HY USMLE Q#1  Concepts CVS Step 2 CK

​Step 2ck/ 3 level (inspired from UWORLD) ​

A 72-year-old male presents with vomiting and generalized abdominal distension and is diagnosed with small bowel obstruction. He undergoes an exploratory laparotomy without postoperative complications. A few hours after extubation, he develops chest discomfort, nausea, and marked diaphoresis. His blood pressure is low, and ECG reveals ST-elevation in leads II, III, and aVF, along with sinus bradycardia. He is given IV normal saline and IV atropine without clinical improvement. What is the next best step in management?

 

A. IV heparin 

B. Alteplase

C. Epinephrine 

D. Temporary Cardiac Pacing 

E. Norepinephrine 

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Explanation: 

✅ D. Correct Answer = Temporary Cardiac Pacing = Appropriate for symptomatic bradycardia unresponsive to atropine (as in this case), especially if it's causing hemodynamic instability. Temporary cardiac pacing which helps to treat bradycardia by providing electrical stimulation to the heart, essentially it is acting as an artifical pacemaker to increase heart rate when it's too slow.  Recall that 60% of the SA node is supplied by the RCA and 90% of the AV nodes are supplied by the AV node.  Recall that the RCA will supply the inferior parts of the heart as it will give the branch of the Posterior descending artery hence it will supply the inferior parts of the heart. 

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It is essential to note that the Right coronary artery gives rise to numerous vital branches. For example, the SA nodal artery ( in 60 to 70% of people), and AV nodal artery (80 to 85%) also come from the RCA, right marginal artery, and the posterior descending artery in a right dominant circulation which is common in 85% of patients this comes from the RCA that supplies the posterior interventricular septum.

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❌ A. IV Heparin → contraindicated in anyone with a recent intra-abdominal surgery but it is unlikely to be administered during PCI to intervene with patient MI Pacing is better to help the MI of this patient.

❌ B. Alteplase → Contraindicated in people with recent surgery. 

❌ C. Epinephrine → Within the beta receptors, epinephrine binds to β1 and β2 with roughly equal affinity. Within the beta receptors, epinephrine binds to β1 and β2 with roughly equal affinity, Receptor Density: β1-adrenergic receptors are highly concentrated in the heart.

❌ E. Norepinephrine → a1 receptor hence the used for sepsis.