Continuous Electrocardiography Research Articles

Post-operative atrial fibrillation after noncardiac surgery: diagnostic role of ambulatory rhythm monitoring for recurrent arrhythmia after hospital discharge

Abstract Introduction Postoperative atrial fibrillation (POAF) after noncardiac surgery constitutes 10-15% of all cases of incident atrial fibrillation (AF) in the community and has been associated with an increased risk of stroke. The risk of subsequent AF among patients with POAF is not well defined. Purpose To evaluate the role of systematic 30-day electrocardiographic (ECG) monitoring in the detection of AF recurrence after POAF. Methods In a prospective interventional study, patients who underwent major noncardiac surgeries and had new AF documented by ECG in the post-operative period between May 2022 and April 2023 were identified. For these patients, a 30-day ambulatory ECG monitor was recommended upon discharge, with final ordering deferred to the primary inpatient teams. Rates of recurrent AF of any duration detected by 30-day monitoring plus routine care versus routine care alone after the surgery were compared. Results Eighty-five patients with new-onset POAF were included (mean age 72 years, male 67%). Of these, 35 (41%) patients underwent up to 30 days [median 23 (IQR 6-27) days] of continuous ECG monitoring after hospital discharge. There were no significant differences in baseline characteristics between patients who did or did not undergo monitoring (Table 1). During median 281 (IQR 197-385) days of follow-up, recurrent AF was documented in 14/35 (40%) patients in the monitoring group as opposed to 7/50 (14%) patients in the usual care group (log-rank p=0.003, Figure 1). The median time from day of surgery until documented AF recurrence was 25 (IQR 6-53) days in the monitoring group and 66 (IQR 25-145) in the usual care group. Overall, 81% of recurrent AF events in both groups were detected in the first 3 months after surgery. The median burden of AF in the cardiac monitoring group was 7% (IQR 1-15), with the longest AF event lasting a median of 6 (IQR 2-18) hours. Anticoagulation for AF was prescribed in 24/64 (37%) patients with POAF without recurrence and in 16/21 (76%) patients with recurrent AF. Conclusion Recurrent AF following POAF is common and detected most frequently in the first 3 months after noncardiac surgery. Systematic ambulatory rhythm monitoring is associated with a higher rate of AF detection following hospital discharge and may identify a patient subgroup who might benefit from anticoagulation therapy.Table 1Figure 1

Continuous peripheral electrical nerve stimulation improves cardiac function via autonomic nerve regulation in MI rats

BackgroundPeripheral electrical nerve stimulation (PENS) reportedly improves cardiac function after myocardial ischemia (MI) by rebalancing the cardiac autonomic nervous system. The dynamic and continuous influence of PENS on autonomic and cardiac functioning based on cardiac self-repair is not well understood. ObjectivesThis study aimed to explore the relationship between autonomic nervous balance and functional cardiac repair after MI and to clarify the optimal acupoint selection and time course for PENS. MethodsThe activities of the superior cervical cardiac sympathetic nerve and vagus nerve were recorded to reflect the autonomic tone directly. The Millar pressure-volume loop system was used for left ventricular diastolic and systolic function. Noninvasive continuous electrocardiography and echocardiography were performed to analyze heart rate, heart rate variability, and left ventricular function. The effect of continuous PENS (cPENS) or instant PENS (iPENS) on autonomic and cardiac indications was tested. ResultsSympathetic nerve activity and vagus nerve activity increased as compensatory self-regulation on days 7 and 14 post-MI, followed by an imbalance of autonomic tone and cardiac dysfunction on day 28. cPENS-PC6 maintained autonomic hyperexcitability, improved myocardial systolic and diastolic abilities, and reduced myocardial fibrosis on day 28 post-MI, whereas cPENS-ST36 had a limited effect. Both iPENS-PC6 and iPENS-ST36 improved the autonomic and cardiac function of rats in the cPENS groups. ConclusionRats showed autonomic fluctuations and cardiac dysfunction 28 days post-MI. cPENS produced sympathomimetic action to sustain cardiac self-compensation, but with acupoint specificity. On the basis of cPENS, iPENS evoked autonomic regulation and cardiac benefits without acupoint differentiation.

