Aortic Augmentation Index is Dependent on Bodyside in Healthy Young Subjects.

INTRODUCTION: Aortic augmentation index (AIx) is a commonly used measure to evaluate the arterial stiffness of large elastic arteries. It has been used as an indicator for cardiovascular risk in clinical practice. AIM: To evaluate the difference in the aortic AIx assessed from the left and the right hand in a group of healthy young adults using SphygmoCor and Arteriograph devices. METHODS: 32 subjects were enrolled in this study (27 ± 7 years), 16 male and 16 female volunteers participated. Equally, half of the gender groups were left-handed and another half right-handed. RESULTS: It was found that the aortic AIx values assessed from the pressure waveforms of the right and the left hand are different and significantly higher in the left hand. Using a SphygmoCor device, the mean difference between the aortic AIx values from the right and the left hand among the whole study group was found - 4.78 ± 4.31% and using an Arteriograph the aortic AIx values were - 3.92 ± 3.90%. Aortic AIx values assessed from the right and the left hand were linearly related to each other for both devices. Moreover, it was found that the values of the aortic. CONCLUSIONS: AIx are independent of the subject's handedness. It has to be pointed out that subjects who cannot be subjected to assessment of the aortic AIx from one side of the body could have different AIx values estimated from the recorded pressure waveform from the other bodyside.

Pulse wave velocity and its gender-related associations with cardiovascular risk factors in a high cardiovascular risk population.

INTRODUCTION: Associations found between pulse wave velocity (PWV) and cardiovascular risk factors (CVrF) are diverse. We aimed to evaluate whether differences in PWV and its associations with CVrF in a high cardiovascular risk population exist between genders and between the whole population (WHgr) and groups of apparently healthy (AHgr) and those of hypertensive, obese or diabetics (Rgr). MATERIAL AND METHODS: Pulse wave velocity measured by Arteriograph was investigated in 805 adults aged 20-65, randomly selected from the Tallinn Population Register. RESULTS: Pulse wave velocity was the highest in Rgr and no differences were found between genders of the same group. In women of WHgr and AHgr age and SBP with addition of BMI and apolipoprotein B (ApoB) were associated with 54% and 48%, and without ApoB in Rgr with only 30% of PWV values. In men aged ≥ 50 of WHgr with elevated SBP odds ratios for increased PWV were 25.3 and 3.5, in Rgr 21.2 and 2.2, in those aged ≥ 50 AHgr 28.4. In women aged ≥ 50 of WHgr with elevated SBP and diabetes odds ratios were 5.5, 4.9 and 4.0, in Rgr with elevated SBP and diabetes 3.6 and 3.7, in those aged ≥ 50 AHgr 29.3. CONCLUSIONS: The associations of ApoB and BMI with PWV and diabetes with elevated PWV indicative of increased aortic stiffness were unique for women. Aging and SBP were related to PWV even in AHgr, although age ≥ 50 years in Rgr women and normal SBP in AHgr were not associated with elevated PWV.

QT interval variability index and QT interval duration during different sleep stages in patients with obstructive sleep apnea.

OBJECTIVES: The aim of the study was to investigate the impact of obstructive sleep apnea (OSA) on the QT interval variability and duration in patients during different sleep stages. METHODS: Polysomnographic recordings of 28 (13 male, 15 female) patients with OSA and 30 (15 male, 15 female) patients without OSA were analyzed. The QT interval variability index (QTVI) and the corrected QT interval (QTc) analyses were performed using two awake, 3-4 non-rapid eye movement (NREM) and three rapid eye movement (REM) sleep episodes (each 300 s). The Bazett formula, linear, and parabolic heart rate correction formulas with two separate α values were used. RESULTS: QTVI was statistically higher in OSA than in non-OSA patients for males while awake (awake -0.7 ± 0.3 vs -1.2 ± 0.2, p = 0.001; NREM ‒0.9 ± 0.4 vs -1.1 ± 0.3, p = 0.110; REM ‒1.1 ± 0.3 vs -1.3 ± 0.2, p = 0.667) and for females in all wake-sleep stages (awake -0.3 ± 0.7 vs -0.9 ± 0.5, p = 0.001; NREM ‒0.3 ± 0.5 vs -0.8 ± 0.4, p = 0.002; REM -0.3 ± 0.5 vs -1.0 ± 0.4, p < 0.001). QTVI was significantly higher during awake compared to sleep stages in OSA males (p < 0.05); no difference between wake-sleep stages was found in females (p > 0.05). Significant gender differences in QTVI existed in OSA patients during sleep (p < 0.05) but not while awake. No significant differences in QTc between patients groups were observed. CONCLUSIONS: OSA is associated with increased QT variability. REM sleep per se does not increase QTVI. In OSA patients, QTVI might be a more useful measure to detect ventricular repolarization abnormality than measures of QTc.

