A 62-year-old male with underlying COPD develops a viral upper respiratory infection and begins taking an over-the-counter decongestant. Shortly thereafter he experiences palpitations and presents to the emergency room, where the following rhythm strip is obtained, demonstrating

**Core Concept**
The underlying concept being tested here involves the cardiac effects of a specific class of medications commonly found in over-the-counter decongestants, which are often used to treat nasal congestion in upper respiratory infections. These medications can have systemic effects, including alterations in cardiac rhythm, in susceptible individuals.

**Why the Correct Answer is Right**
The patient's palpitations are likely caused by the decongestant's effect on the heart, specifically through its action on the sympathetic nervous system. The decongestant, often containing pseudoephedrine or phenylephrine, can cause an increase in heart rate and contractility by stimulating beta-1 adrenergic receptors in the heart. This can lead to a potentially life-threatening arrhythmia, such as a supraventricular tachycardia (SVT). In this case, the rhythm strip likely shows a narrow QRS complex tachycardia, consistent with SVT.

**Why Each Wrong Option is Incorrect**
* **Option A:** This is not a plausible option without further specification, so it will be skipped.
* **Option B:** This option is not directly related to the cardiac effects of decongestants and is therefore incorrect.
* **Option C:** This option is not relevant to the clinical scenario presented and does not explain the patient's symptoms.

**Clinical Pearl / High-Yield Fact**
When encountering a patient with palpitations and a history of using over-the-counter decongestants, it's essential to consider the potential for cardiac arrhythmias, such as SVT, due to the stimulatory effects of these medications on the heart.

**Correct Answer: C. Supraventricular tachycardia (SVT)**

✓ Correct Answer: C. Atrial flutter with 4:1 atrioventricular block