2. Department of Medical Engineering, University of Applied Sciences, Jena, Germany.
3. Clinic of Internal MedicineI, University Hospital of Jena, Germany.
Chronic heart failure (CHF) alters heart rate and blood pressure variability (HRV, BPV). Additional prospective studies are needed to clarify their role in cardiac risk stratification. The aim of this study was to prove the value of BPV analysis for risk stratification in CHF compared to HRV. In 88 patients with CHF high-resolution ECG (22 bit resolution, 1600 Hz sampling frequency) and continuous non-invasive blood pressure (NIBP, 22 bit, 500 Hz) were recorded over 30 minutes. Based on volume clamp method the peripheral arterial blood pressure was measured via finger cuff. From the ECG recordings, time series of beat-to-beat intervals were extracted to analyze HRV and from the NIBP recordings, time series of systolic as well as diastolic blood pressure values were extracted to analyze BPV. To get 'normal-to-normal' beat time series (NN), ventricular premature beats and artefacts within the time series were detected and replaced by interpolated normal heartbeats. Standard HRV and systolic as well as diastolic BPV parameters were evaluated for patients with ejection fraction above and below 40% (EF+ and EF-) and for 5-year follow up (cardiac death and worsening of NYHA class). Only one HRV parameter (MEAN NN) but six BPV indices separated EF+ from EF-. In the 5-year follow up systolic BPV but not ejection fraction and HRV predicted worsening of NYHA class with 15% positive and 91.2% negative predictive value. Cardiac death was predicted in 81.8% by using the two best diastolic BPV parameters (dLF/HF and dSDNN). We conclude BPV analysis may be useful in medium range risk stratification in patients with CHF. The analysis of autonomic control should focus more on blood pressure regulation.
Keywords: Blood pressure variability, heart rate variability, chronic heart failure, risk stratification