Question

Define the term acute coronary syndrome and distinguish among chronic stable angina, unstable angina (UA), non-ST–segment elevation myocardial infarction (NSTEMI), and ST-segment elevation myocardial infarction (STEMI) in terms of pathology and symptomatology.

Answer 1

Acute coronary syndrome:

Acute coronary syndrome (ACS) is a syndrome (set of signs and symptoms) due to decreased blood flow in the coronary arteries such that part of the heart muscle is unable to function properly or dies.

The most common symptom is chest pain, often radiating to the left shoulder or angle of the jaw, crushing, central and associated with nausea and sweating.

Pathology and symptoms:

Stable angina:
Also known as 'effort angina', this refers to the classic type of angina related to myocardial ischemia. A typical presentation of stable angina is that of chest discomfort and associated symptoms precipitated by some activity (running, walking, etc.) with minimal or non-existent symptoms at rest or after administration of sublingual nitroglycerin.

Symptoms typically abate several minutes after activity and recur when activity resumes. In this way, stable angina may be thought of as being similar to intermittent claudication symptoms. Other recognized precipitants of stable angina include cold weather, heavy meals, and emotional stress.

Unstable angina:
Unstable angina (UA) (also "crescendo angina"; this is a form of acute coronary syndrome) is defined as angina pectoris that changes or worsens.

It has at least one of these three features:

it occurs at rest (or with minimal exertion), usually lasting more than 10 minutes
it is severe and of new onset (i.e., within the prior 4–6 weeks)
it occurs with a crescendo pattern (i.e., distinctly more severe, prolonged, or frequent than before).
UA may occur unpredictably at rest, which may be a serious indicator of an impending heart attack.

The pathophysiology of unstable angina is the reduction of coronary flow due to transient platelet aggregation on apparently normal endothelium, coronary artery spasms, or coronary thrombosis.

The process starts with atherosclerosis, progresses through inflammation to yield an active unstable plaque, which undergoes thrombosis and results in acute myocardial ischemia, which, if not reversed, results in cell necrosis (infarction).

Studies show that 64% of all unstable anginas occur between 22:00 and 08:00 when patients are at rest.

In stable angina, the developing atheroma is protected with a fibrous cap. This cap may rupture in unstable angina, allowing blood clots to precipitate and further decrease the area of the coronary vessel's lumen. This explains why, in many cases, unstable angina develops independently of activity.

NSTEMI & STEMI:

Each heartbeat shows a visible waveform on an electrocardiogram (ECG). Although the clinical presentation and symptoms of NSTEMIs and STEMIs are the same, their waves look very different on an ECG.

An ECG will show the following characteristics for an NSTEMI:

depressed ST wave or T-wave inversion
no progression to Q wave
partial blockage of the coronary artery

A STEMI will show:

elevated ST wave
progression to Q wave
full blockage of the coronary artery
Both types of heart attack are considered acute coronary syndromes, a term that describes any blockage of blood supply to the heart muscle. As a result, NSTEMI and STEMI can lead to damage of the heart tissue.

Symptoms of NSTEMI :

• shortness of breath
• pressure, tightness, or discomfort in your chest
• pain or discomfort in your jaw, neck, back, or stomach
• dizziness
• lightheadedness
• nausea
• sweating

Symptoms of a STEMI :

• Chest pain or discomfort
• Shortness of breath
• Dizziness or light-headedness
• Nausea or vomiting
• Diaphoresis (sweatiness) unexplained by ambient temperature
• Palpitations (uncomfortable awareness of the heart beat)
• Anxiety or a feeling of impending doom