A 42-year-old man with systolic heart failure secondary to amyloidosis undergoes heart transplantation. The donor heart is obtained from a 17-year-old boy who died in a motor vehicle collision. Examination of the donor heart during the procedure shows a flat, yellow-white discoloration with an irregular border on the luminal surface of the aorta. A biopsy of this lesion is most likely to show which of the following?
Q12
An 80-year-old man is admitted to the hospital after the sudden onset of sub-sternal chest pain and shortness of breath while sitting in a chair. He has hypertension and type 2 diabetes mellitus. He has smoked 1 pack of cigarettes daily for 42 years. Four days after admission, he becomes tachycardic and then loses consciousness; the cardiac monitor shows irregular electrical activity. Cardiac examination shows a new systolic murmur at the apex. Despite appropriate measures, he dies. Microscopic evaluation of the myocardium is most likely to show which of the following?
Q13
A 53-year-old woman presents with a severe headache, nausea, and vomiting for the past 48 hours. Vitals show a blood pressure of 220/134 mm Hg and a pulse of 88/min. Urinalysis shows a 2+ proteinuria and RBC casts. Which of the following renal lesions is most likely to be seen in this patient?
Q14
A 62-year-old woman is evaluated for fatigue 6 months after placement of a mechanical valve due to aortic stenosis. She does not drink alcohol or smoke cigarettes. A complete blood count reports hemoglobin of 9.5 g/dL and a reticulocyte percentage of 5.8%. Platelet and leukocyte counts are within their normal ranges. The patient's physician suspects traumatic hemolysis from the patient's mechanical valve as the cause of her anemia. Which of the following peripheral blood smear findings would most support this diagnosis?
Q15
A 72-year-old man comes to the physician because of a 6-month history of intermittent dull abdominal pain that radiates to the back. He has smoked one pack of cigarettes daily for 50 years. His blood pressure is 145/80 mm Hg. Abdominal examination shows generalized tenderness and a pulsatile mass in the periumbilical region on deep palpation. Further evaluation of the affected blood vessel is most likely to show which of the following?
Q16
A 12-year-old girl with an autosomal dominant mutation in myosin-binding protein C is being evaluated by a pediatric cardiologist. The family history reveals that the patient's father died suddenly at age 33 while running a half-marathon. What was the likely finding on histological evaluation of her father's heart at autopsy?
Q17
A 58-year-old man presents to the emergency department with severe right leg pain accompanied by tingling and weakness. His condition started suddenly 3 hours ago when he was watching a movie. His medical history is remarkable for type 2 diabetes mellitus and hypertension. He has been smoking 20–30 cigarettes per day for the past 35 years. His vital signs include a blood pressure of 149/85 mm Hg, a temperature of 36.9°C (98.4°F), and an irregular pulse of 96/min. On physical examination, his right popliteal and posterior tibial pulses are absent. His right leg is pale and cold. Which of the following is the most likely diagnosis?
Q18
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?
Q19
A 80-year-old woman is brought to the emergency department from a senior living home with a chief complaint of acute onset and severe abdominal pain with 5 episodes of bloody diarrhea. She has a history of having chronic constipation, and postprandial abdominal pain which subsides after taking nitroglycerin. The abdominal pain that she is currently experiencing did not subside using her medication. A week ago, she had a percutaneous intervention for an inferior wall STEMI. On physical examination, the patient looks pale and confused. The vital signs include: blood pressure 80/40 mm Hg, heart rate 108/min, respiratory rate 22/min, and temperature 35.6°C (96.0°F). The patient receives an aggressive treatment consisting of intravenous fluids and vasopressors, and she is transferred to the ICU. Despite all the necessary interventions, the patient dies. During the autopsy, a dark hemorrhagic appearance of the sigmoid colon is noted. What is the most likely pathology related to her death?
Q20
A 19-year-old Caucasian male collapsed from sudden cardiac arrest while playing in a college basketball game. Attempts at resuscitation were unsuccessful. Post-mortem pathologic and histologic examination found asymmetric left ventricular hypertrophy and myocardial disarray. Assuming this was an inherited condition, the relevant gene most likely affects which of the following structures?
