Cardioversion and defibrillation US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Cardioversion and defibrillation. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Cardioversion and defibrillation US Medical PG Question 1: A 55-year-old man presents to his physician with a complaint of recurrent episodes of palpitations over the past 2 weeks. He also mentions that he tends to tire easily. He denies chest pain, breathlessness, dizziness, or syncope, but has a history of ischemic heart disease. He smokes 1 pack of cigarettes every day and drinks alcohol occasionally. The physical examination revealed a temperature of 36.9°C (98.4°F), a pulse of 124/min (irregular), a blood pressure of 142/86 mm Hg, and a respiratory rate of 16/min. Auscultation of his chest is normal with an absence of rales overall lung fields. An ECG was significant for fibrillatory waves and an irregular RR interval. Thus, the physician concludes that the symptoms are due to atrial fibrillation. The patient is prescribed oral diltiazem. Which of the following side effects should the physician warn the patient about?
- A. Stevens-Johnson syndrome
- B. Bloody diarrhea
- C. Hypoglycemia
- D. Bilateral pedal edema (Correct Answer)
- E. Multifocal atrial tachycardia
Cardioversion and defibrillation Explanation: ***Bilateral pedal edema***
- **Diltiazem**, a **calcium channel blocker**, can cause **peripheral vasodilation**, leading to fluid extravasation and **bilateral pedal edema**.
- This is a common and dose-dependent side effect, typically managed by dose reduction or switching to another agent if bothersome.
*Stevens-Johnson syndrome*
- This is a severe, life-threatening **cutaneous adverse drug reaction** characterized by widespread blistering and epidermal detachment, commonly associated with drugs like **antibiotics (sulfonamides)** or **anticonvulsants**.
- It is **not a typical side effect of diltiazem**, although rare idiosyncratic reactions to nearly any drug are possible.
*Bloody diarrhea*
- **Bloody diarrhea** is typically associated with **gastrointestinal infections** (e.g., *E. coli* O157:H7, *Shigella* spp.) or inflammatory bowel disease.
- It is **not a known side effect of diltiazem**; diltiazem may cause constipation, not diarrhea.
*Hypoglycemia*
- **Hypoglycemia** is a common side effect of **insulin** or **sulfonylurea medications** used to treat diabetes.
- Diltiazem does **not directly affect blood glucose levels** or cause hypoglycemia.
*Multifocal atrial tachycardia*
- **Multifocal atrial tachycardia (MAT)** is an **arrhythmia** characterized by at least three distinct P wave morphologies and an irregular rhythm.
- **Diltiazem** is used to **treat arrhythmias** like atrial fibrillation and would not typically cause a new, distinct arrhythmia such as MAT.
Cardioversion and defibrillation US Medical PG Question 2: A 22-year-old woman presents to the emergency department feeling lightheaded and states that her heart is racing. She does not have a history of any chronic medical conditions. She is a college sophomore and plays club volleyball. Although she feels stressed about her upcoming final exams next week, she limits her caffeine intake to 3 cups of coffee per day to get a good night sleep. She notes that her brother takes medication for some type of heart condition, but she does not know the name of it. Both her parents are alive and well. She denies recent illness, injuries, or use of cigarettes, alcohol, or recreational drugs. The pertinent negatives from the review of systems include an absence of fever, nausea, vomiting, sweating, fatigue, or change in bowel habits. The vital signs include: temperature 36.8°C (98.2°F), heart rate 125/min, respiratory rate 15/min, blood pressure 90/75 mm Hg, and oxygen saturation of 100% on room air. The laboratory results are within normal limits. The ECG is significant for a shortened PR interval and widened QRS. Which of the following medications should the patient avoid in this scenario?
- A. Amlodipine
- B. Procainamide
- C. Diltiazem
- D. Verapamil (Correct Answer)
- E. Metoprolol
Cardioversion and defibrillation Explanation: ***Verapamil***
- The ECG findings of a **shortened PR interval** and **widened QRS** are characteristic of **Wolff-Parkinson-White (WPW) syndrome**, an accessory pathway that can bypass the AV node.
- Verapamil is a **non-dihydropyridine calcium channel blocker** that blocks the AV node and can paradoxically increase conduction down the accessory pathway in WPW, potentially leading to **ventricular fibrillation** if an atrial tachyarrhythmia is present.
