A 56-year-old man is brought to the Emergency Department with intense chest pain that radiates to his left arm and jaw. He also complains of feeling lightheaded. Upon arrival, his blood pressure is 104/60 mm Hg, pulse is 102/min, respiratory rate is 25/min, body temperature is 36.5°C (97.7°F), and oxygen saturation is 94% on room air. An electrocardiogram shows an ST-segment elevation in I, aVL, and V5-6. The patient is transferred to the cardiac interventional suite for a percutaneous coronary intervention. The patient is admitted to the hospital after successful revascularization. During his first night on the ICU floor his urinary output is 0.15 mL/kg/h. Urinalysis shows muddy brown casts. Which of the following outcomes specific to the patient’s condition would you expect to find?
Q32
Two days after undergoing an uncomplicated total thyroidectomy, a 63-year-old woman has acute, progressive chest pain. The pain is sharp and burning. She feels nauseated and short of breath. The patient has a history of hypertension, type 1 diabetes mellitus, medullary thyroid cancer, multiple endocrine neoplasia type 2A, anxiety, coronary artery disease, and gastroesophageal reflux disease. She smoked half a pack of cigarettes daily for 24 years but quit 18 years ago. Current medications include lisinopril, insulin glargine, insulin aspart, sertraline, aspirin, ranitidine, and levothyroxine. She appears anxious and diaphoretic. Her temperature is 37.4°C (99.3°F), pulse is 64/min, respirations are 17/min, and blood pressure is 148/77 mm Hg. The lungs are clear to auscultation. Examination shows a 3-cm linear incision over the anterior neck with 1 mm of surrounding erythema and mild serous discharge. The chest wall and abdomen are nontender. There is 5/5 strength in all extremities and decreased sensation to soft touch on the feet bilaterally. The remainder of the examination shows no abnormalities. Which of the following is the most appropriate next step in management?
Q33
A 68-year-old woman, otherwise healthy, is admitted to the coronary care unit due to acute ischemic cardiomyopathy. No other significant past medical history. Her vital signs include: pulse 116/min, respiratory rate 21/min, temperature 37.4°C (99.3°F), and blood pressure 160/100 mm Hg. On physical examination, the patient is in distress. Cardiopulmonary exam is positive for bilateral pulmonary crackles at the lung bases, tachycardia, and jugular venous distension. Her laboratory findings are significant for a hemoglobin of 7.8 g/dL. She is initially treated with oxygen, antiplatelet therapy, nitroglycerin, and beta-blockers. In spite of these treatments, her angina does not subside. The patient is not a candidate for percutaneous coronary intervention, so she is being prepared for a coronary artery bypass graft. Which of the following would be the next, best step in management of this patient?
Q34
A 64-year-old male with a past medical history of obesity, diabetes, hypertension, and hyperlipidemia presents with an acute onset of nausea, vomiting, diaphoresis, and crushing substernal chest pain. Vital signs are temperature 37° C, HR 110, BP 149/87, and RR of 22 with an oxygen saturation of 99% on room air. Physical exam reveals a fourth heart sound (S4), and labs are remarkable for an elevated troponin. EKG is shown below. The pathogenesis of the condition resulting in this patient’s presentation involves:
Q35
A 70-year-old man presents to the emergency department with severe substernal chest pain of one hour’s duration. The patient was taking a morning walk when the onset of pain led him to seek care. His past medical history includes coronary artery disease, hyperlipidemia, and hypertension. Medications include aspirin, losartan, and atorvastatin. An electrocardiogram reveals ST elevations in the inferior leads II, III, and avF as well as in leads V5 and V6. The ST elevations found in leads V5-V6 are most indicative of pathology in which of the following areas of the heart?
Q36
A 46-year-old man accountant is admitted to the emergency department with complaints of retrosternal crushing pain that radiates to his left arm and jaw. The medical history is significant for hyperlipidemia and arterial hypertension, for which he is prescribed a statin and ACE inhibitor, respectively. An ECG is obtained and shows an ST-segment elevation in leads avF and V2-V4. The blood pressure is 100/50 mm Hg, the pulse is 120/min, and the respiratory rate is 20/min. His BMI is 33 kg/m2 and he has a 20-year history of smoking cigarettes. Troponin I is elevated. The patient undergoes percutaneous coronary intervention immediately after admission. Angioplasty and stenting were successfully performed. On follow-up the next day, the ECG shows decreased left ventricular function and local hypokinesia. The patient is re-evaluated 14 days later. The echocardiography reveals a normal ejection fraction and no hypokinesis. Which of the phenomena below explains the patient’s clinical course?
