The vagal maneuver is the first line of therapeutic available for patients with paroxysmal supraventricular tachycardia. It increases vagal tone and includes the traditional ocular compression, carotid sinus massage, and Valsalva maneuver. A 40-year-old man was admitted because of 180 beats/min regular narrow QRS-complex tachycardia. The physician in the emergency department had performed an ocular compression, and at its ending, the tachycardia degenerated into unstable hemodynamically high ventricular rate atrial fibrillation. It was reverted to sinus rhythm by electrical shock. The electrophysiologic study documented a latent posterolateral bypass tract, with an anterograde refractory period of 210 milliseconds, which was successfully ablated.