Adapting detection sensitivity based on evidence of irregular sinus arrhythmia to improve atrial fibrillation detection in insertable cardiac monitors.

Aims: Intermittent change in p-wave discernibility during periods of ectopy and sinus arrhythmia is a cause of inappropriate atrial fibrillation (AF) detection in insertable cardiac monitors (ICM). To address this, we developed and validated an enhanced AF detection algorithm. Methods and results: Atrial fibrillation detection in Reveal LINQ ICM uses patterns of incoherence in RR intervals and absence of P-wave evidence over a 2-min period. The enhanced algorithm includes P-wave evidence during RR irregularity as evidence of sinus arrhythmia or ectopy to adaptively optimize sensitivity for AF detection. The algorithm was developed and validated using Holter data from the XPECT and LINQ Usability studies which collected surface electrocardiogram (ECG) and continuous ICM ECG over a 24-48 h period. The algorithm detections were compared with Holter annotations, performed by multiple reviewers, to compute episode and duration detection performance. The validation dataset comprised of 3187 h of valid Holter and LINQ recordings from 138 patients, with true AF in 37 patients yielding 108 true AF episodes ≥2-min and 449 h of AF. The enhanced algorithm reduced inappropriately detected episodes by 49% and duration by 66% with <1% loss in true episodes or duration. The algorithm correctly identified 98.9% of total AF duration and 99.8% of total sinus or non-AF rhythm duration. The algorithm detected 97.2% (99.7% per-patient average) of all AF episodes ≥2-min, and 84.9% (95.3% per-patient average) of detected episodes involved AF. Conclusion: An enhancement that adapts sensitivity for AF detection reduced inappropriately detected episodes and duration with minimal reduction in sensitivity.

Non-Contact, Simple Neonatal Monitoring by Photoplethysmography.

This paper presents non-contact vital sign monitoring in neonates, based on image processing, where a standard color camera captures the plethysmographic signal and the heart and breathing rates are processed and estimated online. It is important that the measurements are taken in a non-invasive manner, which is imperceptible to the patient. Currently, many methods have been proposed for non-contact measurement. However, to the best of the authors' knowledge, it has not been possible to identify methods with low computational costs and a high tolerance to artifacts. With the aim of improving contactless measurement results, the proposed method based on the computer vision technique is enhanced to overcome the mentioned drawbacks. The camera is attached to an incubator in the Neonatal Intensive Care Unit and a single area in the neonate's diaphragm is monitored. Several factors are considered in the stages of image acquisition, as well as in the plethysmographic signal formation, pre-filtering and filtering. The pre-filter step uses numerical analysis techniques to reduce the signal offset. The proposed method decouples the breath rate from the frequency of sinus arrhythmia. This separation makes it possible to analyze independently any cardiac and respiratory dysrhythmias. Nine newborns were monitored with our proposed method. A Bland-Altman analysis of the data shows a close correlation of the heart rates measured with the two approaches (correlation coefficient of 0.94 for heart rate (HR) and 0.86 for breath rate (BR)) with an uncertainty of 4.2 bpm for HR and 4.9 for BR (k = 1). The comparison of our method and another non-contact method considered as a standard independent component analysis (ICA) showed lower central processing unit (CPU) usage for our method (75% less CPU usage).

Serum interleukin-6: Association with circulating cytokine serum levels in patients with sinus arrhythmia and patients with coronary artery disease.