Q37
A 65-year-old man presents to the emergency room with chest pain. Coronary angiography reveals significant stenosis of the left anterior descending (LAD) artery. Which of the following factors best predicts the risk of myocardial necrosis in this clinical setting?
Q38
A 73-year-old man presents to the outpatient clinic complaining of chest pain with exertion. He states that resting for a few minutes usually resolves the chest pain. Currently, he takes 81 mg of aspirin daily. He has a blood pressure of 127/85 mm Hg and heart rate of 75/min. Physical examination reveals regular heart sounds and clear lung sounds bilateral. Which medication regimen below should be added?
Q39
A 43-year-old man comes to the emergency room complaining of chest discomfort. He describes the feeling as "tightness," and also reports weakness and palpitations for the past hour. He denies shortness of breath, diaphoresis, or lightheadedness. He has no significant past medical history, and does not smoke, drink, or use illicit drugs. His father had a myocardial infarction at age 72. He is afebrile, heart rate is 125 bpm, and his blood pressure is 120/76. He is alert and oriented to person, place, and time. His electrocardiogram is shown below. Which of the following tests should be ordered in the initial work-up of this patient's condition?
Q40
One hour after being admitted to the hospital for sharp, acute chest pain and diaphoresis, a 55-year-old woman with type 2 diabetes mellitus loses consciousness in the emergency department. There are no palpable pulses. Chest compressions are started. The patient has a history of breast cancer that was surgically treated 4 years ago. Prior to admission, the patient was on a long bus ride to visit her sister. Her medications include tamoxifen, atorvastatin, metoprolol, metformin, and insulin. Serum troponin levels are elevated. The cardiac rhythm is shown. Which of the following is the most appropriate next step in management?
ACS US Medical PG Practice Questions and MCQs
Question 31: A 56-year-old man is brought to the Emergency Department with intense chest pain that radiates to his left arm and jaw. He also complains of feeling lightheaded. Upon arrival, his blood pressure is 104/60 mm Hg, pulse is 102/min, respiratory rate is 25/min, body temperature is 36.5°C (97.7°F), and oxygen saturation is 94% on room air. An electrocardiogram shows an ST-segment elevation in I, aVL, and V5-6. The patient is transferred to the cardiac interventional suite for a percutaneous coronary intervention. The patient is admitted to the hospital after successful revascularization. During his first night on the ICU floor his urinary output is 0.15 mL/kg/h. Urinalysis shows muddy brown casts. Which of the following outcomes specific to the patient’s condition would you expect to find?
A. Blood urea nitrogen (BUN):Serum creatinine ratio (Cr) < 15:1 (Correct Answer)
B. Urinary osmolality 900 mOsmol/kg (normal: 500–800 mOsmol/kg)
C. Urinary osmolality 550 mOsmol/kg (normal: 500–800 mOsmol/kg)
D. FENa+ < 1%
E. Blood urea nitrogen (BUN):Serum creatinine ratio (Cr) > 20:1
Explanation: ***Blood urea nitrogen (BUN):Serum creatinine ratio (Cr) < 15:1***
- The patient's presentation with **ST-segment elevation myocardial infarction (STEMI)** followed by low urinary output and **muddy brown casts** strongly indicates **acute tubular necrosis (ATN)**, a form of intrinsic renal failure.
- In ATN, **tubular damage** impairs reabsorption of urea more than creatinine, leading to a **BUN:Cr ratio typically less than 15:1**.
*Urinary osmolality 900 mOsmol/kg (normal: 500–800 mOsmol/kg)*
- A urinary osmolality of 900 mOsmol/kg indicates appropriately concentrated urine, which is characteristic of **prerenal azotemia**, not ATN.
- In ATN, the damaged tubules lose their ability to concentrate urine, resulting in **isosthenuric** urine with osmolality typically **< 350 mOsmol/kg** (approaching plasma osmolality).
*Urinary osmolality 550 mOsmol/kg (normal: 500–800 mOsmol/kg)*
- While 550 mOsmol/kg is within the normal range, it is still **too concentrated for ATN**.
- In ATN, damaged tubules cannot effectively concentrate urine, resulting in **urine osmolality < 350 mOsmol/kg** (isosthenuric, similar to plasma osmolality of ~290 mOsmol/kg).
- This value of 550 mOsmol/kg suggests preserved concentrating ability, which would be more consistent with prerenal azotemia or normal renal function.
