Unit 1: Cardiovascular System
Maihart Hertz is a 65yo male who presented to the emergency department after feeling like "an elephant is sitting on his chest". He has a history of thrombophilia (causes excess clotting) and deep vein thrombosis (DVT) 5 years prior.
Initial Tests and History
1. Looking at the patient's past medical history, you see they have a specific thrombophilia known as antithrombin III deficiency (can be acquired or congenital). Antithrombin III's primary action is inhibition of thrombin. Inhibition of thrombin would cause which of the following?
a. Decreased levels of fibrinogen to fibrin formation.
b. Increased clotting time.
c. Increased levels of fibrin and possible excessive clotting.
d. Excessive bleeding and need for monitoring.
​
​
​
​
​
2. The patient has an elevated hematocrit of 53. Explain what hematocrit is, what cell type it represents, and at least one possible cause for elevation in this patient (there are multiple correct answers).
​
3. The patient's EKG is shown in Figure 3. You interpret it as an ST-elevation. Describe what each wave of the EKG normally represents: P wave, QRS complex, T wave.
​
4. Why isn't atrial repolarization depicted on the EKG?
​
5. How is the EKG different than what is represented in Figure 4?
​
​
​
​
​
​
​
​
​
​
Figure 1. Clotting cascade
Figure 2. Test tube with blood after centrifugation.
Figure 3. Brief EKG segment showing ST elevation.
Figure 4. Electrical activity
Pathophysiology
6. What is the most likely diagnosis given the patient's presenting complaint and lab tests? What causes this condition?
​
7. Why are myocardial muscle cells heavily reliant on a near-constant blood flow? (hint: think about how these cells generate energy)
​
8. Explain how this condition would effect stroke volume, ejection fraction, and cardiac output.
​
9. One of the biggest concerns with this condition is how if affects electrical conductivity of the heart. Ectopic pacemakers can develop, leading to arrhythmias. What is the normal pacemaker of the heart and its rate and what are the backups and their rates?
​
10. What modifies the pacemaker cells of the heart to allow the heart to beat at faster or slower speeds than the default pacemaker rate?
Figure 5. Cardiac anatomy with coronary and great vessels.
Treatment
11. The patient was treated in the angio suite, where they removed the blockage in his left anterior descending (LAD) artery. The patient was sent home with new medications, one of which is a calcium channel blocker. How will calcium channel blockers effect the patient?
a. Decreased heart contractility
b. Increased heart contractility
c. Increased blood pressure
d. The heart muscle will work harder and use more oxygen.
Figure 6. Amlodipine 2.5mg, a calcium channel blocker.
Extending your Knowledge: VIR
DVT occurs when a clot forms in one of the veins, typically in the leg. It is a potentially deadly condition if the clot dislodges and goes somewhere, such as the lungs. This patient had a DVT 5 years prior, which he was at risk for due to his antithrombin III deficiency. One possible treatment for DVT is placement of a filter in a blood vessel to prevent the clot from dislodging into the lungs or other area. This filter is put in by a vascular & interventional radiologist under image-guidance and is there to "catch" the clot if it dislodges from its original site. Other treatment options can be seen in Figure 7.
​
12. Which of the following places does it make the most sense to place a filter in a patient who has a clot in a deep leg vein?
a. Femoral artery
b. Inferior vena cava
c. Abdominal aorta
d. Superior vena cava
Figure 7. Various ways to treat DVT through minimally invasive VIR.
Figure 8. Abdominal CT.