A 42-year-old woman presents to the urgent care clinic with recurrent chest pain and pressure radiating to her jaw. ECG is obtained and shows ST-segment elevation, but her cardiac enzymes are repeatedly found to be within normal ranges. She has a heart rate of 82/min and a blood pressure of 128/76 mm Hg. Physical examination reveals regular heart sounds with no friction rub. Which of the following options is an acceptable treatment regimen for this patient’s suspected condition?

Calcium channel blockers and nitrates

Beta-blockers, nitrates and aspirin

Aspirin, clopidogrel, beta-blockers, and nitrates

A 76-year-old man is admitted to the hospital for evaluation of sudden-onset chest pain. Three days after admission, he develops severe shortness of breath. Despite appropriate care, the patient dies. The heart at autopsy is shown. Which of the following most likely contributed to this patient's cause of death?

Occlusion of the posterior descending artery

Rupture of the interventricular septum

Pseudoaneurysmal dilation of the left ventricle

Exudative inflammation of the pericardium

Bacterial infection of the mitral valve endocardium

A 58-year-old man comes to the emergency department for complaints of crushing chest pain for 4 hours. He was shoveling snow outside when the pain started. It is rated 7/10 and radiates to his left arm. An electrocardiogram (ECG) demonstrates ST-segment elevation in leads V2-4. He subsequently undergoes percutaneous coronary intervention (PCI) and is discharged with aspirin, clopidogrel, carvedilol, atorvastatin, and lisinopril. Five days later, the patient is brought to the emergency department by his wife with complaints of dizziness. He reports lightheadedness and palpitations for the past 2 hours but otherwise feels fine. His temperature is 99.7°F (37.6°C), blood pressure is 95/55 mmHg, pulse is 105/min, and respirations are 17/min. A pulmonary artery catheter is performed and demonstrates an increase in oxygen concentration at the pulmonary artery. What finding would you expect in this patient?

Harsh, loud, holosystolic murmur at the lower left sternal border

Widespread ST-segment elevations

Drop of systolic blood pressure by 20 mmHg during inspiration

A 78-year-old man with a history of myocardial infarction status post coronary artery bypass grafting and a 60-pack-year history of smoking is found deceased in his apartment after not returning calls to his family for the last 2 days. The man was last known to be alive 3 days ago, when his neighbor saw him getting his mail. The family requests an autopsy. On autopsy, the man is found to have a 100% blockage of his left anterior descending artery of his heart and likely passed from sudden cardiac death 2 days prior. Which of the following findings is expected to be found on histologic examination of his damaged myocardium?

Uniform binding of acidophilic dyes

Cellular debris and lymphocytes

Cellular debris and macrophages

A 57-year-old man presents to his primary care provider because of chest pain for the past 3 weeks. The chest pain occurs after climbing more than 2 flight of stairs or walking for more than 10 minutes and resolves with rest. He is obese, has a history of type 2 diabetes mellitus, and has smoked 15-20 cigarettes a day for the past 25 years. His father died from a myocardial infarction at 52 years of age. Vital signs reveal a temperature of 36.7 °C (98.06°F), a blood pressure of 145/93 mm Hg, and a heart rate of 85/min. The physical examination is unremarkable. Which of the following best represents the most likely etiology of the patient’s condition?

Fixed, atherosclerotic coronary stenosis (> 70%)

Hypertrophy of the interventricular septum

Multivessel atherosclerotic disease with or without a nonocclusive thrombus

Intermittent coronary vasospasm with or without coronary atherosclerosis

Sudden disruption of an atheromatous plaque, with a resulting occlusive thrombus

A 50-year-old man presents the emergency department for intense chest pain, profuse sweating, and shortness of breath. The onset of these symptoms was 3 hours ago. The chest pain began after a heated discussion with a colleague at the community college where he is employed. Upon arrival, he is found conscious and responsive; the vital signs include a blood pressure of 130/80 mm Hg, a heart rate at 90/min, a respiratory rate at 20/min, and a body temperature of 36.4°C (97.5°F). His medical history is significant for hypertension diagnosed 7 years ago, which is well-controlled with a calcium channel blocker. The initial electrocardiogram (ECG) shows ST-segment depression in multiple consecutive leads, an elevated cardiac troponin T level, and normal kidney function. Which of the following would you expect to find in this patient?

