Chế độ này đã được phổ biến trước khi DDD đã có sẵn và không phải là thường được sử dụng. Nó vẫn còn có sẵn như là một chế độ lập trình trên máy điều hòa nhịp tim nhiều DDD. DVI có thể được nhìn thấy trong một cảm giác chức năng khi dẫn tâm nhĩ mất nó khả năng cảm nhận trong một thiết bị lập trình | 40 Handbook of Cardiac Pacing 4 well. This mode was common before DDD was available and is not commonly used now. It is still available as a programmed mode on many DDD pacemakers. DVI may be seen in a functional sense when the atrial lead loses it ability to sense in a device programmed to DDD. DVI may exist in two forms 1 Committed Once the device delivers an atrial impulse it will ALWAYS deliver a ventricular impulse even if an intrinsic R-wave occurs after the atrial pace Fig. . This is often misinterpreted as pacemaker malfunction with ventricular under-sensing. Though this wastes energy it does provide complete protection against crosstalk ventricular oversensing and inhibition by the atrial pace output-see chapter 11 . 2 Noncommitted The pacemaker will be inhibited as would be expected by an intrinsic R-wave even if it has delivered an atrial output Fig . DDI Mode This is a nontracking mode as is DVI. It provides Dual chamber pacing Dual chamber sensing but only Inhibition on a sensed event. The operation is similar Fig. . PV pacing. The atrium is inhibited by the intrinsic P-wave and pacing occurs in the ventricle because it has not depolarized prior to the end of the programmed AVI. This device was programmed to DDD with a lower rate of 45 and an AVI of 170 ms. Fig. . DVI-C committed mode will pace both atrium and ventricle but sense only the ventricle. P waves are never sensed resulting in competition with native P-waves. Total inhibition of both atrial and ventricular output occurs only when a QRS is sensed before the end of the AEI. In this variation of DVI any time an atrial output is delivered a ventricular output is committed as is seen on the third ARS. This committed operation is frequently mistaken for undersensing of the ventricular lead. Dual Chamber Pacing 41 to DVI except that there is atrial sensing. Therefore an intrinsic atrial event will inhibit the atrial output Fig. . Since this will reduce or eliminate pacing .