- **Verapamil is the most classically contraindicated medication in WPW syndrome** and is the prototype drug to avoid in this condition.
*Amlodipine*
- Amlodipine is a **dihydropyridine calcium channel blocker** primarily used for hypertension and angina.
- It has minimal effect on the AV node and does not carry the same risk as non-dihydropyridine calcium channel blockers in WPW syndrome.
*Procainamide*
- **Procainamide is a Class Ia antiarrhythmic** that can be used to treat tachyarrhythmias related to WPW syndrome, as it prolongs the refractory period of the accessory pathway.
- It would be a potential **treatment option**, not a medication to avoid, especially for antidromic atrioventricular reentrant tachycardia (AVRT) in WPW.
*Diltiazem*
- Similar to verapamil, diltiazem is a **non-dihydropyridine calcium channel blocker** that blocks the AV node.
- While it carries similar risks to verapamil in WPW syndrome, **verapamil is more classically emphasized** as the prototypical contraindicated medication in medical education and board examinations.
*Metoprolol*
- Metoprolol is a **beta-blocker** that slows conduction through the AV node.
- While beta-blockers are also generally **avoided in WPW syndrome with atrial fibrillation**, **AV nodal blocking calcium channel blockers (especially verapamil) are considered the primary contraindication** due to more pronounced effects on accessory pathway conduction.
Cardioversion and defibrillation US Medical PG Question 3: Two days after admission for myocardial infarction and subsequent coronary angioplasty, a 65-year-old man becomes distressed and diaphoretic in the cardiac intensive care unit. Suddenly he is no longer responsive. Pulse oximetry does not show a tracing. He has a history of hypertension and depression. Prior to his admission, his medication included ramipril and aripiprazole. Examination shows no carotid pulse. An ECG is shown. After beginning chest compressions, which of the following is the most appropriate step in management of the patient?
- A. Intravenous procainamide
- B. Cardiac catheterization
- C. Intravenous amiodarone
- D. Intravenous magnesium sulfate
- E. Defibrillation (Correct Answer)
Cardioversion and defibrillation Explanation: ***Defibrillation***
- The ECG shows a **wide complex tachycardia** consistent with either **ventricular fibrillation (VF)** or **pulseless ventricular tachycardia (VT)**.
- In a patient who is **unresponsive and pulseless**, both VF and pulseless VT are treated identically with **immediate unsynchronized defibrillation** after initiating CPR, according to **ACLS guidelines**.
- **Defibrillation** is the definitive treatment to restore a perfusing rhythm and is the priority intervention after chest compressions have begun.
*Intravenous procainamide*
- **Procainamide** is an antiarrhythmic drug used for certain types of **stable ventricular tachycardia** or wide-complex tachycardia of uncertain type when the patient has a pulse.
- It is **contraindicated** in pulseless arrhythmias like VF or pulseless VT, where electrical therapy (defibrillation) is paramount.
- Administration would cause dangerous delay in definitive treatment.
*Cardiac catheterization*
- **Cardiac catheterization** is an invasive diagnostic and interventional procedure typically performed to evaluate and treat coronary artery disease.
- It is **not an immediate life-saving intervention** for a patient in **cardiac arrest**, which requires immediate electrical therapy.
- Catheterization may be considered after return of spontaneous circulation (ROSC) to address underlying ischemia.
*Intravenous amiodarone*
- **Amiodarone** is an antiarrhythmic agent used in **VF/pulseless VT that is refractory to initial defibrillation attempts** and after epinephrine administration.
- It is administered **after initial defibrillation attempts have failed**, not as the primary or first-line treatment.
- The ACLS algorithm recommends amiodarone after the third shock if VF/pulseless VT persists.
*Intravenous magnesium sulfate*
- **Magnesium sulfate** is the treatment of choice for **Torsades de Pointes**, a polymorphic ventricular tachycardia often associated with **prolonged QT interval**.
- The clinical presentation and ECG do not suggest Torsades de Pointes, and magnesium is not indicated as the initial treatment for VF or monomorphic VT.
- Magnesium may also be considered for refractory VF/VT with suspected hypomagnesemia.
Cardioversion and defibrillation US Medical PG Question 4: 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
Cardioversion and defibrillation 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.
