Chien-Ping Wu

Long-term β-blocker therapy improves autonomic nervous regulation in advanced congestive heart failure: A longitudinal heart rate variability study ☆ ☆☆

BACKGROUND beta-Blocker therapy is believed to modulate the detrimental effect of overcompensating neurohormonal activation in chronic heart failure. However, clinical doubts remain, particularly the physiologic sympathovagal balance. METHODS To respond to clinical concern about worsening autonomic nervous perturbation in beta-blocker therapy of advanced congestive heart failure, 15 consecutive patients were longitudinally studied to elucidate the evolution of cardiac function versus 24-hour heart rate variability (HRV) before and after 1, 3, and 6 to 9 months of atenolol-combined therapy. RESULTS Two patients died prematurely within 1 month. All 13 surviving patients showed improvement in New York Heart Association functional class, with decrease in left ventricular end-systolic and end-diastolic dimensions and increase in fraction shortening and ejection fraction by echocardiography after at least 3 months of atenolol use. The retarded therapeutic effect was accompanied by a general rise of total, very low, low-, and high-frequency components (9.0 +/- 0.5, 8.8 +/- 0.5, 6.2 +/- 0.6, and 6.1 +/- 0.5 vs 10.9 +/- 0.3, 10.7 +/- 0.4, 8.6 +/- 0.3, and 7.8 +/- 0.3; all P <.02) of daily HRV. This implied recovery of parasympathetic and baroreceptor function. Return of sympathovagal interaction was further supported by the suppression of Cheyne-Stokes type HRV as detected by Wigner-Ville distribution. CONCLUSIONS Long-term beta-blocker therapy for advanced congestive heart failure upwardly regulates the autonomic nervous interaction in synchrony with the evolution of cardiac function performance.

Preamplifier with a second-order high-pass filtering characteristic

A new preamplifier for suppressing low-frequency interference is presented. The proposed preamplifier, with its front end being implemented by an instrumentation amplifier, enjoys the following advantages: differential high-pass filtering, high input impedance, high common--mode rejection ratio and low passive sensitivity. This circuit can be realized with commercial operational amplifiers with enough phase margin, or fabricated in a chip for practical measurement of physiological signals.

Time–frequency distribution of heart rate variability below 0.05 Hz by Wigner–Ville spectral analysis in congestive heart failure patients

The Wigner-Ville spectral analysis was utilized to demonstrate a high-resolution time-frequency distribution of heart rate variability below 0.05 Hz. There are different time-frequency characteristics between the normal subject and the patient with severe congestive heart failure. The former consists of multiple and broad-band spectral peaks, while the latter presents unique spectral peaks. Based on Bayes theory, a classifier for the unique spectral peaks was developed. After the beneficial improvement with low-dose beta-blockers, the unique spectral peaks had disappeared or the time of occurrence was reduced in most patients.

Elimination of interference component in Wigner-Ville distribution for the signal with 1/f spectral characteristic

A new technique for interference-term suppression in Wigner-Ville distribution (WVD) is proposed for the signal with 1/f spectrum shape. The spectral characteristic of the signal is altered by f alpha filtering before time-frequency analysis and compensated after analysis. With the utilization of the proposed technique in smoothed pseudo Wigner-Ville distribution, an excellent suppression of interference component can be achieved.

An active comb filter design for harmonic interference removal

Abstract The active comb filter without the use of inductors is very useful for removing harmonic noise such as power line interference in bio‐medical signals. This paper presents an approach for the design of an active comb filter. A table composed of 62 bandpass filters is proposed, which can be used in the design of the presented active comb filter. Simulation results and performance tests are given to demonstrate the feasibility of the presented active comb filter

Harmonic interference elimination by an active comb filter [ECG application]

A new approach for an active comb filter design is proposed to remove the difficult harmonic interference contaminating the biomedical signals. The filter consists of four narrow-band bandpass filters. The center frequency of each bandpass filters is just the unwanted frequency characterized by the harmonic interference. The circuit demonstrates the capability to eliminate the interference of 60, 180, 300, and 420 Hz. The general 741 type operational amplifier has been used to realize the circuit presented. Triangular wave testing shows the effectiveness of harmonic interference cancellation.<<ETX>>

A NEW APPROACH FOR TIME-FREQUENCY ANALYSIS OF HEART RATE VARIABILITY AND ASSESSMENT OF TIME-FREQUENCY REPRESENTATIONS

ABSTRACT Heart rate variability signals usually contain several special characteristics and interference, such as multiple oscillations, 1/f fluctuations, transient changes, very low frequency trends, and noises. Nevertheless, the effects of these special phenomena on time-frequency signal analysis are seldom discussed. In this paper, a new approach is presented to suppress the interfering cross terms in the Wigner-Ville distribution. In comparison with various time-frequency methods, our method provides excellent cross-term suppression at the presence of multiple oscillations, 1/f characteristics, and very low frequency trends, and inherits the advantages of the Wigner-Ville distribution dealing with transient changes and noises.

Time-frequency analysis of 24-hour heart rate fluctuation for the characterization of very low-frequency component

A smooth pseudo Wigner-Ville distribution was employed to investigate both time and frequency characteristics in a very low-frequency component (less than 0.04 Hz) of 24-hour heart rate fluctuation. In some cases of heart failure the authors could see remarkable and very low-frequency oscillations of the Wigner-Ville distribution, which are related to Cheyne-Stokes respiration. However the Wigner-Ville distribution of normal subjects did not have such oscillations, but more random spectral characteristics instead. Furthermore, the authors calculated 1/f/sup /spl alpha// regression slopes of average spectrum to be a crude estimate of fractal dimensions. The slopes are more negative in heart failure patients than normals (-1.866/spl plusmn/0.888 vs. -0.957/spl plusmn/0.180 p<0.005), which associates a loss of dimensionality of heart rate fluctuation in heart failure.