Cardiac Poisons — MCQs
Hippus occurs in which poisoning?
Which of the following is a contraindication for the use of digitalis?
What are the primary mechanisms behind cardiac toxicity associated with Tricyclic antidepressants?
Which of these is not a cardiac poison?
Laudanosine is a toxic metabolite of?
Which of the following conditions does not enhance the toxicity of digoxin?
A woman consumes several tablets of amitriptyline (a case of amitriptyline poisoning). Which of the following is NOT an appropriate management step?
Which of the following is NOT a post-mortem finding in carbon monoxide poisoning?
All are causes of wrist drop (condition shown in the image below) except:
A patient is admitted with insomnia, agitation, diarrhea, dilated pupils, and sweating. What is the type of poisoning?
Cardiac Poisons Indian Medical PG Practice Questions and MCQs
Question 1: Hippus occurs in which poisoning?
- A. Aconite poisoning (Correct Answer)
- B. Opioid poisoning
- C. Neuromuscular blocking agent poisoning
- D. Belladonna poisoning
Explanation: ***Aconite poisoning*** - **Hippus**, characterized by alternating **pupillary constriction and dilation**, is a hallmark of aconite poisoning. - This unusual pupil activity results from the **neurotoxic effects** of aconite on the autonomic nervous system. *Opioid poisoning* - Opioid poisoning typically causes characteristic **pinpoint pupils (miosis)** due to parasympathetic overstimulation. - Hippus is not a feature of opioid toxicity. *Neuromuscular blocking agent poisoning* - Neuromuscular blocking agents primarily affect the **skeletal muscles**, leading to **paralysis** but generally do not directly impact pupil size or reactivity. - Pupils usually remain **mid-dilated and fixed** in severe paralysis, but not hippus. *Belladonna poisoning* - Belladonna (atropine) poisoning causes **mydriasis (dilated pupils)** due to its anticholinergic effect, blocking parasympathetic activity. - The pupils are typically fixed and dilated, not exhibiting hippus.
Question 2: Which of the following is a contraindication for the use of digitalis?
- A. WPW Syndrome (Correct Answer)
- B. Thyrotoxicosis
- C. Acute rheumatic carditis
- D. Atrial fibrillation with rapid ventricular response
Explanation: ***WPW Syndrome*** - In **WPW syndrome**, digitalis can **accelerate conduction** through the accessory pathway, leading to a rapid and potentially life-threatening ventricular response, especially during **atrial fibrillation**. - This can trigger **ventricular tachycardia** or **ventricular fibrillation** in patients with pre-excitation. - This is an **absolute contraindication** to digitalis use. *Acute rheumatic carditis* - Acute rheumatic carditis is a **relative contraindication** to digitalis due to increased risk of **digitalis toxicity** in inflamed myocardium. - The inflamed heart muscle is more **sensitive to arrhythmogenic effects** of digitalis. - However, **WPW syndrome is a more absolute contraindication** as the mechanism of harm is more predictable and severe. - If heart failure is present, digitalis may be used with **extreme caution** under close monitoring. *Thyrotoxicosis* - While digitalis may be used cautiously in patients with thyrotoxicosis experiencing **tachyarrhythmias** or heart failure, it's not an absolute contraindication. - Digitalis effectiveness is **reduced in hyperthyroid states**, often requiring higher doses. - The primary treatment for thyrotoxicosis is to manage the **hyperthyroid state**, which often resolves the cardiac symptoms. *Atrial fibrillation with rapid ventricular response* - Digitalis is often used to **slow the ventricular rate** in atrial fibrillation with a rapid ventricular response by **increasing vagal tone** and inhibiting the AV node. - This is a common **indication** for digitalis therapy, not a contraindication.
Question 3: What are the primary mechanisms behind cardiac toxicity associated with Tricyclic antidepressants?