Cardioversion and defibrillation US Medical PG Question 5: Two days after coronary artery stent placement for a posterior myocardial infarction, a 70-year-old woman complains of difficulty breathing and retrosternal chest pain. She has a history of atrial fibrillation, for which she takes verapamil. Following stent placement, the patient was started on aspirin and clopidogrel. She appears to be in acute distress and is disoriented. Respirations are 22/min. Pulse oximetry on room air shows an oxygen saturation of 80%. Diffuse crackles are heard on auscultation of the chest. The patient is intubated and mechanical ventilation is started. Shortly afterwards, she becomes unresponsive. Heart sounds are inaudible and her carotid pulses are not palpable. The cardiac monitor shows normal sinus rhythm with T-wave inversion. Which of the following is the most appropriate next step in management?
- A. Synchronized cardioversion
- B. Coronary angiography
- C. Unsynchronized cardioversion
- D. Intravenous epinephrine therapy
- E. Chest compressions (Correct Answer)
Cardioversion and defibrillation Explanation: ***Chest compressions***
- The patient presents with **pulselessness** despite a **normal sinus rhythm on the monitor** (pulseless electrical activity or PEA). In PEA, the immediate intervention is **high-quality chest compressions** as per ACLS guidelines.
- The preceding events (difficulty breathing, chest pain, disorientation, hypoxemia, diffuse crackles, and sudden unresponsiveness with unpalpable pulses) point towards acute cardiovascular collapse likely due to **cardiac tamponade** or other cause of obstructive shock, but the immediate response to pulselessness is compressions.
*Synchronized cardioversion*
- This is indicated for patients who are **unstable with a perfusing tachyarrhythmia**, such as unstable atrial fibrillation with rapid ventricular response or ventricular tachycardia with a pulse.
- The patient has no palpable pulses and exhibits **pulseless electrical activity (PEA)**, not a perfusing tachyarrhythmia, making synchronized cardioversion inappropriate.
*Coronary angiography*
- This is a diagnostic and interventional procedure used to assess and treat **coronary artery disease** or stent thrombosis.
- While post-stent complications are a concern, the patient is in **cardiac arrest (PEA)**, making immediate diagnostic angiography unfeasible and not the priority life-saving intervention.
*Unsynchronized cardioversion*
- Also known as **defibrillation**, this is indicated for **ventricular fibrillation (VF)** or **pulseless ventricular tachycardia (pVT)**.
- The cardiac monitor shows a **normal sinus rhythm**, not VF or pVT, therefore unsynchronized cardioversion is not indicated.
*Intravenous epinephrine therapy*
- Epinephrine is a **vasopressor** used during cardiac arrest to improve coronary and cerebral perfusion.
- While epinephrine is part of the **ACLS algorithm for PEA**, it is given *after* initiating chest compressions, not as the very first step in a pulseless patient.
Cardioversion and defibrillation US Medical PG Question 6: A patient with a history of hypertension presents with atrial fibrillation, shortness of breath, and bilateral basal crackles on auscultation. Which of the following would be the least important in the management of this patient?
- A. Start on anticoagulants
- B. Start β-blocker
- C. Cardioversion to correct rhythm if hemodynamically remains unstable even after medical management
- D. IV Digoxin for control rate (Correct Answer)
- E. Administer diuretics for fluid overload
Cardioversion and defibrillation Explanation: ***IV Digoxin for control rate***
- While **Digoxin** can be used for **rate control in atrial fibrillation**, its role is limited, especially in patients with **congestive heart failure** due to its delayed onset of action and narrow therapeutic window.
- In a patient with **shortness of breath** and **bilateral basal crackles** (suggesting acute decompensated heart failure), rapid rate control with a **β-blocker** or **calcium channel blocker** is usually preferred for immediate symptom relief.
- Digoxin is not first-line therapy in this acute setting and is therefore the **least important** among the management options listed.
*Start on anticoagulants*
- **Anticoagulation** is crucial for patients with **atrial fibrillation** to prevent **thromboembolic events**, particularly strokes.
- Given the patient's history of **hypertension** and presence of **atrial fibrillation**, their **CHA2DS2-VASc score** is likely elevated, necessitating anticoagulation.
*Start β-blocker*
- **Beta-blockers** are first-line agents for **rate control in atrial fibrillation**, especially in patients with **hypertension** and signs of **heart failure**.
