The Prediction of Atherosclerosis Index Based on Photoplethysmograph

Current atherosclerosis (AS) assessment devices have a disadvantage for users to carry around. In response to this shortcoming, we propose to collect the wrist photoplethysmograph (PPG) signal and create models to predict the indicators of atherosclerosis (cardiovascular age and right brachial and ankle pulse wave velocity (baPWV)). This study uses the maximum correlation coefficient method for feature selection and establishes multiple models to predict cardiovascular age and the right baPWV. The study results show that the prediction of cardiovascular age using the backpropagation (BP) neural network model is the best. Its Pearson correlation coefficient (PCC) is 0.9501 ( P < 0.05 ), and the model finds the best six physiological features as crest time (CT), crest time ratio (CTR), slop K, stiffness index (SI), reflection index (RI), and heart rate (HR). When predicting the right baPWV value on the right side, we propose a hybrid method MLR_BP, which has better experimental results than BP and MLR. The MLR_BP model improves the prediction accuracy, the predicted PCC value is 0.9204 ( P < 0.05 ), and the model only needs two features, HR and cardiovascular age. This study further verified the results of related literature and proved the relationship between AS and related physiological parameters. The proposed method is applied to wearable devices and has an application value for diagnosing AS and preventing cardiovascular diseases.

Photoplethysmography Analysis with Duffing–Holmes Self-Synchronization Dynamic Errors and 1D CNN-Based Classifier for Upper Extremity Vascular Disease Screening

Common upper limb peripheral artery diseases (PADs) are atherosclerosis, embolic diseases, and systemic diseases, which are often asymptomatic, and the narrowed arteries (stenosis) will gradually reduce blood flow in the right or left upper limbs. Upper extremity vascular disease (UEVD) and atherosclerosis are high-risk PADs for patients with Type 2 diabetes or with both diabetes and end-stage renal disease. For early UEVD detection, a fingertip-based, toe-based, or wrist-based photoplethysmography (PPG) tool is a simple and noninvasive measurement system for vital sign monitoring and healthcare applications. Based on time-domain PPG analysis, a Duffing–Holmes system with a master system and a slave system is used to extract self-synchronization dynamic errors, which can track the differences in PPG morphology (in amplitudes (systolic peak) and time delay (systolic peak to diastolic peak)) between healthy subjects and PAD patients. In the preliminary analysis, the self-synchronization dynamic errors can be used to evaluate risk levels based on the reflection index (RI), which includes normal condition, lower PAD, and higher PAD. Then, a one-dimensional convolutional neural network is established as a multilayer classifier for automatic UEVD screening. The experimental results indicated that the self-synchronization dynamic errors have a positive correlation with the RI (R2 = 0.6694). The K-fold cross-validation is used to verify the performance of the proposed classifier with recall (%), precision (%), accuracy (%), and F1 score.

Induced Resistance by Ascorbate Oxidation Involves Potentiating of the Phenylpropanoid Pathway and Improved Rice Tolerance to Parasitic Nematodes

Anticipating an increased ecological awareness, scientists have been exploring new strategies to reduce the use of chemical pesticides to control pests and diseases. Triggering the intrinsic plant defense system is one of the promising strategies to reduce yield loss by pathogenic organisms, such as nematodes. Ascorbate oxidase (AO) enzyme plays an important role in plant defense by regulating the apoplastic ascorbate/dehydroascorbate (DHA) ratio via the ascorbate oxidation process. Ascorbate oxidation is known to induce systemic resistance in rice against parasitic root-knot nematodes (RKN). Here, we sought to evaluate if AO- or DHA-induced resistance (IR) against RKN M. graminicola involves activation of the phenylpropanoid pathway and whether this IR phenotype has potential effects on growth of rice seedlings under stressed and unstressed conditions. Our results show that AO/DHA-IR against these parasitic nematodes is dependent on activation of phenylalanine ammonia lyase (PAL). However, application of reduced ascorbic acid (AA) did not induce this response. Gene expression analysis via qRT-PCR showed that OsPAL2 and OsPAL4 are highly expressed in AO/DHA-sprayed nematode-infected roots and PAL-activity measurements confirmed that AO/DHA spraying triggers the plants for primed activation of this enzyme upon nematode infection. AO/DHA-IR is not effective in plants sprayed with a chemical PAL inhibitor confirming that AO/DHA-induced resistance is dependent on PAL activity. Improved plant growth and low nematode infection in AO/DHA-sprayed plants was found to be correlated with an increase in shoot chlorophyll fluorescence (Fv/Fm), chlorophyll index (ChlIdx), and modified anthocyanin reflection index which were proven to be good above-ground parameters for nematode infestation. A detailed growth analysis confirmed the improved growth of AO/DHA-treated plants under nematode-infected conditions. Taken together, our results indicate that ascorbate oxidation enhances the phenylpropanoid-based response to nematode infection and leads to a tolerance phenotype in treated rice plants.

