Heart rate variability and early recurrence of atrial fibrillation after electrical cardioversion

Artificial-intelligence-based risk prediction and mechanism discovery for atrial fibrillation using heart beat-to-beat intervals

BACKGROUND

Early diagnosis of atrial fibrillation (AF) is important for preventing stroke and other complications. Predicting AF risk in advance can improve early diagnostic efficiency. Deep learning has been used for disease risk prediction; however, it lacks adherence to evidence-based medicine standards. Identifying the underlying mechanisms behind disease risk prediction is important and required.

METHODS

We developed an explainable deep learning model called HBBI-AI to predict AF risk using only heart beat-to-beat intervals (HBBIs) during sinus rhythm. We proposed a possible AF mechanism based on the model's explainability and verified this conjecture using confirmed AF risk factors while also examining new AF risk factors. Finally, we investigated the changes in clinicians' ability to predict AF risk using only HBBIs before and after learning the model's explainability.

FINDINGS

HBBI-AI consistently performed well across large in-house and external public datasets. HBBIs with large changes or extreme stability were critical predictors for increased AF risk, and the underlying cause was autonomic imbalance. We verified various AF risk factors and discovered that autonomic imbalance was associated with all these factors. Finally, cardiologists effectively understood and learned from these findings to improve their abilities in AF risk prediction.

CONCLUSIONS

HBBI-AI effectively predicted AF risk using only HBBI information through evaluating autonomic imbalance. Autonomic imbalance may play an important role in many risk factors of AF rather than in a limited number of risk factors.

FUNDING

This study was supported in part by the National Key R&D Program and the National Natural Science Foundation of China.

Skin sympathetic nerve activity in different ablation settings for atrial fibrillation

BACKGROUND

Modifying the autonomic system after catheter ablation may prevent the recurrence of atrial fibrillation (AF). Evaluation of skin sympathetic nerve activity (SKNA) is a noninvasive method for the assessment of sympathetic activity. However, there are few studies on the effects of different energy settings on SKNA.

OBJECTIVE

To investigate the changes in SKNA in different energy settings and their relationship to AF ablation outcomes.

METHODS

Seventy-two patients with paroxysmal and persistent AF were enrolled. Forty-three patients received AF ablation with the conventional (ConV) energy setting (low power for long duration), and 29 patients using a high-power, short-duration (HPSD) strategy. The SKNA was acquired from the right arm 1 day before and after the radiofrequency ablation. We analyzed the SKNA and ablation outcomes in the different energy settings.

RESULTS

Both groups had a similar baseline average SKNA (aSKNA). We found that the median aSKNA increased significantly from 446.82 μV to 805.93 μV (p = 0.003) in the ConV group but not in the HPSD group. In the ConV group, patients without AF recurrence had higher aSKNA values. However, the 1-year AF recurrence rate remained similar between both groups (35 % vs. 28 %, p = 0.52).

CONCLUSION

The post-ablation aSKNA levels increased significantly in the ConV group but did not change significantly in the HPSD group, which may reflect different neuromodulatory effects. However, the one-year AF recurrence rates were similar for both groups. These results demonstrate that the HPSD strategy has durable lesion creation but less lesion depth, which may reduce collateral damage.

Autonomic Nervous System and Cardiac Metabolism: Links Between Autonomic and Metabolic Remodeling in Atrial Fibrillation

Simultaneous activation of the sympathetic and parasympathetic nervous systems is crucial for the initiation of paroxysmal atrial fibrillation (AF). However, unbalanced activation of the sympathetic system is characteristic of autonomic remodeling in long-standing persistent AF. Moreover, the adrenergic activation-induced metabolic derangements provide a milieu for acute AF and promote the transition from the paroxysmal to the persistent phase of AF. On the other hand, cholinergic activation ameliorates the maladaptive metabolic remodeling in the face of metabolic challenges. Selective inhibition of the sympathetic system and restoration of the balance of the cholinergic system by neuromodulation is emerging as a novel nonpharmacologic strategy for managing AF. This review explores the link between cardiac autonomic and metabolic remodeling and the potential roles of different autonomic modulation strategies on atrial metabolic aberrations in AF.

