An 8-year-old girl is brought to the physician because of repetitive involuntary movements, including neck twisting, grimacing, grunting, and blinking, for the past 18 months. Her symptoms seem to improve with concentration and worsen with fatigue. During the past 3 months, they have become so severe that she has missed many school days. Her mother says she also has too much anxiety about her involuntary movements to see her friends and prefers staying home in her room. Her birth and development until 18 months ago were normal. Her father suffers from bipolar disorder. Vital signs are within normal limits. Mental status examination shows intact higher mental function and thought processes. Neurological examination shows multiple motor and vocal tics. Physical examination is otherwise within normal limits. Which of the following is the most appropriate initial pharmacotherapy for this condition?
Q872
While playing in the woods with friends, a 14-year-old African-American male is bitten by an insect. Minutes later he notices swelling and redness at the site of the insect bite. Which substance has directly led to the wheal formation?
Q873
A 34-year-old woman with a history of depression is brought to the emergency department by her husband 45 minutes after ingesting an unknown amount of a termite poison in a suicide attempt. She has abdominal pain, nausea, and vomiting. Her husband reports that she has had two episodes of watery diarrhea on the way to the emergency department. A distinct, garlic-like odor on the breath is noted on examination. An ECG shows sinus tachycardia and QTc prolongation. Administration of which of the following is most appropriate?
Q874
A 44-year-old man presents to his primary care physician due to a tremor. His tremor has been progressively worsening over the course of several weeks and he feels embarrassed and anxious about going to social events. He says these movements are involuntary and denies having an urge to have these movements. Medical history is significant for depression which is being treated with escitalopram. His mother is currently alive and healthy but his father committed suicide and had a history of depression. Physical examination is remarkable for impaired saccade initiation and brief, abrupt, and non-stereotyped movements involved the right arm. He also has irregular finger tapping. Which of the following is the best treatment for this patient's symptoms?
Q875
A 65-year-old man presents to the emergency department by ambulance following a motor vehicle accident. He was a restrained passenger. At the hospital, he is bleeding heavily from a large wound in his left leg. A review of medical records reveals a history of atrial fibrillation for which he takes warfarin. His international normalized ratio (INR) 2 days ago was 2.6. On physical exam he is cool and clammy. The vital signs include: heart rate 130/min and blood pressure 96/54 mm Hg. Aggressive resuscitation with intravenous normal saline is begun. Which of the following is the next best step to correct this patient's underlying coagulopathy?
Q876
A 3-year-old male is evaluated for frequent nose bleeds. Physical examination shows diffuse petechiae on the patient's distal extremities. Peripheral blood smear shows an absence of platelet clumping. An ELISA binding assay reveals that platelet surfaces are deficient in GpIIb/IIIa receptors. Which of the following drugs pharmacologically mimics this condition?
Q877
A 72-year-old man presents to his primary care physician with a 1 week history of persistent dry cough and worsening shortness of breath. He says that he has also been experiencing some abdominal pain and weakness. He has never experienced these symptoms before. His past medical history is significant for persistent ventricular tachycardia, and he started a new medication to control this arrhythmia about 1 month prior to presentation. Chest radiograph reveals patchy opacification bilaterally, and computed tomography (CT) scan shows diffuse ground glass changes. The drug that is most likely responsible for this patient's symptoms has which of the following mechanisms of action?
Q878
A 72-year-old man with coronary artery disease comes to the physician because of intermittent episodes of substernal chest pain and shortness of breath. The episodes occur only when walking up stairs and resolves after resting for a few minutes. He is a delivery man and is concerned because the chest pain has impacted his ability to work. His pulse is 98/min and blood pressure is 132/77 mm Hg. Physical examination is unremarkable. An ECG shows no abnormalities. A drug that blocks which of the following receptors is most likely to prevent future episodes of chest pain from occurring?
Q879
A 62-year-old woman is brought to the emergency department after briefly losing consciousness while walking her dog. She spontaneously regained consciousness 20 seconds later. She has a history of atrial fibrillation. Current medications include metoprolol. She reports that she forgot to take her medication the day before and took double the dose this morning instead. A decrease in which of the following most likely contributed to this patient's episode?