Cardiovascular US Medical PG Practice Questions and MCQs
Question 11: A 42-year-old man with systolic heart failure secondary to amyloidosis undergoes heart transplantation. The donor heart is obtained from a 17-year-old boy who died in a motor vehicle collision. Examination of the donor heart during the procedure shows a flat, yellow-white discoloration with an irregular border on the luminal surface of the aorta. A biopsy of this lesion is most likely to show which of the following?
A. Apoptotic smooth muscle cells
B. Necrotic cell debris
C. Proteoglycan accumulation
D. Collagen deposition
E. Lipoprotein-laden macrophages (Correct Answer)
Explanation: ***Lipoprotein-laden macrophages***
- The description of a flat, yellow-white discolored lesion with an irregular border on the luminal surface of the aorta in a 17-year-old is classic for a **fatty streak**, the earliest lesion of **atherosclerosis**.
- Fatty streaks are histologically characterized by the accumulation of **macrophages that have ingested oxidized lipoproteins**, appearing as foam cells within the intima.
*Apoptotic smooth muscle cells*
- While apoptosis of various cell types, including smooth muscle cells, can occur in advanced atherosclerotic lesions, it is not the primary or defining feature of an early **fatty streak**.
- **Apoptosis** contributes to the necrotic core formation in later stages of plaque development, not the initial yellow-white discoloration of a fatty streak.
*Necrotic cell debris*
- **Necrotic cell debris** is a prominent feature of more advanced, **complicated atherosclerotic plaques**, forming the necrotic core.
- In a **fatty streak**, the cells are primarily viable foam cells, and significant necrosis is not yet present.
*Proteoglycan accumulation*
- **Proteoglycan accumulation** occurs in the arterial intima and is involved in the retention of lipoproteins, contributing to the development of atherosclerosis.
- However, the immediate and most characteristic histological finding of the **yellow-white discoloration** in a fatty streak is the lipid-laden macrophage.
*Collagen deposition*
- **Collagen deposition** is a key feature of the fibrous cap in **advanced atherosclerotic plaques**, laid down by migrating smooth muscle cells.
- It is not the primary histological characteristic of an early, flat, yellow-white **fatty streak**.
Question 12: An 80-year-old man is admitted to the hospital after the sudden onset of sub-sternal chest pain and shortness of breath while sitting in a chair. He has hypertension and type 2 diabetes mellitus. He has smoked 1 pack of cigarettes daily for 42 years. Four days after admission, he becomes tachycardic and then loses consciousness; the cardiac monitor shows irregular electrical activity. Cardiac examination shows a new systolic murmur at the apex. Despite appropriate measures, he dies. Microscopic evaluation of the myocardium is most likely to show which of the following?
A. Wavy myocardial fibers without inflammatory cells
B. Coagulative necrosis with dense neutrophilic infiltrate
C. Low cellularity with dense, non-contractile scar tissue
D. Dense granulation tissue with collagenous scar formation
E. Hyperemic granulation tissue with abundance of macrophages (Correct Answer)
Explanation: ***Hyperemic granulation tissue with abundance of macrophages***
- The patient experienced an **acute myocardial infarction (MI)** with subsequent complications, including sudden death occurring 4 days after the initial event.
- At 4 days post-MI, the characteristic microscopic finding is **hyperemic granulation tissue**, where **macrophages** are prominent in clearing necrotic debris, and new blood vessels start to form.
*Wavy myocardial fibers without inflammatory cells*
- This finding is typically seen within the first few hours (0-4 hours) after an MI, representing early irreversible ischemic injury before significant inflammation begins.
- The patient died 4 days later; therefore, more advanced changes would be expected.
*Coagulative necrosis with dense neutrophilic infiltrate*
- This stage is observed between 12 hours and 3 days post-MI, as neutrophils infiltrate the necrotic tissue to initiate breakdown and removal of dead cells.