Sympathovagal Balance Is a Strong Predictor of Post High-Volume Endurance Exercise Cardiac Arrhythmia

Regular physical activity is important for cardiovascular health. However, high-volume endurance exercise has been associated with increased number of electrocardiogram (ECG) abnormalities, including disturbances in cardiac rhythm (arrhythmias) and abnormalities in ECG pattern. The aim of this study was to assess if heart rate variability (HRV) is associated with ECG abnormalities. Fifteen participants with previous cycling experience completed a 21-day high-volume endurance exercise cycle over 3,515 km. Participants wore a 5-lead Holter monitor for 24 h pre- and post-exercise, which was used to quantify ECG abnormalities and export sinus R-to-R intervals (NN) used to calculate HRV characteristics. As noise is prevalent in 24-h HRV recordings, both 24-h and heart rate collected during stable periods of time (i.e., deep sleep) were examined. Participants experienced significantly more arrhythmias post high-volume endurance exercise (median = 35) compared to pre (median = 12; p = 0.041). All 24-h and deep sleep HRV outcomes were not different pre-to-post high-volume endurance exercise (p > 0.05). Strong and significant associations with arrhythmia number post-exercise were found for total arrhythmia (total arrhythmia number pre-exercise, ρ = 0.79; age, ρ = 0.73), supraventricular arrhythmia (supraventricular arrhythmia number pre-exercise: ρ = 0.74; age: ρ = 0.66), and ventricular arrhythmia (age: ρ = 0.54). As a result, age and arrhythmia number pre-exercise were controlled for in hierarchical regression, which revealed that only deep sleep derived low frequency to high frequency (LF/HF) ratio post high-volume endurance exercise predicted post total arrhythmia number (B = 0.63, R2Δ = 34%, p = 0.013) and supraventricular arrhythmia number (B = 0.77, R2Δ = 69%, p < 0.001). In this study of recreationally active people, only deep sleep derived LF/HF ratio was associated with more total and supraventricular arrhythmias after high-volume endurance exercise. This finding suggests that measurement of sympathovagal balance during deep sleep might be useful to monitor arrhythmia risk after prolonged high-volume endurance exercise performance.

Impact of maze procedure in patients with severe tricuspid regurgitation and persistent atrial fibrillation

OBJECTIVE

Patients with severe tricuspid regurgitation and persistent atrial fibrillation may not be good candidates for maze procedure due to preoperative atrial remodeling and various comorbidities. We attempted to evaluate the rhythm and clinical outcomes of maze procedure in these patients.

METHODS

Patients with severe tricuspid regurgitation and persistent atrial fibrillation who underwent tricuspid valve surgery between January 1994 and December 2017 at a single tertiary center were analyzed. The primary end point was sinus rhythm restoration. The key secondary end point was major adverse cardiovascular and cerebrovascular event rate, which is the composite event of stroke, cardiac death, major bleeding, and readmission for heart failure. Propensity score matching analysis was used.

RESULTS

A total of 388 patients underwent tricuspid valve surgery, and among them 172 patients (44%) underwent concomitant maze procedure. The maze group had sinus rhythm restoration rate of 56% in 9 years. Further, in the matched cohort, the maze group had higher freedom from major adverse cardiovascular and cerebrovascular event rate at 10 years than the nonmaze group (55.6% vs 36.2%; P = .047). Preoperative left atrial diameter (hazard ratio, 1.022; 95% CI, 1.012-1.033; P < .001) and right atrial diameter (hazard ratio, 1.012; 95% CI, 1.003-1.022; P = .013) were independent risk factors for failure of sinus rhythm.

CONCLUSIONS

Maze procedure in severe tricuspid regurgitation and persistent atrial fibrillation had acceptable rates of sinus rhythm restoration and reduced major adverse cardiovascular and cerebrovascular events in the long-term. Careful patient selection considering preoperative atrial diameters is needed to enhance maze success rate and long-term clinical outcomes.

