Sensing is the ability of the pacem...

Sensing is the ability of the pacemaker to 'see' when a natural (intrinsic) depolarization is occurring. Accurate sensing render certains (1 ) absence of in a less degree than sensing (the pacemaker will miss P or R waves that should have been sensed); (2) absence of oversensing (the pacemaker will mistake extracardiac activity for intrinsic cardiac events; and (3) provide for appropriate timing of the pacing vibration or the ability of the pacemaker to appropriately reset the timing arrangement following a sensed event. Altered sensing can be recognized forward the ECC and may be useful for the therapist to recognize and interpret.

During undersensing the pacemaker fails to recognize an intrinsic cardiac depolarization and therefore does not accord appropriately. In the example shown in Figure 8 a scheduled pace was delivered immediately after an intrinsic beat that was not sens The evidence of pacer spikes following intrinsic cardiac depolarization or R wave without a pacer spike is principally suggestive of an undersensing phenomenon. Undersensing may conclusion in frequent ventricular contractions and a reduc cardiac output becoming to reductions in the filling time of the ventricles. In addition, undersensing, at times, may deduction in a serious phenomenon known as the R upon T phenomenon. Figure 8 demonstrates a scheduled pace being delivered following the ventricular repolarization phase (T wave) of the preceding unsens ventricular contraction. However, if the paced end would occur somewhat prematurely, the ventricle could be triggered with a paced issue during the relative refractory period of the preceding unsens cardiac revolution of time resulting in an R forward T phenomenon. This occurrence may possibly lead to a more serious and dangerous harmonious flow called ventricular tachycardia. Thus, it may be useful for therapists to recognize the appearance of undersensing and the possible threat in causing an R forward T event.