**Question:** A-10-year old girl was admitted in ER with history of ingesting 10 crushed seeds of a plant, she couldn't recall how much she had and her ECG looks like this (Figure). Probable cause is ............

**Core Concept:** Ethylene, a plant hormone, can cause sinus bradycardia and heart block when consumed in large quantities, leading to ECG abnormalities.

**Why the Correct Answer is Right:**

Option A (Ethylene): Ethylene is a plant hormone that has various physiological effects, including growth and ripening. Ingestion of large quantities of ethylene-producing plants can lead to toxic effects. In this case, the ingestion of crushed seeds of the plant might have released a high amount of ethylene, causing sinus bradycardia and heart block.

Option B (Digoxin): Digoxin is a cardiac glycoside that primarily affects the sinoatrial and atrioventricular nodes, leading to bradycardia and heart block. However, the age of the patient and the specific ECG findings in this question, such as the P waves being narrow, tall, and positive, do not match those seen with digoxin toxicity.

Option C (Propafenone): Propafenone is a class IC antiarrhythmic drug used to treat certain types of arrhythmias. However, in this case, the patient's age and ECG findings do not match those seen with propafenone toxicity.

Option D (Verapamil): Verapamil is a class IC antiarrhythmic drug used to treat certain types of arrhythmias. Similar to the previous options, the patient's age and ECG findings do not match those seen with verapamil toxicity.

**Why Each Wrong Option is Incorrect:**

Option A (Ethylene): Although ethylene has been mentioned as a possible cause, the specific ECG findings are more consistent with the toxic effects of the plant seeds.

Option B (Digoxin): As mentioned before, the ECG findings do not match those seen with digoxin toxicity.

Option C (Propafenone): The ECG findings do not match those seen with propafenone toxicity.

Option D (Verapamil): The ECG findings do not match those seen with verapamil toxicity.

**Core Concept:** The ECG findings in this case are more consistent with the toxic effects of the plant seeds, which contain ethylene. Ethylene is a plant hormone that can lead to sinus bradycardia and heart block when consumed in large amounts.

**Clinical Pearls:**

1. Ingestion of ethylene-producing plants or seeds can lead to toxic effects in children.
2. The ECG findings in this case are more consistent with ethylene toxicity, which can cause sinus bradycardia and heart block due to its effect on the autonomic nervous system.
3. Ingesting ethylene-producing plants should be avoided, especially in children, to prevent potential toxic effects.

**Why This is a Challenge for Medical Students:**

Understanding the toxic effects of ethylene