Acute Coronary Syndrome (Heart Attack) - Unstable Angina vs NSTEMI vs STEMI | With ECGs

Summary

Acute coronary syndrome (ACS) encompasses a range of conditions caused by thrombus formation in the coronary arteries following plaque rupture, leading to ischemia. The spectrum includes unstable angina, non-ST elevation myocardial infarction (NSTEMI), and ST elevation myocardial infarction (STEMI). ACS can present with chest pain, discomfort, or other subtle symptoms, especially in women and older patients. Diagnosis involves ECG changes, cardiac biomarkers like troponin, and coronary angiography. Treatment includes analgesia, oxygen, antiplatelets, and reperfusion therapy. Secondary prevention focuses on statins, ACE inhibitors, and beta-blockers to reduce the risk of recurrence and improve long-term outcomes.

Takeaways

• 😀 ACS (Acute Coronary Syndrome) is a spectrum of conditions caused by reduced blood flow to the heart, often due to a clot formed after plaque rupture in the coronary arteries.
• 😀 The main types of ACS are unstable angina, NSTEMI (Non-ST Elevation Myocardial Infarction), and STEMI (ST Elevation Myocardial Infarction), with varying levels of heart muscle damage.
• 😀 The heart receives blood from the coronary arteries, which can become narrowed over time due to atherosclerosis, potentially leading to ischemia and angina during physical exertion.
• 😀 ACS occurs when atherosclerotic plaques rupture, exposing thrombogenic material to blood, leading to clot formation and a sudden reduction in blood flow to the heart.
• 😀 Common symptoms of ACS include chest pain (often radiating to the arm or jaw), back pain, nausea, sweating, and shortness of breath. Not all patients present with chest pain, particularly women and diabetics.
• 😀 Diagnosis of ACS is supported by ECG changes: STEMI shows elevated ST segments, while NSTEMI and unstable angina typically show ST depressions or T-wave inversions.
• 😀 Cardiac biomarkers, such as Troponin I, are used to confirm heart muscle damage. Elevated levels are indicative of myocardial injury.
• 😀 The gold standard for diagnosing ACS is coronary angiography, which visualizes the coronary arteries and any blockages or narrowing.
• 😀 Management of ACS includes pain relief (morphine), oxygen therapy, aspirin, nitrates, and antiemetics. Reperfusion therapy with PCI (balloon angioplasty and stent) or fibrinolytics is crucial for STEMI.
• 😀 Secondary prevention for ACS patients involves medications like statins, ACE inhibitors, antiplatelets, and beta-blockers to prevent further cardiovascular events and manage underlying risk factors.

Q & A

What is acute coronary syndrome (ACS)?

Acute coronary syndrome (ACS) refers to a spectrum of conditions resulting from the formation of a thrombus in the coronary arteries after the rupture of an atherosclerotic plaque. It includes unstable angina, non-ST elevation myocardial infarction (NSTEMI), and ST elevation myocardial infarction (STEMI).

How does the heart receive blood, and how does this relate to ACS?

The heart receives blood through the coronary arteries, which are connected to the aorta near the aortic valve. During diastole, the backflow of blood to the aortic valve leads to perfusion of the coronary arteries. If these arteries become narrowed or blocked, it can lead to ischemia and eventually acute coronary syndrome.

What are the two main coronary arteries and their roles?

The two main coronary arteries are the left and right coronary arteries. The left coronary artery divides into the left anterior descending artery (supplying the left ventricle and interventricular septum) and the circumflex artery (supplying the left atrium and part of the left ventricle). The right coronary artery supplies the right atrium, right ventricle, and the SA and AV nodes.

What is the pathophysiology of acute coronary syndrome?

In acute coronary syndrome, atherosclerotic plaques in the coronary arteries rupture, exposing thrombogenic material to the bloodstream. This triggers the formation of a clot, which leads to a sudden reduction in blood flow, causing ischemia in the cardiac muscle. Depending on the severity, this may result in unstable angina, NSTEMI, or STEMI.

What are the differences between STEMI and NSTEMI?

STEMI (ST elevation myocardial infarction) is characterized by a complete occlusion of the coronary artery, leading to transmural necrosis (death of the cardiac muscle across the full thickness of the wall). In contrast, NSTEMI (non-ST elevation myocardial infarction) involves partial occlusion and necrosis that does not extend across the full thickness of the myocardial wall.

What are the major modifiable and non-modifiable risk factors for ACS?

Modifiable risk factors for ACS include smoking, hypertension, diabetes, hyperlipidemia, obesity, and drug use (including cocaine). Non-modifiable risk factors include age, male sex, family history, and ethnicity.

What are the common symptoms of acute coronary syndrome?

Common symptoms of ACS include chest pain or discomfort (often heavy or dull, radiating to the jaw, arm, or shoulder), upper back pain, indigestion-like symptoms, lightheadedness, nausea, vomiting, diaphoresis (heavy sweating), palpitations, and shortness of breath. Some people, particularly women, older adults, and those with diabetes, may present without chest pain.

What is the role of ECG in diagnosing ACS?

An ECG is crucial for diagnosing ACS. In STEMI, there will be ST segment elevation in at least two contiguous leads, indicating a complete blockage of a coronary artery. In NSTEMI, there may be ST segment depression or T-wave inversions, indicating partial occlusion and ischemia. Additionally, pathological Q waves may appear in large infarctions.

What is the significance of cardiac troponin I in ACS diagnosis?

Cardiac troponin I is a protein released from cardiac muscle cells upon cell death. Its elevated levels are a key indicator of myocardial injury. Values above the 99th percentile are considered abnormal. Troponin levels typically rise within 2 hours after the onset of chest pain, peaking at 12-48 hours and remaining elevated for 4 to 15 days.

What are the primary treatments for acute coronary syndrome?

Initial treatment for ACS includes pain relief (often morphine), oxygen therapy to maintain saturation above 94%, nitrates (e.g., glycerol trinitrate), and aspirin. STEMI patients undergo reperfusion therapy (primary percutaneous coronary intervention or fibrinolysis). Further treatments include antiplatelets (P2Y12 inhibitors) and anticoagulants (e.g., heparin), with secondary prevention involving statins, ACE inhibitors, and beta blockers.