Photoplethysmographic signal waveform index for detection of increased arterial stiffness.

The aim of this research was to assess the validity of the photoplethysmographic (PPG) waveform index PPGAI for the estimation of increased arterial stiffness. For this purpose, PPG signals were recorded from 24 healthy subjects and from 20 type II diabetes patients. The recorded PPG signals were processed with the analysis algorithm developed and the waveform index PPGAI similar to the augmentation index (AIx) was calculated. As a reference, the aortic AIx was assessed and normalized for a heart rate of 75 bpm (AIx@75) by a SphygmoCor device. A strong correlation (r = 0.85) between the PPGAI and the aortic AIx@75 and a positive correlation of both indices with age were found. Age corrections for the indices PPGAI and AIx@75 as regression models from the signals of healthy subjects were constructed. Both indices revealed a significant difference between the groups of diabetes patients and healthy controls. However, the PPGAI provided the best statistical discrimination for the group of subjects with increased arterial stiffness. The waveform index PPGAI based on the inexpensive PPG technology can be considered as a perspective measure of increased arterial stiffness estimation in clinical screenings.

[Dynamics of prevalence of arterial hypertension and other risk factors of development of cardiovascular diseases in female population of Tallin (10 year prospective study)].

Aim of the study was to assess dynamics of prevalence of arterial hypertension (AH) and main cardiovascular risk factors (RF) in a women population of Tallin during 10 years of follow up. In 2008-2009 we repeated measurements of arterial pressure (AP), electrocardiographic, echocardiographic, and complex laboratory examinations in 314 participants of epidemiological study undertaken in 1999-2000. Most prevalent RF was hypercholesterolemia. Rate of its detection substantially rose from 69.1 to 81.2%. Number of subjects who continuously took cholesterol lowering drugs and had target levels of lipid profile was sporadic. Prevalence of hypertriglyceridemia, obesity, and diabetes mellitus insignificantly increased. Only prevalence of smoking had tendency to reduction. AH was found in 28.7 and 44.6% of women in 1999-2000 and 2009, respectively. Obesity and hypercholesterolemia contributed significantly to development of new cases of AH. Among subjects with AH 25% of women received antihypertensive therapy and achieved target AP levels--3 times more than in 2000. Thus prevalence of AH and other main RF in female population of Tallin increased during 10 years follow-up. However control of AP in patients with AH notably improved.

[Arterial hypertension, echocardiographically determined left ventricular hypertrophy and N-terminal pro-B type natriuretic peptide levels in women population aged 56-65 years].

Aim of the study was to investigate relationship between arterial hypertension (AH), left ventricular myocardial mass (LVMM), and levels of N-terminal pro-B type natriuretic peptide (pro-NT BNP) in a population of women inhabitants of Tallinn aged 56-65 years. Of 163 women aged 50-59 years who had participated in epidemiological study in 2000 in 132 measurement of arterial pressure (AP), electrocardiography, echocardiography, complex laboratory diagnostics including determination of pro-NT BNP were repeated in 2007. Most frequent risk factor was AH which was detected in 56.1% of cases. In women with normal AP normal LVMM was noted in 81.1% of cases, while in women with elevated AP normal LVMM was significantly less frequent (28.4%). Only in 5 of 28 women with elevated pro-NT BNP deviations of systolic-diastolic function were observed. Elevated levels of pro-NT BNP were found with almost equal rates among patients with normal and increased LWMM (in 9.1 and 8.3% of cases, respectively). Thus increase of content of pro-NT BNP is of limited significance for diagnosis of left ventricular hypertrophy in women aged 56-65 years without clinical signs of disease.

[Association between QT-interval and its dispersion with factors determining prognosis of cardiovascular morbidity and mortality].

AIM: To elucidate relation between prolongation of corrected maximal QT intervals and QT dispersion (QTcmax, QTcD) and presence and severity of arterial hypertension, as well as other factors determining high cardiovascular risk in female population of Tallinn aged 56 - 66 years. MATERIAL AND METHODS: A sample of female citizens of Tallinn (n=123, age 56 - 65 years) were subjected to standard examination including blood pressure measurement, electrocardiography, echocardiography, and laboratory tests. RESULTS: Presence of prolonged QTcmax and/or QTcD were associated with elevation of pulse pressure, which reflected strain and elasticity of the aorta, as well as with presence of left ventricular hypertrophy, especially concentric variant of changes of left ventricular geometry. Participants with prolonged QTcmax and/or QTcD had higher total 10 year risk of cardiovascular morbidity and mortality.

A novel method for reducing pain sensation at transesophageal atrial stimulation.

Transesophageal atrial stimulation (TAS) is widely used in evaluation and treatment of supraventricular arrhythmias. It can yield important information in most situations, where invasive atrial stimulation is usually done, but is safe, rapid, inexpensive and can often be performed in an outpatient setting. However, in clinical practice TAS pacing usually causes patients some degree of discomfort and/or pain. The aim of the study was to evaluate the possibility and methods to obtain successful atrial capture using multiple electrical pulses in order to reduce pain sensation during the procedure. The study was performed in 17 patients aged 22 to 54 years, special experimental arrangement was used. We elaborated a novel method of combining very short electric pulses (splitting the impulse) from different locations which resulted in desired current density and pulse length in target tissue. As the result the stimulation could be less painful for patient than routinely used single 10ms current pulse.

Continuous blood pressure monitoring during exercise using pulse wave transit time measurement.

This paper gives an overview of a research, which is focused on the development of the convenient device for continuous non-invasive monitoring of arterial blood pressure. The blood pressure estimation method is based on a presumption that there is a singular relationship between the pulse wave propagation time in arterial system and blood pressure. The parameter used in this study is pulse wave transit time (PWTT). The measurement of PWTT involves the registration of two time markers, one of which is based on ECG R peak detection and another on the detection of pulse wave in peripheral arteries. The reliability of beat to beat systolic blood pressure calculation during physical exercise was the main focus for the current paper. Sixty-one subjects (healthy and hypertensive) were studied with the bicycle exercise test. As a result of current study it is shown that with the correct personal calibration it is possible to estimate the beat to beat systolic arterial blood pressure during the exercise with comparable accuracy to conventional noninvasive methods.

Evaluation of the quality of rate adaptation algorithms for cardiac pacing.

The aim of this study was a comparative evaluation of some commonly used pacemaker control parameter combinations and algorithms for heart rate (HR) reconstruction. The quality of heart rate reconstruction was estimated comparing the reconstructed heart rate and intrinsic heart rate on the basis of a healthy person model. The model was developed on the basis of simultaneous measurement of intrinsic HR and different control parameters, which can electrically be recorded: QT-interval, (QT), ventilation (V)- and body movement activity (ACT). Relative mean square error (RMSE) between natural and reconstructed HR was used as a measure of HR reconstruction quality. It was shown that the results of linear and polynomial approximations for HR reconstruction practically coincided inside the range of interest for pacing in clinical practice 60-120 beats.min(-1) and there was no need to implement more complex algorithms. As for single-parameter systems the QT parameter had better reconstruction accuracy compared with ACT and V. All double-parameter systems presented HR reconstruction error level of around 10% that were within the limits suitable for clinical practice. The application of more than two parameters for HR reconstruction seems to be unnecessary, as the triple-parameter models appeared not to improve remarkably the quality of HR reconstruction.