The Coronary Arteries
Coronary arteries are the first branches from the ascending aorta and they originate within a specific area known as the coronary sinus. The left main stem artery originates above the left coronary cusp of the aortic valve and right coronary artery originates from the right coronary cusp.
The relevance of the anatomical locations of the coronary arteries will become more apparent later on when we look at the positioning of ECG leads and how to localise a myocardial infarction on a 12 lead ECG.
Right Coronary Artery
And It's Branches
Conus (infundibular) branch: Usually the first branch, supplying the right ventricular outflow tract.This branch may arise separately from the aorta as a “third coronary artery.” During angiograms, forceful injection of contrast down this artery can cause a VF cardiac arrest
Atrial branches: Supply the right atrium. One of these often becomes the SA nodal artery, which supplies the sinoatrial (SA) node in about 60% of people. These arteries were too small to mark on the above diagram. Fun fact: This is why RCA disease can cause bradycardia.
Acute marginal branch
Runs along the acute margin of the heart and supply the right ventricle.
Posterior descending artery (PDA):
In right-dominant circulation (≈70% of people), the RCA gives rise to the PDA, which runs in the posterior interventricular groove. It supplies the inferior wall of the left ventricle, the inferior septum, and parts of both ventricles.
Left Coronary Arteries
And Their Branches
Left Main Stem Artery (LMS)
The left main stem artery passes between the left atrial appendage and the pulmonary trunk, then typically divides into the left anterior descending (LAD) and left circumflex (LCx) arteries. Branches of the circumflex artery are called the obtuse marginal arteries.
The LMS and its distal branch the left anterior descending artery is nicknamed the “widow-maker” because when compromised it jeopardizes blood flow to a huge portion of the myocardium.
Left anterior descending artery (LAD)
The LAD runs down the anterior interventricular groove toward the apex of the heart.
Septal perforators:
These arteries penetrate the interventricular septum to supply the anterior two-thirds of the septum, including the bundle branches.
Diagonal branches:
These supply the anterolateral wall of the left ventricle.
Coronaries In Angiography
In cardiology, we use a multitude of different imaging modalities to visualise different parts of the heart. Coronary imaging traditionally was done using invasive angiography. Nowadays, diagnostic only angiography is being phased out and replaced by CT coronary angiograms. As we are primarily focussed on ECG interpretation, we suggest visiting our friends at "Medmastery.com" if you would like to learn more about coronary imaging
Coronary Angiography
A coronary angiogram is a test used to examine the blood vessels that supply the heart.
During the procedure, the patient lies on a table in a specialised X-ray room called a catheter laboratory. The doctor numbs the skin at the wrist or groin and gently inserts a thin tube into an artery. This tube is guided to the heart using X-ray imaging. A special dye is then injected, allowing the heart arteries to be seen clearly on the X-ray screen.
The patient may feel a brief warm sensation when the dye is injected, but the procedure is usually not painful. It typically takes about 30–45 minutes. Afterward, the tube is removed and pressure is applied to prevent bleeding. Most patients can go home the same day.
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