiac muscle. This occurs due to the accumulation of potassium ions (K+) and the loss of sodium ions (Na+) within the cardiac muscle cells, leading to a shift in the electrical potential.
**Why the Correct Answer is Right**
ST segment elevation is a classic ECG finding in acute myocardial infarction (MI), particularly in the setting of an occluded coronary artery. The injury to the cardiac muscle cells leads to the loss of membrane integrity, resulting in the leakage of ions and the accumulation of potassium ions. This, in turn, causes a shift in the electrical potential, resulting in ST segment elevation. The ST segment elevation can be further classified into different types, such as hyperacute, acute, or subacute, depending on the duration and severity of the myocardial injury.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because ST segment elevation can also be seen in pericarditis, a condition characterized by inflammation of the pericardium, the sac surrounding the heart. This occurs due to the irritation of the pericardial tissues, leading to the release of inflammatory mediators and the accumulation of fluid in the pericardial space.
**Option B:** ST segment elevation can also be seen in Brugada syndrome, a genetic disorder affecting the cardiac sodium channels, leading to abnormal electrical activity in the heart.
**Option C:** ST segment elevation can also be seen in Takotsubo cardiomyopathy, a condition characterized by a transient left ventricular dysfunction, often precipitated by emotional or physical stress.
**Clinical Pearl / High-Yield Fact**
Remember that ST segment elevation can have various causes, including myocardial infarction, pericarditis, Brugada syndrome, and Takotsubo cardiomyopathy. A thorough history, physical examination, and diagnostic workup are essential to determine the underlying cause of ST segment elevation.
**Correct Answer:** D