Effects of bradycardia, hypoxemia and early intubation on bronchopulmonary dysplasia in very preterm infants: An observational study

BackgroundBronchopulmonary dysplasia (BPD) is the most common pulmonary complication in preterm infants. ObjectivesThe study aimed to explore the effects of bradycardia, hypoxemia, and early intubation on BPD in very preterm infants. MethodsThis is a prospective observational cohort study. Preterm infants with a mean gestational age of 28.67 weeks were recruited from two level III neonatal intensive care units (NICUs) in Taiwan. Continuous electrocardiography was used to monitor heart rates and oxygen saturation (SpO2). Infants were monitored for heart rates of <100 beats per minute and SpO2 levels of <90 % lasting for 30 s. Generalized estimating equations were used to analyze the effects of bradycardia, hypoxemia, and early intubation on BPD in very preterm infants. Model fit was visually assessed using receiver operating characteristic curve analysis. ResultsBradycardia, hypoxemia, and early intubation significantly increased the odds of BPD among the preterm infants (N = 39) during NICU stay; the odds ratios for bradycardia, hypoxemia, and early intubation for BPD versus non-BPD were 1.058, 1.013, and 29.631, respectively (all p < 0.05). A model combining bradycardia, hypoxemia, and early intubation accurately predicted BPD development (area under the curve = 0.919). ConclusionsBradycardia, hypoxemia, and early intubation significantly increased the odds of BPD among very preterm infants during NICU stay. The model combining bradycardia, hypoxemia, and early intubation accurately predicted BPD development.

Evaluation of an algorithm-guided photoplethysmography for atrial fibrillation burden using a smartwatch.

Wearable devices based on the PPG algorithm can detect atrial fibrillation (AF) effectively. However, further investigation of its application on long-term, continuous monitoring of AF burden is warranted. The performance of a smartwatch with continuous photoplethysmography (PPG) and PPG-based algorithms for AF burden estimation was evaluated in a prospective study enrolling AF patients admitted to Beijing Anzhen Hospital for catheter ablation from September to November 2022. A continuous Electrocardiograph patch (ECG) was used as the reference device to validate algorithm performance for AF detection in 30-s intervals. A total of 578669 non-overlapping 30-s intervals for PPG and ECG each from 245 eligible patients were generated. An interval-level sensitivity of PPG was 96.3% (95% CI 96.2%-96.4%), and specificity was 99.5% (95% CI 99.5%-99.6%) for the estimation of AF burden. AF burden estimation by PPG was highly correlated with AF burden calculated by ECG via Pearson correlation coefficient (R2 = 0.996) with a mean difference of -0.59 (95% limits of agreement, -7.9% to 6.7%). The subgroup study showed the robust performance of the algorithm in different subgroups, including heart rate and different hours of the day. Our results showed the smartwatch with an algorithm-based PPG monitor has good accuracy and stability in continuously monitoring AF burden compared with ECG patch monitors, indicating its potential for diagnosing and managing AF.

Continuous Atrial Fibrillation Monitoring From Photoplethysmography: Comparison Between Supervised Deep Learning and Heuristic Signal Processing

BackgroundContinuous monitoring for atrial fibrillation (AF) using photoplethysmography (PPG) from smartwatches or other wearables is challenging due to periods of poor signal quality during motion or suboptimal wearing. As a result, many consumer wearables sample infrequently and only analyze when the user is at rest, which limits the ability to perform continuous monitoring or to quantify AF. ObjectivesThis study aimed to compare 2 methods of continuous monitoring for AF in free-living patients: a well-validated signal processing (SP) heuristic and a convolutional deep neural network (DNN) trained on raw signal. MethodsWe collected 4 weeks of continuous PPG and electrocardiography signals in 204 free-living patients. Both SP and DNN models were developed and validated both on holdout patients and an external validation set. ResultsThe results show that the SP model demonstrated receiver-operating characteristic area under the curve (AUC) of 0.972 (sensitivity 99.6%, specificity: 94.4%), which was similar to the DNN receiver-operating characteristic AUC of 0.973 (sensitivity 92.2, specificity: 95.5%); however, the DNN classified significantly more data (95% vs 62%), revealing its superior tolerance of tracings prone to motion artifact. Explainability analysis revealed that the DNN automatically suppresses motion artifacts, evaluates irregularity, and learns natural AF interbeat variability. The DNN performed better and analyzed more signal in the external validation cohort using a different population and PPG sensor (AUC, 0.994; 97% analyzed vs AUC, 0.989; 88% analyzed). ConclusionsDNNs perform at least as well as SP models, classify more data, and thus may be better for continuous PPG monitoring.

Noninvasive neuromodulation of subregions of the human insula differentially affect pain processing and heart-rate variability: a within-subjects pseudo-randomized trial.

