**Question:** A 54-year-old man presents after a syncopal episode. The patient has no recollection of the event; according to bystanders, he awakened about 45 seconds after he "fell out." The patient has a history of bipolar disorder managed with quetiapine. He recently had an episode of prostatitis treated with ciprofloxacin. His other medications include lisinopril and hydrochlorothiazide (HCTZ) for hypertension and cyclobenzaprine and a hydrocodone/acetaminophen combination pill for low back pain. On examination, the patient is alert and oriented. Neurological examination is non-focal. Cardiac examination is unremarkable, without murmur, gallop, or jugular distension. ECG shows nonspecific ST and T wave changes and a prolonged QT interval (QTc of 540 milliseconds). What is the best initial management approach?

A. Discontinue quetiapine and consider a long QT syndrome.
B. Discontinue cyclobenzaprine and hydrocodone/acetaminophen combination.
C. Discontinue lisinopril and hydrochlorothiazide (HCTZ).
D. Discontinue ciprofloxacin and re-evaluate for hypokalemia.

**Correct Answer:**

**Core Concept:** A prolonged QT interval is a risk factor for life-threatening arrhythmias such as torsades de pointes, which can lead to sudden cardiac death. A prolonged QT interval is associated with certain medications, electrolyte imbalances, and underlying cardiac conditions. The presence of nonspecific ST and T wave changes on ECG suggests myocardial ischemia or injury, which can be caused by medications, electrolyte imbalances, or other medical conditions.

**Why the Correct Answer is D:**

The prolonged QT interval (QTc of 540 milliseconds) is a significant risk factor for life-threatening arrhythmias. In this case, the patient has been taking ciprofloxacin, which is known to cause QT prolongation and arrhythmias. Therefore, the best initial management approach would be to discontinue ciprofloxacin (option D).

**Why the Correct Answer is NOT A, B, or C:**

Option A is incorrect because quetiapine is not associated with prolongation of QT interval. Quetiapine is an atypical antipsychotic drug used to treat bipolar disorder and schizophrenia, which is unrelated to QT interval prolongation.

Option B is incorrect because cyclobenzaprine (cycloserine) is an antispasmodic drug used for low back pain, which is not directly related to QT interval prolongation. Discontinue cyclobenzaprine and hydrocodone/acetaminophen combination (option B) may lead to worsening of his back pain, which is not the primary concern in this scenario.

Option C is incorrect because lisinopril (an angiotensin-converting enzyme inhibitor)

✓ Correct Answer: A. Admit the patient for telemetry, check serum electrolytes including potassium and magnesium levels, and withhold all medications