- While neutrophil infiltration is important, the primary characteristic at 4 days would shift towards macrophage predominance and early granulation tissue.
*Low cellularity with dense, non-contractile scar tissue*
- This describes the **final stage of MI healing**, typically observed several weeks to months after the event, when the necrotic tissue has been completely replaced by a mature collagenous scar.
- At 4 days, the process is still actively inflammatory and reparative.
*Dense granulation tissue with collagenous scar formation*
- This stage represents a later phase of healing, usually from 1 to 2 weeks post-MI, where the granulation tissue becomes more dense and collagen deposition increases.
- While granulation tissue is present at 4 days, it would be described as more hyperemic with a prominent macrophage presence rather than dense collagenous scar formation.
Question 13: A 53-year-old woman presents with a severe headache, nausea, and vomiting for the past 48 hours. Vitals show a blood pressure of 220/134 mm Hg and a pulse of 88/min. Urinalysis shows a 2+ proteinuria and RBC casts. Which of the following renal lesions is most likely to be seen in this patient?
A. Papillary necrosis
B. Fibrinoid necrosis (Correct Answer)
C. Acute tubular necrosis (ATN)
D. Acute pyelonephritis
E. Acute interstitial nephritis (AIN)
Explanation: ***Fibrinoid necrosis***
- The patient's presentation with **severe hypertension** (220/134 mm Hg), **proteinuria**, and **RBC casts** is highly suggestive of a **hypertensive crisis with malignant nephrosclerosis**.
- **Fibrinoid necrosis** refers to the accumulation of **fibrin-like material** in the walls of arterioles, a characteristic pathological finding in **malignant hypertension** leading to vascular damage in the kidney.
*Papillary necrosis*
- This condition is typically associated with **analgesic nephropathy**, **diabetes mellitus**, and **urinary tract obstruction** or **sickle cell disease**.
- While it can cause renal dysfunction, it does not directly explain the acute severe hypertension and RBC casts unique to hypertensive emergencies.
*Acute tubular necrosis (ATN)*
- While ATN can cause **acute kidney injury**, it is usually characterized by **muddy brown casts** and is often precipitated by **ischemic** or **nephrotoxic insults**.
- The prominent hypertension and RBC casts point away from primary ATN in this context.
*Acute pyelonephritis*
- Acute pyelonephritis is an **infection of the kidney** characterized by **fever**, **flank pain**, and **pyuria** (white blood cells in urine), usually not severe hypertension and RBC casts.
- The main findings in this patient are related to vascular damage, not infection.
*Acute interstitial nephritis (AIN)*
- AIN is often caused by **drug reactions** or systemic diseases, presenting with **fever**, **rash**, **eosinophilia**, and **white blood cell casts**.
- The clinical picture of severe hypertension and RBC casts is not typical for AIN.
Question 14: A 62-year-old woman is evaluated for fatigue 6 months after placement of a mechanical valve due to aortic stenosis. She does not drink alcohol or smoke cigarettes. A complete blood count reports hemoglobin of 9.5 g/dL and a reticulocyte percentage of 5.8%. Platelet and leukocyte counts are within their normal ranges. The patient's physician suspects traumatic hemolysis from the patient's mechanical valve as the cause of her anemia. Which of the following peripheral blood smear findings would most support this diagnosis?
A. RBC fragments and schistocytes (Correct Answer)
B. Bite cells and Heinz bodies
C. Round macrocytes and target cells
D. Macrocytes and hypersegmented neutrophils
E. Sickle cells and target cells
Explanation: ***RBC fragments and schistocytes***
- The presence of **RBC fragments** (schistocytes) on a peripheral blood smear is the hallmark of **microangiopathic hemolytic anemia** (MAHA), often seen in traumatic hemolysis caused by mechanical heart valves.
- Mechanical valves can create **high-shear stress**, physically damaging red blood cells as they pass through, leading to their fragmentation.
*Bite cells and Heinz bodies*
- **Bite cells** and **Heinz bodies** are characteristic of **oxidative hemolysis**, typically seen in G6PD deficiency or reactions to certain drugs.
