Discussion
This report is the first to describe SonR signal amplitude changes according to patients' clinical status. In the two first patients, the SonR amplitude increases concomitantly to clinical status improvement after CRT-D implantation. In the third patient, a decrease in SonR amplitude is observed concomitantly to an atrial fibrillation episode and clinical status deterioration.
Further adjustments to the SonR device could be of benefit to the monitoring process of CRT-D patients: (1) while AV and VV delays optimization are automatically performed weekly by SonR, displaying daily SonR amplitude values would be preferable for monitoring purposes; (2) finally, the percentage of modification in clinical status could be quantified for the development of an alert.
Combined with remote monitoring, which is now widely accepted based on accumulating evidence that outcomes are better compared with standard in-clinic follow-up, early SonR signal amplitude remote monitoring could be a promising tool for HF patients' management. Several recent trials on HF monitoring based on device diagnostic information confirmed the difficulty to monitor HF using a sole indicator and suggested the need to incorporate multiple parameters. In this context, the SonR signal amplitude could be combined with other device-based parameters in order to improve the accuracy of the diagnostic. However, technical improvements and outcome prospective trials are warranted.