*FENa+ < 1%*
- A **fractional excretion of sodium (FENa+) less than 1%** indicates good tubular reabsorption of sodium and is characteristic of **prerenal azotemia**, where the kidneys are attempting to conserve volume.
- In ATN, the damaged tubules cannot effectively reabsorb sodium, so the **FENa+ is typically greater than 2%**.
*Blood urea nitrogen (BUN):Serum creatinine ratio (Cr) > 20:1*
- A **BUN:Cr ratio greater than 20:1** is characteristic of **prerenal azotemia**, reflecting decreased renal perfusion causing increased urea reabsorption relative to creatinine.
- In ATN, the **tubular damage** leads to inefficient urea reabsorption, keeping the ratio **below 15:1**.
Question 32: Two days after undergoing an uncomplicated total thyroidectomy, a 63-year-old woman has acute, progressive chest pain. The pain is sharp and burning. She feels nauseated and short of breath. The patient has a history of hypertension, type 1 diabetes mellitus, medullary thyroid cancer, multiple endocrine neoplasia type 2A, anxiety, coronary artery disease, and gastroesophageal reflux disease. She smoked half a pack of cigarettes daily for 24 years but quit 18 years ago. Current medications include lisinopril, insulin glargine, insulin aspart, sertraline, aspirin, ranitidine, and levothyroxine. She appears anxious and diaphoretic. Her temperature is 37.4°C (99.3°F), pulse is 64/min, respirations are 17/min, and blood pressure is 148/77 mm Hg. The lungs are clear to auscultation. Examination shows a 3-cm linear incision over the anterior neck with 1 mm of surrounding erythema and mild serous discharge. The chest wall and abdomen are nontender. There is 5/5 strength in all extremities and decreased sensation to soft touch on the feet bilaterally. The remainder of the examination shows no abnormalities. Which of the following is the most appropriate next step in management?
A. Obtain an ECG and troponin T levels (Correct Answer)
B. Administer IV pantoprazole and schedule endoscopy
C. Discontinue levothyroxine and obtain fT4 levels
D. Administer IV levofloxacin and obtain chest radiograph
E. Obtain urine and plasma metanephrine levels
Explanation: **Obtain an ECG and troponin T levels**
- The patient presents with acute, progressive **chest pain that is sharp and burning**, along with nausea and shortness of breath, which are classic symptoms of an acute coronary syndrome, especially given her history of **coronary artery disease**, hypertension, diabetes, and prior smoking.
- An **ECG** and **troponin T levels** are crucial first steps to evaluate for myocardial ischemia or infarction in this high-risk patient.
*Administer IV pantoprazole and schedule endoscopy*
- While the patient has a history of gastroesophageal reflux disease (GERD) and her pain is described as "burning," the **acuteness, progression, and associated symptoms** (nausea, shortness of breath) in a patient with significant cardiac risk factors make a GI cause less likely as the primary concern.
- Empiric treatment for GERD without first ruling out a life-threatening cardiac event would be inappropriate and potentially dangerous.
*Discontinue levothyroxine and obtain fT4 levels*
- The patient is taking levothyroxine after a thyroidectomy for medullary thyroid cancer, but there is no immediate indication of thyroid hormone imbalance (e.g., hyperthyroidism causing chest pain) that would warrant discontinuing her medication or rushing fT4 levels as the first step in an acute chest pain presentation.
- Her pulse of 64/min is not suggestive of hyperthyroidism, which typically causes tachycardia.
*Administer IV levofloxacin and obtain chest radiograph*
- While shortness of breath can be a symptom of pneumonia, the **sharp, burning nature of the chest pain**, coupled with the absence of fever (temperature 37.4°C is mild), cough, or abnormal lung sounds (lungs clear to auscultation), makes an acute infection like pneumonia less probable as the primary diagnosis.
- Antibiotics and a chest radiograph would be considered after ruling out more immediate life-threatening conditions like acute coronary syndrome.
*Obtain urine and plasma metanephrine levels*
- The patient has a history of multiple endocrine neoplasia type 2A (MEN2A), which includes medullary thyroid cancer and can be associated with pheochromocytoma (adrenal tumor secreting catecholamines). However, her blood pressure (148/77 mm Hg) is not acutely elevated to crisis levels, and her symptoms are more consistent with cardiac ischemia than a pheochromocytoma crisis.
- While metanephrine levels would be important for long-term follow-up of MEN2A, they are not the immediate next step for acute chest pain in a patient with known coronary artery disease.