- They are formed when denatured hemoglobin precipitates and is removed by splenic macrophages, leaving "bites" out of the red cells.
*Round macrocytes and target cells*
- **Round macrocytes** are characteristic of **folate or B12 deficiency**, which leads to impaired DNA synthesis and ineffective erythropoiesis.
- **Target cells** are often associated with **thalassemia**, liver disease, or hemoglobinopathies, where there is an increased surface area to volume ratio of the red blood cell.
*Macrocytes and hypersegmented neutrophils*
- **Macrocytes** and **hypersegmented neutrophils** (>5 lobes) are classic findings in **megaloblastic anemias** due to **vitamin B12** or **folate deficiency**.
- These findings indicate impaired DNA synthesis affecting both erythroid and myeloid cell lines.
*Sickle cells and target cells*
- **Sickle cells** are pathognomonic for **sickle cell anemia**, a genetic disorder characterized by abnormal hemoglobin leading to red blood cell distortion under low oxygen conditions.
- While **target cells** can sometimes be seen in sickle cell disease, their primary association is with other hemoglobinopathies or liver disease, and sickle cells are not a feature of traumatic hemolysis.
Question 15: A 72-year-old man comes to the physician because of a 6-month history of intermittent dull abdominal pain that radiates to the back. He has smoked one pack of cigarettes daily for 50 years. His blood pressure is 145/80 mm Hg. Abdominal examination shows generalized tenderness and a pulsatile mass in the periumbilical region on deep palpation. Further evaluation of the affected blood vessel is most likely to show which of the following?
A. Obliterative inflammation of the vasa vasorum
B. Formation of giant cells in the tunica media
C. Necrotizing inflammation of the entire vessel wall
D. Fragmentation of elastic tissue in the tunica media (Correct Answer)
E. Accumulation of foam cells in the tunica intima
Explanation: ***Fragmentation of elastic tissue in the tunica media***
- This patient's presentation with **intermittent dull abdominal pain radiating to the back**, a **pulsatile periumbilical mass**, and a history of **heavy smoking** is highly suggestive of an **abdominal aortic aneurysm (AAA)**.
- The pathological hallmark of AAA is **degradation and fragmentation of elastic tissue in the tunica media**, caused by chronic inflammation and increased activity of **matrix metalloproteinases (MMPs)**.
- This medial degeneration leads to **weakening of the vessel wall** and progressive **dilation**, ultimately forming an aneurysm.
- While atherosclerosis initiates the process, the actual aneurysm formation is characterized by this elastic tissue destruction in the media.
*Accumulation of foam cells in the tunica intima*
- This describes the **early lesion of atherosclerosis**, which is a **risk factor** for AAA development.
- However, when examining an **established AAA**, the predominant finding is not intimal foam cells but rather **medial degeneration** with elastic tissue fragmentation.
- Atherosclerosis is the underlying cause, but the question asks about findings in the affected vessel (the aneurysm itself).
*Obliterative inflammation of the vasa vasorum*
- This is characteristic of **syphilitic aortitis** (tertiary syphilis), which typically affects the **ascending thoracic aorta**.
- While syphilis can cause aneurysms, the patient's presentation and demographics are more consistent with atherosclerotic AAA.
*Formation of giant cells in the tunica media*
- This finding is associated with **giant cell arteritis** (temporal arteritis), which affects large and medium-sized arteries, particularly the temporal and ophthalmic arteries.
- It presents with headache, jaw claudication, and visual disturbances—features absent in this case.
*Necrotizing inflammation of the entire vessel wall*
- This describes **necrotizing vasculitis** such as **polyarteritis nodosa**, which affects medium-sized muscular arteries.
- While vasculitis can cause aneurysms, the clinical picture of AAA in an elderly smoker with atherosclerotic risk factors points to atherosclerotic pathogenesis, not primary vasculitis.
