Acute Coronary Syndromes and Ischemic Syndromes - NREMT Paramedic Level

1. Which blood pressure threshold is a common contraindication to nitroglycerin in ACS?

   Systolic blood pressure $<90$ mmHg (or signs of shock). Low SBP indicates hemodynamic instability where nitroglycerin's vasodilatory effects could worsen hypotension and perfusion.

2. What opioid is commonly used for refractory ischemic chest pain when protocols allow?

   Fentanyl (titrate to effect per protocol). Opioids like fentanyl reduce pain and sympathetic drive, decreasing myocardial oxygen demand in persistent ACS symptoms.

3. Identify the best next step: inferior STEMI with hypotension and clear lungs after nitro.

   Give IV fluid bolus; suspect right ventricular infarction. Hypotension post-nitroglycerin in inferior STEMI suggests RV involvement, where fluids restore preload without overloading the left ventricle.

4. Which option best indicates cardiogenic shock complicating ACS in the field assessment?

   Hypotension with pulmonary edema and signs of poor perfusion. This presentation indicates pump failure from extensive myocardial damage, leading to low output and congestion in ACS.

5. Which anatomic wall is suggested by ST elevation in leads V1 through V4?

   Anterior (anteroseptal) myocardial infarction. Precordial leads V1-V4 correspond to the anterior septum and wall, supplied by the left anterior descending artery, indicating occlusion there.

6. Which ACS scenario makes nitroglycerin potentially harmful due to preload dependence?

   Right ventricular infarction (often with inferior STEMI). RV infarction relies on preload for output, so nitroglycerin's venodilation can precipitate hypotension and shock.

7. What is the standard adult aspirin dose for suspected ACS if not contraindicated?

   Aspirin $162$–$324$ mg, chewable. Aspirin inhibits platelet aggregation via cyclooxygenase blockade, reducing thrombus progression in ACS when given early.

8. What is the key clinical distinction between unstable angina and NSTEMI?

   NSTEMI has positive cardiac biomarkers; unstable angina does not. Cardiac biomarkers like troponin indicate myocardial cell death in NSTEMI, distinguishing it from unstable angina where ischemia occurs without necrosis.

9. What is the first priority action when STEMI is suspected based on symptoms and ECG?

   Activate rapid reperfusion pathway and transport to PCI-capable facility. Early reperfusion via PCI minimizes myocardial damage, so prompt activation and transport optimize outcomes in STEMI.

10. Which anatomic wall is suggested by ST elevation in leads II, III, and aVF?

    Inferior wall myocardial infarction. Leads II, III, and aVF view the inferior cardiac wall, so elevation there localizes ischemia to the right coronary artery territory.

11. What ECG change most commonly reflects myocardial ischemia without infarction?

    ST depression and/or T-wave inversion. These changes indicate subendocardial ischemia due to reduced coronary perfusion without complete occlusion or transmural involvement.

12. Which medication is first-line for suspected ACS when hypoxemic, and what is the target?

    Oxygen to maintain $94\%$ SpO$_2$. Supplemental oxygen corrects hypoxemia to ensure adequate myocardial oxygenation, targeting SpO$_2$ ≥94% to avoid hyperoxia risks.

13. Which ECG finding is most specific for acute transmural myocardial injury?

    ST-segment elevation in a contiguous lead set. ST elevation reflects acute transmural ischemia or infarction from epicardial coronary occlusion, distinguishing it from subendocardial processes.

14. Identify the correct action: suspected ACS with SpO$_2$ $=98\%$ on room air and no distress.

    Do not administer routine oxygen; monitor and reassess. Routine oxygen in normoxic patients lacks benefit and may cause vasoconstriction, so monitoring suffices per evidence-based guidelines.

15. Which ECG lead is most useful to detect right ventricular infarction in inferior MI?

    Lead V4R (right-sided ECG). V4R provides a right-sided view to detect ST elevation indicative of right ventricular involvement, often from proximal right coronary occlusion.

16. What is the classic mechanism of most STEMIs at the coronary artery level?

    Acute thrombotic occlusion after plaque rupture. Plaque rupture exposes thrombogenic material, promoting platelet aggregation and thrombus formation that fully occludes the coronary artery in STEMI.

17. Which recent medication class is an absolute contraindication to nitroglycerin use?

    PDE-5 inhibitors taken recently (for example, sildenafil). PDE-5 inhibitors potentiate nitroglycerin's nitric oxide-mediated vasodilation, risking severe hypotension or cardiovascular collapse.

18. Which dysrhythmia is most commonly associated with inferior wall MI due to AV node ischemia?

    Bradycardia or AV block (especially $2^{\text{nd}}$-degree type I). Inferior MI often involves the right coronary artery supplying the AV node, causing ischemic conduction delays like bradycardia or blocks.

19. Which ACS entity is defined by myocardial necrosis with ST-segment elevation on ECG?

    ST-elevation myocardial infarction (STEMI). STEMI involves complete coronary occlusion leading to full-thickness myocardial necrosis, evidenced by persistent ST-segment elevation on ECG and elevated cardiac biomarkers.

20. What is the typical nitroglycerin dose and repeat interval for ACS chest pain?

    Nitroglycerin $0.4$ mg SL every $5$ minutes as tolerated. Nitroglycerin relieves ischemia by vasodilating coronary arteries and reducing preload, repeated as needed if hemodynamically stable.

21. What is the minimum number of contiguous leads required to call STEMI on a 12-lead ECG?

    At least 2 contiguous leads. Diagnostic criteria require ST elevation in at least two anatomically contiguous leads to confirm regional myocardial involvement in STEMI.

22. Which clinical triad suggests right ventricular infarction with an inferior MI?

    Hypotension, clear lungs, and jugular venous distension. This triad reflects right ventricular dysfunction causing reduced preload and cardiac output without left-sided failure or congestion.

23. Which ACS entity has myocardial necrosis without ST-segment elevation on ECG?

    Non–ST-elevation myocardial infarction (NSTEMI). NSTEMI results from partial coronary occlusion causing subendocardial necrosis, detected by elevated cardiac biomarkers without ST elevation on ECG.

24. Which anatomic wall is suggested by ST elevation in leads I, aVL, V5, and V6?

    Lateral wall myocardial infarction. These leads reflect the lateral wall, perfused by the left circumflex artery, localizing the infarction to that region.

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