Effect of increasing heart rate on finger photoplethysmography fitness index (PPGF) in subjects with implanted cardiac pacemakers

The effects of pedometer-based exercise on central and peripheral vascular functions among young sedentary men with CVD risk factors

Introduction: Cardiovascular diseases (CVDs) remain the main cause of morbidity and mortality in Malaysia and worldwide. This is mainly due to an increase in the prevalence of CVD risk factors such as hypertension, dyslipidemia, smoking, and obesity. Increased physical activity has been recommended as a modality to improve CVD risk. Pulse wave velocity (PWVCF), augmentation index (AI), and finger photoplethysmography fitness (PPGF) index have been introduced to assess the vascular functions related to CVD risk factors. The effects of long-term exercise on PPGF index are not established.

Materials and Methods: A total of 70 young men who were sedentary with two or more cardiovascular risk factors were recruited. Subjects were randomly assigned to a control group (CG) (n = 34; no change in walking) and pedometer group (PG) (n = 36; minimum target: 8,000 steps/day). PWVCF and AI were measured via the Vicorder system. The PPGF index was obtained via the finger photoplethysmography method. All parameters were measured at baseline and after 6 and 12 weeks.

Results: After intervention, the PG had significant increased step count from 4,996 ± 805 to 10,128 ± 511 steps/day (p < 0.001). The PG showed significant improvement in anthropometric variables, lipid, PWVCF, AI, and PPGF index (time and group effect p < 0.001). No changes were observed in CG.

Conclusion: This signifies that pedometer-based walking program is beneficial in improving markers of vascular functions among young working sedentary men with CVD risk factors. Pedometer-based exercise should be encouraged to improve cardiovascular health.

Discrimination of vascular aging using the arterial pulse spectrum and machine-learning analysis

Aging contributes to the progression of vascular dysfunction and is a major nonreversible risk factor for cardiovascular disease. The aim of this study was to determine the effectiveness of using arterial pulse-wave measurements, frequency-domain pulse analysis, and machine-learning analysis in distinguishing vascular aging. Radial pulse signals were measured noninvasively for 3 min in 280 subjects aged 40-80 years. The cardio-ankle vascular index (CAVI) was used to evaluate the arterial stiffness of the subjects. Forty frequency-domain pulse indices were used as features, comprising amplitude proportion (C_n), coefficient of variation of C_n, phase angle (P_n), and standard deviation of P_n (n = 1-10). Multilayer perceptron and random forest with supervised learning were used to classify the data. The detected differences were more prominent in the subjects aged 40-50 years. Several indices differed significantly between the non-vascular-aging group (aged 40-50 years; CAVI <9) and the vascular-aging group (aged 70-80 years). Fivefold cross-validation revealed an excellent ability to discriminate the two groups (the accuracy was >80%, and the AUC was >0.8). For subjects aged 50-60 and 60-70 years, the detection accuracies of the two trained algorithms were around 80%, with AUCs of >0.73 for both, which indicated acceptable discrimination. The present method of frequency-domain analysis may improve the index reliability for further machine-learning analyses of the pulse waveform. The present noninvasive and objective methodology may be meaningful for developing a wearable-device system to reduce the threat of vascular dysfunction induced by vascular aging.

The Association between Inflammation and Pulse Wave Velocity in Dyslipidemia: An Evidence-Based Review

Dyslipidemia is associated with increased arterial stiffness (AS) which may lead to hypertension. Among the methods to assess AS are carotid-femoral and brachial-ankle pulse wave velocity. Dyslipidemia is also known to trigger inflammation. C-reactive protein (CRP) is one of the commonest inflammatory markers measured in the clinical setting. However, the association between inflammation and pulse wave velocity (PWV) in people with dyslipidemia is less studied. Therefore, this review investigated the association between inflammation (as measured by CRP) and PWV in dyslipidemia patients. The search of the literature was conducted via PubMed and Scopus database. The keywords used were "aortic stiffness" OR "arterial stiffness" OR "pulse wave velocity" OR "vascular stiffness" OR "carotid femoral pulse wave velocity" OR "pulse wave analysis" AND "inflammation" OR "c reactive protein" OR "c-reactive protein" OR "high sensitivity c reactive protein" AND "dyslipidemia" OR "hyperlipidemia" OR "hypercholesterolemia" OR "hyperlipoproteinemia" OR "hypertriglyceridemia". The following criteria were used: (1) only full-length original articles published in English language, (2) articles that reported the association between arterial stiffness measured as carotid-femoral PWV (cfPWV) or brachial-ankle PWV (baPWV) and CRP or high-sensitivity CRP, and (3) study involving human subjects. The search identified 957 articles published between 1980 and February 2020. Only eight articles fulfilled the inclusion criteria and were used for data extraction. Five of the studies were cross-sectional studies while another three studies were interventional studies. Seven out of eight papers found a significant positive association between AS and CRP, and the correlation ranged from mild to moderate association (Pearson r = 0.33 to r = 0.624). In conclusion, inflammation is associated with increased PWV in patients with dyslipidemia. This supports the involvement of inflammation in the development of AS in dyslipidemia.

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.