Question 16: A 12-year-old girl with an autosomal dominant mutation in myosin-binding protein C is being evaluated by a pediatric cardiologist. The family history reveals that the patient's father died suddenly at age 33 while running a half-marathon. What was the likely finding on histological evaluation of her father's heart at autopsy?
A. Amyloid deposits
B. Wavy myocytes
C. Eosinophilic infiltration
D. Myocyte disarray (Correct Answer)
E. Viral particles
Explanation: ***Myocyte disarray***
- The patient's father likely had **hypertrophic cardiomyopathy (HCM)**, given the autosomal dominant inheritance, mutation in myosin-binding protein C, and sudden cardiac death during exertion.
- **Myocyte disarray** (disorganized bundles of cardiomyocytes) is a classic histological hallmark of HCM and a key feature contributing to arrhythmias and sudden death.
*Amyloid deposits*
- **Amyloidosis** is characterized by the deposition of abnormal protein fibrils in tissues, which can cause restrictive cardiomyopathy.
- While amyloid can mimic some features of HCM, it is not associated with mutations in **myosin-binding protein C** and would show specific apple-green birefringence with Congo red stain, not myocyte disarray.
*Wavy myocytes*
- **Wavy myocytes** are a histological finding typically seen in early myocardial infarction due to cellular stretching and retraction.
- This finding is indicative of myocardial ischemia and necrosis, not the chronic structural abnormalities found in genetic cardiomyopathies like HCM.
*Eosinophilic infiltration*
- **Eosinophilic infiltration** of the myocardium is characteristic of **Loeffler endocarditis** or other forms of eosinophilic myocarditis.
- This is an inflammatory condition and is not a feature of hypertrophic cardiomyopathy or associated with mutations in myosin-binding protein C.
*Viral particles*
- The presence of **viral particles** within myocytes suggests **viral myocarditis**, which can lead to dilated cardiomyopathy or acute heart failure.
- This is an infectious cause of heart disease and is distinct from the genetic structural abnormalities seen in hypertrophic cardiomyopathy.
Question 17: A 58-year-old man presents to the emergency department with severe right leg pain accompanied by tingling and weakness. His condition started suddenly 3 hours ago when he was watching a movie. His medical history is remarkable for type 2 diabetes mellitus and hypertension. He has been smoking 20–30 cigarettes per day for the past 35 years. His vital signs include a blood pressure of 149/85 mm Hg, a temperature of 36.9°C (98.4°F), and an irregular pulse of 96/min. On physical examination, his right popliteal and posterior tibial pulses are absent. His right leg is pale and cold. Which of the following is the most likely diagnosis?
A. Buerger's disease
B. Leriche syndrome
C. Acute limb ischemia (Correct Answer)
D. CREST syndrome
E. Deep vein thrombosis
Explanation: ***Acute limb ischemia***
- The sudden onset of **severe leg pain**, **tingling**, **weakness**, and the **six P's** (pain, pallor, pulselessness, paresthesias, poikilothermia, and paralysis) are classic signs of acute limb ischemia.
- The patient's history of **smoking**, **hypertension**, **diabetes**, and an **irregular pulse** (suggesting atrial fibrillation) are significant risk factors for **thromboembolism**, which is a common cause of acute limb ischemia.
*Buerger's disease*
- This condition primarily affects **small and medium-sized arteries and veins** in the limbs and is strongly associated with **heavy tobacco use**.
- However, it typically presents with **distal extremity ischemia**, superficial phlebitis, and Raynaud's phenomenon, rather than the sudden, severe, large vessel occlusion described here.
*Leriche syndrome*
- This syndrome involves **atherosclerotic occlusion of the distal aorta** at or just below the renal arteries, affecting both lower limbs.
- It classically presents with a triad of **bilateral buttock/thigh claudication**, **impotence**, and **absent femoral pulses**, which does not align with the unilateral symptoms and specific pulse deficits described in the case.
*CREST syndrome*
- CREST (Calcinosis, Raynaud's phenomenon, Esophageal dysmotility, Sclerodactyly, Telangiectasias) is a subtype of **systemic sclerosis**, a **connective tissue disease**.
