Refractory atrial flutter icd 103/22/2023 ![]() ![]() If P-wave oversensing occurs during a 1:1 rhythm, the considerations are similar to those for R-wave double counting, provided the sensed PR or RP interval is less than the VF detection interval. It is rare in adults with defibrillation leads near the RV apex, but may occur in children or in adults if the RV electrode dislodges or is positioned in the proximal septum or inflow portion of the RV. P-wave oversensing may occur if the distal coil of an integrated bipolar lead is close to the tricuspid valve, and the sensed PR interval exceeds the ventricular blanking period. A corresponding "railroad track" pattern of atrial intervals occurs with far-field R-wave oversensing on the atrial channel. This "railroad track" pattern of ventricular intervals also occurs with P-wave oversensing and may occur with T-wave oversensing. Sensed "ventricular intervals" alternate. At the onset of SVT, there is an abrupt decrease in atrial intervals. The initial rhythm is atrial sensed, ventricular paced with a cycle length of ~700 ms. Upper left panel: Plot shows atrial intervals as open squares and ventricular intervals as closed circles. AS = sensed atrial intervals AR = atrial intervals in postventricular atrial refractory period VS = interval sin sinus zone FS = intervals in VF zone. For example, if the VT detection interval is 400 ms and the double-counted RV-LV interval is 140 ms, inappropriate detection occurs for any tachycardia cycle length less than 540 ms. This interval represents the difference between the true SVT cycle length (CL, dotted line segment in upper right insert) and the double-counted RV-LV interval. Inappropriate detection occurs when the interval represented by the solid line segment (asterisk) in the upper right insert is less than the VT detection interval. The double-counted, RV-LV interval measures within 20 ms of the ventricular blanking period of 120 ms (see Marker Channel) and is always classified in the VF zone. Insert also illustrates conditions for inappropriate detection of SVT. ![]() Insert shows that the first component of the ventricular electrogram represents RV activation and the second component represents LV activation. The third atrial complex is premature and initiates SVT faster than the programmed upper tracking limit, resulting in intermittent R-wave double counting. The first two complexes show atrial-sensed, ventricular paced rhythm. Main panel: Atrial and extended bipolar ventricular electrograms are shown with Marker Channels. R-wave double counting in a patient with a Y-adapted cardiac resynchronization ICD and LBBB. RR intervals usually alternate, but the magnitude of alternation may be small. T-wave oversensing is identified by alternating electrogram morphologies. Oversensing of spontaneous T waves may cause inappropriate detection of either VT or VF, depending on the sensed RT interval and programmed VF detection interval. Ventricular oversensing of physiologic intracardiac signals results in two detected ventricular electrograms for each cardiac cycle, which may result in inappropriate detection of VT or VF. Reprinted with permission from Swerdlow and Shivkumar. RA = right atrium RV = right ventricular sensing electrogram HV = high-voltage electrogram. (F) Lead fracture noise results in intermittent saturation of amplifier range denoted by arrow. Note that noise level is constant, but oversensing does not occur until automatic gain control increases the gain sufficiently, about 600 ms after the sensed R waves. (E) Diaphragmatic myopotential oversensing in a patient with an integrated bipolar lead at the RV apex. (D) Electromagnetic interference from a power drill has higher amplitude on widely spaced high-voltage electrogram than on closely spaced true bipolar sensing electrogram. (C) T-wave oversensing in patient with low-amplitude R wave (note mV calibration marker). (B) R-wave double counting during conducted AF in a biventricular-sensing ICD. (A) P-wave oversensing in sinus rhythm from integrated bipolar lead with distal coil near the tricuspid valve. D–F show oversensing of extracardiac signals. A–C show oversensing of physiological, intracardiac signals. Types of oversensing resulting in inappropriate detection of VT/VF. ![]()
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