The effects of submaximal exercise on a treadmill on the recovery of the stiffness index and reflection index in men with untreated hypertension

Aim. Increased arterial stiffness is a risk factor for cardiovascular disease (CVD). Adult men with untreated hypertension are at risk of future CVD. The study aimed to compare the effects of a submaximal exercise on the recovery of the two descriptors of arterial pressure waveform, i.e. stiffness index (SI) and reflection index (RI), between men with untreated hypertension (HA) and healthy peers. Material and Methods. The study included 70 Caucasian men with untreated primary HA and 30 normotensive men. Blood pressure, SI and RI were determined by photoplethysmography before and 6 minutes after a submaximal (up to 85% of age-predicted maximal heart rate) exercise on a treadmill. Results. Baseline SI was higher in HA than control men (6.06 [0.66] vs. 6.61 [0.84] m/s; p=0.0019) and remained significantly increased during post-exercise recovery only in HA men (7.59 [1.6] vs. 6.18 [0.85] m/s; p<0.0001). Pre-exercise RI did not differ between HA and healthy men (50.74 [14.17] vs 48.9 [14.86]%). Six minutes after the exercise, RI higher in HA patients than in healthy men (45.26[15.33] vs 36.2 [13.18]%; p=0.0058). Conclusions. Arterial stiffness is higher in men with HA both at rest and 6 minutes after exercise. Compared with healthy men, those with HA have more increased arterial tone and impaired vasodilation but only during the recovery. It suggests that untreated HA patients have abnormal mechanical properties of arterial pressure waveforms during the post-exercise recovery.

Method for determining significant components for assessing pulse wave shape variability

Background and Objectives: The conventional approach to the quantification of the pulse wave is based on the assessment of the features of its shape within each beat to beat heart interval. Usually, a set of indices is calculated (such as heart efficiency index, reflection index, stiffness index), which are determined by the reference points of the wave contour. We have developed an alternative method aimed to analyze the variability of the pulse waveform regardless of the variability of its rhythm. A distinctive feature of the method is that the classical spectral analysis tool – the Fourier series expansion in harmonic functions – is used not for frequency analysis, but for describing the features of the pulse waveform, regardless of its frequency-time characteristics. Materials and Methods: The data is represented by the signal as separate sets of fragments, each of which corresponds to one cardiointerval. Further, information about the current heart rate, including its variability, is removed from the data. We do this by resampling each cardiointerval by the same predetermined number of samples. The shape variability of each waveform is quantified by calculating the amplitudes and phases of the harmonics of each waveform as a representative of a strictly periodic sequence. This is an important point, since the original pulse wave signal belongs to the class of random signals and for it, as for the whole, the amplitude and phase of the Fourier spectra are not determined. As a result of the procedure, the analysis of the pulse waveform for each cardiointerval is reduced to the analysis of the amplitude and phases of the required number of harmonics. The method described above was used to process the data of an experiment aimed at quantitatively calculating the relationship between the central and distal pulses. The measurements were carried out on a group of 16 healthy volunteers aged 20–35 years after being in a calm state for 20 minutes. Then, rheographic signals were synchronously recorded from three points on the human skin surface (aortic region, wrist and distal phalanx of the finger). Results: The study revealed significant differences in the stability of the shape of the pulse waves recorded in different parts of the vascular bed, which is expressed in different degrees of variability of their main components. It is important that the central pulse has a smaller number of significant harmonics in comparison with the distal one, and is more stable at the first 4 harmonics containing the main signal power. Conclusion: We proposed and tested a method for analyzing the variability of the pulse waveform, based on the harmonic analysis of the re-sampled signal for each of the cardiointervals, aimed at studying the variability of the pulse waveform separately from the variability of its rhythm. The obtained quantitative data on the stability of the harmonics of the central pulse wave indicate the prospects for further development of the transfer function method in the problem of restoring the shape of the central pulse based on distal measurements.