- Its symptoms are unrelated to the acute vascular event presented, which involves sudden limb ischemia.
*Deep vein thrombosis*
- DVT primarily involves the formation of a **blood clot in a deep vein**, leading to symptoms like **swelling**, **pain**, and **redness** in the affected limb.
- It does not typically cause the **acute pallor**, **coldness**, **pulselessness**, and severe neurologic deficits (tingling, weakness) seen with arterial occlusion.
Question 18: 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?
A. Rupture of the interventricular septum
B. Pseudoaneurysmal dilation of the left ventricle
C. Exudative inflammation of the pericardium
D. Occlusion of the posterior descending artery (Correct Answer)
E. Bacterial infection of the mitral valve endocardium
Explanation: ***Occlusion of the posterior descending artery***
- The image suggests a **large inferoposterior myocardial infarction**, impacting the posterior descending artery (PDA) territory, which supplies the posterior 1/3 of the interventricular septum and inferior wall of the left ventricle.
- An extensive infarction three days prior could lead to **cardiac rupture** or severe heart failure, resulting in sudden death.
*Rupture of the interventricular septum*
- A septal rupture can lead to a **ventricular septal defect**, causing a left-to-right shunt and heart failure, which might manifest as shortness of breath.
- This complication typically occurs within the first week following an **anterior or inferior myocardial infarction**, but the image points more directly to the cause of the infarction itself.
*Pseudoaneurysmal dilation of the left ventricle*
- A pseudoaneurysm is an **incomplete myocardial rupture** contained by pericardial adhesions, which can develop days to weeks post-MI and may rupture.
- While a life-threatening complication, the image primarily shows the infarct and not a distinct pseudoaneurysm.
*Exudative inflammation of the pericardium*
- **Fibrinous pericarditis** is common after transmural MI (Dressler syndrome or early pericarditis) and causes chest pain but rarely leads to death.
- It does not typically cause acute severe shortness of breath leading to death within three days in this context.
*Bacterial infection of the mitral valve endocardium*
- **Infective endocarditis** affects valve function and can cause heart failure, but it's typically a subacute process with systemic symptoms like fever.
- The presented acute timeline and image findings are not consistent with primary infective endocarditis as the cause of sudden death following acute chest pain.
Question 19: A 80-year-old woman is brought to the emergency department from a senior living home with a chief complaint of acute onset and severe abdominal pain with 5 episodes of bloody diarrhea. She has a history of having chronic constipation, and postprandial abdominal pain which subsides after taking nitroglycerin. The abdominal pain that she is currently experiencing did not subside using her medication. A week ago, she had a percutaneous intervention for an inferior wall STEMI. On physical examination, the patient looks pale and confused. The vital signs include: blood pressure 80/40 mm Hg, heart rate 108/min, respiratory rate 22/min, and temperature 35.6°C (96.0°F). The patient receives an aggressive treatment consisting of intravenous fluids and vasopressors, and she is transferred to the ICU. Despite all the necessary interventions, the patient dies. During the autopsy, a dark hemorrhagic appearance of the sigmoid colon is noted. What is the most likely pathology related to her death?
A. Mucosal infarct
B. Toxic megacolon
C. Adenocarcinoma
D. Transmural infarction (Correct Answer)
E. Twisting of sigmoid colon around its mesentery
Explanation: ***Transmural infarction***
- The patient's history of **postprandial abdominal pain** relieved by nitroglycerin, recent **STEMI**, and presentation with **severe abdominal pain**, bloody diarrhea, shock, and subsequent death with **dark hemorrhagic sigmoid colon** are all highly suggestive of **acute mesenteric ischemia** leading to transmural infarction. The hemodynamic instability after a recent cardiac event suggests a non-occlusive mesenteric ischemia contributing to the widespread tissue death.
- **Transmural infarction** involves all layers of the bowel wall, leading to necrosis, hemorrhage, and ultimately perforation or systemic shock, which aligns with the patient’s clinical course and autopsy findings.