In this study, we were focused on the differences between certain circulating cytokine levels in patients with or without sinus arrhythmia, according to the median IL-6 level. All patients were stable with regards to symptoms and therapy for at least one month prior to the measurements conducted within this study.Exclusion criteria were: patients with sleep apnea, asthma, respiratory insufficiency of any genesis, active infection, allergy, inflammatory diseases, cancer, diabetes of any type and treatment with anti-inflammatory drugs. The study was approved by the Institutional Review Board. All recruited patients gave their verbal and written consent for participation in the study. The study group consisted of 74 patients divided into two groups: with (38) and without sinus arrhythmia but with diagnosed coronary artery disease (36). Sinus arrhythmia was confirmed by 24h Holter monitoring. From all test parameters only cytokines IL-2, IL-8, IL-10, IL-17 and IL-18, showed statistically significant increasing in patients with statistically higher IL-6 levels. It is possible that IL-6 may not be a marker for the selection of patients with sinus arrhythmia or coronary artery disease. The findings indicate that IL-6 represents a reliable indicator for increased expression of IL-2, IL-8, IL-10, IL-17 and IL-18 in patients with sinus arrhythmia or coronary artery disease. Further studies in a large number of patients would be necessary to confirm our observations.

ECG Of The Month: Sepsis, ARDS, and Tracheal Intubation.

A furuncle on the leg of a 23-year-old woman led to methicillin-resistant staphylococcus aureus sepsis and adult respiratory distress syndrome (ARDS) requiring tracheal intubation in the intensive care unit (ICU). Initially her electrocardiograms (ECGs) showed sinus tachycardia, but otherwise were unchanged from prior ECGs. A week into her ICU stay a different rhythm occurred.

Accuracy of the OMRON HEM-7361T blood pressure monitor in the differentiation between atrial fibrillation and sinus rhythm.

OBJECTIVE: We investigated the accuracy of the OMRON HEM-7361T automated oscillometric blood pressure (BP) monitor in the differentiation between atrial fibrillation and sinus rhythm. METHODS: An approximately equal number of patients with persistent atrial fibrillation and individuals with sinus rhythm were recruited from outpatients and inpatients of Ruijin Hospital, Shanghai, China. BP was measured three times consecutively with a 30-s interval with the OMRON HEM-7361T automatic electronic BP monitor for atrial fibrillation detection. A hand-held single lead electrocardiogram device was used for simultaneous electrocardiogram recordings. RESULTS: The device accurately identified atrial fibrillation in 100 (99.0%) of the 101 patients, with only 1 patient incorrectly classified as non-atrial fibrillation. The device correctly identified 99 (95.2%) of the 104 participants with sinus rhythm as non-atrial fibrillation, with five participants incorrectly classified as atrial fibrillation. The device had a positive predictive value of 95.2%, negative predictive value of 99.0%, and overall accuracy of 97.1%. Among the six misclassified participants, one with atrial fibrillation had a heart rate of 65 beats/min, and four of the five participants with sinus rhythm had cardiac arrhythmias (atrial or ventricular premature beat in one participants, sinus tachycardia in one participant, and both arrhythmias in one participant). CONCLUSION: The OMRON HEM-7361T BP monitor is accurate in the differentiation between atrial fibrillation and sinus rhythm. Whether the device is sufficiently accurate in the differentiation between atrial fibrillation and other cardiac arrhythmias remains under investigation.

"But for the blind spot": Accuracy and diagnostic performance of smart watch cardiac features in pediatric patients.

BACKGROUND: The Apple Watch™ (AW) offers heart rate (HR) tracking by photoplethysmography (PPG) and single-lead electrocardiographic (ECG) recordings. The accuracy of AW-HR and diagnostic performance of AW-ECGs among children during both sinus rhythm and arrhythmias have not been explored. OBJECTIVE: The purposes of this study were to assess the accuracy of AW-HR measurements compared to gold standard modalities in children during sinus rhythm and arrhythmias and to identify non-sinus rhythms using AW-ECGs. METHODS: Subjects ≤18 years wore an AW during (1) telemetry admission, (2) electrophysiological study (EPS), or (3) exercise stress test (EST). AW-HRs were compared to gold standard modality values. Recorded AW-ECGs were reviewed by 3 blinded pediatric electrophysiologists. RESULTS: Eighty subjects (median age 13 years; interquartile range 1.0-16.0 years; 50% female) wore AW (telemetry 41% [n = 33]; EPS 34% [n = 27]; EST 25% [n = 20]). A total of 1090 AW-HR measurements were compared to time-synchronized gold standard modality HR values. Intraclass correlation coefficient (ICC) was high 0.99 (0.98-0.99) for AW-HR during sinus rhythm compared to gold standard modalities. ICC was poor comparing AW-HR to gold standard modality HR in tachyarrhythmias (ICC 0.24-0.27) due to systematic undercounting of AW-HR values. A total of 126 AW-ECGs were reviewed. Identification of non-sinus rhythm by AW-ECG showed sensitivity of 89%-96% and specificity of 78%-87%. CONCLUSIONS: We found high levels of agreement for AW-HR values with gold standard modalities during sinus rhythm and poor agreement during tachyarrhythmias, likely due to hemodynamic effects of tachyarrhythmias on PPG-based measurements. AW-ECGs had good sensitivity and moderate specificity in identification of non-sinus rhythm in children.

