To the Editor: West Nile virus

emerging as a public health and veterinary concern. Since its introduction into North America in 1999, it has spread rapidly, reaching th

Heart rate variability monitored by the implanted device predicts response to CRT and long-term clinical outcome in patients with advanced heart failure

Background: Few data exist on the long-term changes and the prognostic value of heart rate variability (HRV) assessed by implanted devices in heart failure (HF) patients treated with resynchronization therapy (CRT). Aims: To analyze the long-term changes in the standard deviation of 5-minute median atrial-atrial sensed intervals (SDANN), and assess its role in predicting CRT efficacy and major cardiovascular events. Methods and results: We included 509 consecutive patients implanted with CRT devices. At 12-month follow-up, 44 patients had died and 86 patients had at least one HF hospitalisation. A significant increase in SDANN occurred after 4 weeks of CRT (from 69+/-22 ms to 82+/-27 ms, p<0.001). A further increase in SDANN was observed 6 months after implantation. Multivariable analysis identified SDANN as the sole predictor of major cardiovascular events (p=0.03) among several baseline parameters. SDANN< or =65 ms at the first week and SDANN< or =76 ms after 4 weeks of CRT yielded the best prediction of all-cause mortality and urgent heart transplantation on Kaplan-Meier analysis (log-rank test p=0.015 and p=0.011, respectively for week 1 and 4 values). Moreover, relative reduction in LVESV after CRT significantly correlated with SDANN at week 1 (r=-0.596, p=0.012), and week 4 (r=-0.703, p=0.001). Conclusions: Device-monitored HRV is a useful tool to identify, early after implantation, patients with a low likelihood of long-term benefits from CRT and at high risk for cardiovascular events