Influence of gender on the QT interval variability and duration in different wake-sleep stages in non-sleep apneic individuals: Analysis of polysomnographic recordings.

INTRODUCTION: The aim of the study was to determine the influence of gender and sleep stages, especially rapid eye movement sleep (REM), on QT interval variability and duration in normal subjects. METHODS: Polysomnographic recordings of 24 male and 24 female patients without obstructive sleep apnea were analyzed. In each patient, the QT interval variability index (QTVI) and the corrected QT interval (QTc) values were calculated as means of 2 awake, 4 non-rapid eye movement sleep (NREM) and 3 REM episodes, 300s each. For the QTc calculation, five different correction formulas were used. RESULTS: Gender-related differences in the QT interval variability and duration were detected between all sleep stages (P<0.05). In males, mean values of QTVI while awake, in NREM and REM sleep were -1.1±0.2, -1.1±0.3, -1.3±0.2. In females, mean values of QTVI were -0.9±0.4, -0.9±0.4, and -1.1±0.3, respectively. No difference between sleep stages was detected in the mean values of QTVI and QTc in both groups (P>0.05). CONCLUSION: The results of our study demonstrate no significant overall impact of sleep stages on ventricular repolarization variability and duration during physiological sleep in both genders. We found gender differences in the mean values of QTVI and QTc during different sleep stages, which confirm that gender is a modulating factor of ventricular repolarization.

QT Interval Variability Index and QT Interval Duration in Different Sleep Stages: Analysis of Polysomnographic Recordings in Nonapneic Male Patients.

The aim of the study was to determine whether different sleep stages, especially REM sleep, affect QT interval duration and variability in male patients without obstructive sleep apnea (OSA). Polysomnographic recordings of 30 patients were analyzed. Beat-to-beat QT interval variability was calculated using QTV index (QTVI) formula. For QTc interval calculation, in addition to Bazett's formula, linear and parabolic heart rate correction formulas with two separate α values were used. QTVI and QTc values were calculated as means of 2 awake, 3 NREM, and 3 REM sleep episodes; the duration of each episode was 300 sec. Mean QTVI values were not statistically different between sleep stages. Therefore, elevated QTVI values found in patients with OSA cannot be interpreted as physiological sympathetic impact during REM sleep and should be considered as a risk factor for potentially life-threatening ventricular arrhythmias. The absence of difference of the mean QTc interval values between NREM and REM stages seems to confirm our conclusion that sympathetic surges during REM stage do not induce repolarization variability. In patients without notable structural and electrical remodeling of myocardium, physiological elevation in sympathetic activity during REM sleep remains subthreshold concerning clinically significant increase of myocardial electrical instability.

Pulse wave registration from radial artery using photoplethysmographic method.

This pilot study was aimed to investigate the possibilities to use the photoplethysmographic (PPG) method for the pulse wave registration from radial artery. The PPG sensor with different separation distances between light emitting diodes (LED) and photodiode was built. The PPG signal registration was carried out at the locations with two different depths of artery and at the locations without large blood vessels under the sensor. In addition, two different forces were applied on the sensor in order to decrease the blood volume in underlying tissue and lower the pulsations that originates from smaller vessels. As a result, it was found that the artery was possible to locate under the sensor, where the value of DC component is minimal. Furthermore, the pressure has to be applied on sensor and optimal separation distance has to be selected between LED and photodiode for the pulse wave registration from radial artery. Further studies and improvements of the sensor are needed.