Parasympathetic nervous system activity and children's sleep.

We examined indices of children's parasympathetic nervous system activity (PNS), including respiratory sinus arrhythmia during baseline (RSAB) and RSA reactivity (RSAR), to a laboratory challenge, and importantly the interaction between RSAB and RSAR as predictors of multiple parameters of children's sleep. Lower RSAR denotes increased vagal withdrawal (reductions in RSA between baseline and task) and higher RSAR represents decreased vagal withdrawal or augmentation (increases in RSA between baseline and task). A community sample of school-attending children (121 boys and 103 girls) participated [mean age = 10.41 years; standard deviation (SD) = 0.67]. Children's sleep parameters were examined through actigraphy for 7 consecutive nights. Findings demonstrate that RSAB and RSAR interact to predict multiple sleep quality parameters (activity, minutes awake after sleep onset and long wake episodes). The overall pattern of effects illustrates that children who exhibit more disrupted sleep (increased activity, more minutes awake after sleep onset and more frequent long wake episodes) are those with lower RSAB in conjunction with lower RSAR. This combination of low RSAB and low RSAR probably reflects increased autonomic nervous system arousal, which interferes with sleep. Results illustrate the importance of individual differences in physiological regulation indexed by interactions between PNS baseline activity and PNS reactivity for a better understanding of children's sleep quality.

The ventriculophasic response: relationship to sinus arrhythmia and the duration of interposed QRS complexes.

BACKGROUND: The ventriculophasic response (VR) refers to shortening of sinus cycle length during heart block when a QRS complex is interposed between 2 P waves. Our purpose was to analyze its relationship to respiratory sinus arrhythmia (SA) and to compare VR in relation to paced versus intrinsic QRS complexes. METHODS: Patients with advanced heart block had their pacer devices temporarily programmed to ventricular inhibited mode at 30 ppm. In 35 subjects, we analyzed VR and SA before, during and after 3 cycles of deep breathing. In 16 other patients we compared VR in the presence of paced versus narrower intrinsic QRS complexes. RESULTS: The magnitude of P-P interval shortening surrounding QRS complexes during inspiration correlated with SA (r = 0.36, P = 0.03). The prevalence of VR increased from 37% at baseline to 77% of subjects during deep breathing (P = 0.02). The mean P-P interval shortening was greater surrounding intrinsic QRS complexes than paced QRS complexes (3.6 ± 3.6% vs. 1.4 ± 1.1%, P = 0.02). The prevalence of VR increased from 25% during paced rhythm to 56% when intrinsic complexes were present. CONCLUSION: VR, like SA, increases with deep breathing and likely reflects intact parasympathetic nervous system function. Its increase in the presence of narrower beats suggests it may reflect ventricular synchrony.

Incoherent oscillations of respiratory sinus arrhythmia during acute mental stress in humans.