Q880
A 26-year-old woman comes to the physician for evaluation of nausea and fatigue. Her last menstrual period was 8 weeks ago. She has a history of bipolar disorder controlled by a drug known to sometimes cause hypothyroidism and nephrogenic diabetes insipidus. She does not smoke cigarettes or drink alcohol. A urine pregnancy test is positive. An ultrasound of the pelvis shows a viable intrauterine pregnancy. The fetus is most likely at increased risk for which of the following anomalies?
Autonomic/CV Drugs US Medical PG Practice Questions and MCQs
Question 871: An 8-year-old girl is brought to the physician because of repetitive involuntary movements, including neck twisting, grimacing, grunting, and blinking, for the past 18 months. Her symptoms seem to improve with concentration and worsen with fatigue. During the past 3 months, they have become so severe that she has missed many school days. Her mother says she also has too much anxiety about her involuntary movements to see her friends and prefers staying home in her room. Her birth and development until 18 months ago were normal. Her father suffers from bipolar disorder. Vital signs are within normal limits. Mental status examination shows intact higher mental function and thought processes. Neurological examination shows multiple motor and vocal tics. Physical examination is otherwise within normal limits. Which of the following is the most appropriate initial pharmacotherapy for this condition?
A. Fluoxetine
B. Alprazolam
C. Chlorpromazine
D. Risperidone (Correct Answer)
E. Buspirone
Explanation: ***Risperidone***
- This patient's symptoms are highly suggestive of **Tourette syndrome**, characterized by multiple motor and vocal tics persisting for over a year, and *risperidone*, an **atypical antipsychotic**, is a first-line treatment for severe tics.
- Risperidone works by blocking **D2 dopamine receptors**, which helps reduce the frequency and severity of tics, especially when symptoms cause functional impairment.
*Fluoxetine*
- *Fluoxetine* is a **selective serotonin reuptake inhibitor (SSRI)** primarily used to treat depression, anxiety, and obsessive-compulsive disorder.
- While comorbidities like anxiety or OCD are common in Tourette patients, *fluoxetine* would not directly address the **tics** themselves as a first-line agent.
*Alprazolam*
- *Alprazolam* is a **benzodiazepine** used for short-term relief of anxiety or panic disorders, working by enhancing *GABA*ergic activity.
- It does not effectively treat tics associated with Tourette syndrome and carries risks of **tolerance and dependence**.
*Chlorpromazine*
- *Chlorpromazine* is a **typical antipsychotic** that could reduce tics, but it has a higher risk of **extrapyramidal symptoms** and other side effects compared to atypical antipsychotics like *risperidone*.
- It is generally reserved for cases unresponsive to newer, better-tolerated agents.
*Buspirone*
- *Buspirone* is an **anxiolytic** that primarily affects serotonin receptors, used for generalized anxiety disorder.
- It does not have significant efficacy in treating the motor and vocal tics of **Tourette syndrome**.
Question 872: While playing in the woods with friends, a 14-year-old African-American male is bitten by an insect. Minutes later he notices swelling and redness at the site of the insect bite. Which substance has directly led to the wheal formation?
A. IFN-gamma
B. IL-4
C. IL-22
D. Histamine (Correct Answer)
E. Arachidonic acid
Explanation: ***Histamine***
- **Histamine** is a key mediator released by **mast cells** and basophils during immediate hypersensitivity reactions, such as an insect bite.
- It causes vasodilation, increased vascular permeability, and itching, leading to the characteristic **wheal and flare** response.
*IFN-gamma*
- **IFN-gamma** is primarily involved in **Type IV hypersensitivity** (delayed-type) reactions and viral/intracellular bacterial defense.
- It would not directly cause immediate wheal formation from an insect bite.
*IL-4*
- **IL-4** is crucial for **Th2 differentiation** and IgE production, which is involved in allergic reactions.
- While essential for the underlying allergic response, it does not directly cause the acute wheal formation.
*IL-22*
- **IL-22** is involved in host defense, particularly against extracellular bacteria, and plays a role in tissue repair and inflammation, especially in epithelial tissues.
- It is not a primary mediator of immediate hypersensitivity reactions or wheal formation.
