The Hidden Reveals the Hidden.

A 59-year-old man with no history of cardiovascular disease was admitted to the emergency department with sudden onset of rapid palpitations and dizziness 2 hours before admission. ECG (Figure 1) revealed a rapid irregular wide QRS complex tachycardia with right bundle-branch block morphology and alternating QRS width. Twelve-lead ECG once sinus rhythm was restored after electrical cardioversion. [Extracted from the article]