- A. Norepinephrine reuptake inhibition only
- B. Anticholinergic effects on the heart
- C. Both norepinephrine reuptake inhibition and anticholinergic effects on the heart (Correct Answer)
- D. Direct membrane stabilizing effects only
Explanation: ***Both norepinephrine reuptake inhibition and anticholinergic effects on the heart*** - **Tricyclic antidepressants (TCAs)** block the reuptake of **norepinephrine**, which can lead to increased sympathetic tone on the heart and potentially **tachyarrhythmias** or other cardiac complications. - TCAs also have potent **anticholinergic effects**, blocking muscarinic receptors in the heart; this can increase **heart rate** and affect cardiovascular stability. - While **direct membrane stabilizing effects** (sodium channel blockade) are critical for **QRS widening and conduction delays**, the combination of norepinephrine reuptake inhibition and anticholinergic effects accounts for the broader spectrum of **TCA-induced cardiac toxicity** including tachycardia and hemodynamic instability. *Norepinephrine reuptake inhibition only* - While TCAs do inhibit norepinephrine reuptake contributing to tachycardia and increased sympathetic tone, this mechanism alone does not fully explain the breadth of cardiac effects seen with these drugs. - The **anticholinergic effects** play a significant additional role in altering cardiac function. *Anticholinergic effects on the heart* - While TCAs do exert anticholinergic effects that can impact heart rate and cardiovascular function, this mechanism alone fails to account for the additional contributions from **norepinephrine reuptake inhibition** to the overall cardiac toxicity. - The combination of both mechanisms is necessary for a complete understanding of **TCA-induced cardiac effects**. *Direct membrane stabilizing effects only* - This option refers to the **quinidine-like action** of TCAs, which involves blocking myocardial fast sodium channels, leading to a **prolonged QRS interval** and increased risk of **ventricular arrhythmias** and **conduction defects**. - While direct membrane stabilization is the **primary mechanism of TCA-induced conduction abnormalities** (QRS widening, heart blocks), the question asks for mechanisms of broader **cardiac toxicity**, which includes the combined effects of norepinephrine reuptake inhibition and anticholinergic actions on heart rate and hemodynamics.
Question 4: Which of these is not a cardiac poison?
- A. Aconite
- B. Atropa belladonna (Correct Answer)
- C. Cerbera thevetia
- D. Nicotiana tabacum
Explanation: ***Atropa belladonna*** - This plant primarily contains **atropine** and other **belladonna alkaloids**, which are **anticholinergic** and cause symptoms like dry mouth, dilated pupils, tachycardia, and hallucinations. - While it can cause *tachycardia*, its primary toxic effects are not directly on the cardiac muscle contractility or rhythmicity leading to a **"cardiac poison"** classification (e.g. arrhythmias or heart failure), but rather through autonomic nervous system modulation. *Aconite* - Aconite, derived from the **monkshood plant**, contains **aconitine**, a potent neurotoxin and cardiotoxin. - It causes severe **arrhythmias**, including ventricular fibrillation, which can be rapidly fatal by directly affecting **sodium channels** in myocardial cells. *Cerbera thevetia* - Commonly known as Yellow Oleander, it contains **cardiac glycosides** similar to digoxin. - These glycosides inhibit the **Na+/K+-ATPase pump** in cardiac myocytes, leading to increased intracellular calcium, enhanced contractility, and dose-dependent **arrhythmias** (bradycardia, heart blocks, ventricular arrhythmias). *Nicotiana tabacum* - Tobacco contains **nicotine**, which primarily acts on **nicotinic acetylcholine receptors**. - Acute poisoning can lead to initial stimulation followed by depression of the autonomic ganglia, causing a range of cardiac effects including **tachycardia**, **hypertension**, and **arrhythmias** due to sympathetic nervous system activation.
Question 5: Laudanosine is a toxic metabolite of?
- A. Mivacurium
- B. Atracurium (Correct Answer)
- C. Vecuronium
- D. Pancuronium
Explanation: ***Atracurium*** - Atracurium undergoes **Hofmann elimination**, a non-enzymatic degradation process, which produces **laudanosine** as a metabolite. - **Laudanosine** can accumulate, particularly in patients with renal or hepatic dysfunction, and at high concentrations, it may cause **CNS excitation** and seizures. *Mivacurium* - Mivacurium is rapidly metabolized by **plasma pseudocholinesterase**, an enzyme also responsible for the breakdown of succinylcholine. - Its breakdown products do not include laudanosine, and it has a relatively **short duration of action** due to this rapid metabolism. *Vecuronium* - Vecuronium is primarily eliminated by the **liver** and, to a lesser extent, the kidneys, with metabolites having some neuromuscular blocking activity. - It does not undergo Hofmann elimination and therefore does not produce laudanosine as a metabolite. *Pancuronium* - Pancuronium is primarily eliminated by the **kidneys**, with a significant portion excreted unchanged. - It is a long-acting neuromuscular blocker and does not produce laudanosine as a metabolite.