- They effectively reduce ventricular response rate, improve diastolic filling, and can alleviate symptoms like **shortness of breath**.
*Cardioversion to correct rhythm if hemodynamically remains unstable even after medical management*
- If a patient with **atrial fibrillation** and signs of **heart failure** remains **hemodynamically unstable** despite initial medical management (e.g., rate control, diuretics), **cardioversion** (electrical or pharmacological) is an essential intervention to restore sinus rhythm.
- This can acutely improve cardiac output and resolve symptoms of **decompensated heart failure**.
*Administer diuretics for fluid overload*
- **Diuretics** (e.g., furosemide) are essential for managing the **volume overload** in this patient, as evidenced by **bilateral basal crackles** and **shortness of breath**.
- Reducing preload helps improve **pulmonary congestion** and alleviates acute heart failure symptoms.
- Loop diuretics are a cornerstone of acute decompensated heart failure management.
Cardioversion and defibrillation US Medical PG Question 7: A 52-year-old woman presents with decreased exercise tolerance and difficulty breathing on exertion and while sleeping at night. She says that she requires 2 pillows to sleep at night to alleviate her shortness of breath. These symptoms started 6 months ago and are gradually increasing in severity. She does not have any chronic health problems. She has smoked 15 cigarettes per day for the past 20 years and drinks alcohol occasionally. Vital signs include: blood pressure 110/70 mm Hg, temperature 36.7°C (98.0°F), and regular pulse 90/min. On physical examination, the first heart sound is loud, and there is a low pitched rumbling murmur best heard at the cardiac apex. This patient is at high risk of developing which of the following complications?
- A. Cardiac arrhythmia (Correct Answer)
- B. Infective endocarditis
- C. Systemic thromboembolism
- D. Pulmonary hypertension
- E. Right heart failure
Cardioversion and defibrillation Explanation: ***Cardiac arrhythmia***
- The patient's symptoms, including **paroxysmal nocturnal dyspnea**, **orthopnea**, **exertional dyspnea**, and an apical **low-pitched rumbling diastolic murmur** with a **loud S1**, are highly suggestive of **mitral stenosis**.
- **Mitral stenosis** leads to increased **left atrial pressure** and progressive **left atrial enlargement**, making the left atrium particularly vulnerable to developing **atrial fibrillation**, which is the **most common complication** occurring in 30-40% of patients.
- Atrial fibrillation can cause palpitations, worsen heart failure symptoms, and significantly increase stroke risk.
*Infective endocarditis*
- While patients with **mitral stenosis** have an increased risk of endocarditis, this is a less common complication compared to atrial fibrillation.
- There are no signs of active infection such as fever, new murmur changes, or systemic inflammatory response in this presentation.
*Systemic thromboembolism*
- **Thromboembolism** is a serious complication of mitral stenosis, particularly when complicated by atrial fibrillation, but the **left atrial enlargement** and stasis that predispose to arrhythmias occur first.
- Without established atrial fibrillation, the immediate risk of arrhythmia development is higher than thromboembolic events.
*Pulmonary hypertension*
- **Pulmonary hypertension** develops as a consequence of chronic elevation in left atrial pressure transmitting back to the pulmonary vasculature.
- While this is a recognized complication, it typically develops later in the disease course, and **atrial fibrillation** remains the most common complication.
*Right heart failure*
- **Right heart failure** can occur secondary to pulmonary hypertension from long-standing mitral stenosis.
- This represents a later-stage complication, whereas atrial arrhythmias occur earlier and more frequently in the natural history of mitral stenosis.
Cardioversion and defibrillation US Medical PG Question 8: A 63-year-old woman is brought to the emergency department 1 hour after the onset of right-sided weakness. She was eating breakfast when suddenly she could not lift her spoon. She cried out to her husband but her speech was slurred. For the past 4 months, she has been more anxious than usual and felt fatigued. She used to exercise regularly but had to give up her exercise routine 3 months ago because of lightheadedness and shortness of breath with exertion. She has a history of hypertension. She is a tax accountant and has had increased stress at work recently. She takes lisinopril daily and alprazolam as needed. Her temperature is 37.2°C (99.0°F), pulse is 138/min, respirations are 14/min, and blood pressure is 146/86 mm Hg. Her lungs are clear to auscultation bilaterally and she has an S1 with variable intensity. On neurologic examination, she has a right facial droop and 2/5 strength in the right shoulder, elbow, wrist, and fingers. Sensation is diminished in the right face and arm. Further evaluation is most likely to show which of the following?