The insula is an intriguing target for pain modulation. Unfortunately, it lies deep to the cortex making spatially specific noninvasive access difficult. Here, we leverage the high spatial resolution and deep penetration depth of low-intensity focused ultrasound (LIFU) to nonsurgically modulate the anterior insula (AI) or posterior insula (PI) in humans for effect on subjective pain ratings, electroencephalographic (EEG) contact heat-evoked potentials, as well as autonomic measures including heart-rate variability (HRV). In a within-subjects, repeated-measures, pseudo-randomized trial design, 23 healthy volunteers received brief noxious heat pain stimuli to the dorsum of their right hand during continuous heart-rate, electrodermal, electrocardiography and EEG recording. Low-intensity focused ultrasound was delivered to the AI (anterior short gyrus), PI (posterior longus gyrus), or under an inert Sham condition. The primary outcome measure was pain rating. Low-intensity focused ultrasound to both AI and PI similarly reduced pain ratings but had differential effects on EEG activity. Low-intensity focused ultrasound to PI affected earlier EEG amplitudes, whereas LIFU to AI affected later EEG amplitudes. Only LIFU to the AI affected HRV as indexed by an increase in SD of N-N intervals and mean HRV low-frequency power. Taken together, LIFU is an effective noninvasive method to individually target subregions of the insula in humans for site-specific effects on brain biomarkers of pain processing and autonomic reactivity that translates to reduced perceived pain to a transient heat stimulus.

Exercise-Induced Electrocardiography Changes in Pulmonary Arterial Hypertension

Cardiopulmonary exercise testing (CPET) is an important tool in assessing the functional status of patients with pulmonary arterial hypertension (PAH). During CPET, continuous electrocardiography (ECG) is used as a marker of exercise-induced ischemia or arrhythmia. We hypothesize that ECG changes with exercise may be an early indicator of clinical worsening in PAH and could predict adverse outcomes. Clinical, hemodynamic, and CPET data of 155 children and young adult patients with PAH who underwent CPET between 2012 and 2019 in our pulmonary hypertension (PH) center were included in this retrospective analysis. ECGs were analyzed for ST depressions and T-wave inversions, along with coincident hemodynamic data. These data were correlated with adverse outcomes divided into 2 categories: severe worsening (death or receiving lung transplant) and mild to moderate worsening (PAH medication escalation, hospitalization, shunt creation, or listing for lung transplant). The median age was 19years (range 7 to 40years), 69% were female, and the average follow-up time was 5years (range 1 to 8years). A total of 63 patients (41%) had at least 1 adverse outcome. A total of 39 patients (25%) demonstrated significant ST-T-wave changes with exercise. Patients with ST-T-wave changes were 20% more likely to die or need lung transplant than those without. The multiple linear regression found that ST-T-wave changes were a predictor of elevated mean pulmonary arterial pressure (mPAP) found on catheterization (R=0.489, p=0.003), although not of pulmonary vascular resistance index (R=-0.112, p=0.484). An mPAP of 55mm Hg was the most sensitive and specific point in identifying when ST-T-wave changes with exercise begin to appear. In conclusion, ST-T-wave changes on exercise ECG are significantly associated with adverse outcomes in PH in a medium-term follow-up study, and the presence of ST-T-wave changes correlates with higher mPAP. These ECG changes with exercise may be used as early indicators of clinical worsening in PH and predictors of adverse outcomes.

Hyperacute autonomic and cortical function recovery following cardiac arrest resuscitation in a rodent model.

There is a complex interaction between nervous and cardiovascular systems, but sparse data exist on brain-heart electrophysiological responses to cardiac arrest resuscitation. Our aim was to investigate dynamic changes in autonomic and cortical function during hyperacute stage post-resuscitation. Ten rats were resuscitated from 7-min cardiac arrest, as indicators of autonomic response, heart rate (HR), and its variability (HRV) were measured. HR was monitored through continuous electrocardiography, while HRV was assessed via spectral analysis, whereby the ratio of low-/high-frequency (LF/HF) power indicates the balance between sympathetic/parasympathetic activities. Cortical response was evaluated by continuous electroencephalography and quantitative analysis. Parameters were quantified at 5-min intervals over the first-hour post-resuscitation. Neurological outcome was assessed by Neurological Deficit Score (NDS, range 0-80, higher = better outcomes) at 4-h post-resuscitation. A significant increase in HR was noted over 15-30 min post-resuscitation (p < 0.01 vs.15-min, respectively) and correlated with higher NDS (rs = 0.56, p < 0.01). LF/HF ratio over 15-20 min was positively correlated with NDS (rs = 0.75, p < 0.05). Gamma band power surged over 15-30 min post-resuscitation (p < 0.05 vs. 0-15 min, respectively), and gamma band fraction during this period was associated with NDS (rs ≥0.70, p < 0.05, respectively). Significant correlations were identified between increased HR and gamma band power during 15-30 min (rs ≥0.83, p < 0.01, respectively) and between gamma band fraction and LF/HF ratio over 15-20 min post-resuscitation (rs = 0.85, p < 0.01). Hyperacute recovery of autonomic and cortical function is associated with favorable functional outcomes. While this observation needs further validation, it presents a translational opportunity for better autonomic and neurologic monitoring during early periods post-resuscitation to develop novel interventions.

