Wavelet analysis for early identification of HRV changes in offspring with genetic predisposition to hypertension in Oman.

BACKGROUND: Offspring with a genetic predisposition to hypertension may have higher blood pressure (BP) at rest compared with those without a genetic predisposition to hypertension. They are also expected to have a higher sympathetic component in the heart rate variability (HRV) which could be computed with signal processing algorithms. OBJECTIVE: The purpose of this study is to design a wavelet-based system to estimate the heart rate variability that can be used to detect early cardiovascular changes in offspring with a genetic predisposition to hypertension. Early detection will help in the treatment of those young people. In this work, the relation between the hypertension and the changes in HRV is investigated. METHODS: The frequency domain and time domain analysis of heart rate variability (HRV) are studied to understand their relationship to the autonomic nervous system in offspring with and without a genetic predisposition to hypertension in Oman at resting state. The wavelet-based soft-decision algorithm is used as the spectral analysis tool to obtain different features from the HRV signal and to select the best performing features for detection of hypertension. The main task is to classify between three categories of subjects: 36 subjects with both normotensive parents (ONT), 22 subjects with single hypertensive parent (OHT1), and 11 subjects with both hypertensive parents (OHT2). RESULTS: The summation of the power of bands B4 and B5 of the 32 bands HRV wavelet-based spectrum, which is equivalent to the frequency range (0.046875 Hz-0.078125 Hz), is used as a classification factor among OHT2, OHT1, and ONT groups. The efficiency of classification between ONT and OHT2 is 85.10%, and between OHT1 and OHT2 is 81.81%. The result of classifying between (ONT and OHT1 as one group) and OHT2 is 85.50%. CONCLUSIONS: The work proves that the wavelet-based spectral analysis technique is a successful tool for classifying the three groups of subjects (ONT, OHT1, and OHT2) with different susceptibility for development of hypertension.

Identification of patients with preeclampsia from normal subjects using wavelet-based spectral analysis of heart rate variability.

BACKGROUND: The spectral analysis of the heart rate variability (HRV) shows a decrease in the power of the high frequency (HF) component in preeclamptic pregnancy compared with normal pregnancy; such a decrease is associated with an increase in the low frequency (LF) and the very low frequency (VLF) power. The physiological interpretation is that preeclamptic pregnancy is associated with a facilitation of sympathetic regulation and an attenuation of parasympathetic influence of HR compared with non-pregnancy and normal pregnancy. OBJECTIVE: To use an efficient nased on spectral analysis non-invasive technique to identify preeclamptic pregnant subjects from normal pregnant in Oman. METHODS: The soft-decision wavelet-based technique is implemented to find the power of the HRV bands in high resolution manner compared to the classical fast Fourier Transform method. Data was obtained from 20 preeclamptic pregnant subjects and 20 normal pregnant controls of the same pregnancy duration, obtained from Nizwa and Sultan Qaboos University hospitals in Oman. RESULTS: The soft-decision wavelet method succeeds to identify patients from normal pregnant with specificity, sensitivity and accuracy of 90%, 80% and 85%, respectively, compared to the FFT which results in 75% specificity, sensitivity and accuracy. CONCLUSION: The LF power obtained by Soft-decision wavelet decomposition is shown to be a successful feature for identification of preeclampsia.

Investigation of heart rate variability of patients undergoing coronary artery bypass grafting (CABG).

BACKGROUND: Myocardial revascularization by coronary artery bypass grafting (CABG) is an effective measure for reducing symptoms and mortality in patients with unstable or severe coronary artery disease (CAD). Autonomic function can be estimated non-invasively using heart rate variability (HRV). HRV of patients undergoing CABG is investigated before and after CABG using a soft-decision wavelet based spectral analysis. OBJECTIVE: The main purpose of this work is to evaluate non-invasively HRV in patients undergoing CABG before operation; and to monitor the status of patients through HRV investigation on day 6 and day 30 after the CABG operation. The study intends to contribute scientific value to understanding the effect of CABG on the cardiovascular autonomic function and surgical outcome. METHODS: The soft-decision wavelet-based technique is used in this work in order to measure the power spectral density of the three main bands (VLF, LF, and HF) of HRV in 24 patients undergoing CABG operation, before the operation (Group 1: G1), and 6 days after operation (Group 2: G2) and 30 days after operation (Group 3: G3). The data is obtained from Sultan Qaboos University hospital in Oman. RESULTS: The HF power increases in 22 out of 24 patients in G2 compared to G1. While the LF power decreases in 21 out of 24 patients in G2 compared to G1. Comparing G3 to G1 the LF power decreases in 20 patients. The sum of the VLF and LF power is reduced in G2 in all 24 subjects compared to G1, and in 19 subjects in G3 compared to G1. CONCLUSIONS: The power spectral density of the HF shows increase in patients recorded on day 6 after operation compared to patients before the operation. The LF shows a decrease in G2 compared to G1. The results of G3 after 30 days of operation still show an increase of the HF power and a decrease in the LF power in most of the patients compared to their values before operation.

