ECG Cardiac Anatomy 3 — Questions and Answers
Question 1: The fossa ovalis is a remnant of which fetal structure?
- Ductus venosus
- Foramen ovale (Correct answer)
- Ductus arteriosus
- Umbilical vein
Correct answer: Foramen ovale
After birth, the foramen ovale closes and becomes the fossa ovalis, a thin depression in the interatrial septum.
Question 2: Which ECG lead best reflects the lateral wall of the left ventricle supplied by the left circumflex artery?
- V1–V2
- II, III, aVF
- V3–V4
- I, aVL, V5–V6 (Correct answer)
Correct answer: I, aVL, V5–V6
Leads I, aVL, V5, and V6 face the lateral wall, making them most sensitive to lateral ischemia from circumflex disease.
Question 3: How many pulmonary veins typically drain into the left atrium?
- Two
- Three
- Four (Correct answer)
- Six
Correct answer: Four
Normally four pulmonary veins (two from each lung) return oxygenated blood to the left atrium.
Question 4: The moderator band (septomarginal trabecula) is found in which cardiac chamber?
- Left atrium
- Left ventricle
- Right ventricle (Correct answer)
- Right atrium
Correct answer: Right ventricle
The moderator band crosses the right ventricular cavity and carries part of the right bundle branch to the anterior papillary muscle.
Question 5: Which artery is the most common culprit in anterior ST-elevation MI?
- Right coronary artery
- Left circumflex artery
- Left anterior descending artery (Correct answer)
- Obtuse marginal artery
Correct answer: Left anterior descending artery
The LAD supplies the anterior left ventricular wall and septum; its occlusion causes anterior STEMI seen in V1–V4.
Question 6: Pectinate muscles are most prominent in which chamber?
- Left ventricle
- Right atrium (Correct answer)
- Left atrium
- Right ventricle
Correct answer: Right atrium
Pectinate muscles are ridged muscular bands lining the right atrial appendage and anterior right atrium.
Question 7: Which structure forms the posterior border of the heart as seen on a chest X-ray?
- Right ventricle
- Left atrium (Correct answer)
- Right atrium
- Left ventricle
Correct answer: Left atrium
The left atrium forms most of the posterior cardiac border and is enlarged in mitral valve disease.
ECG Cardiac Anatomy 3
The fossa ovalis is a remnant of which fetal structure?