Acute Coronary Syndromes (ACS) Week 1

Right ventricle (RV)

Pumps against low pulmonary resistance; highly preload dependent and has a thinner wall.

Left ventricle (LV)

Generates high pressure to overcome systemic vascular resistance; has a much thicker wall.

Diastole

The phase of the heartbeat where the heart muscle relaxes and coronary perfusion mainly occurs.

Local myocardial oxygen demand (MVO_2)

Regulates coronary blood flow based on the heart's need for oxygen.

Right Coronary Artery (RCA)

Supplies the right atrium, right ventricle, SA node, AV node, and inferior wall of the left ventricle.

Left Coronary Artery (LCA)

Supplies the left atrium and left ventricle with major branches: LAD, LCX, and Left Marginal Artery.

Atherosclerosis

Patchy plaque buildup in medium and large arteries, causing reduced blood flow.

Arteriosclerosis

A general term for thickened and less elastic arteries.

Foam cells

Macrophages that ingest LDL and accumulate in the arterial wall.

Myocardial ischemia

A condition in which blood flow to the heart muscle is reduced, preventing it from receiving enough oxygen.

Stable angina

Chest discomfort due to increased MVO_2 exceeding supply, generally resolves with rest or nitroglycerin.

Unstable angina

Angina occurring at rest or minimal exertion, often with a crescendo pattern and high risk of progression to MI.

Myocardial Infarction (MI)

Prolonged ischemia leading to irreversible myocardial necrosis.

STEMI

ST elevation myocardial infarction; indicates transmural damage causing elevation due to potassium efflux.

NSTEMI

Non-ST elevation myocardial infarction; implies incomplete obstruction and subendocardial damage.

Collateral circulation

Alternative pathways of blood flow that may develop following occlusion of a primary artery.

Symptoms of MI

Include hypotension, tachycardia, arrhythmias, pulmonary crackles, and left ventricular failure.

Complications of MI

Can include arrhythmias, heart failure, hypoxemia, hypotension, and cardiogenic shock.

High-risk populations for atypical ACS presentations

Elderly, females, and diabetics may present with atypical symptoms.

Atypical symptoms of ACS

May include epigastric pain, nausea, vomiting, unexplained shortness of breath, and diaphoresis.

What percentage of ventricular filling is contributed by atrial contraction?

About 20%; ventricular filling is primarily passive.

Why are atria thin-walled compared to ventricles?

They only move blood into the ventricles and do not overcome significant afterload.

Why are ventricles thick-walled?

To generate enough force to overcome afterload and eject blood.

Why is the right ventricle thinner than the left ventricle?

It pumps against low pulmonary resistance and relies heavily on preload (Frank–Starling law).

Why is the left ventricle much thicker than the right ventricle?

It must generate high pressure to overcome systemic vascular resistance.

Where do the coronary arteries originate?

They are the first branches off the aorta.

When does most myocardial perfusion occur?

During diastole when the ventricles are relaxed.

What primarily regulates coronary blood flow?

Local myocardial oxygen demand (MVO_2).

What structures does the right coronary artery (RCA) supply?

Right atrium, right ventricle, SA node, AV node, and inferior wall of the left ventricle.