Classification of sleep apnea using wavelet-based spectral analysis of heart rate variability.

BACKGROUND: Obstructive Sleep Apnea (OSA) is the cessation of breathing during sleep due to the collapse of upper airway. Polysomnographic recording is a conventional method for detection of OSA. Although it provides reliable results, it is expensive and cumbersome. Thus, an advanced non-invasive signal processing based technique is needed. OBJECTIVE: The main purpose of this work is to predict the severity of sleep apnea using an efficient wavelet-based spectral analysis method of the heart rate variability (HRV) to classify sleep apnea into three different levels (mild, moderate, and severe) according to its severity and to distinguish them from normal subjects. METHODS: The standard FFT spectrum analysis method and the soft-decision wavelet-based technique are to be used in this work in order to rank patients to full polysomnography. Data of 20 normal subjects and 20 patients with mild apnea and 20 patients with moderate apnea and 20 patients of severe apnea are used in this study. The data is obtained from the sleep laboratory of Sultan Qaboos University hospital in Oman. Four different classification versions have been used in this work. RESULTS: Accuracy result of 90% was obtained between severe and normal subjects and 85% between mild and normal and 75% between severe and moderate and 83.75% between normal and patients. CONCLUSIONS: The VLF/LF power spectral ratio of the wavelet-based soft-decision analysis of the RRI data after a high-pass filter resulted in the best accuracy of classification in all versions.

A preliminary investigation into maximal expiratory pressures in some village children.

A clinical mercury sphygmomanometer was used to measure Maximal Expiratory Pressure (MEP) in 29 boys (mean age 8 +/- 1.4 yr) and 21 girls (mean age 7.6 +/- 1.5 yr) of a village in interior Maharashtra. The values of 70.6 +/- 13.4 mmHg SD for the boys and 61.9 +/- 18.9 mmHg for the girls were quite comparable to the respiratory pressures reported elsewhere in literature, even though the subjects were apparently poorly nourished. There was no statistical difference between the MEPs of boys and girls. The MEP was positively and significantly (P<0.01) correlated to height (r=0.51) and weight (r=0.05) in the boys. The MEP denoting respiratory muscle strength also correlated positively with handgrip power used to represent non-respiratory muscle strength (r=0.34) (P>0.05). The simple, reproducible method of measuring MEP as described may be useful for measuring this important physiological parameter at the bedside in children whose respiratory muscle function needs to be evaluated.

Heart rate and blood pressure responses of left-handers and right-handers to autonomic stressors.

We hypothesized that cerebral dominance may contribute to differences in cardio-vascular responses of right-handers (RH) and left-handers (LH) to autonomic stressors. We tested this hypothesis by exposing 14 RH, and 14 LH males to category I tests in which the hand and cerebral cortex were involved in performing the test viz.--i) Cold pressor test (CPT), ii) Handgrip dynamometry (HGD) and; category II (no use of hand)--i) Orthostatic Tolerance Test (OTT), ii) Valsalva Manuever (VM), iii) Controlled Breathing Test for sinus arrhythmia (SA) in a random sequence, and measured their heart rate (HR/min) and blood pressure (MAP mmHg). All subjects had similar resting HR and MAP values, and responded to the category I interventions with increased HR and BP. The absolute HR values of LH and RH did not differ significantly during the interventions. However, the increase in HR from control induced by the CPT, and the HGD was greater for LH (P<0.05). Also, LH showed a greater decrease in HR and MAP in the recovery phase (P<0.05). The VAS scores for degree of discomfort during the CPT were similar for both the groups. During the OTT, the increase in HR was more in RH (P<0.05). The Valsalva ratios for LH and RH were similar. Our findings suggest that the autonomic control over the cardio-vascular system may be different in LH and RH, and that this imbalance could be attributable to a variation in cerebral dominance.

Comparison of respiratory sensations induced by J receptor stimulation with lobeline in left handers & right handers.

We examined the hypothesis that right handers and left handers may differ in sensory perceptions and respiratory responses to J receptor stimulation with intravenous injections of lobeline HCl in incremental doses. The comparison was made between 6 right handers and 9 left handers (all males) for (i) the dose of lobeline required to produce sensory threshold (viz., first appearance of respiratory sensations) and cough threshold (first appearance of cough); and (ii) latency and duration of sensations for sensory and cough threshold. All these comparisons were not found to be significant statistically. The sensation of breathlessness, and feelings of drowsiness, giddiness and headache were perceived in 3 of the 9 left handers, and in none of the right handers, but the difference was not significant. Reflex bradycardia was recorded only in left handers (5 of 9). The time (sec) for cough threshold was negatively correlated to threshold dose of lobeline (r = -0.5, and P < 0.05). The left handers perceived cough at the threshold as more distressing as compared with right handers (VAS P < 0.05). In conclusion, handedness did not influence J receptor responses to i.v. lobeline.