The indications for defibrillation are all kinds of ectopic tachyarrhythmias, especially those with ineffective drug therapy or severe hemodynamic disorders, mainly applicable to ventricular fibrillation and flutter, ventricular tachycardia, preexcitation syndrome, caused by acute rapid atrial fibrillation, as well as certain supraventricular tachycardia, atrial fibrillation, atrial flutter and so on. Contraindications to defibrillation are: 1, arrhythmia caused by digitalis intoxication; 2, supraventricular arrhythmia with high or complete atrioventricular block; 3, sick sinus node syndrome associated with fast-slow syndrome; 4, paroxysmal tachycardia recurrent and frequent occurrence of authors; 5, hypokalemia not corrected.