Poincaré plot analysis of autocorrelation function of RR intervals in patients with acute myocardial infarction.

The Poincaré plot of RR intervals (RRI) is obtained by plotting RRIn+1 against RRIn. The Pearson correlation coefficient (ρRRI), slope (SRRI), Y-intercept (YRRI), standard deviation of instantaneous beat-to-beat RRI variability (SD1RR), and standard deviation of continuous long-term RRI variability (SD2RR) can be defined to characterize the plot. Similarly, the Poincaré plot of autocorrelation function (ACF) of RRI can be obtained by plotting ACFk+1 against ACFk. The corresponding Pearson correlation coefficient (ρACF), slope (SACF), Y-intercept (YACF), SD1ACF, and SD2ACF can be defined similarly to characterize the plot. By comparing the indices of Poincaré plots of RRI and ACF between patients with acute myocardial infarction (AMI) and patients with patent coronary artery (PCA), we found that the ρACF and SACF were significantly larger, whereas the RMSSDACF/SDACF and SD1ACF/SD2ACF were significantly smaller in AMI patients. The ρACF and SACF correlated significantly and negatively with normalized high-frequency power (nHFP), and significantly and positively with normalized very low-frequency power (nVLFP) of heart rate variability in both groups of patients. On the contrary, the RMSSDACF/SDACF and SD1ACF/SD2ACF correlated significantly and positively with nHFP, and significantly and negatively with nVLFP and low-/high-frequency power ratio (LHR) in both groups of patients. We concluded that the ρACF, SACF, RMSSDACF/SDACF, and SD1ACF/SD2ACF, among many other indices of ACF Poincaré plot, can be used to differentiate between patients with AMI and patients with PCA, and that the increase in ρACF and SACF and the decrease in RMSSDACF/SDACF and SD1ACF/SD2ACF suggest an increased sympathetic and decreased vagal modulations in both groups of patients.

Power spectral analysis of finger plethysmographic waveform in patients with coronary artery disease and after coronary artery bypass graft surgery.

BACKGROUND: The aim of the present study was to assess the clinical significance of spectral analysis of plethysmographic waveform in patients with coronary artery disease (CAD) and after coronary artery bypass graft (CABG) surgery. METHODS AND RESULTS: The study group comprised 26 healthy subjects, 15 CAD patients, and 24 CAD patients after CABG. Finger plethysmographic waveforms from both right and left index fingers were recorded and analyzed using power spectral analysis. The total power of the right pulse was found to be higher than that of left pulse in the 3 groups of subjects. In CABG patients, the total power of both pulses was increased, the right-to-left ratio of bilateral total power was decreased, and the power of the harmonics of the right pulse shifted from high-frequency to low-frequency. The normalized power of the 4th harmonic of the left pulse and of the 3rd and 4th harmonics of right pulse decreased, whereas that of the 1st harmonic of right pulse increased in CABG patients. Several harmonics correlated significantly to some heart rate variability measures in both controls and CAD patients, but not in CABG patients. CONCLUSIONS: The increase in the total power of both pulses, the shift of the normalized power of harmonics of the right pulse from high- to low-frequency, and the decrease in the right-to-left ratio of the total power of both pulses are the 3 significant changes in the power spectra of the pulses in CAD patients after CABG. The plethysmographic waveform of normal controls and CAD patients may be modulated by the autonomic nervous system, and in CAD patients the CABG surgery may have diminished the effect of autonomic nervous modulation on the pulse waveforms.

Short-term effect of transdermal estrogen on autonomic nervous modulation in postmenopausal women.

OBJECTIVE: To evaluate the effect of short-term transdermal estradiol-l7b on cardiac autonomic nervous modulation in postmenopausal women. DESIGN: Prospective study. SETTING: A tertiary medical center. PATIENT(S): Twenty-one postmenopausal women. INTERVENTION(S): Transdermal estradiol or placebo therapy for 3 weeks in randomized, double-blinded, crossover fashion. MAIN OUTCOME MEASURE(S): Heart rate variability measures in both time and frequency domains, serum biochemistry, and climacteric symptoms were compared among baseline, placebo and transdermal estrogen therapies. RESULT(S): Plasma concentration of estradiol rose significantly from 11.0 +/- 5.2 pg/ml to 48.2 +/- 34.0 pg/ml after transdermal estrogen. The standard deviation of RR-interval increased significantly from 30.3 +/- 9.9 ms (placebo) to 31.3 +/- 7.4 ms (transdermal estrogen), and the coefficient of variation of RR-interval increased significantly as compared with the baseline session. The total power was marginally increased as compared among baseline, placebo, and transdermal estrogen sessions. The irritability symptom decreased significantly after transdermal estrogen therapy, as compared with baseline and placebo treatment. CONCLUSION(S): Transdermal estradiol for 3 weeks could significantly increase the global heart rate variability and reduce the irritability symptom in the postmenopausal women. Short-term transdermal estrogen for 3 weeks could improve cardiac autonomic nervous modulation and climacteric symptoms, and might have some cardioprotective effect in postmenopausal women.