Zuzana Nováková

Variability of Phase Shift Between Blood Pressure and Heart Rate Fluctuations A Marker of Short-Term Circulation Control

Background We postulated that the variability of the phase shift between blood pressure and heart rate fluctuation near the frequency of 0.10 Hz might be useful in assessing autonomic circulatory control. Methods and Results We tested this hypothesis in 4 groups of subjects: 28 young, healthy individuals; 13 elderly healthy individuals; 25 patients with coronary heart disease; and 19 patients with a planned or implanted cardioverterdefibrillator (ICD recipients). Data from 5 minutes of free breathing and at 2 different, controlled breathing frequencies (0.10 and 0.33 Hz) were used. Clear differences (P<0.001) in variability of phase were evident between the ICD recipients and all other groups. Furthermore, at a breathing frequency of 0.10 Hz, differences in baroreflex sensitivity (P<0.01) also became evident, even though these differences were not apparent at the 0.33‐Hz breathing frequency. Conclusions—The frequency of 0.10 Hz represents a useful and potentially important one for controlled breathing, at which differences in blood pressure‐RR interactions become evident. These interactions, whether computed as a variability of phase to define stability of the blood pressure‐heart rate interaction or defined as the baroreflex sensitivity to define the gain in heart rate response to blood pressure changes, are significantly different in patients at risk for sudden arrhythmic death. In young versus older healthy individuals, only baroreflex gain is different, with the variability of phase being similar in both groups. These measurements of short‐term circulatory control might help in risk stratification for sudden cardiac death. (Circulation. 2003;108:292‐297.)

Short-term Effects of Cardiac Resynchronization Therapy on Sleep-Disordered Breathing in Patients With Systolic Heart Failure

OBJECTIVES We evaluated the short-term effect of cardiac resynchronization therapy (CRT) on sleep apnea in patients with systolic heart failure. BACKGROUND Sleep-disordered breathing is common in patients with left ventricular systolic dysfunction. METHODS Twelve patients (mean [+/-SE] age, 59.6+/-7.8 years; mean left ventricular ejection fraction, 28.0+/-2.8%) with an implanted atrial-synchronized biventricular pacemaker for the treatment of left ventricular systolic dysfunction were selected and studied. Each subject underwent polysomnography on 3 consecutive nights with CRT on the first night, CRT off the second night, and CRT on the third night. Echocardiography was performed prior to each polysomnogram. RESULTS The central sleep event index (ie, the number of central sleep apneas [CSAs] and hypopneas per hour of sleep) score was lower with CRT compared to that without CRT (mean central sleep event index score with CRT on, 6.9+/-1.7 events per hour of sleep; mean central sleep event index score with CRT off, 14.3+/-2.9 events per hour of sleep; mean central sleep event index score with CRT on, 8.1+/-1.5 events per hour of sleep; p<0.001). Similarly, the cumulative duration of central sleep events (the number of minutes per hour of sleep during CRT) was one half that observed without CRT (CRT on, 2.8+/-0.7 min per hour of sleep; CRT OFF 6.2+/-1.2 min per hour of sleep; CRT ON 3.1+/-0.7 min per hour of sleep; p<0.001). There was a significant correlation between mitral regurgitant volume and central sleep event index on all three nights (r>or=0.77; p<0.01). CONCLUSIONS CRT reduces CSA severity in the short term. This reduction correlated significantly with the CRT-mediated reduction of mitral regurgitation.

Influence of age, body mass index, and blood pressure on the carotid intima-media thickness in normotensive and hypertensive patients

Abstract We investigated whether body mass index and blood pressure have an additive influence on the carotid intima-media thickness (IMT). In 27 patients treated for hypertension (47.2±8.7 years) and 23 normotensive subjects (44.1±8.1 years), 24-h recording of blood pressure was performed. The carotid IMT was determined by ultrasonography and baroreflex sensitivity by a spectral method from 5-min recordings of blood pressure. Significant differences between hypertensive and normotensive subjects were observed for carotid IMT (0.60±0.08 vs. 0.51±0.07 mm; p<0.001) and baroreflex sensitivity (3.5±1.8 vs. 5.6±2.1 ms/mm Hg; p<0.001). Hierarchical multiple regression analysis (p<0.01) showed that carotid IMT was positively correlated with age (p<0.001) and body mass index (p<0.05) in normotensive subjects. The increased carotid IMT in hypertensive patients was not additively influenced by either age or body mass index. Baroreflex sensitivity decreased with age (p<0.01) and with carotid IMT (p<0.05) in normotensive subjects only. Multiregression analysis showed that an additive influence of age and body mass index on the development of carotid IMT is essential only in normotensive subjects. In hypertensive subjects the influence of blood pressure predominates, as documented by a comparison of the carotid IMT between hypertensive and normotensive subjects.

Hidden Markov model in wavelet analysis of myocardial ischemia in rabbit

Deals with analysis of myocardial ischemia caused by left anterior coronary artery occlusion. A system based on hidden Markov models has been designed. The vectorcardiograms recorded before and during the episode of local ischemia were preprocessed by wavelet transform to reveal short-time events during ventricular depolarization. To verify the models, 11 Langendorf-perfused rabbit hearts have been used. The presented results show that models can detect early ischemia in one of three orthogonal electrocardiograms in more than 90% of cases.

