Ventilatory threshold (VT) have been shown to assess exercise tolerance and prescribe exercise rehabilitation in patients with chronic heart failure (CHF). However, the VT cannot always be detected in CHF by classical methods. Previous investigations also revealed that the assessment from heart rate variability (HRV) analysis gives an accurate estimation of VT in trained subjects. Therefore, the purpose of this study was to examine whether HRV analysis could helped in the VT determination in CHF.

18 patients with CHF (12 males and 6 females, age: 62±13-years, weight: 73±17-kg, left ventricular ejection fraction: 0.32±0.7, VO2peak: 17±5-ml. min-1.kg-1) performed on cycle ergometer an incremental exercise (CPX testing). Beat-to-beat RR interval, VO2, carbon production (VCO2) and minute ventilation (VE) were collected during the test. VT corresponded to the last point before a first non-linear increase in both VE and VE/VO2. A time domain (RMSSD) and a time-frequency domain (HFp) indexes both extrapolated to the RR time series. A marked RMSSD and HFp deflection points were found in the region of VT, and were identified as heart rate threshold (HRVT and RSA, respectively). No significant difference was found between VT, HRVT and RSA (p<0.05) in term of VO2, heart rate values and exercise intensity. Correlations between the different measures ranged from 0.97 to 0.99 with a strong agreement between all methods.

These data reveal that HRV analysis using time-frequency indexes during CPX testing can provide useful help to VT determination in patients with CHF.