Respiratory sinus arrhythmia (RSA) has been widely used as a measure of the cardiac vagal control in response to stress. However, RSA seems not to be a generalized indicator because of its dependency on respiratory parameter and individual variations of RSA amplitude (A(RSA)). We hypothesized that phase-lag variations between RSA and respiration may serve as a normalized index of the degree of mental stress. Twenty healthy volunteers performed mental arithmetic task (ART) after 5 min of resting control followed by 5 min of recovery. Breathing pattern, beat-to-beat R-R intervals, and blood pressure (BP) were determined using inductance plethysmography, electrocardiography, and a Finapres device, respectively. The analytic signals of breathing and RSA were obtained by Hilbert transform and the degree of phase synchronization (λ) was quantified. With the use of spectral analysis, heart rate variability (HRV) was estimated for the low-frequency (LF) and high-frequency (HF) bands. A steady-state 3-min resting period (REST), the first 3 min (ART1), and the last 3 min (ART2) of the ART period (ranged from 6- to 19 min) and the last 3 min of the recovery period (RCV) were analyzed separately. Heart rate, systolic BP, and breathing frequency (f(R)) increased and λ, A(RSA), and HF power decreased from REST to ART (P < 0.01). The λ was correlated with normalized A(RSA) and the HF power. The decrease in λ could not be explained solely by the increase in f(R). We conclude that mental stress exerts an influence on RSA oscillations, inducing incoherent phase lag with respect to breathing, in addition to a decrease in RSA.

Atrial fibrillation or flutter on initial electrocardiogram is associated with worse outcomes in patients admitted for worsening heart failure with reduced ejection fraction: findings from the EVEREST Trial.

BACKGROUND: Heart failure (HF) complicated by atrial fibrillation/flutter (AF/AFL) is associated with worse outcomes. However, the clinical profile and outcomes of patients following hospitalization for HF with AF/AFL on initial electrocardiogram (ECG) has not been well studied. METHODS: EVEREST was a randomized trial of vasopressin-2 receptor blockade, in addition to standard therapy, in 4133 patients hospitalized with HF with ejection fraction ≤40%. A post hoc analysis was performed comparing the clinical characteristics and outcomes [all-cause mortality and cardiovascular mortality/HF hospitalization] of patients with AF/AFL versus sinus rhythm (SR) on baseline ECG, which were centrally analyzed. Times to events were compared using log-rank tests and Cox regression models. RESULTS: Of the 4133 patients, 1195 (29%) were classified with AF/AFL and 2071(50%) with SR. The remaining patients (21%) were excluded because ECGs were unavailable (n = 106), rhythm was paced (n = 727), or junctional/other supraventricular (n = 34). AF/AFL patients were older, with increased weight, faster heart rate, higher blood urea nitrogen, and natriuretic peptide levels compared to SR patients. Anticoagulation was prescribed in 67% of AF/AFL patients on discharge. AF/AFL patients were less likely to receive ß-blockers or angiotensin-converting enzyme inhibitors/angiotensin receptor blockers (all P < .05). After risk adjustment, AF/AFL was associated with increased mortality (hazard ratio 1.23; 95% CI, 1.04-1.46) and cardiovascular mortality/HF hospitalization (hazard ratio 1.26; 95% CI, 1.07-1.47). CONCLUSION: AF/AFL on initial ECG in patients hospitalized with HF with reduced ejection fraction is associated with lower use of evidence-based therapies and increased mortality and rehospitalization compared to patients in SR.

Trajectories of children's internalizing symptoms: the role of maternal internalizing symptoms, respiratory sinus arrhythmia and child sex.

BACKGROUND: We assessed trajectories of children's internalizing symptoms as predicted by interactions among maternal internalizing symptoms, respiratory sinus arrhythmia (RSA) and child sex. METHOD: An ethnically and socioeconomically diverse sample of children (n = 251) participated during three study waves. Children's mean ages were 8.23 years (SD = 0.72) at T1, 9.31 years (SD = 0.79) at T2 and 10.28 years (SD = 0.99) at T3. RESULTS: Multiple-indicator multilevel latent growth analyses showed maternal internalizing symptoms interacted with child RSA and sex to predict children's internalizing symptoms. Girls with higher RSA whose mothers had lower levels of internalizing symptoms showed the steepest decline in internalizing symptoms across time. Girls with lower RSA whose mothers had higher levels of internalizing symptoms showed the highest levels of internalizing symptoms at T3, whereas boys with higher RSA whose mothers had higher levels of internalizing symptoms showed the highest levels of internalizing symptoms at T3. CONCLUSIONS: Findings build on this scant literature and support the importance of individual differences in children's physiological regulation in the prediction of psychopathology otherwise associated with familial risk.