Question 33: A 68-year-old woman, otherwise healthy, is admitted to the coronary care unit due to acute ischemic cardiomyopathy. No other significant past medical history. Her vital signs include: pulse 116/min, respiratory rate 21/min, temperature 37.4°C (99.3°F), and blood pressure 160/100 mm Hg. On physical examination, the patient is in distress. Cardiopulmonary exam is positive for bilateral pulmonary crackles at the lung bases, tachycardia, and jugular venous distension. Her laboratory findings are significant for a hemoglobin of 7.8 g/dL. She is initially treated with oxygen, antiplatelet therapy, nitroglycerin, and beta-blockers. In spite of these treatments, her angina does not subside. The patient is not a candidate for percutaneous coronary intervention, so she is being prepared for a coronary artery bypass graft. Which of the following would be the next, best step in management of this patient?
A. Transfuse packed red blood cells (Correct Answer)
B. Administer intravenous iron
C. Treat with erythropoietin
D. Transfuse whole blood
E. Observation and supportive care
Explanation: ***Transfuse packed red blood cells***
- The patient has **acute ischemic cardiomyopathy** and a **hemoglobin of 7.8 g/dL**, indicating significant anemia that can exacerbate myocardial ischemia and compromise oxygen delivery.
- Given her ongoing angina despite medical therapy and preparation for **coronary artery bypass graft (CABG)**, **transfusing packed red blood cells (PRBCs)** is crucial to rapidly improve oxygen-carrying capacity and stabilize her condition.
*Administer intravenous iron*
- **Intravenous iron** is used to treat **iron deficiency anemia**, which typically allows for a more gradual increase in hemoglobin.
- This patient's anemia is severe and contributing to acute cardiac ischemia, requiring a **rapid increase in hemoglobin** that iron therapy cannot provide.
*Treat with erythropoietin*
- **Erythropoietin** stimulates red blood cell production over several weeks and is typically used for **chronic anemia**, especially in patients with chronic kidney disease.
- It is not suitable for **acute, severe anemia** like in this case, where immediate improvement in oxygen delivery is critical.
*Transfuse whole blood*
- **Whole blood transfusions** are rarely used in modern medical practice, primarily reserved for massive hemorrhage and hypovolemic shock.
- In this scenario, the primary goal is to increase **oxygen-carrying capacity** with minimal volume, making **packed red blood cells** a more appropriate choice.
*Observation and supportive care*
- The patient is in **acute distress** with ongoing angina despite initial treatments, and severe anemia exacerbates her cardiac condition.
- **Observation alone** is insufficient and would likely lead to further cardiac complications and instability, especially with a significant surgery like CABG impending.
Question 34: A 64-year-old male with a past medical history of obesity, diabetes, hypertension, and hyperlipidemia presents with an acute onset of nausea, vomiting, diaphoresis, and crushing substernal chest pain. Vital signs are temperature 37° C, HR 110, BP 149/87, and RR of 22 with an oxygen saturation of 99% on room air. Physical exam reveals a fourth heart sound (S4), and labs are remarkable for an elevated troponin. EKG is shown below. The pathogenesis of the condition resulting in this patient’s presentation involves:
A. Genetic inheritance of a mutation in β-myosin or troponin expressed in cardiac myocytes
B. A stable atheromatous lesion without overlying thrombus
C. Destruction of the vasa vasorum caused by vasculitic phenomena
D. A fully obstructive thrombus at the site of a ruptured, ulcerated atherosclerotic plaque (Correct Answer)
E. A partially occlusive thrombus at the site of a ruptured, ulcerated atherosclerotic plaque
Explanation: ***A fully obstructive thrombus at the site of a ruptured, ulcerated atherosclerotic plaque***
- The patient's findings of **acute onset crushing substernal chest pain**, nausea, diaphoresis, elevated heart rate, and an **elevated troponin** are highly suggestive of an **acute myocardial infarction (MI)**. The EKG pattern, showing **ST-segment elevations**, is indicative of a STEMI (ST-elevation MI).
- The pathogenesis of a STEMI involves the **rupture of an atherosclerotic plaque**, leading to the formation of a **fully occlusive thrombus** that completely blocks a coronary artery, causing transmural ischemia and myocyte necrosis.
*Genetic inheritance of a mutation in β-myosin or troponin expressed in cardiac myocytes*
- This description refers to the pathogenesis of **hypertrophic cardiomyopathy**, a genetic disorder characterized by abnormal thickening of the heart muscle.
- While it can cause chest pain and arrhythmias, it typically does not present with the acute, crushing chest pain, diaphoresis, and classic EKG changes (ST elevation) seen in an acute MI, nor is elevated troponin as specific for this condition.