First principles DFT calculations of the optical properties of A4BX6 group crystals

The results of investigating of the electron band energy structure and optical properties of A4BX6 (Tl4HgI6 and Tl4CdI6) group crystals are presented. The energy band structures of Tl4HgI6 and Tl4CdI6 crystals are calculated from the first principles within generalized gradient approximation (GGA). The band structure and reflection index were calculated using a pseudopotential method in the framework of density functional theory. Optical absorption edge in Tl4HgI6 and Tl4CdI6 is formed by direct optical transitions. The spectral dependence of the reflection index was calculated on the basis of the energy band results with using the Kramers–Kronig method. The spectra show pronounced anisotropy in E||a(b) and E||c polarizations. It was found the anomalous by large values of the birefringence (Δn > 0.18 for Tl4HgI6 and Δn > 0.03 for Tl4CdI6) in the visible and near infrared region.

Endothelial dysfunction and inflammation in patients with non-obstructive coronary arteries

Aim To determine levels of markers for endothelial dysfunction and inflammation, endothelin-1, E-selectin, and tumor necrosis factor α (TNF-α) in patients with ischemic heart disease (IHD) and non-obstructive and obstructive coronary artery (CA) disease.Material and methods This study included 32 patients with verified IHD and non-obstructive (main group, n=19) and obstructive (comparison group, n=13) CA disease. Endothelial dysfunction was diagnosed by photoplethysmography and videocapillaroscopy. Serum concentrations of endothelin-1, E-selectin, and TNF- α were measured in all patients.Results Patients with non-obstructive CA disease showed a tendency towards more pronounced endothelial dysfunction (alternative stiffness index, 7.8 m /s [6.35; 9.08]; reflection index, 36.95 % [23.4; 52.65]; capillary density following reactive hyperemia, 54.33 cap /mm2 [48.92; 75.83]; capillary density following venous occlusion, 74.33 cap /mm2 [67.83; 93.00]) compared to the comparison group (alternative stiffness index, 9.05 m/s [7.08; 10.58]; reflection index, 28.25 % [23.35; 53.75]; capillary density following reactive hyperemia, 66.83 cap /mm2 [50.83; 78.67]; capillary density following venous occlusion, 87.0 cap /mm2 [77.58; 78.67]), although statistically significant differences were not found. Concentration of endothelin-1 was significantly higher in the IHD group with non-obstructive CA disease (0.45 ng/ml [0.28;0.65]) compared to patients with CA atherosclerotic stenosis (0.35 ng/ml [0.25; 0.38], p=0.035). Concentrations of E-selectin did not significantly differ between the groups (main group, 21.1 ng/ml [18.45; 35.03]; comparison group, 28.55 ng/ml [19.08; 35.01], p=0.29). In both groups, concentrations of TNF-α did not exceed the lower threshold of sensitivity (<2.3 pg/ml).Conclusion Endothelial dysfunction and increased endothelin-1 in patients with non-obstructive CA disease along with inflammation may additionally contribute to the pathogenesis of IHD in the absence of hemodynamically significant CA stenoses. Too low level of TNFα in both groups prevented us from using it as a diagnostic marker. Further study is needed that would include a greater number of patients and a search for alternative markers.

