Transmission

The alert indicates that the LV Threshold value is over the maximal tested amplitude (5.0 V) and we observe that the output is programmed at 4V. Looking at the Autothreshold curves, we can see that the threshold for the LV lead has always been elevated but increased even more the last few days. The %biV (CRT) is close to 100% which means the LV lead is pacing but it does not mean the LV lead is capturing. On the real-time EGM we can not discriminate between biventricular capture and single site (RV) capture.

Next steps

There is a suspected LV lead dysfunction but we cannot guarantee the proper functioning of the LV lead using remote medicine. These patients are known with heart failure and the clinical condition can deteriorate quickly when the LV is not captured. While the percentage of CRT may seem normal, the percentage of actual CRT may be a lot lower, increasing the risk of decompensated heart failure and LV remodeling. Therefore the patient should be called to the clinic to perform manual LV capture tests. In this patient, the 12-lead ECG confirmed loss of LV capture; ECG was identical during biventricular pacing and RV pacing only. The vector was changed from LV-ring-to-R-coil to RV-tip-to-RV-ring which resulted in a high but acceptable pacing threshold. The 12-lead ECG confirmed biventricular capture and the patient was discharged. The patient has been informed that the LV lead is at risk, meaning that in the future it a new LV lead may have to be implanted. With a correctly working LV lead in place, even with elevated thresholds, it is often decided to postpone this invasive procedure, as it is not without risk. Remote monitoring (with LV autothreshold on auto or monitoring) is essential in order to precede symptoms of LV lead failure through alerts.