Practice Test 4 - USMLE Step 1

20 questions. Answer them in any order, then submit to see your score and every explanation.

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1. Changes in which of the following factors will have the greatest impact on blood flow?
2. Which of the following would most directly increase stroke volume via the Frank-Starling mechanism?
3. Which of the following cellular changes is the most reliable indicator that irreversible myocyte injury has occurred?
4. A 57-year-old man with chronic atrial fibrillation is evaluated for progressive shortness of breath and a nonproductive cough that developed over 3 months. He has no fever, hemoptysis, or recent infections. Medications include warfarin, lisinopril, metoprolol, and an antiarrhythmic started 10 months ago after failure of rate control therapy. Physical examination shows digital clubbing and fine inspiratory crackles at both lung bases. Chest radiograph reveals diffuse reticular opacities. Which of the following drugs is the most likely cause of this patient's pulmonary findings?
5. A 55-year-old man with multidrug-resistant Staphylococcus aureus bacteremia is started on daptomycin. Two days later he develops worsening dyspnea. Chest radiograph demonstrates new bilateral infiltrates, and sputum culture grows the same MRSA strain. Which property of daptomycin best explains its failure to treat this pulmonary infection?
6. A 59-year-old man with type 2 diabetes and obesity is started on liraglutide. Four weeks later he reports early satiety, 4-kg weight loss, and occasional post-prandial nausea. Which of the following best describes the principal mechanism by which liraglutide lowers blood glucose in this patient?
7. This component of the anthrax toxin is known as which of the following?
8. This medication aims to improve cognitive symptoms by increasing the synaptic availability of which neurotransmitter?
9. A deficiency of which of the following enzymes is most likely responsible for this patient's presentation?
10. A 70-year-old man with long-standing type 2 diabetes is admitted with sepsis and is treated with high-dose glucocorticoids. Within 48 hours his fasting plasma glucose rises to 280 mg/dL despite maximal metformin therapy. Intravenous regular insulin infusion is started. Compared with lispro insulin, regular insulin is preferable in this setting mainly because it:
11. A 45-year-old man with CKD stage 4 is prescribed a renally eliminated antiviral. The drug follows first-order kinetics and has Vd 30 L. In healthy adults, clearance is 6 L/h (half-life $\approx 3.5$ h). In this patient, measured clearance is 2 L/h due to reduced GFR. No hepatic disease. Which of the following best describes how the pharmacokinetics of this drug is altered in this patient?
12. Excluding these patients from the final analysis violates the principle of intention-to-treat and introduces which type of bias?
13. Which of the following enzymes is the primary target of this medication in gram-negative bacteria?
14. Which of the following cytokines has these potent immunosuppressive and anti-inflammatory properties?
15. Blockade of which hypothalamic-pituitary interaction most directly accounts for her hyperprolactinemia?
16. Pudendal nerve blockade during defecation would most directly impair:
17. This patient's condition leads to hypoxemia primarily by causing a marked increase in which of the following?
18. A randomized controlled trial enrolls 210 adults (ages 19–55) with moderate persistent asthma and frequent nighttime symptoms despite inhaled corticosteroids. Investigators test the hypothesis that adding a new leukotriene antagonist reduces exacerbations over 24 weeks. Participants are randomized 1:1 using sealed, opaque envelopes prepared by an independent pharmacist; tablets are identical, and both patients and clinicians are blinded. Exacerbations are defined as need for systemic steroids or urgent visit. Results: 22/105 (21%) in treatment vs 35/105 (33%) in placebo have an exacerbation. However, 18% of participants correctly guess their assignment due to mild headache occurring more often in the active group (26% vs 10%). What is the primary advantage of the study design described?
19. This patient's auscultatory findings are best explained by which of the following underlying valvular pathologies?
20. High prolactin levels in this patient most directly suppress which hypothalamic hormone, leading to her lactational amenorrhea?

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