*Arachidonic acid*
- **Arachidonic acid** is a precursor to eicosanoids (prostaglandins, leukotrienes), which mediate later phases of inflammation and pain.
- While contributing to the overall inflammatory response, it does not directly cause the initial, rapid wheal formation.
Question 873: A 34-year-old woman with a history of depression is brought to the emergency department by her husband 45 minutes after ingesting an unknown amount of a termite poison in a suicide attempt. She has abdominal pain, nausea, and vomiting. Her husband reports that she has had two episodes of watery diarrhea on the way to the emergency department. A distinct, garlic-like odor on the breath is noted on examination. An ECG shows sinus tachycardia and QTc prolongation. Administration of which of the following is most appropriate?
A. Deferoxamine
B. Dimercaprol (Correct Answer)
C. Fomepizole
D. N-acetylcysteine
E. Physostigmine
Explanation: ***Dimercaprol***
- The patient's symptoms (abdominal pain, nausea, vomiting, watery diarrhea, garlic-like odor on breath, QTc prolongation, and ingestion of termite poison) are highly suggestive of **acute arsenic poisoning**.
- **Dimercaprol** (BAL) is a chelating agent indicated for severe arsenic poisoning by forming stable renally excreted complexes with arsenic.
*Deferoxamine*
- Is a chelating agent primarily used for **iron overdose** by binding to free iron in the bloodstream.
- It is not effective for arsenic poisoning and would not address the patient's specific symptoms.
*Fomepizole*
- Is an **alcohol dehydrogenase inhibitor** used in cases of **methanol** or **ethylene glycol poisoning** to prevent the formation of toxic metabolites.
- It has no role in the management of arsenic poisoning due to a different mechanism of toxicity.
*N-acetylcysteine*
- Is an antidote primarily used for **acetaminophen overdose** by replenishing glutathione stores, and as a mucolytic.
- It is not indicated for arsenic poisoning and would not mitigate the toxic effects of arsenic.
*Physostigmine*
- Is an **acetylcholinesterase inhibitor** used to reverse anticholinergic toxicity.
- The patient's symptoms are not consistent with anticholinergic poisoning, and physostigmine would be inappropriate and potentially harmful.
Question 874: A 44-year-old man presents to his primary care physician due to a tremor. His tremor has been progressively worsening over the course of several weeks and he feels embarrassed and anxious about going to social events. He says these movements are involuntary and denies having an urge to have these movements. Medical history is significant for depression which is being treated with escitalopram. His mother is currently alive and healthy but his father committed suicide and had a history of depression. Physical examination is remarkable for impaired saccade initiation and brief, abrupt, and non-stereotyped movements involved the right arm. He also has irregular finger tapping. Which of the following is the best treatment for this patient's symptoms?
A. Cognitive behavioral therapy
B. Switch to sertraline
C. Valproic acid
D. Deutetrabenazine (Correct Answer)
E. Carbidopa-levodopa
Explanation: ***Deutetrabenazine***
- This patient's symptoms of **abrupt, non-stereotyped movements**, **impaired saccade initiation**, irregular finger tapping, and a **family history of psychiatric illness** are highly suggestive of **Huntington's disease**. Deutetrabenazine is a **vesicular monoamine transporter 2 (VMAT2) inhibitor** approved for the treatment of **chorea** associated with Huntington's disease.
- VMAT2 inhibitors reduce the amount of dopamine released into the synapse, which helps alleviate the **hyperkinetic movements (chorea)** characteristic of Huntington's disease.
*Cognitive behavioral therapy*
- While **cognitive behavioral therapy (CBT)** can be beneficial for managing **anxiety** and **depression** often associated with chronic neurological conditions, it does not directly address the **neurological signs** and movement disorders themselves.
- CBT is a psychotherapy approach, not a pharmacological treatment for **chorea**.
*Switch to sertraline*
- Switching antidepressants from **escitalopram to sertraline** would primarily target the patient's **depressive symptoms**, but would not directly treat the **involuntary movements**.
- While some antidepressants can have mild effects on movement, they are not indicated as a primary treatment for **chorea** in Huntington's disease.
*Valproic acid*
- **Valproic acid** is an **anticonvulsant** and mood stabilizer primarily used for epilepsy, bipolar disorder, and migraine prevention.