- A. Irregularly irregular rhythm without P waves on ECG (Correct Answer)
- B. Left-sided carotid stenosis on duplex ultrasound
- C. Crescent-shaped hyperdense lesion on head CT
- D. Intraparenchymal hyperdensity on head CT
- E. Spikes and sharp waves in temporal region on EEG
Cardioversion and defibrillation Explanation: ***Irregularly irregular rhythm without P waves on ECG***
- The sudden onset of right-sided weakness and slurred speech suggests an **acute ischemic stroke**. The patient's history of lightheadedness, shortness of breath on exertion, and a pulse of 138/min with variable S1 intensity are highly suggestive of **atrial fibrillation (Afib)**, a common cause of cardioembolic stroke.
- An **irregularly irregular rhythm without P waves on ECG** is the hallmark finding of atrial fibrillation.
*Spikes and sharp waves in temporal region on EEG*
- **Spikes and sharp waves on EEG** are characteristic findings in **epilepsy**, particularly in the temporal lobe for temporal lobe epilepsy.
- While a seizure could present with focal neurological deficits, the sudden onset, persistent deficits, and history of cardiac symptoms make stroke more likely than an acute seizure as the primary etiology here.
*Left-sided carotid stenosis on duplex ultrasound*
- **Carotid stenosis** is a common cause of ischemic stroke, usually ipsilateral to the symptomatic side. However, the patient's symptoms are on the right side, suggesting a lesion in the **left cerebral hemisphere**.
- While **left-sided carotid stenosis** could cause a stroke affecting the right side of the body, the cardiac symptoms and examination findings (tachycardia, variable S1) make a cardioembolic source (like Afib) a more likely primary cause in this specific scenario.
*Crescent-shaped hyperdense lesion on head CT*
- A **crescent-shaped hyperdense lesion** on head CT is characteristic of a **subdural hematoma**, which is typically caused by trauma and results from venous bleeding.
- The patient's presentation of sudden-onset neurological deficits without trauma is inconsistent with a subdural hematoma.
*Intraparenchymal hyperdensity on head CT*
- An **intraparenchymal hyperdensity** on head CT indicates an **intracerebral hemorrhage**. While this can cause sudden neurological deficits, the patient's other symptoms, especially the rapid heart rate and variable S1, point more strongly towards an **ischemic event** secondary to an embolic source.
- An intracerebral hemorrhage is less likely given the absence of typical risk factors for hemorrhagic stroke (e.g., uncontrolled severe hypertension, anticoagulant use) and the strong indicators for a cardiac embolic source.
Cardioversion and defibrillation US Medical PG Question 9: A 30-year-old man presents with progressive muscle weakness for the past 6 hours. He says he had significant bilateral ankle pain which onset shortly after completing a triathlon earlier in the day. Then, he says he awoke this morning with bilateral upper and lower extremity weakness, which has progressively worsened. He has no significant past medical history and takes no current medication. The vital signs include: temperature 37.0℃ (98.6℉), pulse 66/min, respiratory rate 21/min, and blood pressure 132/83 mm Hg. On physical examination, the patient has diffuse moderate to severe muscle pain on palpation. His strength is 5 out of 5, and deep tendon reflexes are 2+ in the upper and lower extremities bilaterally. Laboratory findings are significant for the following:
Laboratory test
Sodium 141 mEq/L
Potassium 6.3 mEq/L
Chloride 103 mEq/L
Bicarbonate 25 mEq/L
Blood urea nitrogen (BUN) 31 mg/dL
Creatinine 6.1 mg/dL
BUN/Creatinine 5.0
Glucose (fasting) 80 mg/dL
Calcium 6.3 mg/dL
Serum creatine kinase (CK) 90 mcg/L (ref: 10–120 mcg/L)
Which of the following is the next best step in the management of this patient?
- A. IV calcium chloride
- B. Blood transfusion
- C. ECG (Correct Answer)
- D. Kayexalate
- E. Hemodialysis
Cardioversion and defibrillation Explanation: ***ECG***
- This patient presents with **hyperkalemia** (potassium 6.3 mEq/L) and **hypocalcemia** (calcium 6.3 mg/dL), which can lead to life-threatening cardiac arrhythmias.