[Wavelet analysis for electrocardiogram variation of arrhythmia patients].

To explore the energy proportion of the QRS complexes in the electrocardiogram (ECG), a new method, wavelet analysis, has been presented. Using wavelet transform of ECG, we can calculate the energy proportion of QRS complexes in multiple scales. The electrocardiograms (ECGs) were used as the experimental data, which were collected from a young (21-34 yr) group and an elderly (68-81 yr) group of healthy subjects, as well as from a group of arrhythmia patients (66-81 yr). the data analysis was performed with the energy proportion of the QRS complexes in the ECG using Mexican-Hat as a mother wavelet in multiple scales. Results showed that the energy proportion of the QRS complexes had no changes with ages increasing (P > 0.44), but in the same age group, the arrhythmia patients' energy proportion of the QRS complexes near 17Hz are obviously less than that in the healthy group (P < 0.01), so the energy proportion of the QRS complexes calculated by wavelet analysis can be used as a feature index to judge whether a person is a sinus arrhythmia patient or not.

Symptomatic 5-fluorouracil-induced sinus bradycardia.

5-Fluorouracil (5-FU) is a commonly used anti-neoplastic agent. 5-FU has been not uncommonly associated with cardiotoxicity, although the many potentially causative mechanisms are yet to be established. Here, we present the case of a 61-year-old gemstone miner who developed symptomatic sinus bradycardia while receiving a continuous 5-FU infusion combined with radiotherapy for locally advanced rectal cancer. This dysrhythmia is an unusual type of 5-FU toxicity, our case being the second described. We review the actions of 5-FU and the various proposed mechanisms of its cardiotoxic effects.

Resumption of sinus rhythm from fetal complete atrioventricular block after maternally administered ritodrine.

Reports have indicated that maternal administration of ritodrine increased the ventricular rate and thus ameliorated signs of heart failure in a fetus with complete atrioventricular block (CAVB). A fetus from a mother without the anti-SS-A/SS-B antibody had CAVB, with atrial rate 148-154 bpm and ventricular rate 53-57 bpm. After maternal administration of ritodrine, the ventricular rate increased to 60-65 bpm, and then sinus rhythm resumed. Ritodrine may not only increase the ventricular rate but also induce sinus rhythm in a fetus with CAVB.

Model-Based Evaluation of Methods for Respiratory Sinus Arrhythmia Estimation.

OBJECTIVE: Respiratory sinus arrhythmia (RSA) refers to heart rate oscillations synchronous with respiration, and it is one of the major representations of cardiorespiratory coupling. Its strength has been suggested as a biomarker to monitor different conditions, and diseases. Some approaches have been proposed to quantify the RSA, but it is unclear which one performs best in specific scenarios. The main objective of this study is to compare seven state-of-the-art methods for RSA quantification using data generated with a model proposed to simulate, and control the RSA. These methods are also compared, and evaluated on a real-life application, for their ability to capture changes in cardiorespiratory coupling during sleep. METHODS: A simulation model is used to create a dataset of heart rate variability, and respiratory signals with controlled RSA, which is used to compare the RSA estimation approaches. To compare the methods objectively in real-life applications, regression models trained on the simulated data are used to map the estimates to the same measurement scale. Results, and conclusion: RSA estimates based on cross entropy, time-frequency coherence, and subspace projections showed the best performance on simulated data. In addition, these estimates captured the expected trends in the changes in cardiorespiratory coupling during sleep similarly. SIGNIFICANCE: An objective comparison of methods for RSA quantification is presented to guide future analyses. Also, the proposed simulation model can be used to compare existing, and newly proposed RSA estimates. It is freely accessible online.