*A stable atheromatous lesion without overlying thrombus*
- A stable atheromatous lesion typically causes **stable angina**, characterized by chest pain that is exertional and relieved by rest or nitroglycerin.
- It does not involve acute plaque rupture or thrombus formation, and therefore would not cause the acute symptoms, EKG changes (ST elevation), and significant troponin elevation indicative of an acute MI.
*Destruction of the vasa vasorum caused by vasculitic phenomena*
- Destruction of the **vasa vasorum** (small blood vessels supplying large arteries) can occur in conditions like **syphilitic aortitis**, leading to aortic aneurysm or dissection.
- This mechanism is not directly related to acute coronary artery occlusion and myocardial infarction, and the clinical presentation would be distinct, focusing on aortic rather than myocardial pathology.
*A partially occlusive thrombus at the site of a ruptured, ulcerated atherosclerotic plaque*
- A partially occlusive thrombus at the site of a ruptured plaque is characteristic of an **unstable angina (UA)** or a **non-ST-elevation myocardial infarction (NSTEMI)**.
- While these also involve plaque rupture and thrombus formation, they typically do not present with the **ST-segment elevations** on EKG that indicate a fully occluded coronary artery (STEMI), which is suggested by the patient's EKG.
Question 35: A 70-year-old man presents to the emergency department with severe substernal chest pain of one hour’s duration. The patient was taking a morning walk when the onset of pain led him to seek care. His past medical history includes coronary artery disease, hyperlipidemia, and hypertension. Medications include aspirin, losartan, and atorvastatin. An electrocardiogram reveals ST elevations in the inferior leads II, III, and avF as well as in leads V5 and V6. The ST elevations found in leads V5-V6 are most indicative of pathology in which of the following areas of the heart?
A. Lateral wall of left ventricle, left circumflex coronary artery (Correct Answer)
B. Left atrium, left main coronary artery
C. Inferior wall, right coronary artery
D. Interventricular septum, left anterior descending coronary artery
E. Right ventricle, right coronary artery
Explanation: ***Lateral wall of left ventricle, left circumflex coronary artery***
- **ST elevations in leads V5 and V6** are characteristic findings for an **anterolateral or high lateral myocardial infarction**.
- These leads correspond to the **lateral wall of the left ventricle**, which is primarily supplied by the **left circumflex coronary artery**.
*Left atrium, left main coronary artery*
- The **left atrium** is involved in atrial arrhythmias or hypertrophy, but **ST segment changes** on an ECG primarily reflect **ventricular ischemia or infarction**.
- While the **left main coronary artery** supplies a large portion of the left ventricle, its occlusion typically presents with more widespread and severe **ST elevations**, potentially affecting multiple lead groups beyond just V5-V6, and often indicates extensive damage.
*Inferior wall, right coronary artery*
- **Inferior wall infarctions** are indicated by **ST elevations in leads II, III, and aVF** (which are also present in this patient), primarily supplied by the **right coronary artery**.
- Although there is an inferior MI, the question specifically asks about the V5-V6 changes, which point to a distinct region.
*Interventricular septum, left anterior descending coronary artery*
- **ST elevations in V1-V4** are typically associated with an **anterior myocardial infarction**, affecting the **interventricular septum** and anterior wall, often due to occlusion of the **left anterior descending coronary artery**.
- The given leads V5-V6 do not primarily represent the interventricular septum.
*Right ventricle, right coronary artery*
- **Right ventricular infarction** is indicated by **ST elevations in lead V4R** (a right-sided lead) and can accompany inferior infarctions; however, V5-V6 do not specifically represent the right ventricle.
- The **right ventricle** is primarily supplied by the **right coronary artery**, not branches of the left coronary system, and RV infarction would require right-sided ECG leads for diagnosis.
Question 36: A 46-year-old man accountant is admitted to the emergency department with complaints of retrosternal crushing pain that radiates to his left arm and jaw. The medical history is significant for hyperlipidemia and arterial hypertension, for which he is prescribed a statin and ACE inhibitor, respectively. An ECG is obtained and shows an ST-segment elevation in leads avF and V2-V4. The blood pressure is 100/50 mm Hg, the pulse is 120/min, and the respiratory rate is 20/min. His BMI is 33 kg/m2 and he has a 20-year history of smoking cigarettes. Troponin I is elevated. The patient undergoes percutaneous coronary intervention immediately after admission. Angioplasty and stenting were successfully performed. On follow-up the next day, the ECG shows decreased left ventricular function and local hypokinesia. The patient is re-evaluated 14 days later. The echocardiography reveals a normal ejection fraction and no hypokinesis. Which of the phenomena below explains the patient’s clinical course?