Sechenov First Moscow State Medical University of the Ministry of Health of the Russian Federation (Sechenov University), Moscow

Aim To study changes in markers for myocardial direct injury and dysfunction and endothelial dysfunction (ED) indexes in patients with indolent lymphoma during the antitumor treatment.Material and methods Current antitumor therapy for lymphoma is often associated with cardio- and vasculotoxicity, studying of which is a relevant scientific direction. Markers for myocardial direct injury and dysfunction and ED indexes were studied in patients with indolent lymphomas receiving polychemotherapy (PCT). The study included 77 patients with newly diagnosed indolent type lymphoma. The main group (n=52): mean age, 63.4±2.8 years, 15 (28.8 %) men who had received one course of PCT. The comparison group (n=25): mean age, 61.8±3.7 years, 8 (32 %) men who had not received PCT. Troponin I (TnI), high-sensitivity troponin I (hs-сTnI), heart-type fatty acid binding protein (h-FAВР), and N-terminal pro-B-type natriuretic peptide (NT-prоBNP) were measured in patients of both groups. ED was evaluated by measuring the level of vascular cell adhesion molecule (VCAM) and by assessing the structure and function condition of small blood vessels using photoplethysmography. In both groups, the study parameters were determined at the start of the study (T1) and following the PCT course in the main group; if the PCT schedule included anthracycline antibiotics, the second point (T2) was assessed at 6 h following the drug administration.Results In both groups, the level of NT-proBNP was increased. This increase was significantly more pronounced in the comparison group (49.896±23.228 vs 20.877±8.534 pmol/l, respectively, p=0.011) whereas a tendency to its increase was observed after the PCT course. Before the start of the treatment, laboratory and instrumental signs of ED were noticed: the level of VCAM was 4951±1297 and 3225±757 ng/ml in the comparison group and the main group, respectively (р=0.246); reflection index was <1.8 in 23 (44.2%) patients of the main group and in 16 (64%) patients of the comparison group (р=0.098). During the PTC course, the endothelial function significantly improved; the level of VCAM decreased by 748 ng/ml (p=0.016), which was associated with significant decreases in erythrocyte sedimentation rate by 2.71 mm/h (р=0.027) and lactate dehydrogenase level by 62.38 U/l (р=0.026). Statistically significant decreases in other inflammatory markers (alpha-2-globulin, fibrinogen, C-reactive protein, neutrophil count) were not observed.Conclusion The level of NT-proBNP showed the highest sensitivity in assessing the cardiotoxic effect of PCT. The dynamics of VCAM level suggested a possible role of the disease itself in the development of ED in this patient group.

Is Heart Rate a Confounding Factor for Photoplethysmography Markers? A Systematic Review

Finger photoplethysmography (PPG) waveform is blood volume change of finger microcirculation that reflects vascular function. Reflection index (RI), stiffness index (SI) and second derivative of photoplethysmogram (SDPPG) are derived from PPG waveforms proposed as cardiovascular disease (CVD) markers. Heart rate (HR) is a known factor that affects vascular function. Individual resting HR variation may affect RI, SI and SDPPG. This review aims to identify studies about the relationship between HR with RI, SI and SDPPG among humans. A literature search was conducted in Medline via the Ebscohost and Scopus databases to find relevant articles published within 11 years. The main inclusion criteria were articles in the English language that discuss the relationship between HR with RI, SI and SDPPG using PPG among humans. The search found 1960 relevant articles but only six articles that met the inclusion criteria. SI and RI showed an association with HR. SDPPG (SDPPG-b/SDPPG-a ratio, SDPPG-d/SDPPG-a ratio, aging index (AGI) and revised aging index (RAGI)) also had an association with HR. Only RI had a considerable association with HR, the association between SI and HR was non-considerable and the association between HR and SDPPG was inconclusive. Further interventional studies should be conducted to investigate this issue, as a variation in resting HR may challenge the validity of PPG-based CVD markers.