Acupuncture at the auricular branch of the vagus nerve enhances heart rate variability in humans: An exploratory study

BACKGROUND

Recent animal and human studies have shown antiarrhythmic effects inhibiting inducibility of atrial fibrillation through low-level transcutaneous electrical stimulation at the auricular branch of the vagus nerve (ABVN).

OBJECTIVE

The present study investigated effects of acupuncture at the ABVN on the autonomic cardiac nervous system in humans through analysis of heart rate and heart rate variability (HRV) parameters.

METHODS

We enrolled 24 healthy male volunteers and compared acupuncture at the ABVN to placebo-acupuncture performed at the Ma-35 point (an acupuncture point used in traditional Chinese medicine to treat pain caused by gonarthrosis). An additional measurement without acupuncture served as control. We analyzed the following heart rate and HRV parameters: standard deviation of normal-to-normal intervals (SDNN), root mean square of successive R-R interval differences (RMSSD), high frequency (HF), low frequency (LF), LF/HF ratio.

RESULTS

In comparison to placebo acupuncture, acupuncture at the ABVN led to a significant reduction in heart rate (approximately 4%-6%, P < .05) and an increase in overall HRV demonstrated by SDNN (approximately 19%, P < .05). RMSSD and power spectral density parameters (HF, LF, LF/HF) showed statistical trends (P < .1) induced by auricular acupuncture in favor of vagal tone. No relevant difference was shown between control and placebo group.

CONCLUSION

Acupuncture of the region innervated by the ABVN may activate the parasympathetic nervous system, as suggested by reduction in heart rate and increase in SDNN. However, given the lack of clear significant changes in other HRV parameters, this effect seems modest and its evaluation requires further investigation.

Heart Rate Variability and Clinical Features as Predictors of Atrial Fibrillation Recurrence After Catheter Ablation: A Pilot Study

Single-procedure catheter ablation success rate is as low as 52% in atrial fibrillation (AF) patients. This study evaluated the feasibility of using clinical data and heart rate variability (HRV) features extracted from an implantable cardiac monitor (ICM) to predict recurrences in patients prior to undergoing catheter ablation for AF. HRV-derived features were extracted from the 500 beats preceding the AF onset and from the first 2 min of the last AF episode recorded by an ICM of 74 patients (67% male; 57 ± 12 years; 26% non-paroxysmal AF; 57% AF recurrence) before undergoing their first AF catheter ablation. Two types of classification algorithm were studied to predict AF recurrence: single classifiers including support vector machines, classification and regression trees, and K-nearest neighbor classifiers as well as ensemble classifiers. The sequential forward floating search algorithm was used to select the optimum feature set for each classification method. The optimum weighted voting method, which used an optimum combination of the single classifiers, was the best overall classifier (accuracy = 0.82, sensitivity = 0.76, and specificity = 0.87). Clinical and HRV features can be used to predict rhythm outcome using an ensemble classifier which would enable a more effective pre-ablation patient triage that could reduce the economic and personal burden of the procedure by increasing the success rate of first catheter ablation.

A Batteryless Motion-Adaptive Heartbeat Detection System-on-Chip Powered by Human Body Heat

This paper presents a batteryless heartbeat detection system-on-chip (SoC) powered by human body heat. An adaptive threshold generation architecture using pulse-width locked loop (PWLL) is developed to detect heartbeats from electrocardiogram (ECG) in the presence of motion artifacts. The sensing system is autonomously powered by harvesting thermal energy from human body heat using a thermoelectric generator (TEG) coupled to a low-voltage, self-starting boost converter and integrated power management system. The SoC was implemented in a 0.18 μm CMOS process and is fully functional with a minimum input power of 20 μW, provided by a portable TEG at 20 mV with a ~0.5 °C temperature gradient. The complete system demonstrates motion-adaptive, power-autonomous heartbeat detection for sustainable healthcare using wearable devices.