- An **ECG** is crucial for assessing for cardiac manifestations of hyperkalemia, such as **peaked T waves**, prolonged PR interval, and widened QRS complex, to guide immediate treatment.
*IV calcium chloride*
- While **IV calcium chloride** (or calcium gluconate) is indicated in hyperkalemia with ECG changes, the **ECG needs to be performed first** to confirm the cardiac effects and guide the urgency and necessity of calcium administration.
- Administering calcium without an ECG could delay the diagnosis of significant arrhythmias or mask changes, leading to inappropriate management.
*Blood transfusion*
- There is no indication for a **blood transfusion** in this patient; his hemoglobin and hematocrit levels are not provided, and there is no mention of acute blood loss or symptomatic anemia.
- Transfusions carry risks and should only be given when clearly indicated.
*Kayexalate*
- **Kayexalate** (sodium polystyrene sulfonate) is a potassium-binding resin used to lower potassium levels, but its onset of action is slow (hours).
- Given the patient's acute symptoms and significantly high potassium, more immediate measures to stabilize the myocardium and shift potassium intracellularly are prioritized, with Kayexalate considered as an adjunctive treatment.
*Hemodialysis*
- **Hemodialysis** is the most effective way to rapidly remove potassium and is indicated in severe, refractory hyperkalemia or when there are signs of advanced renal failure with complications.
- However, it is an invasive procedure and other less invasive, yet rapid-acting, treatments (like calcium for cardiac stabilization, insulin-dextrose, or beta-agonists for potassium shift) should be considered and an ECG should be obtained first to determine the severity and direct initial management.
Cardioversion and defibrillation US Medical PG Question 10: A 40-year-old man is brought to the emergency department 20 minutes after his wife found him unconscious on the bathroom floor. On arrival, he is conscious and alert. He remembers having palpitations and feeling lightheaded and short of breath before losing consciousness. He takes captopril for hypertension and glyburide for type 2 diabetes mellitus. His vitals are within normal limits. Physical examination shows no abnormalities. Random serum glucose concentration is 85 mg/dL. An ECG shows a short PR interval and a wide QRS complex with initial slurring. Transthoracic echocardiography reveals normal echocardiographic findings with normal left ventricular systolic function. Which of the following is the most likely underlying cause of this patient's findings?
- A. Ischemic myocardial necrosis
- B. Ectopic foci within the ventricles
- C. Accessory atrioventricular pathway (Correct Answer)
- D. A dysfunctional AV node
- E. Low serum glucose levels
Cardioversion and defibrillation Explanation: ***Accessory atrioventricular pathway***
- The ECG findings of a **short PR interval**, **wide QRS complex**, and **initial slurring (delta wave)** are characteristic of **Wolff-Parkinson-White (WPW) syndrome**, which is caused by an **accessory atrioventricular pathway**.
- Symptoms like **palpitations, lightheadedness, and syncope** in a patient with these ECG findings suggest an underlying **tachyarrhythmia originating from the accessory pathway**.
*Ischemic myocardial necrosis*
- While syncope can be a symptom of **myocardial ischemia**, the ECG findings (short PR, wide QRS with delta wave) are not typical for **ischemia or infarction**.
- The **normal echocardiogram** and absence of chest pain also make **ischemic myocardial necrosis** less likely.
*Ectopic foci within the ventricles*
- **Ventricular ectopic foci** can cause wide QRS complexes (e.g., in ventricular tachycardia), but they typically do not involve a **short PR interval or a delta wave**.
- The characteristic ECG pattern observed points away from primary **ventricular ectopy** as the underlying cause.
*A dysfunctional AV node*
- A **dysfunctional AV node** typically leads to **AV blocks** (prolonged PR interval, dropped beats) or sometimes reentrant tachycardias, but it does not cause a **short PR interval with a delta wave and wide QRS complex**.
- The described ECG pattern indicates a bypass of the **AV node's normal delay function**.
*Low serum glucose levels*
- Although the patient takes **glyburide** (which can cause hypoglycemia), his **random serum glucose** was 85 mg/dL, which is within the normal range and does not indicate **hypoglycemia**.
- While hypoglycemia can cause syncope, it does not explain the specific ECG abnormalities observed.
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