Aortic dissection can cause ST elevation on an electrocardiogram (ECG) because it can obstruct coronary arteries, leading to myocardial infarction. The dissection flap, a tear in the inner layer of the aorta, can extend into the coronary arteries, either directly occluding them or compressing them, thus reducing blood flow to the heart muscle. This restricted blood flow causes myocardial ischemia, and if the ischemia is severe and prolonged, it can lead to myocardial necrosis, which is what an ST elevation on the ECG indicates.
Here’s a more detailed explanation:
Dissection and Coronary Artery Involvement:
Aortic dissection, especially Type A dissection, can involve the coronary arteries. This can happen when the tear in the aorta extends into the origin of the coronary arteries, known as the coronary ostium, or when the dissection flap directly occludes the coronary artery.
Myocardial Ischemia:
When the coronary arteries are obstructed or narrowed, blood flow to the heart muscle is reduced, leading to myocardial ischemia. This means the heart muscle isn’t getting enough oxygen and nutrients.
ST Elevation:
On an ECG, ST-segment elevation is a key sign of acute myocardial infarction (STEMI). It indicates that a portion of the heart muscle is experiencing a significant lack of blood flow, which can progress to heart tissue death if not addressed promptly.
Mimicking STEMI:
Because aortic dissection can cause ST elevation, it can sometimes be misdiagnosed as a heart attack (STEMI). It’s important to recognize that aortic dissection and STEMI can present with similar symptoms and ECG findings, making diagnosis challenging.
Importance of Differentiation:
Accurate diagnosis of aortic dissection is crucial because treatment for aortic dissection is significantly different from treatment for STEMI. For example, thrombolytics (medications that dissolve blood clots) used in STEMI can be harmful in aortic dissection, potentially leading to rupture and hemorrhage.