Physical activity and atrial tachyarrhythmia recurrence in atrial fibrillation patients after catheter ablation

BACKGROUND

The association between physical activity (PA) and atrial tachyarrhythmia (AT) recurrence after ablation for atrial fibrillation (AF) remains unclear.

METHODS

We consecutively enrolled 496 patients treated with AF ablation therapy in Beijing Anzhen Hospital. After excluding six patients with valvular heart disease, seven patients with congenital heart disease, 33 patients lost to follow-up, and 14 patients who did not provide PA level during follow-ups, 436 patients had their PA level assessed by the International Physical Activity Questionnaire-Short Form before ablation and each time of follow-up. The association between PA level (measured at the time closest to AT recurrence, or the end of 12-month follow-up if no AT recurrence), as well as active PA during follow-up, and postablation AT recurrence was tested by multivariate logistic regression.

RESULTS

Of the enrolled patients, 134 (30.7%) patients experienced AT recurrence in the first 12 months postablation. Compared to patients with low PA, patients with moderate or high PA had a lower risk of AT recurrence (odds ratio [OR] = .44; 95% confidence interval [CI], .25-.80; P = .01 for patients with moderate PA; and OR = .43 [95% CI, .21-.85], P = .02 for patients with high PA). Compared to patients without active PA, patients with active PA had a lower risk of AT recurrence (OR = .44 [95% CI, .27-.70], P < .01).

CONCLUSIONS

Moderate and high PA are associated with a lower risk of AT recurrence after AF ablation. Active PA during follow-up is also associated with a significantly lower risk of AT recurrence in the postablation AF population.

Multi-scale Entropy Evaluates the Proarrhythmic Condition of Persistent Atrial Fibrillation Patients Predicting Early Failure of Electrical Cardioversion

Atrial fibrillation (AF) is nowadays the most common cardiac arrhythmia, being associated with an increase in cardiovascular mortality and morbidity. When AF lasts for more than seven days, it is classified as persistent AF and external interventions are required for its termination. A well-established alternative for that purpose is electrical cardioversion (ECV). While ECV is able to initially restore sinus rhythm (SR) in more than 90% of patients, rates of AF recurrence as high as 20-30% have been found after only a few weeks of follow-up. Hence, new methods for evaluating the proarrhythmic condition of a patient before the intervention can serve as efficient predictors about the high risk of early failure of ECV, thus facilitating optimal management of AF patients. Among the wide variety of predictors that have been proposed to date, those based on estimating organization of the fibrillatory (f-) waves from the surface electrocardiogram (ECG) have reported very promising results. However, the existing methods are based on traditional entropy measures, which only assess a single time scale and often are unable to fully characterize the dynamics generated by highly complex systems, such as the heart during AF. The present work then explores whether a multi-scale entropy (MSE) analysis of the f-waves may provide early prediction of AF recurrence after ECV. In addition to the common MSE, two improved versions have also been analyzed, composite MSE (CMSE) and refined MSE (RMSE). When analyzing 70 patients under ECV, of which 31 maintained SR and 39 relapsed to AF after a four week follow-up, the three methods provided similar performance. However, RMSE reported a slightly better discriminant ability of 86%, thus improving the other multi-scale-based outcomes by 3-9% and other previously proposed predictors of ECV by 15-30%. This outcome suggests that investigation of dynamics at large time scales yields novel insights about the underlying complex processes generating f-waves, which could provide individual proarrhythmic condition estimation, thus improving preoperative predictions of ECV early failure.

Ranking of the most reliable beat morphology and heart rate variability features for the detection of atrial fibrillation in short single-lead ECG

OBJECTIVE

This study participated in the 2017 PhysioNet/CinC Challenge dedicated to the classification of atrial fibrillation (AF), normal sinus rhythm (Normal), other arrhythmia (Other) and strong noise, using single-lead electrocardiogram (ECG) recordings with a duration  <60 s. The aim is to apply a linear threshold-based strategy for arrhythmia classification, ranking the most powerful time domain ECG features that could be easily reproduced on any platform.