A. Coronary steal syndrome
B. Coronary collateral circulation
C. Reperfusion injury
D. Myocardial hibernation
E. Myocardial stunning (Correct Answer)
Explanation: ***Myocardial stunning***
- This condition is characterized by **transient post-ischemic myocardial dysfunction** that recovers spontaneously, despite the restoration of normal blood flow. The patient's initial decreased left ventricular function and hypokinesia, followed by a return to normal ejection fraction and no hypokinesis after 14 days, is a classic presentation of myocardial stunning after successful reperfusion.
- It occurs when the myocardium rapidly recovers normal blood flow after a period of **ischemia**, but the contractile function remains depressed for hours to days or even weeks due to cellular damage incurred during the ischemic event, involving calcium overload and oxidative stress, without actual cell death.
*Coronary steal syndrome*
- This phenomenon occurs when **vasodilation of collateral vessels** in compromised coronary beds diverts blood flow away from ischemic areas, potentially worsening ischemia. It does not explain the recovery of myocardial function seen after reperfusion.
- It is typically observed during conditions that cause maximal coronary vasodilation, such as exercise or administration of certain drugs, leading to **worsening angina** or ischemia, rather than a subsequent improvement in function after an acute event.
*Coronary collateral circulation*
- This refers to the development of **alternative blood flow pathways** when a major coronary artery is obstructed, providing some blood supply to ischemic regions. While beneficial in mitigating damage during ischemia, it does not explain the initial dysfunction followed by improvement after revascularization.
- **Well-developed collaterals** can reduce the size of an infarct and improve outcomes, but they don't cause the phenomenon of transient contractile dysfunction that fully recovers after reperfusion, which is the hallmark of myocardial stunning.
*Reperfusion injury*
- This describes the **damage to myocardial tissue** that occurs *after* blood flow is restored to an ischemic area, often due to oxidative stress, calcium overload, and inflammation. This can lead to worsening dysfunction or even cell death, which is contrary to the overall recovery observed in the patient.
- While it can cause some **transient stunning**, the primary definition of reperfusion injury refers to additional damage, and the patient's complete recovery of left ventricular function suggests stunning rather than persistent injury.
*Myocardial hibernation*
- This is a state of **chronically depressed myocardial function** due to persistent reduction in coronary blood flow, where the myocardium adapts by reducing its metabolic activity to match the reduced blood supply. It improves upon revascularization.
- Unlike stunning, which is an acute post-ischemic event, hibernation is a **chronic adaptation to hypoperfusion**, and the recovery in this patient was more typical of an acute, transient phenomenon following infarction and reperfusion.
Question 37: A 65-year-old man presents to the emergency room with chest pain. Coronary angiography reveals significant stenosis of the left anterior descending (LAD) artery. Which of the following factors best predicts the risk of myocardial necrosis in this clinical setting?
A. Presence of vulnerable plaque features
B. ST-segment elevation on ECG
C. Elevated troponin levels
D. Time to reperfusion therapy
E. Degree of coronary stenosis (>70%) (Correct Answer)
Explanation: **_Degree of coronary stenosis (>70%)_**
- A **high degree of coronary stenosis**, particularly >70%, significantly **limits blood flow** and oxygen supply to the myocardium, predisposing it to necrosis during periods of increased demand or sustained ischemia.
- This fixed obstruction makes the myocardium vulnerable to **ischemic injury** even before plaque rupture or thrombus formation, especially in the context of increased myocardial oxygen demand.
*Presence of vulnerable plaque features*
- **Vulnerable plaque** features (e.g., large lipid core, thin fibrous cap) predict the **risk of plaque rupture and acute thrombotic occlusion**, which then leads to myocardial infarction, rather than directly predicting myocardial necrosis from existing stenosis.
- While significant, these features indicate a **predisposition to future events** rather than current necrosis from a fixed, high-grade stenosis.
*ST-segment elevation on ECG*
- **ST-segment elevation** on an ECG is a direct indicator of **acute myocardial injury** and ongoing transmural ischemia, suggesting a blockage leading to necrosis.
- However, it signifies that necrosis is **already occurring or imminent**, rather than serving as a **predictor of susceptibility** to necrosis in a patient with known chronic stenosis.
*Elevated troponin levels*
- **Elevated troponin levels** are a **biomarker of myocardial cell death** itself, indicating that necrosis has already happened.