- It does not have a primary role in the treatment of **chorea** associated with Huntington's disease.
*Carbidopa-levodopa*
- **Carbidopa-levodopa** is the cornerstone treatment for **Parkinson's disease**, aiming to increase dopamine levels in the brain to alleviate **bradykinesia** and rigidity.
- In Huntington's disease, the primary issue is **dopamine overactivity**, so increasing dopamine with carbidopa-levodopa would worsen, rather than improve, the **chorea**.
Question 875: A 65-year-old man presents to the emergency department by ambulance following a motor vehicle accident. He was a restrained passenger. At the hospital, he is bleeding heavily from a large wound in his left leg. A review of medical records reveals a history of atrial fibrillation for which he takes warfarin. His international normalized ratio (INR) 2 days ago was 2.6. On physical exam he is cool and clammy. The vital signs include: heart rate 130/min and blood pressure 96/54 mm Hg. Aggressive resuscitation with intravenous normal saline is begun. Which of the following is the next best step to correct this patient's underlying coagulopathy?
A. Give platelets
B. Give intravenous vitamin K
C. Give fresh frozen plasma (FFP) (Correct Answer)
D. Give cryoprecipitate
E. Give packed red blood cells
Explanation: ***Give fresh frozen plasma (FFP)***
- This patient is in **hemorrhagic shock** due to severe bleeding while on **warfarin**, evidenced by tachycardia (HR 130), hypotension (BP 96/54), and cool/clammy skin with an INR of 2.6.
- **Fresh frozen plasma (FFP)** contains all vitamin K-dependent clotting factors (II, VII, IX, X) and is the best option **among those listed** to immediately reverse warfarin's effects in this life-threatening hemorrhage.
- FFP provides rapid reversal within minutes to hours, though it requires large volumes (10-15 mL/kg) and carries risk of transfusion-associated circulatory overload (TACO).
- **Note:** In modern practice, **4-factor prothrombin complex concentrate (PCC)** is preferred over FFP for warfarin reversal (faster, smaller volume, fewer complications), but it is not listed among the options here.
*Give intravenous vitamin K*
- **Vitamin K** reverses warfarin by enabling synthesis of vitamin K-dependent clotting factors (II, VII, IX, X).
- However, it takes **6-24 hours** to produce clinical effect, making it unsuitable as monotherapy for **life-threatening acute bleeding**.
- Vitamin K should be given as **adjunct therapy** alongside FFP, but cannot be the sole intervention in hemorrhagic shock.
*Give platelets*
- **Platelets** are indicated for **thrombocytopenia** (typically <50,000 in active bleeding) or **platelet dysfunction**.
- Warfarin affects **clotting factors**, not platelet count or function, so platelets will not reverse the coagulopathy.
- No indication of thrombocytopenia is mentioned in this case.
*Give cryoprecipitate*
- **Cryoprecipitate** contains **fibrinogen, Factor VIII, Factor XIII, von Willebrand factor, and fibronectin**.
- It does **not contain** the vitamin K-dependent factors (II, VII, IX, X) depleted by warfarin.
- Cryoprecipitate is used for **hypofibrinogenemia** (fibrinogen <100 mg/dL) in massive transfusion or DIC, not for warfarin reversal.
*Give packed red blood cells*
- **Packed red blood cells (PRBCs)** replace blood volume and improve oxygen-carrying capacity in hemorrhagic shock.
- While PRBCs are critical for managing hypovolemia, they **do not contain clotting factors** and will not correct the **warfarin-induced coagulopathy**.
- PRBCs should be transfused in this patient, but they must be combined with FFP to address the underlying bleeding disorder.
Question 876: A 3-year-old male is evaluated for frequent nose bleeds. Physical examination shows diffuse petechiae on the patient's distal extremities. Peripheral blood smear shows an absence of platelet clumping. An ELISA binding assay reveals that platelet surfaces are deficient in GpIIb/IIIa receptors. Which of the following drugs pharmacologically mimics this condition?