Question 6: Which of the following conditions does not enhance the toxicity of digoxin?
- A. Hypercalcemia
- B. Hyperkalemia (Correct Answer)
- C. Renal failure
- D. Hypomagnesemia
Explanation: ***Hyperkalemia*** - **Hyperkalemia** actually reduces the binding of digoxin to the Na+/K+-ATPase, thereby antagonizing its effect and decreasing its toxicity. - While very high potassium levels can be dangerous, they tend to mitigate, rather than enhance, **digoxin toxicity**. *Hypercalcemia* - **Hypercalcemia** enhances the inotropic effects of digoxin, leading to increased risk of toxicity, particularly arrhythmias. - High calcium levels contribute to the **calcium overload** within cardiac myocytes, which is a mechanism of digoxin toxicity. *Renal failure* - Digoxin is primarily excreted renally, so **renal failure** leads to reduced clearance and accumulation of the drug, increasing its serum concentration and toxicity. - Patients with impaired kidney function require **lower doses** of digoxin to avoid toxic levels. *Hypomagnesemia* - **Hypomagnesemia** exacerbates digoxin toxicity by increasing the binding affinity of digoxin to the Na+/K+-ATPase and contributing to the development of arrhythmias. - Low magnesium levels can destabilize the cardiac muscle, making it more susceptible to the **proarrhythmic effects** of digoxin.
Question 7: A woman consumes several tablets of amitriptyline (a case of amitriptyline poisoning). Which of the following is NOT an appropriate management step?
- A. Gastric lavage
- B. Atropine as antidote (Correct Answer)
- C. Sodium bicarbonate infusion
- D. Activated charcoal administration
Explanation: ***Atropine as antidote*** - **Atropine** is primarily used to counteract **cholinergic toxicity** (e.g., organophosphate poisoning), while amitriptyline causes **anticholinergic effects**. Administering atropine would worsen the patient's condition by exacerbating these effects (tachycardia, hyperthermia, delirium, urinary retention). - The main toxic effects of amitriptyline are related to its impact on cardiac conduction (sodium channel blockade), central nervous system depression, and profound anticholinergic actions, none of which are reversed by atropine. *Sodium bicarbonate infusion* - **Sodium bicarbonate** is the **gold standard treatment** for **QRS widening >100 ms** and **ventricular arrhythmias** caused by amitriptyline. - It increases extracellular sodium concentration and alkalinizes the plasma, which helps to overcome the **sodium channel blockade** and reduces TCA binding to cardiac sodium channels. - Bolus dosing (1-2 mEq/kg) followed by infusion to maintain alkaline pH (7.45-7.55) is recommended. *Gastric lavage* - **Gastric lavage is NOT routinely recommended** in modern toxicology practice for amitriptyline poisoning due to **limited efficacy** and **significant risks** (aspiration, especially with CNS depression). - Current evidence shows **no improvement in clinical outcomes** and potential for harm. - While historically mentioned as an option for recent, massive ingestions, it has been largely abandoned in favor of activated charcoal, making this a questionable management step in contemporary practice. *Activated charcoal administration* - **Activated charcoal** is the **preferred decontamination method** to reduce absorption of amitriptyline from the gastrointestinal tract. - It has a **large surface area** and effectively binds TCAs, preventing systemic absorption. - Most effective when administered within **1-2 hours** of ingestion; single dose of 1 g/kg (usually 25-50 g in adults) is recommended if airway is protected.
Question 8: Which of the following is NOT a post-mortem finding in carbon monoxide poisoning?
