An 18-year old man collapsed while playing softball. He was resuscitated by a witness using an automatic external defibrillator (AED) and was transferred to a hospital. An analysis of the AED revealed that the cause of collapse was ventricular fibrillation. He was referred to our hospital for the purpose of catheter ablation. An accessory pathway in the lateral side of the mitral valve was detected in an electrophysiological study. The antegrade refractory period of this pathway was short enough (230msec) to fulfill the requirement for a high risk of sudden cardiac death. Tachycardia with a wide and narrow QRS was induced both by atrial extra stimulation. Neither pseudo ventricular tachycardia nor ventricular tachycardia could be confirmed. During a wide QRS tachycardia, a slow pathway and an accessory pathway were used as a retrograde and an antegrade pathyway, respectively. A narrow QRS tachycardia was still induced after ablation of the accessory pathway. After ablation of the retrograde slow pathway, no tachycardia was induced. Wide QRS tachycardia was diagnosed as an antidromic atrioventricular reentrant tachycardia from the above result.
A 66-year-old female was admitted to our hospital for the treatment of cardiogenic cerebral infarction. She had a history of paroxysmal atrial fibrillation. Ambulatory monitoring revealed cardiac arrest for 11.4sec.A DDD pacemaker was implanted normally (P amplitude 6.1mV, pacing threshold 0.5V/0.4msec). Three days after the implantation, pacing failure was observed. P wave was not sensed at 0.15mV sensitivity, and the pacing threshold was more than 8V/1.0msec. Seven days after implantation, P wave amplitude and pacing threshold returned to their initial values at the time of implantation. Local myocardial injury due to tined lead tip could be a cause of transient atrial damage.