A. Clopidogrel
B. Cilostazol
C. Aspirin
D. Abciximab (Correct Answer)
E. Warfarin
Explanation: ***Abciximab***
- The patient exhibits symptoms of **Glanzmann thrombasthenia**, a genetic disorder characterized by a deficiency or qualitative defect of **glycoprotein IIb/IIIa (GpIIb/IIIa) receptors** on platelet surfaces, leading to impaired platelet aggregation. Abciximab is a **monoclonal antibody** that directly targets and inhibits the **GpIIb/IIIa receptor**, thus pharmacologically mimicking this condition.
- Abciximab binds to the **GpIIb/IIIa receptor** on activated platelets, preventing the binding of **fibrinogen** and **von Willebrand factor**, which are essential for platelet aggregation and thrombus formation.
*Clopidogrel*
- Clopidogrel is an **antiplatelet agent** that works by irreversibly blocking the **P2Y12 ADP receptor** on platelets, preventing **ADP-induced platelet activation** and aggregation.
- This mechanism is distinct from inhibiting the GpIIb/IIIa receptor directly and does not mimic Glanzmann thrombasthenia.
*Cilostazol*
- Cilostazol is a **phosphodiesterase-3 (PDE3) inhibitor** that increases **cyclic AMP (cAMP)** levels in platelets, leading to **reduced platelet aggregation** and **vasodilation**.
- Its mechanism of action is primarily related to inhibiting cAMP breakdown, which is different from GpIIb/IIIa receptor dysfunction.
*Aspirin*
- Aspirin is a **nonsteroidal anti-inflammatory drug (NSAID)** that irreversibly inhibits **cyclooxygenase-1 (COX-1)** in platelets, thereby reducing the production of **thromboxane A2 (TXA2)**.
- TXA2 is a potent platelet aggregator and vasoconstrictor. While aspirin is an antiplatelet agent, its mechanism does not involve the GpIIb/IIIa receptor.
*Warfarin*
- Warfarin is an **oral anticoagulant** that acts as a **vitamin K antagonist**, thereby inhibiting the synthesis of **vitamin K-dependent clotting factors** (II, VII, IX, X, and proteins C and S) in the liver.
- This drug affects the coagulation cascade rather than platelet function directly, and therefore does not mimic Glanzmann thrombasthenia.
Question 877: A 72-year-old man presents to his primary care physician with a 1 week history of persistent dry cough and worsening shortness of breath. He says that he has also been experiencing some abdominal pain and weakness. He has never experienced these symptoms before. His past medical history is significant for persistent ventricular tachycardia, and he started a new medication to control this arrhythmia about 1 month prior to presentation. Chest radiograph reveals patchy opacification bilaterally, and computed tomography (CT) scan shows diffuse ground glass changes. The drug that is most likely responsible for this patient's symptoms has which of the following mechanisms of action?
A. Sodium channel blocker with shortened refractory period
B. Beta-adrenergic blocker
C. Potassium channel blocker (Correct Answer)
D. Sodium channel blocker with prolonged refractory period
E. Calcium channel blocker
Explanation: ***Potassium channel blocker***
- The patient's symptoms (dry cough, shortness of breath, bilateral patchy opacification, diffuse ground glass changes) developing one month after starting a new antiarrhythmic for **persistent ventricular tachycardia** strongly suggest **amiodarone-induced pulmonary toxicity**.
- **Amiodarone** is a **Class III antiarrhythmic** that primarily works by **blocking potassium channels**, which prolongs the action potential duration and refractory period in cardiac tissue.
- Amiodarone is highly effective for both ventricular and supraventricular arrhythmias but has numerous serious side effects including **pulmonary fibrosis/pneumonitis** (most serious), thyroid dysfunction (hypo- or hyperthyroidism), hepatotoxicity, corneal deposits, and skin discoloration.
- The classic presentation of amiodarone pulmonary toxicity includes dyspnea, dry cough, and ground glass opacities on CT scan, typically occurring weeks to months after initiation.
*Sodium channel blocker with prolonged refractory period*
- This describes **Class IC antiarrhythmics** (e.g., flecainide, propafenone) which block sodium channels and prolong the action potential.
- While these can be used for ventricular arrhythmias, they are not associated with the severe pulmonary toxicity seen in this patient.
- These agents carry a risk of proarrhythmic effects, especially in patients with structural heart disease.