157 Budget impact analysis of Holter monitors provision in an outpatient clinic

Abstract Background Outpatient clinic attendees (aged &amp;gt;64) commonly present with falls, dizziness, syncope and palpitations. The most common non-invasive investigation ordered includes continuous ambulatory electrocardiography monitoring, namely the Holter monitor. The clinic is outsourcing Holter monitor requests to the Cardiology Department, with a long waiting list. If the patient wishes the test to be done sooner in a private hospital, it costs between 160 to 295 euros, covered by the patient’s private healthcare insurance. Methods A budget analysis was carried out to further evaluate by provisioning 5 Holter monitors in the outpatient clinic to quicken patient turnover and reduce the cardiology department waiting list. The intervention scope was limited to the designated clinic of approximately 450 patients a month. The intervention is not for generating revenue for the clinic. The budget analysis doesn’t include sensitivity analysis from the best-case towards worst-case scenarios of Holter frequency usage and duration of Holter monitoring. The objectives of the proposed change are to lessen the turnaround time by 20% for the patients from being assessed until discharge from the clinic without having delayed investigation of the Holter monitor, to have a timely and accurate diagnosis of suspected arrhythmia and the appropriate management within the new intervention. Results The decision tree, utilising the Decision analytic modelling, resource identification, cost implication, estimated changes including 2-hour staff training, capital, year one to year five costs, potential cost savings year-on-year, cost-per-wear comparison against the private hospital provider, pre and post-intervention scenario analysis were constructed. Conclusion The budget impact analysis designed a simple cost calculator to add additional tests of Holter monitors that rely on the decision model approach. It shows a potential cost saving within a five-year horizon and increases the number of patients’ attendance by optimising patient turnover. Apart from the cost and organisation, there are other positive impacts towards financial and clinical areas, ensuring high-quality service for the population.

SRECG: ECG Signal Super-Resolution Framework for Portable/Wearable Devices in Cardiac Arrhythmias Classification

A combination of cloud-based deep learning (DL) al-gorithms with portable/wearable (P/W) devices has been devel-oped as a smart heath care system to support automatic cardiac arrhythmias (CAs) classification using electrocardiography (ECG). However, long-term and continuous ECG monitoring is challenging because of limitations of batteries and transmission bandwidth of P/W devices while incorporated with consumer elec-tronics (CE). A feasible approach to address this challenge is to decrease sampling rates. However, low sampling rates lead to low-resolution signals that hinder the CAs classification performance. In this study, we propose a DL-based ECG signal super-resolution framework (called SRECG) to enhance low-resolution ECG sig-nals by jointly considering the accuracies when applied to the DL-based high-resolution multiclass classifier (HMC) of CAs. In our experiments, we downsampled the ECG signals from the CPSC2018 dataset and evaluated their HMC accuracies with and without the SRECG. Experimental results show that SRECG can well improve the HMC accuracies as compared to traditional in-terpolation methods. Moreover, approximately half of the CAs classification accuracies of HMC were maintained within the en-hanced ECG signals by SRECG. The promising results confirm that SRECG can be suitably used to enhance low-resolution ECG signals from P/W devices with CE to improve their cloud-based HMC performances.

A comprehensive wireless neurological and cardiopulmonary monitoring platform for pediatrics.

Neurodevelopment in the first 10 years of life is a critical time window during which milestones that define an individual's functional potential are achieved. Comprehensive multimodal neurodevelopmental monitoring is particularly crucial for socioeconomically disadvantaged, marginalized, historically underserved and underrepresented communities as well as medically underserved areas. Solutions designed for use outside the traditional clinical environment represent an opportunity for addressing such health inequalities. In this work, we present an experimental platform, ANNE EEG, which adds 16-channel cerebral activity monitoring to the existing, USA FDA-cleared ANNE wireless monitoring platform which provides continuous electrocardiography, respiratory rate, pulse oximetry, motion, and temperature measurements. The system features low-cost consumables, real-time control and streaming with widely available mobile devices, and fully wearable operation to allow a child to remain in their naturalistic environment. This multi-center pilot study successfully collected ANNE EEG recordings from 91 neonatal and pediatric patients at academic quaternary pediatric care centers and in LMIC settings. We demonstrate the practicality and feasibility to conduct electroencephalography studies with high levels of accuracy, validated via both quantitative and qualitative metrics, compared against gold standard systems. An overwhelming majority of parents surveyed during studies indicated not only an overall preference for the wireless system, but also that its use would improve their children's physical and emotional health. Our findings demonstrate the potential for the ANNE system to perform multimodal monitoring to screen for a variety of neurologic diseases that have the potential to negatively impact neurodevelopment.