- A. Froth at mouth and nose
- B. Blue skin discoloration (Correct Answer)
- C. Cerebral edema
- D. Cherry red discoloration of skin
Explanation: ***Blue skin discoloration*** - **Cyanosis**, or blue skin discoloration, indicates **hypoxia** due to deoxygenated hemoglobin. - In carbon monoxide poisoning, **carboxyhemoglobin** prevents oxygen release but does not cause deoxygenation of the remaining hemoglobin, thus typically avoiding cyanosis. *Froth at mouth and nose* - **Frothing** at the mouth and nose can be seen in various forms of asphyxia and pulmonary edema, which can be secondary to carbon monoxide poisoning if there is significant cardiac or respiratory compromise. - While not universally present, it is a possible finding associated with acute physiological distress preceding death. *Cerebral edema* - **Cerebral edema** is a common post-mortem finding in severe carbon monoxide poisoning due to **hypoxic brain injury**. - Carbon monoxide directly impairs cellular respiration, leading to widespread tissue hypoxia, including the brain, which can manifest as swelling. *Cherry red discoloration of skin* - **Cherry red discoloration** of the skin and lividity is a classic and highly characteristic post-mortem sign of carbon monoxide poisoning. - This color is due to the formation of **carboxyhemoglobin**, which has a bright red hue and is visible through the skin.
Question 9: All are causes of wrist drop (condition shown in the image below) except:
- A. Arsenic toxicity
- B. Lead poisoning
- C. Use of crutches
- D. Zinc poisoning (Correct Answer)
Explanation: ***Zinc poisoning*** - **Zinc poisoning** is not a characteristic cause of **wrist drop**, which is typically associated with **radial nerve palsy**. - While excessive zinc can cause copper deficiency and neurological issues, it does not directly lead to **radial nerve entrapment** or damage causing wrist drop. *Arsenic toxicity* - **Chronic arsenic poisoning** can lead to **peripheral neuropathy**, which may include motor weakness such as **wrist drop**. - The neurological damage is often dose-dependent and can affect various peripheral nerves. *Lead poisoning* - **Lead poisoning** is a well-known cause of **radial nerve palsy**, leading to **wrist drop**. - This is often seen in occupational exposures and can be quite specific to the **radial nerve**. *Use of crutches* - Prolonged or improper use of **crutches** can cause compression of the **radial nerve** in the axilla, leading to **crutch palsy**. - **Crutch palsy** manifests as weakness of the **forearm and hand extensors**, resulting in **wrist drop**.
Question 10: A patient is admitted with insomnia, agitation, diarrhea, dilated pupils, and sweating. What is the type of poisoning?
- A. Cannabis
- B. Ecstasy
- C. Heroin
- D. Cocaine (Correct Answer)
Explanation: **Cocaine** - The symptoms of **insomnia, agitation, diarrhea, dilated pupils, and sweating** are classic manifestations of **sympathomimetic toxicity**, characteristic of cocaine poisoning. - Cocaine acts by **blocking the reuptake of norepinephrine, dopamine, and serotonin**, leading to excessive stimulation of the central and peripheral nervous systems. - This presentation represents a **pure sympathomimetic toxidrome** without additional complicating features, which is most classically associated with cocaine intoxication. *Heroin* - Heroin poisoning (opioid overdose) typically presents with **CNS depression**, including **respiratory depression**, **pinpoint pupils (miosis)**, and **constipation**, which are opposite to the symptoms described. - Patients are usually **sedated or comatose**, not agitated or insomniac. - This represents an **opioid toxidrome**, not a sympathomimetic one. *Cannabis* - Cannabis intoxication usually causes **conjunctival injection (red eyes)**, **tachycardia**, **dry mouth**, and **increased appetite**, often accompanied by euphoria or drowsiness. - While it can cause some anxiety/agitation in higher doses or naive users, it does **not cause mydriasis (dilated pupils)** or the severe physical stimulation seen here. - Cannabis does not produce a sympathomimetic toxidrome. *Ecstasy* - Ecstasy (MDMA) is also a sympathomimetic and can cause similar symptoms including agitation, dilated pupils, and sweating. - However, MDMA intoxication is more characteristically associated with **severe hyperthermia**, **hyponatremia**, **bruxism (teeth grinding)**, **serotonin syndrome**, and **rhabdomyolysis** in severe cases. - While both are sympathomimetics, the presentation described represents a **classic pure sympathomimetic picture** most consistent with **cocaine**, which is the more common cause of this toxidrome in clinical practice.
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