This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular system, Subject name: Pharmacology
A patient has been diagnosed as having "long QT syndrome." The patient is experiencing significant pain following a bout with shingles. What would be an appropriate drug for his pain? 
Select and explain. 
A. Amitriptyline, B. Fentanyl, C. Acyclovir, D. Gabapentin
D: Gabapentin
Answer: D: Gabapentin 
Explanation: It's a case of post-herpetic neuralgia. Gabapentin is the drug of choice. Amitriptyline can also be used for pain but it can also cause arrhythmia.