*Sodium channel blocker with shortened refractory period*
- This mechanism is characteristic of **Class IB antiarrhythmics** (e.g., lidocaine, mexiletine), which block sodium channels but shorten the action potential duration.
- These agents are used primarily for ventricular arrhythmias but do not cause the diffuse pulmonary toxicity described.
- Common side effects are primarily neurological (dizziness, tremor, seizures at high doses).
*Beta-adrenergic blocker*
- Beta-blockers (e.g., metoprolol, propranolol) primarily slow heart rate and reduce myocardial contractility.
- While they can cause bronchospasm in susceptible individuals (especially non-selective beta-blockers), they do not typically cause **pulmonary fibrosis** with ground glass changes as seen in this patient.
- Beta-blockers may be used for arrhythmias but are not first-line for persistent ventricular tachycardia.
*Calcium channel blocker*
- Non-dihydropyridine calcium channel blockers (e.g., verapamil, diltiazem) are used primarily for **supraventricular arrhythmias** and rate control, not persistent ventricular tachycardia.
- Their primary side effects include **bradycardia**, **hypotension**, **constipation**, and **peripheral edema**, but they are not associated with pulmonary toxicity.
Question 878: A 72-year-old man with coronary artery disease comes to the physician because of intermittent episodes of substernal chest pain and shortness of breath. The episodes occur only when walking up stairs and resolves after resting for a few minutes. He is a delivery man and is concerned because the chest pain has impacted his ability to work. His pulse is 98/min and blood pressure is 132/77 mm Hg. Physical examination is unremarkable. An ECG shows no abnormalities. A drug that blocks which of the following receptors is most likely to prevent future episodes of chest pain from occurring?
A. Angiotensin II receptors
B. M2 muscarinic receptors
C. Aldosterone receptors
D. Beta-1 adrenergic receptors (Correct Answer)
E. Alpha-2 adrenergic receptors
Explanation: ***Beta-1 adrenergic receptors***
- The patient's symptoms are classic for **stable angina**, triggered by exertion and relieved by rest, which indicates myocardial oxygen demand exceeding supply. Blocking **beta-1 adrenergic receptors** with a beta-blocker **reduces heart rate** and **contractility**, thereby decreasing myocardial oxygen consumption.
- Beta-blockers are a cornerstone in the treatment of stable angina to prevent future episodes of chest pain by **reducing cardiac workload**.
*Angiotensin II receptors*
- Blocking **Angiotensin II receptors** (e.g., with ARBs) is primarily used for **hypertension**, **heart failure**, and **renal protection**, not as a first-line treatment for acute angina prevention by reducing myocardial oxygen demand.
- While beneficial for overall cardiovascular risk reduction, ARBs do not directly lower heart rate or contractility to the same extent as beta-blockers for immediate angina symptom control.
*M2 muscarinic receptors*
- Blocking **M2 muscarinic receptors** would primarily **increase heart rate** and contractility by inhibiting parasympathetic tone, which would worsen, not prevent, angina by increasing myocardial oxygen demand.
- This is the opposite effect desired for angina management.
*Aldosterone receptors*
- Aldosterone receptor blockade (e.g., with spironolactone) is mainly used in **heart failure** and **hypertension** to reduce fluid retention and remodeling, but it does not directly impact myocardial oxygen demand or supply to prevent exertional angina.
- It does not have a direct anti-anginal effect on heart rate or contractility.
*Alpha-2 adrenergic receptors*
- Alpha-2 adrenergic receptor agonists (e.g., clonidine) are centrally acting sympatholytics that **decrease sympathetic outflow**, leading to vasodilation and reduced heart rate and blood pressure. However, they are not first-line agents for stable angina due to potential side effects and less direct impact on myocardial oxygen demand compared to beta-blockers.
- Their primary role is in **hypertension management**, and sudden discontinuation can lead to **rebound hypertension**.
Question 879: A 62-year-old woman is brought to the emergency department after briefly losing consciousness while walking her dog. She spontaneously regained consciousness 20 seconds later. She has a history of atrial fibrillation. Current medications include metoprolol. She reports that she forgot to take her medication the day before and took double the dose this morning instead. A decrease in which of the following most likely contributed to this patient's episode?