The effect of local cold and warm exposure on index finger photoplethysmographic signal waveform.

The study was carried out in order to analyse the changes in photoplethysmographic (PPG) signal waveform, which are caused by cold and warm stimulation. The study was carried out on 7 subjects. The right hand was immersed in cold and warm water up to the wrist during the experiment. The PPG signal was registered from right hand index finger. As a reference, the temperatures of index finger and pulse transit time (PTT) values were measured. A correlation of r = -0.70 was found between normalised slope of the PPG signal and the subject's age. The normalised slope increased noticeably due to the cold and decreased due to the warm water stimulation. It was opposite to the expected results with PTTs and the behaviour has to be investigated in future studies.

New photoplethysmographic signal analysis algorithm for arterial stiffness estimation.

The ability to identify premature arterial stiffening is of considerable value in the prevention of cardiovascular diseases. The "ageing index" (AGI), which is calculated from the second derivative photoplethysmographic (SDPPG) waveform, has been used as one method for arterial stiffness estimation and the evaluation of cardiovascular ageing. In this study, the new SDPPG analysis algorithm is proposed with optimal filtering and signal normalization in time. The filter parameters were optimized in order to achieve the minimal standard deviation of AGI, which gives more effective differentiation between the levels of arterial stiffness. As a result, the optimal low-pass filter edge frequency of 6 Hz and transitionband of 1 Hz were found, which facilitates AGI calculation with a standard deviation of 0.06. The study was carried out on 21 healthy subjects and 20 diabetes patients. The linear relationship (r = 0.91) between each subject's age and AGI was found, and a linear model with regression line was constructed. For diabetes patients, the mean AGI value difference from the proposed model y AGI was found to be 0.359. The difference was found between healthy and diabetes patients groups with significance level of P < 0.0005.

An experimental measurement complex for probable estimation of arterial stiffness.

Current work is a part of long term research, which aim is to study the possibilities to diagnose the atherosclerosis in early stadium by using pulse wave velocity and its waveform analysis. The mobile experimental measurement complex is built and technically tested for the long term study in hospital. Measurement complex consists of ten physiological signal recording channels and reference devices: Sphygmocor, Arteriograph, Finapres. The measurements with this complex are planned to carry out during six month on patients with different severity of coronary disease and diabetes.

Adjustment of adaptive sum comb filter for PPG signals.

AC component of photoplethysmography signal carries important information for diagnostics. Registered signal may be affected by noises, which are sharing the same bandwidth. Adaptive comb filter is used for the AC component extraction. Due to filter averaging behavior it decreases the signal shape difference between consecutive beats. Comb filter needs to be adjusted for PPG signal. Comb filter new weight values are determined through numerical computation. Experiments with generated photoplethysmographic signals were carried out to compare adjusted and non-adjusted adaptive sum comb filter.

Adaptive impulse correlated filter (AICF) improvement for photoplethysmographic signals.

Measured PPG signals are often contaminated with different noises and artifacts. For clinical diagnostics, it is important to have accurate signals. Removing noises and motion artifacts from PPG signal has been actual also in previous studies. In this study, we are proposing new adaptive impulse correlated filter (AICF) improvement for plethysmographic signals. It uses ECG signal to create reference with unit impulses. All signals, which do not correlate with reference signal, will be filtered out. To show, how the filter acts with artifacts with low SNR, the experiment was conducted.

Analogue step-by-step DC component eliminator for 24-hour PPG signal monitoring.

For applications where PPG signal AC component needs to be measured without disturbances in its shape and recorded digitally with high digitalization accuracy, the step-by-step DC component eliminator is developed. This paper describes step-by-step DC component eliminator, which is utilized with analogue comparator and operational amplifier. It allows to record PPG signal without disturbances in its shape in 24-hours PPG signal monitoring system. The experiments with PPG signal have been carried out.