Skin‐Adherent Elastomer‐Hydrogel Patch for Continuous 12‐Lead Cardiac Ambulatory Monitoring during Physical Activities

AbstractContinuous electrocardiography (ECG) monitoring is a necessity to prevent the sudden occurrence of cardiac events and premature death. Wearable bioelectronics provides the opportunity to realize noninvasive 12‐lead ambulatory monitoring for cardiovascular disease (CVD) detection and diagnosis. This work introduces a 12‐lead ECG patch that eliminates the issues associated with compliance, skin damage, and user‐discomfort encountered in conventional ECG sensors. The patch is safe, stretchable, and skin‐adherent with an adaptable design that allows for user‐friendly ECG monitoring. These can be attributed to the unique 3‐bridge patch structure, embedded liquid metal circuitry, and the wet‐adhesive polyacrylamide‐polydopamine‐tannic acid (PAM‐PDA‐TA) hydrogel. The hydrogel displays improved wet adhesiveness and biosafety for long‐term usage on deforming skin. The patch can acquire clean and consistent ECG signals with a higher signal‐to‐noise (SNR) ratio compared to commercial electrodes during both static and dynamic monitoring. The outstanding performance of the patch ascertains its potential for daily continuous ECG monitoring and remote diagnosis.

Premature depolarisations in horses competing in United States Eventing Association and Fédération Equestre Internationale-sanctioned 3-day events.

Injuries and sudden death during the cross-country (XC) phase of eventing have raised interest in the frequency and types of cardiac arrhythmias occurring in these equine athletes. To characterise the frequency and types of rhythm disturbances and examine possible risk factors for premature depolarisations (PDs) occurring during the XC phase of United States Eventing Association (USEA) and Fédération Equestre Internationale (FEI)-sanctioned events. Prospective, cross-sectional study. Continuous electrocardiographic (ECG) recordings were obtained from horses prior to, during and immediately following the XC competition. Physiological rhythms pre-XC were included in the arrhythmia group for analysis. The frequency of PDs was calculated for all horses, as well as by division. PDs were categorised by complexity (singles, couplets, triplets, complex) and variably grouped for statistical analysis. Multiple logistic regression was used to identify risk factors for the presence of specific cardiac arrhythmia groupings during XC. PDs were identified in 42/75 horses (56% [45, 67]) during XC. Horses competing in the upper divisions of eventing had higher odds for having any PD during XC compared to the lower divisions (OR = 17.5 [4.3, 72.01], p = 0.006). The amount of time the heart rate (HR) was greater than 199 beats per minute (BPM) was associated with more complex arrhythmias (triplets, salvos and tachyarrhythmias) (OR = 1.01 [1.0, 1.02], p = 0.005). An arrhythmia at rest (physiological or PD) was associated with arrhythmia in the early recovery period (OR = 3.5 [1.1, 10.8], p = 0.03). Convenience sampling and technical challenges of continuous ECG recordings under competition settings limited the number of enrollments. PDs were seen in a high percentage of horses during the XC competition. Upper levels and time the HR was greater than 199 BPM were related to PD presence and complexity.

Clinical trial report: the electrocardiographic response to ajmaline provocation in healthy subjects

Abstract Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): British Heart Foundation The Robert Lancaster Memorial Fund sponsored by McColl’s Research Group Background The electrocardiographic (ECG) response to diagnostic ajmaline provocation (AP) testing has been studied extensively in clinical cohorts. However, the healthy ECG response has not been described. We undertook a trial examining ECG changes in response to AP in a cohort of systematically recruited asymptomatic Caucasian healthy subjects with no family history of sudden death and normal baseline ECG and echocardiogram. Methods Applicants responded to a national recruitment advertisement and completed an online medical questionnaire. Those fulfilling inclusion criteria were invited to undergo further evaluation with eligible subjects undergoing a diagnostic ajmaline challenge (1mg/kg, max. 100mg over 5 minutes). A continuous ECG was recorded in the standard and high right precordial lead (HRPL) position. Automated analysis of conventional and novel ECG measurements were made at baseline and at peak drug effect, which was defined as the point of maximum QRS duration (excluding precordial leads). Results One hundred healthy Caucasian subjects underwent AP. The mean age was 26.84 years (SD ± 8.01 years) and 52% were male. A drug induced type 1 Brugada pattern (DI-T1BP) was observed in 3/100 (3%) of the cohort. We performed a paired comparison of ECG measures at baseline versus peak drug effect (Table 1). AP had a similar effect on global QRS duration and global PR interval, with both increasing by 28%, mean ∆ 25.66ms and mean ∆ 43.36ms respectively. Changes in S wave parameters in lead II were pronounced, with a 97% increase in S wave duration and a 101% increase in S wave negative amplitude. ST-J point elevation in the anterior, inferior, and lateral regions was comparable, with a 57%, 51% and 57% increase in ST-J amplitude respectively. AP had a greater effect on cardiac conduction in females compared to males (Table 2). In contrast, changes in STJ point amplitude and combined and segmented QRST segment area were greater in males. Conclusion The healthy ECG response to AP elicits a pronounced effect on cardiac conduction, more so in females compared to males, whilst changes in STJ point amplitude and QRST area were greater in male subjects. The DI-T1BP is part of the healthy response to AP.