APPROACH

An algorithm for time domain ECG analysis was designed to extract 44 features with focus on the following: noise detection; heart rate variability (HRV) analysis; beat morphology analysis and delineation of P-, QRS-, and T-waves in the robust average beat; detection of atrial activity by the presence of P-waves in the average beat and atrial fibrillatory waves (f-waves) during TQ intervals. A linear discriminant analysis (LDA) classifier was optimized on the Challenge training set (8528 ECGs) by stepwise selection of a nonredundant feature set until maximization of the Challenge F1 score. Heart rate (HR) was an independent factor for the LDA classifier design, particular to bradycardia (HR  ⩽  50 bpm), normal rhythm (HR  =  50-100 bpm), tachycardia (HR  ⩾  100 bpm).

MAIN RESULTS

The algorithm obtained official Challenge F1 scores of 0.80 (Overall), 0.90 (Normal), 0.81 (AF), 0.70 (Other), and 0.54 (Noise) on the hidden Challenge test set (3658 ECGs). This is equivalent to a true positive rate (TPR)  =  90.1% (Normal), 81.5% (AF), 67.7% (Other), and 69.5% (Noise), and a false positive rate (FPR)  =  13.6% (Normal), 2.3% (AF), 7.7% (Other), and 1.5% (Noise).

SIGNIFICANCE

The top five features, which together contributed to about 94% of the maximal F1 score were ranked: (1) proportion of RR intervals differing by  >50 ms from the preceding RR interval; (2) Poincaré plot geometry estimated by the ratio of the minor-to-major semi-axes of the fitted ellipse; (3) P-wave presence in the average beat; (4) mean percentage of the RR interval first differences; and (5) mean correlation of all beats against the average beat. The global rank of feature extraction methods highlighted that HRV alone was able to provide 92.5% of the maximal F1 score (0.74 versus 0.8). The added value of more complex ECG morphology analysis was less significant for Normal, AF, and Other rhythms (+0.02 to 0.08 points) than for Noise (+0.19 points); however, these were indispensable for wearable ECG recording devices with frequent artefact disturbance.

Dynamic Electrocardiography is Useful in the Diagnosis of Persistent Atrial Fibrillation Accompanied with Second-Degree Atrioventricular Block

BACKGROUND

Periodic electrocardiography (ECG) at every clinical visit is generally performed for heart rhythm surveillance, and 24-h Holter ECG is usually used as the gold standard. We aimed to investigate the electrocardiographic features of persistent atrial fibrillation (AF) accompanied with second-degree atrioventricular block (AVB).

METHODS

From October 2012 to November 2015, 204 patients with an RR interval > 2.0 s before radiofrequency ablation were included. Dynamic ECG (DCG) was performed before and after the radiofrequency ablation. The patients were divided into two groups based on changes in DCG after radiofrequency ablation: group A (non-second-degree AVB group) and group B (second-degree AVB group). An RR interval > 2.0 s, the distribution of escape rhythm, mean heart rate and the long RR interval in the two groups were analyzed.

RESULTS

After radiofrequency ablation, all 204 patients who had persistent AF converted to sinus rhythm successfully. In group A (n = 193), the distribution of an RR interval > 2.0 s and escape rhythm were significantly correlated with sleep or rest, while no correlation was observed in group B (n = 11). The average RR interval prolongation and escape rhythm were significantly higher in group B than in group A (p < 0.05). The average number of long RR intervals > 3.0 s and average number of escape rhythm episodes (< 35 bpm) were significant predictive factors of second-degree AVB after radiofrequency ablation.

CONCLUSIONS

DCG is a useful tool for the diagnosis of persistent AF accompanied with second-degree AVB.

Novel Method to Efficiently Create an mHealth App: Implementation of a Real-Time Electrocardiogram R Peak Detector

Background

In parallel to the introduction of mobile communication devices with high computational power and internet connectivity, high-quality and low-cost health sensors have also become available. However, although the technology does exist, no clinical mobile system has been developed to monitor the R peaks from electrocardiogram recordings in real time with low false positive and low false negative detection. Implementation of a robust electrocardiogram R peak detector for various arrhythmogenic events has been hampered by the lack of an efficient design that will conserve battery power without reducing algorithm complexity or ease of implementation.