A. Diastolic efflux of calcium in cardiomyocytes
B. Activity of protein kinase C in cardiomyocytes
C. Phosphorylation of myosin light chains in vascular smooth muscle cells
D. Activity of protein kinase A in vascular smooth muscle cells
E. Activity of adenylyl cyclase in cardiomyocytes (Correct Answer)
Explanation: ***Activity of adenylyl cyclase in cardiomyocytes***
- A double dose of **metoprolol**, a beta-blocker, would significantly decrease the activity of **adenylyl cyclase** by blocking beta-adrenergic receptors in cardiomyocytes.
- Reduced adenylyl cyclase activity leads to decreased cyclic AMP (cAMP) and protein kinase A (PKA) activity, ultimately lowering heart rate and contractility, which could cause a syncopal episode.
*Diastolic efflux of calcium in cardiomyocytes*
- This process is primarily mediated by the **sodium-calcium exchanger** and sarco/endoplasmic reticulum calcium ATPase (SERCA), and is not directly inhibited by beta-blockers.
- While beta-blockers reduce intracellular calcium **influx** during systole, they do not directly decrease diastolic efflux processes.
*Activity of protein kinase C in cardiomyocytes*
- **Protein kinase C** is primarily involved in pathways activated by phospholipase C and diacylglycerol, which are separate from the beta-adrenergic signaling pathway.
- Metoprolol's action as a beta-blocker does not directly inhibit the activity of protein kinase C.
*Phosphorylation of myosin light chains in vascular smooth muscle cells*
- **Myosin light chain phosphorylation** in vascular smooth muscle primarily mediates **vasoconstriction** and is regulated by calcium-calmodulin-myosin light chain kinase.
- Beta-blockers like metoprolol do not directly inhibit this process, although they can indirectly affect vascular tone.
*Activity of protein kinase A in vascular smooth muscle cells*
- While **PKA** in vascular smooth muscle can cause vasodilation, metoprolol's primary effect is on beta-1 receptors in the heart, not directly lowering PKA activity in vascular smooth muscle.
- However, the patient's symptoms are more consistent with a **cardiac origin** due to the acute change in heart function.
Question 880: A 26-year-old woman comes to the physician for evaluation of nausea and fatigue. Her last menstrual period was 8 weeks ago. She has a history of bipolar disorder controlled by a drug known to sometimes cause hypothyroidism and nephrogenic diabetes insipidus. She does not smoke cigarettes or drink alcohol. A urine pregnancy test is positive. An ultrasound of the pelvis shows a viable intrauterine pregnancy. The fetus is most likely at increased risk for which of the following anomalies?
A. Neural tube defects
B. Aplasia cutis
C. Hypoplastic or absent limbs
D. Abnormal placentation
E. Atrialization of the right ventricle (Correct Answer)
Explanation: ***Atrialization of the right ventricle***
- The patient's history of **bipolar disorder** controlled by a drug causing **hypothyroidism** and **nephrogenic diabetes insipidus** strongly points to **lithium**.
- **Lithium** exposure during the first trimester of pregnancy is associated with an increased risk of **Ebstein's anomaly**, which involves the **apical displacement of the tricuspid valve** leaflets leading to **atrialization of the right ventricle**.
*Neural tube defects*
- These anomalies are often associated with deficiencies in **folic acid** or exposure to certain **antiepileptic drugs** like valproate, not lithium.
- While concerning, there is no information in the vignette to suggest these specific risk factors exist for this patient besides lithium use.
*Aplasia cutis*
- This is a localized absence of skin at birth, most commonly on the scalp. It is associated with gestational exposure to **methimazole** or **carbimazole**, used to treat hyperthyroidism, which is not indicated here.
- There is no direct link between lithium exposure and aplasia cutis.
*Hypoplastic or absent limbs*
- This type of anomaly is historically associated with exposure to **thalidomide** during early pregnancy.
- Lithium is not known to cause limb reduction defects.
*Abnormal placentation*
- Conditions like **placenta previa** or **placenta accreta** can result from previous uterine surgery (e.g., C-section) or advanced maternal age.
- Lithium use is not a recognized risk factor for abnormal placentation.