Sometimes the vagotonic tone induced by neurocardiogenic syncope is so intense that prolonged ventricular standstill ensues. This may cause  hypoxic syncopal convulsions. 

This patient had a history of dramatic collapses. The ECG trace shows  ventricular standstill of 16 seconds followed by one ventricular contraction and then another 13 seconds without an effective contraction.  Ventricular activity then resumed spontaneously . 

Following diagnosis he was fitted with a pacemaker and has been asymptomatic since.