Accurate Non-Invasive Calibration of an Implantable Left Atrial Pressure Monitoring System in Heart Failure Patients During Long-Term Follow-Up

Abstract

not been defined. We investigated whether BNP levels in stable heart failure (HF) patients reflect fluctuations in left atrial pressure (LAP). Methods: Nine outpatients with NYHA II–III HF and an implanted monitoring system measuring direct LAP underwent serial recordings of LAP and BNP. LAP measurements were obtained at the time of venesection, 4 h prior and 12-hourly in the 72h prior to venesection. This was repeated on up to eight occasions during 1 year of follow-up. Intra-patient correlation coefficients of variation (CV) were calculated to relate LAP levels at varying lags from venesection, to BNP andNT-BNP levels at venesection, across sampling occasions. Results: 3–8 serial recordings of LAP and BNP were obtained in all subjects. Despite having stable symptoms there was considerable variability in LAP within sampling occasions (CV 20–65%). BNP levels correlated with LAP at the time of venesection (r= 0.45; p< 0.0001), while NT-proBNP correlated with LAP 4h prior to venesection (r= 0.74; p< 0.001). Intra-individual CVs ranged from 9 to 43% for BNP and 8–86% for NT-proBNP. The intraindividual variation of BNP or NT-proBNP levels over the follow-up period were significantly related to the CV of LAP measurements (r= 0.53; p< 0.01, r= 0.8; p< 0.01, respectively). Conclusion: In ambulant patients with stable HF, variability in BNP and NT-proBNP levels is strongly related Results: VMs were successful on 437/498 (90%) occasions and all patients achieved successful Valsalva calibration. At 11± 5 months follow-up, 24/25 implants had minor offset drift (mean 2± 5mmHg) resolving at 3 months consistent with device healing. One patient with significant drift had a clinically usable device, as drift was predictable and easily corrected. During RHC device LAP measured PCWP within −0.2± 5.7mmHg. All offset drift since implantation was corrected by VM calibration. Conclusion: The VMwaswell tolerated and allowed accurate, clinically useful non-invasive calibration of a new LAP monitoring system. Minimal drift was reliably corrected using this simple method. doi:10.1016/j.hlc.2007.06.057