These three panels are continuous and represent the testing of a Medronic model 7219 defibrillator. The channels are a surface EKG lead, a ventricular intra-cardiac recording and a marker channel from the device. The first panel shows rapid paced ventricular beats followed by a low energy shock which induces VF. The shock is not on the T wave. |

| The second panel shows the VF, note the readings of the marker channel. |

| The last panel shows the termination of the VF with a 20 joule shock and then ventricular pacing. Note the ST elevation of the paced beats. |