Objective

Our goals in this paper are (1) to evaluate the suitability of the MATLAB Mobile platform for mHealth apps and whether it can run on any phone system, and (2) to embed in the MATLAB Mobile platform a real-time electrocardiogram R peak detector with low false positive and low false negative detection in the presence of the most frequent arrhythmia, atrial fibrillation.

Methods

We implemented an innovative R peak detection algorithm that deals with motion artifacts, electrical drift, breathing oscillations, electrical spikes, and environmental noise by low-pass filtering. It also fixes the signal polarity and deals with premature beats by heuristic filtering. The algorithm was trained on the annotated non–atrial fibrillation MIT-BIH Arrhythmia Database and tested on the atrial fibrillation MIT-BIH Arrhythmia Database. Finally, the algorithm was implemented on mobile phones connected to a mobile electrocardiogram device using the MATLAB Mobile platform.

Results

Our algorithm precisely detected the R peaks with a sensitivity of 99.7% and positive prediction of 99.4%. These results are superior to some state-of-the-art algorithms. The algorithm performs similarly on atrial fibrillation and non–atrial fibrillation patient data. Using MATLAB Mobile, we ran our algorithm in less than an hour on both the iOS and Android system. Our app can accurately analyze 1 minute of real-time electrocardiogram signals in less than 1 second on a mobile phone.

Conclusions

Accurate real-time identification of heart rate on a beat-to-beat basis in the presence of noise and atrial fibrillation events using a mobile phone is feasible.

Slowed atrial and atrioventricular conduction and depressed HRV in a murine model of hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a common heritable cardiac disorder with diverse clinical outcomes including sudden death, heart failure, and stroke. Depressed heart rate variability (HRV), a measure of cardiac autonomic regulation, has been shown to predict mortality in patients with cardiovascular disease. Cardiac autonomic remodelling in animal models of HCM are not well characterised. This study analysed Gly203Ser cardiac troponin-I transgenic (TG) male mice previously demonstrated to develop hallmarks of HCM by age 21 weeks. 33 mice aged 30 and 50 weeks underwent continuous electrocardiogram (ECG) recording for 30 min under anaesthesia. TG mice demonstrated prolonged P-wave duration (P < 0.001) and PR intervals (P < 0.001) compared to controls. Additionally, TG mice demonstrated depressed standard deviation of RR intervals (SDRR; P < 0.01), coefficient of variation of RR intervals (CVRR; P < 0.001) and standard deviation of heart rate (SDHR; P < 0.001) compared to controls. Additionally, total power was significantly reduced in TG mice (P < 0.05). No significant age-related difference in either strain was observed in ECG or HRV parameters. Mice with HCM developed slowed atrial and atrioventricular conduction and depressed HRV. These changes were conserved with increasing age. This finding may be indicative of atrial and ventricular hypertrophy or dysfunction, and perhaps an indication of worse clinical outcome in heart failure progression in HCM patients.

Factors related to heart rate variability among firefighters

OBJECTIVES

The aim of this study was to investigate factors associated with heart rate variability in firefighters working in a metropolitan city in South Korea.

METHODS

Self-administered questionnaires including Korean Occupational Stress Scale (KOSS) as well as surveys collecting socio-demographic characteristics and work-related factors were given to 962 firefighters. After exclusion for missing data, 645 firefighters were included, and analysis of covaiance adjusted for the general risk factors and job characteristics were used to assess the relationship between heart rate variability and associated factors.

RESULTS

SDNN and RMSSD and were decreased in the area of occupational climate of the group with high job stress (p = 0.027, p = 0.036). HF(ln) was decreased in the area of organizational system and occupational climate of the group with high stress that statistically significant level (p = 0.034, p = 0.043).