The efficacy of detecting arrhythmia is higher with 7-day continuous electrocardiographic patch monitoring than with 24-h Holter monitoring.

Detecting high-risk arrhythmia is important in diagnosing patients with palpitations. We compared the diagnostic accuracies of 7-day patch-type electrocardiographic (ECG) monitoring and 24-h Holter monitoring for detecting significant arrhythmias in patients with palpitations. This was a single-center prospective trial with 58 participants who presented with palpitations, chest pain or syncope. Outcomes were defined as the detection of any one of six arrhythmias, including supraventricular tachycardia (SVT), atrial fibrillation or atrial flutter lasting more than 30 s, pauses of more than 3 s, high-degree atrioventricular block, ventricular tachycardia (VT) >3 beats, or polymorphic VT/ventricular fibrillation. The McNemar test for paired proportions was used to compare arrhythmia detection rates. The overall arrhythmia detection rate was higher with 7-day ECG patch monitoring than with 24-h Holter monitoring (34.5% vs. 19.0%, p = .008). Compared with the use of 24-h Holter monitors, the use of 7-day ECG patch monitors was associated with higher detection of SVT (29.3% vs. 13.8%, p = .042). No serious adverse skin reactions were reported among the ECG patch-monitored participants. The results suggest that a 7-day patch-type continuous ECG monitor is more effective for the detection of supraventricular tachycardia than is a 24-h Holter monitor. However, the clinical significance of device detected arrhythmia should be consolidated.

PO-03-200 THE RESPONSE TO AJMALINE PROVOCATION IN HEALTHY SUBJECTS

The electrocardiographic (ECG) response to diagnostic ajmaline provocation (AP) testing has been studied extensively in clinical cohorts. However, the healthy ECG response has not been described. We undertook a trial examining ECG changes in response to AP in a cohort of systematically recruited asymptomatic Caucasian healthy subjects with no family history of sudden death and normal baseline ECG and echocardiogram. Applicants responded to a national recruitment advertisement and completed an online medical questionnaire. Those fulfilling inclusion criteria were invited to undergo further evaluation with eligible subjects undergoing a diagnostic ajmaline challenge (1mg/kg, max. 100mg over 5 minutes). A continuous ECG was recorded in the standard and high right precordial lead (HRPL) position. Automated analysis of conventional and novel ECG measurements were made at baseline and at peak drug effect, which was defined as the point of maximum QRS duration (excluding precordial leads). One hundred healthy Caucasian subjects underwent AP. The mean age was 26.84 years (SD ± 8.01 years) and 52% were male. A drug induced type 1 Brugada pattern (DI-T1BP) was observed in 3/100 (3%) of the cohort. We performed a paired comparison of ECG measures at baseline versus peak drug effect (Table 1). AP had a similar effect on global QRS duration and global PR interval, with both increasing by 28%, mean delta 25.66ms and mean delta 43.36ms respectively. Changes in S wave parameters in lead II were pronounced, with a 97% increase in S wave duration and a 101% increase in S wave negative amplitude. ST-J point elevation in the anterior, inferior, and lateral regions was comparable, with a 57%, 51% and 57% increase in ST-J amplitude respectively. AP had a greater effect on cardiac conduction in females compared to males (Figure 1). In contrast, changes in STJ point amplitude and combined and segmented QRST segment area were greater in males. The healthy ECG response to AP elicits a pronounced effect on cardiac conduction, more so in females compared to males, whilst changes in STJ point amplitude and QRST area were greater in male subjects. A DI-T1BP is part of the healthy response to AP.Tabled 1Table 1. Paired analysis of baseline and peak ajmaline effect ECG characteristicsECG CharacteristicsMean at baseline (SD)Mean at Peak Ajmaline Effect (SD)Mean Delta = peak - baseline (SD)% ChangeP value*Global QRS duration ms90.42 (10.59)116.06 (12.06)25.66 (11.98)28.38<0.01Global T wave duration ms210.48 (24.96)225.48 (25.53)15.00 (20.53)7.13<0.01Global PR interval ms153.14 (19.45)196.50 (25.10)43.36 (17.27)28.31<0.01Global QT interval ms408.66 (33.03)414.38 (23.70)5.72 (18.62)1.40<0.01Global RR interval ms958.39 (197.57)813.98 (130.64)-144.41 (154.18)-15.06<0.01Global P wave duration ms102.74 (10.82)121.78 (13.58)19.04 (15.38)18.53<0.01Precordial Tpeak to Tend interval ms75.39 (27.28)81.88 (29.30)6.49 (39.29)8.610.07Precordial QRS duration ms85.59 (8.89)107.69 (11.10)22.10 (8.34)25.82<0.01Precordial T wave duration ms174.48 (24.53)199.81 (26.12)25.33 (26.33)15.00<0.01Anterior STJ amplitude uV47.97 (31.20)75.55 (48.44)27.58 (27.70)57.49<0.01Inferior STJ amplitude uV24.06 (21.97)36.46 (36.96)12.40 (26.33)51.54<0.01Lateral STJ amplitude uV34.45 (21.15)54.33 (30.79)19.89 (18.84)57.74<0.01Precordial QRS area mv/ms-409.59 (242.18)-613.71 (367.56)-204.12 (183.69)48.78<0.01Precordial QRST area mv/ms1481.06 (508.03)1838.87 (681.75)357.82 (278.89)24.32<0.01Precordial T wave area mv/ms483.66 (394.14)606.11 (453.04)122.45 (225.60)25.00<0.01Precordial STJ to Tpeak area mv/ms505.59 (230.36)543.71 (228.57)38.12 (103.28)8.00<0.01Precordial Tpeak to Tend area mv/ms258.31 (110.68)311.07 (147.60)52.76 (74.02)19.23<0.01S wave duration in lead I ms21.53 (15.55)36.01 (19.35)14.48 (14.07)67.25<0.01S wave duration in lead II ms17.34 (14.50)34.24 (20.33)16.90 (14.13)97.46<0.01S wave amplitude in lead I uV-189.09 (172.35)-290.47 (234.30)-110.38 (120.50)61.29<0.01S wave amplitude lead II uV-147.23 (197.92)-298.25 (255.25)-150.02 (155.93)101.89<0.01Inferior J wave amplitude uV43.31 (92.62)25.69 (57.06)-17.62 (68.55)-40.680.01Lateral J wave amplitude uV19.65 (41.36)10.18 (30.62)-9.47 (42.11)-48.190.03Anterior J wave amplitude uV0.77 (4.41)2.31 (7.42)1.55 (6.42)201.290.02 Open table in a new tab