- Therefore, troponin is a **diagnostic marker of myocardial necrosis**, not a predictor of its occurrence based on baseline physiological or anatomical factors.
*Time to reperfusion therapy*
- **Time to reperfusion therapy** is a critical determinant of the **extent of myocardial salvage** and thus the final infarct size, rather than a predictor of the initial likelihood of necrosis.
- While shorter times are associated with less necrosis, this factor relates to **intervention effectiveness** rather than the patient's inherent predisposition to developing necrosis from a fixed stenosis.
Question 38: A 73-year-old man presents to the outpatient clinic complaining of chest pain with exertion. He states that resting for a few minutes usually resolves the chest pain. Currently, he takes 81 mg of aspirin daily. He has a blood pressure of 127/85 mm Hg and heart rate of 75/min. Physical examination reveals regular heart sounds and clear lung sounds bilateral. Which medication regimen below should be added?
A. Metoprolol and a statin daily. Sublingual nitroglycerin as needed. (Correct Answer)
B. Clopidogrel and amlodipine daily. Sublingual nitroglycerin as needed.
C. Amlodipine and a statin daily. Sublingual nitroglycerin as needed.
D. Amlodipine daily. Sublingual nitroglycerin as needed.
E. Metoprolol and ranolazine daily. Sublingual nitroglycerin as needed.
Explanation: ***Metoprolol and a statin daily. Sublingual nitroglycerin as needed.***
- This patient presents with symptoms consistent with **stable angina** (**chest pain with exertion, relieved by rest**). The recommended medical therapy includes **antiplatelet agents** (aspirin, already prescribed), **beta-blockers** (metoprolol) for symptom control and improved survival post-MI, and **high-intensity statins** for lipid management and plaque stabilization. **Sublingual nitroglycerin** is crucial for acute symptom relief.
- Beta-blockers like metoprolol decrease myocardial **oxygen demand** by reducing heart rate and contractility, effectively treating angina. Statins are essential for **atherosclerosis management**.
*Clopidogrel and amlodipine daily. Sublingual nitroglycerin as needed.*
- While clopidogrel is an **antiplatelet agent**, aspirin is typically the first-line choice for stable angina unless there's an intolerance or compelling reason for dual antiplatelet therapy (e.g., recent stent placement), which is not indicated here.
- Amlodipine, a **calcium channel blocker**, can be used for angina but is usually a second-line agent if beta-blockers are contraindicated or insufficient; it doesn't offer the mortality benefit seen with beta-blockers post-MI.
*Amlodipine and a statin daily. Sublingual nitroglycerin as needed.*
- This regimen includes a **statin** and sublingual nitroglycerin, which are appropriate. However, it uses amlodipine instead of a beta-blocker, which is generally the preferred initial therapy for angina due to its benefits in reducing myocardial oxygen demand and improving outcomes, especially in patients with a history of MI or heart failure.
- Beta-blockers provide superior **mortality reduction benefits** in patients with coronary artery disease compared to calcium channel blockers.
*Amlodipine daily. Sublingual nitroglycerin as needed.*
- This option misses two critical components of comprehensive treatment for stable angina: a **statin** for lipid management and plaque stabilization, and a **beta-blocker** for primary symptom control and long-term cardiac protection.
- Relying solely on amlodipine and sublingual nitroglycerin would leave the patient incompletely treated for their underlying **coronary artery disease**.
*Metoprolol and ranolazine daily. Sublingual nitroglycerin as needed.*
- This option lacks a **statin**, which is a cornerstone of therapy for stable angina to manage atherosclerosis.
- While metoprolol is appropriate and ranolazine can be used as an add-on therapy for refractory angina, it's not typically a first-line agent and doesn't replace the need for a statin.
Question 39: A 43-year-old man comes to the emergency room complaining of chest discomfort. He describes the feeling as "tightness," and also reports weakness and palpitations for the past hour. He denies shortness of breath, diaphoresis, or lightheadedness. He has no significant past medical history, and does not smoke, drink, or use illicit drugs. His father had a myocardial infarction at age 72. He is afebrile, heart rate is 125 bpm, and his blood pressure is 120/76. He is alert and oriented to person, place, and time. His electrocardiogram is shown below. Which of the following tests should be ordered in the initial work-up of this patient's condition?
A. Chest x-ray
B. Blood alcohol level
C. Urine free cortisol level
D. Urine metanephrines
E. Thyroid stimulating hormone level (TSH) (Correct Answer)
Explanation: ***Thyroid stimulating hormone level (TSH)***
- The patient presents with **palpitations**, **tachycardia (HR 125 bpm)**, and chest tightness, with an ECG showing a **regular narrow-complex tachycardia** consistent with **supraventricular tachycardia (SVT)**.