CONCLUSIONS

Occupational climate and organizational system are associated with reduction of heart rate variability. Preventive medical care plans for cardiovascular disease of firefighters through the analysis and evaluation of job stress factors are needed.

Developing a New Computer-Aided Clinical Decision Support System for Prediction of Successful Postcardioversion Patients with Persistent Atrial Fibrillation

We propose a new algorithm to predict the outcome of direct-current electric (DCE) cardioversion for atrial fibrillation (AF) patients. AF is the most common cardiac arrhythmia and DCE cardioversion is a noninvasive treatment to end AF and return the patient to sinus rhythm (SR). Unfortunately, there is a high risk of AF recurrence in persistent AF patients; hence clinically it is important to predict the DCE outcome in order to avoid the procedure's side effects. This study develops a feature extraction and classification framework to predict AF recurrence patients from the underlying structure of atrial activity (AA). A multiresolution signal decomposition technique, based on matching pursuit (MP), was used to project the AA over a dictionary of wavelets. Seven novel features were derived from the decompositions and were employed in a quadratic discrimination analysis classification to predict the success of post-DCE cardioversion in 40 patients with persistent AF. The proposed algorithm achieved 100% sensitivity and 95% specificity, indicating that the proposed computational approach captures detailed structural information about the underlying AA and could provide reliable information for effective management of AF.

Increased systemic inflammation is associated with cardiac and vascular dysfunction over the first 12 weeks of antiretroviral therapy among undernourished, HIV-infected adults in Southern Africa

INTRODUCTION

Persistent systemic inflammation is associated with mortality among undernourished, HIV-infected adults starting antiretroviral therapy (ART) in sub-Saharan Africa, but the etiology of these deaths is not well understood. We hypothesized that greater systemic inflammation is accompanied by cardiovascular dysfunction over the first 12 weeks of ART.

METHODS

In a prospective cohort of 33 undernourished (body mass index <18.5 kg/m²) Zambian adults starting ART, we measured C-reactive protein (CRP), tumor necrosis factor-α receptor 1 (TNF-α R1), and soluble CD163 and CD14 at baseline and 12 weeks. An EndoPAT device measured the reactive hyperemia index (LnRHI; a measure of endothelial responsiveness), peripheral augmentation index (AI; a measure of arterial stiffness), and heart rate variability (HRV; a general marker of autonomic tone and cardiovascular health) at the same time points. We assessed paired changes in inflammation and cardiovascular parameters, and relationships independent of time point (adjusted for age, sex, and CD4+ T-cell count) using linear mixed models.

RESULTS

Serum CRP decreased (median change -3.5 mg/l, p=0.02), as did TNF-α R1 (-0.31 ng/ml, p<0.01), over the first 12 weeks of ART. A reduction in TNF-α R1 over 12 weeks was associated with an increase in LnRHI (p=0.03), and a similar inverse relationship was observed for CRP and LnRHI (p=0.07). AI increased in the cohort as a whole over 12 weeks, and a reduction in sCD163 was associated with a rise in the AI score (p=0.04). In the pooled analysis of baseline and 12 week data, high CRP was associated with lower HRV parameters (RMSSD, p=0.01; triangular index, p<0.01), and higher TNF- α R1 accompanied lower HRV (RMSSD, p=0.07; triangular index, p=0.06).

CONCLUSIONS

Persistent inflammation was associated with impaired cardiovascular health over the first 12 weeks of HIV treatment among undernourished adults in Africa, suggesting cardiac events may contribute to high mortality in this population.

Risk factors for atrial fibrillation recurrence: a literature review

Atrial fibrillation is the most common arrhythmia managed in clinical practice and it is associated with an increased risk of mortality, stroke and peripheral embolism. Unfortunately, the incidence of atrial fibrillation recurrence ranges from 40 to 50%, despite the attempts of electrical cardioversion and the administration of antiarrhythmic drugs. In this review, the literature data about predictors of atrial fibrillation recurrence are highlighted, with special regard to clinical, therapeutic, biochemical, ECG and echocardiographic parameters after electrical cardioversion and ablation. Identifying predictors of success in maintaining sinus rhythm after cardioversion or ablation may allow a better selection of patients to undergo these procedures. The aim is to reduce healthcare costs and avoid exposing patients to unnecessary procedures and related complications. Recurrent atrial fibrillation depends on a combination of several parameters and each patient should be individually assessed for such a risk of recurrence.