Evaluation of premature ventricular complexes during in-hospital ECG monitoring as a predictor of ventricular tachycardia in an intensive care unit cohort.

In-hospital electrocardiographic (ECG) monitors are typically configured to alarm for premature ventricular complexes (PVCs) due to the potential association of PVCs with ventricular tachycardia (VT). However, no contemporary hospital-based studies have examined the association of PVCs with VT. Hence, the benefit of PVC monitoring in hospitalized patients is largely unknown. This secondary analysis used a large PVC alarm data set to determine whether PVCs identified during continuous ECG monitoring were associated with VT, in-hospital cardiac arrest (IHCA), and/or death in a cohort of adult intensive care unit patients. Six PVC types were examined (i.e., isolated, bigeminy, trigeminy, couplets, R-on-T, and run PVCs) and were compared between patients with and without VT, IHCA, and/or death. Of 445 patients, 48 (10.8%) had VT; 11 (2.5%) had IHCA; and 49 (11%) died. Isolated and run PVC counts were higher in the VT group (p = 0.03 both), but group differences were not seen for the other four PVC types. The regression models showed no significant associations between any of the six PVC types and VT or death, although confidence intervals were wide. Due to thesmall number of cases, we were unable to test for associations between PVCs and IHCA. Our findings suggest that we should question the clinical relevance of activating PVC alarms as a forewarning of VT, and more work should be done with larger sample sizes. A more precise characterization of clinically relevant PVCs that might be associated with VT is warranted.

Impact of cognitive exertion on autonomic reactivity in individuals with persistent post-concussive symptoms (P7-1.010)