Assessment of Pulse Wave Velocity and Augmentation Index in different arteries in patients with severe coronary heart disease.

The aim of this study was to assess pulse wave velocity (PWV) and augmentation index in different arteries in patients with severe coronary heart disease (CHD). Signal measurements were obtained from 28 subjects. Severe coronary heart disease was confirmed by coronary angiography. Aortic PWV and Augmentation Index were measured using the TENSIOMed Arteriograph. Four other pulse wave velocities (upper limb PWV1, upper limb PWV2, upper limb PWV3 and lower limb PWV) were obtained using PowerLab 4/20T device. It was found that aortic PWV was significantly increased in the CHD group compared with that in the control group (P<0.01). Augmentation index was significantly increased in the CHD group compared with the control group (P<0.01). This study shows the strong association of aortic stiffness and atherosclerosis. Pulse wave analysis can provide inexpensive and noninvasive means for studying changes in the elastic properties of the vascular system with the coronary heart disease.

Self-mixing in a diode laser as a method for cardiovascular diagnostics.

Our aim is the development of a simple optical method for pulse wave profile, pulse wave delay time, and blood flow measurement. The method is based on recording the Doppler frequency shift related to a moving target--blood vessel walls or small particles. The Doppler signal is detected using the self-mixing that occurs in the diode laser cavity when radiation scatters back from the moving target into the laser and interferes with the field inside. Two different ways can be simultaneously used for the self-mixing signal extraction: a photodiode accommodated in the rear facet of the diode laser package and a resistor from the laser pump current. An experimental device with a pigtail laser diode is developed that is able to detect the pulsation of major arteries with potentially useful information, including the pulse wave profile and the pulse wave delay time. The pulse wave delay time in different regions of the human body is measured relative to the electrocardiogram (ECG) signal. Also the flow velocity of a liquid suspension containing particles the size of erythrocytes (equivalent to blood flow) is measured. Registered signals are stored after digitalization and preprocessed using LabView for a Windows environment. The described device has the application of the self-mixing method and highlights significant advantages of simplicity, compactness, and robustness as well as the self-aligning and self-detecting abilities of such method, compared with the use of conventional interferometric method.

Echocardiographic assessment of the different left ventricular geometric patterns in middle-aged men and women in Tallinn.

The aim of this study was to determine the association of left ventricular (LV) geometry with sex, age, arterial hypertension and obesity in Tallinn. In a framework of a population study for cardiovascular risk factors, echocardiography was carried out in 325 men and 398 women (69.3% of all 1043 participants aged 35-59) in 1999-2001. Left ventricular hypertrophy was defined if left ventricular mass (LVM), LVM/height and LVM/body surface area were 294 g, 163 g/m and 150 g/m2 in men, and 198 g, 121 g/m and 120 g/m2 in women, respectively. LV geometry was analysed according to four types generally recognized (with regard to relative wall thickness > 0.45). The prevalence of concentric hypertrophy was similar in men and women: 7.7% and 9.1%. The prevalence of eccentric hypertrophy was significantly higher in women than in men (33.3% vs 4.9%). Concentric remodelling was also found in women more often than in men (9.5 vs 5.5%; p < 0.05). Regardless of sex and age, concentric hypertrophy was never found in participants with blood pressure < 140/90. In hypertensives, there was a tendency for age-related increase of concentric hypertrophy prevalence: the latter was higher in women than in men: 39.1% vs 25.5%; p < 0.05. In examinees with BMI < 30, this type of LV geometry was seldom found: in 3.1% of men and 5.0% of women; p < 0.05. In obese persons, it increased with age, reaching 26.5% in men and 21.2% in women (p < 0.05). The prevalence of eccentric hypertrophy in men increased with age, and with hypertension and obesity. The prevalence of concentric remodelling in men was not related to BMI; it was significantly more often found in older age groups and in hypertensives. In women, the prevalence of eccentric hypertrophy and concentric remodelling was not related to age, hypertension or obesity.