Incomplete occlusion of a coronary artery

An 18-year-old man presents with a sudden loss of consciousness while playing college football. There was no history of a concussion. Echocardiography shows left ventricular hypertrophy and increased thickness of the interventricular septum. Which is the most likely pathology underlying the present condition?

Mutation in the myosin heavy chain

Autoimmunity of myocardial fibers

A 74-year-old man presents with complaints of sudden severe crushing retrosternal pain. The pain radiated to his left arm shortly after it began, and he was subsequently rushed to the emergency department for evaluation. His troponins and creatine kinase-MB (CK-MB) were elevated. Unfortunately, the patient died within the next 2 hours and an autopsy was performed immediately. The gross examination of the heart will show?

White, patchy, non-contractile scar

Red granulation tissue surrounding the infarction

Ischemic heart disease for USMLE Step 1: High-Yield Pathology Lessons

IHD Fundamentals - The Clogged Pipes

Pathophysiology: Myocardial O₂ supply-demand mismatch, typically from ↓ supply.
Etiology: Atherosclerosis is the primary cause, leading to coronary artery stenosis.
- Stable Plaque: Thick fibrous cap, small lipid core → predictable, exertional angina.
- Unstable Plaque: Thin cap, large lipid core, high inflammation → prone to rupture.
Acute Coronary Syndrome (ACS): Plaque rupture exposes thrombogenic core → thrombus formation → acute occlusion.

Stable vs. Unstable Atherosclerotic Plaque Comparison

⭐ The Left Anterior Descending (LAD) artery is the most common site of thrombotic occlusion.

Angina Pectoris - The Warning Pains

Chest pain due to transient, reversible myocardial ischemia. No myocyte necrosis.

Type	Pathophysiology	Presentation & ECG	Treatment
Stable	Atherosclerosis (>70% stenosis)	Exertional; relieved by rest/NTG. ST depression.	Nitrates, β-blockers
Unstable	Plaque rupture, thrombosis	Rest/crescendo pain. ST depression.	Hospitalize, antiplatelets
Prinzmetal	Coronary vasospasm	Episodic, often at rest/night. ST elevation.	Ca²⁺ channel blockers, Nitrates

⭐ Prinzmetal Angina Treatment Pearl: Avoid non-selective β-blockers as they can worsen vasospasm by blocking β₂-mediated vasodilation, leading to unopposed α₁-receptor vasoconstriction.

Myocardial Infarction - The Big One

Irreversible necrosis of cardiac muscle from prolonged ischemia, typically due to acute thrombotic occlusion of a coronary artery (LAD > RCA > LCX).
Key diagnostic markers include elevated cardiac troponins (most sensitive and specific), characteristic ECG changes, and clinical presentation.

Myocardial stunning and troponin I levels after ischemia

⭐ The period of greatest risk for ventricular free wall rupture is 3-14 days post-MI. This is when macrophages have removed necrotic debris, but the collagenous scar is not yet fully formed, leaving the wall at its weakest.

Post-MI Complications - The Domino Effect

Timeline of Events: Complications are predictable based on the post-infarct timeline.

Mechanical Complications (Days 3-14): Result from macrophage-mediated degradation.
- Free Wall Rupture: Leads to cardiac tamponade, sudden death. Most common cause of death from rupture.
- Septal Rupture: New holosystolic murmur, ↑O₂ sat in RV.
- Papillary Muscle Rupture: Severe mitral regurgitation.

Post-MI Cardiac Rupture Locations and Clinical Features

⭐ Posteromedial papillary muscle is more prone to rupture due to its singular blood supply from the posterior descending artery (PDA).

Atherosclerosis of the coronary arteries is the overwhelming cause of IHD, typically in the left anterior descending (LAD) artery.

Stable angina presents as exertional chest pain from >70% stenosis; unstable angina is pain at rest due to plaque rupture and thrombosis.

Myocardial infarction means irreversible necrosis; troponins are the most sensitive and specific biomarkers.

STEMI reflects a transmural infarct with ST elevation, while NSTEMI indicates a subendocardial infarct.

Key MI complications include arrhythmias, mural thrombus, and ventricular aneurysm.

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