*Mucosal infarct*
- A **mucosal infarct** is a milder form of ischemia, often reversible, and typically does not lead to the severe systemic shock, extensive hemorrhage, and rapid death described in this case, especially with aggressive medical management.
- While mucosal ischemia can cause bloody diarrhea, the **extent of necrosis** (dark hemorrhagic appearance) and fatal outcome points to a more severe, full-thickness injury.
*Toxic megacolon*
- **Toxic megacolon** is characterized by acute colonic distension and systemic toxicity, often associated with inflammatory bowel disease or *Clostridium difficile* infection, which are not suggested by the patient’s history.
- Although it can present with fever and abdominal pain, the absence of prior inflammatory bowel disease, the specific history of ischemic symptoms, and the autopsy finding of a **dark hemorrhagic colon** (rather than just distension) make this less likely.
*Adenocarcinoma*
- **Adenocarcinoma of the colon** typically presents with chronic symptoms such as changes in bowel habits, weight loss, and occult bleeding, rather than acute onset of severe abdominal pain, bloody diarrhea, and rapid deterioration leading to death within a day, as seen here.
- While it can cause obstruction, the acute ischemic signs and massive hemorrhage rule out adenocarcinoma as the primary cause of death.
*Twisting of sigmoid colon around its mesentery*
- This describes a **sigmoid volvulus**, which presents with acute abdominal pain, constipation, and signs of bowel obstruction, often with a characteristic "coffee bean" sign on imaging.
- While it can lead to ischemia and necrosis, the patient's history of **postprandial pain relieved by nitroglycerin** and recent STEMI strongly point to vascular compromise as the underlying etiology, not a mechanical twisting.
Question 20: A 19-year-old Caucasian male collapsed from sudden cardiac arrest while playing in a college basketball game. Attempts at resuscitation were unsuccessful. Post-mortem pathologic and histologic examination found asymmetric left ventricular hypertrophy and myocardial disarray. Assuming this was an inherited condition, the relevant gene most likely affects which of the following structures?
A. Cardiac cell sarcomere proteins (Correct Answer)
B. Membrane potassium channel proteins
C. Membrane sodium channels
D. Ryanodine receptors
E. Autoimmune beta-cell antibodies
Explanation: ***Cardiac cell sarcomere proteins***
- The clinical presentation of **sudden cardiac arrest** in a young athlete, along with post-mortem findings of **asymmetric left ventricular hypertrophy** and **myocardial disarray**, are classic for **hypertrophic cardiomyopathy (HCM)**.
- HCM is most commonly caused by mutations in genes encoding **sarcomeric proteins**, leading to abnormal myocardial structure and function.
*Membrane potassium channel proteins*
- Mutations in voltage-gated **potassium channels** are typically associated with cardiac arrhythmias such as **long QT syndrome** and **short QT syndrome**.
- These conditions primarily affect cardiac electrical activity and do not directly cause asymmetric left ventricular hypertrophy or myocardial disarray.
*Membrane sodium channels*
- Defects in **sodium channels** are predominantly linked to conditions like **Brugada syndrome** and certain forms of **long QT syndrome**.
- These channelopathies are characterized by specific ECG abnormalities and increased risk of sudden cardiac death due to arrhythmias, but not structural heart disease like HCM.
*Ryanodine receptors*
- Mutations in the **ryanodine receptor 2 (RyR2) gene** are associated with **catecholaminergic polymorphic ventricular tachycardia (CPVT)**.
- CPVT causes life-threatening arrhythmias, particularly during exercise or emotional stress, but it does not typically present with the structural cardiac abnormalities of HCM.
*Autoimmune beta-cell antibodies*
- **Autoimmune beta-cell antibodies** are characteristic of **Type 1 diabetes mellitus**, an autoimmune disease affecting the pancreas.
- These antibodies are unrelated to cardiac structural or electrical abnormalities and would not explain sudden cardiac arrest with left ventricular hypertrophy and myocardial disarray.
