Wrist band photoplethysmography in detection of individual pulses in atrial fibrillation and algorithm-based detection of atrial fibrillation.

AIMS: Atrial fibrillation (AF) is the most common tachyarrhythmia and a significant cause of cardioembolic strokes. Atrial fibrillation is often intermittent and asymptomatic making detection a major clinical challenge. We evaluated a photoplethysmography (PPG) wrist band in individual pulse detection in patients with AF and tested the reliability of two commonly used algorithms for AF detection. METHODS AND RESULTS: A 5-min PPG was recorded from patients with AF or sinus rhythm (SR) with a wrist band and analysed with two AF detection algorithms; AFEvidence and COSEn. Simultaneously registered electrocardiogram served as the golden standard for rhythm analysis and was interpreted by two cardiologists. The study population consisted of 213 (106 AF, 107 SR) patients. The wrist band PPG achieved individual pulse detection with a sensitivity of 91.7 ± 11.2% and a positive predictive value (PPV) of 97.5 ± 4.6% for AF, with a sensitivity of 99.4 ± 1.5% [7.7% (95% confidence interval, 95% CI 5.5% to 9.9%); P < 0.001] and PPV of 98.1 ± 4.1% [0.6% (95% CI -0.6% to 1.7%); P = 0.350] for SR. The pulse detection sensitivity was lower 86.7 ± 13.9% with recent-onset AF (AF duration <48 h, n = 43, 40.6%) as compared to late AF (≥48 h, n = 63, 59.4%) with 95.1 ± 7.2% [-8.3% (95% CI -12.9% to -3.7%); P = 0.001]. For the detection of AF from the wrist band PPG, the sensitivities were 96.2%/95.3% and specificity 98.1% with two algorithms. CONCLUSION: The wrist band PPG enabled accurate algorithm-based detection of AF with two AF detection algorithms and high individual pulse detection. Algorithms allowed accurate detection of AF from the PPG. A PPG wrist band provides an easy solution for AF screening.

The effects of views of nature on autonomic control.

Previously studies have shown that nature improves mood and self-esteem and reduces blood pressure. Walking within a natural environment has been suggested to alter autonomic nervous system control, but the mechanisms are not fully understood. Heart rate variability (HRV) is a non-invasive method of assessing autonomic control and can give an insight into vagal modulation. Our hypothesis was that viewing nature alone within a controlled laboratory environment would induce higher levels of HRV as compared to built scenes. Heart rate (HR) and blood pressure (BP) were measured during viewing different scenes in a controlled environment. HRV was used to investigate alterations in autonomic activity, specifically parasympathetic activity. Each participant lay in the semi-supine position in a laboratory while we recorded 5 min (n = 29) of ECG, BP and respiration as they viewed two collections of slides (one containing nature views and the other built scenes). During viewing of nature, markers of parasympathetic activity were increased in both studies. Root mean squared of successive differences increased 4.2 ± 7.7 ms (t = 2.9, p = 0.008) and natural logarithm of high frequency increased 0.19 ± 0.36 ms(2) Hz(-1) (t = 2.9, p = 0.007) as compared to built scenes. Mean HR and BP were not significantly altered. This study provides evidence that autonomic control of the heart is altered by the simple act of just viewing natural scenes with an increase in vagal activity.

Dynamic modeling of respiratory sinus arrhythmia component from HRV with multivariate Kalman smoother.

The estimates of heart rate variability (HRV) low frequency (LF) and high frequency (HF) components with constant frequency bands may distort when the frequency of respiratory sinus arrhythmia induced HF component approaches the LF-HF frequency limit. In this study we present a method for dynamically estimating the LF-HF limit and dividing the spectrum to LF and HF components that can overlap. The method is based on multivariate autoregressive model which is solved dynamically with Kalman smoother algorithm. The spectra of each individual pole with all the zeros are calculated and then multiplied with a Hanning window on the pole frequency. These spectra are summed to LF or HF components. The method was applied to three subjects whose electrocardiogram and respiration was recorded during a controlled breathing protocol. The results show that the HF component power increases when breathing frequency decreases. Also the component powers obtained with the presented method are reliable even when LF and HF frequencies are close to each other.

Cerebral cortex and sub-cortex lateralization in cardiovascular regulation: correlations of BOLD fMRI and heart rate variability.

The role of cerebral cortex in cardiovascular regulation has not yet been mapped in detail. Especially the lateralization of different regions that are connected to cardiovascular modulation is still unknown. In this study we used simultaneously measured electrocardiography (ECG) and blood oxygen level dependent (BOLD) fMRI to examine the correlation of cerebral cortex and sub-cortex activation and heart rate variability parameters. Correlations were calculated for 11 subjects. Regions of interest (ROIs) were predefined from observations made in previous studies. Lateralization was studied by forming ratios of left and right hemisphere activations in ROIs and calculating correlations of these to heart rate variability (HRV) parameters. Statistically significant correlations were found in every ROI.