<h3>Objective:</h3> Examine the impact of cognitive exertion on autonomic reactivity in symptomatic and asymptomatic individuals with history of concussion and controls without history of concussion. <h3>Background:</h3> Following concussive head injuries, many individuals continue to experience physical, cognitive, and emotional symptoms that can persist for months or years. Recent studies suggest that concussive head injuries can also produce persistent dysfunction of the autonomic nervous system. However, it remains unclear if acute bouts of cognitive exertion moderate autonomic dysfunction in individuals with persistent post-concussion symptoms. <h3>Design/Methods:</h3> A cross-sectional design was used to investigate autonomic reactivity in 23 individuals without history of concussion (HC-) and 35 individuals with history of concussion, including 20 symptomatic (HCx-S) and 15 asymptomatic (HCx-A). Participants were classified based on clinical history and symptom reports obtained from a comprehensive questionnaire of their medical history and the Rivermead Post-Concussion Questionnaire (RPQ). Participants initially completed a seated, six-minute resting assessment with eyes open in the dimly lit room. They then completed a continuous reaching variant of the traditional Go/NoGo task. Continuous electrocardiography was recorded and utilized to compute time-domain metrics of heart rate variability (HRV) during the resting assessment and cognitive task. <h3>Results:</h3> HCx-S participants reported greater symptom burden on the RPQ and performed significantly worse on the Go/NoGo task compared to HC- and HCx-A participants. While HRV metrics failed to reveal any significant differences between HCx-S, HCx-A, and HC-participants during resting assessment (p’s &gt; 0.8), HCx-S participants exhibited significantly greater HRV than HCx-A and HC-participants during the Go/NoGo task (p’s &lt; 0.03). <h3>Conclusions:</h3> Increased HRV in HCx-S participants compared to HC- and HCx-A participants during the Go/NoGo task indicates that concussion may induce greater autonomic reactivity, characterized by higher levels of vagal/parasympathetic tone. This may reflect impairments in the capacity of the autonomic nervous system to efficiently adapt to situational demands. <b>Disclosure:</b> Dr. Moore has nothing to disclose. Taylor Marie Wynne has nothing to disclose. Dr. Broglio has received personal compensation in the range of $5,000-$9,999 for serving as a Consultant for MCW. Dr. Broglio has received personal compensation in the range of $0-$499 for serving as a Consultant for U Calgary. Dr. Broglio has received personal compensation in the range of $5,000-$9,999 for serving as an Expert Witness for Montgomery McCracken Walker &amp; Rhoads LLP. The institution of Dr. Broglio has received research support from DoD. The institution of Dr. Broglio has received research support from NCAA. The institution of Dr. Herter has received research support from Woodcock Institute. The institution of Dr. Herter has received research support from National Institutes of Health. The institution of Dr. Herter has received research support from National Institutes of Health. The institution of an immediate family member of Dr. Herter has received research support from Centers for Disease Control and Prevention.

Methods for analyzing infant heart rate variability: A preliminary study.

Heart rate (HR) and heart rate variability (HRV) reflect autonomic development in infants. To better understand the autonomic response in infants, reliable HRV recordings are vital, yet no protocol exists. The purpose of this paper is to present reliability of a common procedure for analysis from two different file types. In the procedure, continuous electrocardiograph recordings of 5-10 min are obtained at rest in infants at 1 month of age by using a Hexoskin Shirt-Junior's (Carre Technologies Inc., Montreal, QC, Canada). Electrocardiograph (ECG; .wav) and R-R interval (RRi; .csv) files are extracted. The RRi of the ECG signal is generated by VivoSense (Great Lakes NeuroTechnologies, Independence, OH). Two MATLAB (The MathWorks, Inc., Natick, MA) scripts converted files for analysis with Kubios HRV Premium (Kubios Oy, Kuopio, Finland). A comparison was made between RRi and ECG files for HR and HRV parameters, and then tested with t tests and correlations via SPSS. There are significant differences in root mean squared successive differences between recording types, with only HR and low-frequency measures significantly correlated together. Recording with Hexoskin and analysis with MATLAB and Kubios enable infant HRV analysis. Differences in outcomes exist between procedures, and standard methodology for infant HR analysis is needed.

Causal inference based cuffless blood pressure estimation: A pilot study

Enabled by wearable sensing, e.g., photoplethysmography (PPG) and electrocardiography (ECG), and machine learning techniques, study on cuffless blood pressure (BP) measurement with data-driven methods has become popular in recent years. However, causality has been overlooked in most of current studies. In this study, we aim to examine the feasibility of causal inference for cuffless BP estimation. We first attempt to detect wearable features that are causally related, rather than correlated, to BP changes by identifying causal graphs of interested variables with fast causal inference (FCI) algorithm. With identified causal features, we then employ time-lagged link to integrate the mechanism of causal inference into the BP estimated model. The proposed method was validated on 62 subjects with their continuous ECG, PPG and BP signals being collected. We found new causal features that can better track BP changes than pulse transit time (PTT). Further, the developed causal-based estimation model achieved an estimation error of mean absolute difference (MAD) being 5.10 mmHg and 2.85 mmHg for SBP and DBP, respectively, which outperformed traditional model without consideration of causality. To the best of our knowledge, this work is the first to study the causal inference for cuffless BP estimation, which can shed light on the mechanism, method and application of cuffless BP measurement.