Four signal processing techniques for continuous baroreflex determination

Heart rate baroreflex sensitivity (BRS) is given as a ratio of inter-beat intervals (IBI) and systolic blood pressure (SBP) variations. This paper compares the feasibility of four techniques for continuous BRS determination: sequence technique, modified complex demodulation and alpha index technique and LP model technique. Blood pressure of healthy subjects (age 21-22 years) was recorded at rest (3 min), during exercise (0.5 W/kg of body weight, 9 min) and at rest (6 min) after exercise. The controlled breathing (20 breaths per min) was used at rest. To test the methods thirty-eight records were analyzed. The sequence technique determines the BRS from spontaneous variations of IBI and SBP in time. The complex demodulation technique determines the BRS as a ratio of the IBI and SBP signal amplitudes filtered by a band-pass filter with a 0.1 Hz frequency center. The alpha techniques and the LP techniques are spectral techniques, In the last two techniques a window of a few tenths of seconds duration simultaneously slides from the beginning to the end of both IBI and SBP signals. For each window the spectra of both signals are computed. The standard Fourier transform is used to determine the spectra for the alpha index technique. The ratio of amplitudes of the dominant spectral components in IBI and SBP spectre having near frequencies gives the BRS at the central window time and the corresponding frequencies. The linear prediction (LP) technique determines the spectrum as the inverse of the whitening filter transfer function. The residue at poles of the IBI and SBP LP spectral functions are determined. The ratio of IBI and SBP transfer functions corresponding to residua of frequency near paired poles gives the BRS at these frequencies. Determined values are attached to the center time of the window. All used techniques of BRS determination yield similar results. Averaged curves of the BRS changes are identical with those of IBI, but they differ from those of SBP and diastolic blood pressure.

Heart rate variability analysed by Poincaré plot in patients with metabolic syndrome

INTRODUCTION The SD1 and SD2 indexes (standard deviations in two orthogonal directions of the Poincaré plot) carry similar information to the spectral density power of the high and low frequency bands but have the advantage of easier calculation and lesser stationarity dependence. METHODS ECG signals from metabolic syndrome (MetS) and control group patients during tilt table test under controlled breathing (20 breaths/minute) were obtained. SD1, SD2, SDRR (standard deviation of RR intervals) and RMSSD (root mean square of successive differences of RR intervals) were evaluated for 31 control group and 33 MetS subjects. RESULTS Statistically significant lower values were observed in MetS patients in supine position (SD1: p=0.03, SD2: p=0.002, SDRR: p=0.006, RMSSD: p=0.01) and during tilt (SD2: p=0.004, SDRR: p=0.007). CONCLUSION SD1 and SD2 combining the advantages of time and frequency domain methods, distinguish successfully between MetS and control subjects.

Changes in time-frequency phase spectra vs. ST-segment deviation for detecting acute coronary artery occlusion

The paper deals with a new method for the detection of myocardial ischemia caused by acute coronary artery occlusion, in the early phases. The method is based on the analysis of intra-QRS changes in time-frequency phase spectra generated by a wavelet transform. To verify the method, 11 Langendorff-perfused rabbit hearts have been used. The presented results show that models can detect early ischemia in one of three orthogonal leads as early as one minute after coronary artery occlusion. In addition, the method is compared to the traditional ST-segment analysis.

TWENTY-FOUR-HOUR BLOOD PRESSURE PROFILE AND BAROREFLEX SENSITIVITY IN CHILDREN AND ADOLESCENTS WITH ESSENTIAL HYPERTENSION: P1.124

Citlivoszt baroreflexu vyjadřena v Hz na mmHg je signifikantně nižsi u děti s vysokou hodnotou systolickeho krevniho tlaku zjistěnou při ambulantnim 24 hodinovem monitorovani.

Evaluation of autonomic nervous system dysfunction by phase shift and XYt graph methods

BACKGROUND: We postulated that the phase shift between blood pressure and heart rate fluctuation near the frequency of 0.10 Hz might be useful in assessing autonomic circulatory control. CONCLUSIONS: The frequency of 0.10 Hz represents a useful and potentially important one for controlled breathing, at which differences in blood pressure-RR interactions become evident. These interactions, whether computed as a variability of phase to define stability of the blood pressure-heart rate interaction or defined as the baroreflex sensitivity to define the gain in heart rate response to blood pressure changes, are significantly different in patients at risk for sudden arrhythmic death.

Disruption of dopamine D1/D2 receptor complex is involved in the function of haloperidol in cardiac H9c2 cells

Aims: Haloperidol is an antipsychotic agent and acts as dopamine D2 receptor (D2R) antagonist, as a prototypical ligand of sigma1 receptors (Sig1R) and it increases expression of type 1 IP3 receptors (IP3R1). However, precise mechanism of haloperidol action on cardiomyocytes through dopaminergic signaling was not described yet. This study investigated a role of dopamine receptors in haloperidol‐induced increase in IP3R1 and Sig1R, and compared physiological effect of melperone and haloperidol on basic heart parameters in rats. Materials and methods: We used differentiated NG‐108 cells and H9c2 cells. Gene expression, Western blot and immunofluorescence were used to evaluate haloperidol‐induced differences; proximity ligation assay (PLA) and immunoprecipitation to determine interactions of D1/D2 receptors. To evaluate cardiac parameters, Wistar albino male rats were used. Key findings: We have shown that antagonism of D2R with either haloperidol or melperone results in upregulation of both, IP3R1 and Sig1R, which is associated with increased D2R, but reduced D1R expression. Immunofluorescence, immunoprecipitation and PLA support formation of heteromeric D1/D2 complexes in H9c2 cells. Treatment with haloperidol (but not melperone) caused decrease in systolic and diastolic blood pressure and significant increase in heart rate. Significance: Because D1R/D2R complexes can engage Gq‐like signaling in other experimental systems, these results are consistent with the possibility that disruption of D1R/D2R complex in H9c2 cells might cause a decrease in IP3R1 activity, which in turn may account for the increase expression of IP3R and Sig1R. D2R is probably not responsible for changes in cardiac parameters, since melperone did not have any effect.