- **Hyperthyroidism** is a critical secondary cause of SVT and atrial arrhythmias that must be ruled out in the initial workup.
- **TSH testing** is essential to identify **thyroid dysfunction** as a reversible and treatable cause of the tachyarrhythmia.
- Treating the underlying hyperthyroidism can resolve the arrhythmia and prevent recurrence.
*Incorrect: Urine metanephrines*
- While **pheochromocytoma** can cause palpitations and tachycardia, it typically presents with **paroxysmal hypertension**, **headaches**, and **diaphoresis** (the classic triad).
- This patient has **normal blood pressure** and denies diaphoresis, making pheochromocytoma less likely.
- TSH is a more appropriate first-line test given the clinical presentation.
*Incorrect: Chest x-ray*
- A chest X-ray may help evaluate for **structural cardiac or pulmonary abnormalities**, but it does not identify the **underlying cause** of SVT.
- It is not specific for diagnosing **metabolic or endocrine triggers** of tachyarrhythmias.
*Incorrect: Blood alcohol level*
- The patient **denies alcohol use**, making this test unnecessary in the initial evaluation.
- Alcohol withdrawal can cause tachycardia, but there is no clinical history suggesting this.
*Incorrect: Urine free cortisol level*
- **Cushing's syndrome** does not typically present with acute palpitations or SVT as the primary manifestation.
- This test is not relevant to the immediate evaluation of **tachyarrhythmia**.
Question 40: One hour after being admitted to the hospital for sharp, acute chest pain and diaphoresis, a 55-year-old woman with type 2 diabetes mellitus loses consciousness in the emergency department. There are no palpable pulses. Chest compressions are started. The patient has a history of breast cancer that was surgically treated 4 years ago. Prior to admission, the patient was on a long bus ride to visit her sister. Her medications include tamoxifen, atorvastatin, metoprolol, metformin, and insulin. Serum troponin levels are elevated. The cardiac rhythm is shown. Which of the following is the most appropriate next step in management?
A. Defibrillation (Correct Answer)
B. Coronary angiography
C. Intravenous dextrose therapy
D. Intravenous epinephrine therapy
E. Intravenous glucagon therapy
Explanation: ***Defibrillation***
- The ECG shows **ventricular fibrillation (VF)**, characterized by chaotic, disorganized electrical activity with no identifiable QRS complexes and no palpable pulse. VF is a **shockable rhythm**.
- According to ACLS guidelines, the immediate management for VF is **unsynchronized defibrillation** along with high-quality chest compressions.
- Defibrillation depolarizes the myocardium simultaneously, allowing the sinoatrial node to potentially resume normal electrical activity and restore organized cardiac rhythm.
- For refractory VF after initial shocks, epinephrine and antiarrhythmics (amiodarone or lidocaine) are added.
*Intravenous epinephrine therapy*
- Epinephrine is a vasopressor used in cardiac arrest to increase coronary and cerebral perfusion pressure.
- While epinephrine is given during VF arrest, it is administered **after** the initial defibrillation attempts, not as the immediate first step.
- Epinephrine is the primary drug for **non-shockable rhythms** (PEA and asystole), but defibrillation takes priority in shockable rhythms like VF.
*Intravenous glucagon therapy*
- Glucagon is used for severe **hypoglycemia** or **beta-blocker/calcium channel blocker overdose**.
- While the patient takes metoprolol (a beta-blocker), the clinical presentation with elevated troponin, chest pain, and VF rhythm clearly indicates an acute cardiac event, not beta-blocker toxicity.
- Glucagon has no role in the immediate management of cardiac arrest from VF.
*Coronary angiography*
- Coronary angiography is indicated for **post-cardiac arrest care** after return of spontaneous circulation (ROSC), especially in patients with suspected acute coronary syndrome.
- The patient has elevated troponin suggesting acute MI, making early angiography important **after** successful resuscitation.
- However, angiography cannot be performed during active cardiac arrest; immediate defibrillation and CPR are required first.
*Intravenous dextrose therapy*
- Dextrose is used to treat **hypoglycemia**.
- While the patient has diabetes and takes insulin (hypoglycemia risk), the presentation with chest pain, elevated troponin, and VF rhythm indicates acute coronary syndrome with cardiac arrest.
- Hypoglycemia does not cause VF; the rhythm is consistent with ischemic cardiac arrest requiring immediate defibrillation.
