Có hai phương pháp chấm dứt tốc độ. Nhịp Underdrive đã được sử dụng đầu máy điều hòa nhịp tim để điều trị tachycardias trên thất và tâm thất. Extrastimuli được giới thiệu tại một khoảng thời gian liên tục, nhưng với tốc độ chậm hơn so với nhịp tim nhanh, cho đến một đến trong một giai đoạn quan trọng, chấm dứt nhịp tim nhanh. | 12 Implantable devices for treating tachyarrhythmias Timothy Houghton Gerry C Kaye Pacing treatment for tachycardia control has achieved success notably in supraventricular tachycardia. Pacing termination for ventricular tachycardia has been more challenging but an understanding of arrhythmia mechanisms combined with increasingly sophisticated pacemakers and the ability to deliver intracardiac pacing and shocks have led to success with implantable cardioverter defibrillators. Mechanisms of pacing termination There are two methods of pace termination. Underdrive pacing was used by early pacemakers to treat supraventricular and ventricular tachycardias. Extrastimuli are introduced at a constant interval but at a slower rate than the tachycardia until one arrives during a critical period terminating the tachycardia. Because of the lack of sensing of the underlying tachycardia there is a risk of a paced beat falling on the T wave producing ventricular fibrillation or ventricular tachycardia or degenerating supraventricular tachycardias to atrial fibrillation. It is also not particularly successful at terminating supraventricular tachycardia or ventricular tachycardia and is no longer used routinely. Overdrive pacing is more effective for terminating both supraventricular and ventricular tachycardias. It is painless quick effective and associated with low battery drain of the pacemaker. Implantation of devices for terminating supraventricular tachycardias is now rarely required because of the high success rate of radiofrequency ablative procedures see previous article . Overdrive pacing for ventricular tachycardia is often successful but may cause acceleration or induce ventricular fibrillation. Therefore any device capable of pace termination of ventricular tachycardia must also have defibrillatory capability. Implantable cardioverter defibrillators Initially cardioverter defibrillator implantation was a major operation requiring thoracotomy and was associated with 3-5