Prediction of cardiac arrest in critically ill patients presenting to the emergency department using a machine learning score incorporating heart rate variability compared with the modified early warning score

Introduction

A key aim of triage is to identify those with high risk of cardiac arrest, as they require intensive monitoring, resuscitation facilities, and early intervention. We aim to validate a novel machine learning (ML) score incorporating heart rate variability (HRV) for triage of critically ill patients presenting to the emergency department by comparing the area under the curve, sensitivity and specificity with the modified early warning score (MEWS).

Methods

We conducted a prospective observational study of critically ill patients (Patient Acuity Category Scale 1 and 2) in an emergency department of a tertiary hospital. At presentation, HRV parameters generated from a 5-minute electrocardiogram recording are incorporated with age and vital signs to generate the ML score for each patient. The patients are then followed up for outcomes of cardiac arrest or death.

Results

From June 2006 to June 2008 we enrolled 925 patients. The area under the receiver operating characteristic curve (AUROC) for ML scores in predicting cardiac arrest within 72 hours is 0.781, compared with 0.680 for MEWS (difference in AUROC: 0.101, 95% confidence interval: 0.006 to 0.197). As for in-hospital death, the area under the curve for ML score is 0.741, compared with 0.693 for MEWS (difference in AUROC: 0.048, 95% confidence interval: -0.023 to 0.119). A cutoff ML score ≥ 60 predicted cardiac arrest with a sensitivity of 84.1%, specificity of 72.3% and negative predictive value of 98.8%. A cutoff MEWS ≥ 3 predicted cardiac arrest with a sensitivity of 74.4%, specificity of 54.2% and negative predictive value of 97.8%.

Conclusion

We found ML scores to be more accurate than the MEWS in predicting cardiac arrest within 72 hours. There is potential to develop bedside devices for risk stratification based on cardiac arrest prediction.

Unprovoked atrial tachyarrhythmias in aging spontaneously hypertensive rats: the role of the autonomic nervous system

Experimental models of unprovoked atrial tachyarrhythmias (AT) in conscious, ambulatory animals are lacking. We hypothesized that the aging, spontaneously hypertensive rat (SHR) may provide such a model. Baseline ECG recordings were acquired with radiotelemetry in eight young (14-wk-old) and eight aging (55-wk-old) SHRs and in two groups of four age-matched Wistar-Kyoto (WKY) rats. Quantification of AT and heart rate variability (HRV) analysis were performed based on 24-h ECG recordings in unrestrained rats. All animals were submitted to an emotional stress protocol (air-jet). In SHRs, carbamylcholine injections were also performed. Spontaneous AT episodes were observed in all eight aging SHRs (median, 91.5; range, 4-444 episodes/24 h), but not in young SHRs or WKY rats. HRV analysis demonstrated significantly decreased low frequency components in aging SHRs compared with age-matched WKY rats (P < 0.01) and decreased low/high frequency ratios in both young (P < 0.01) and aging (P = 0.01) SHRs compared with normotensive controls. In aging SHRs, emotional stress significantly reduced the number of arrhythmic events, whereas carbamylcholine triggered AT and significantly increased atrial electrical instability. This study reports the occurrence of unprovoked episodes of atrial arrhythmia in hypertensive rats, and their increased incidence with aging. Our results suggest that autonomic imbalance with relative vagal hyperactivity may be responsible for the increased atrial arrhythmogenicity observed in this model. We also provide evidence that, in this model, the sympatho-vagal imbalance preceded the occurrence of arrhythmia. These results indicate that aging SHRs may provide valuable insight into the understanding of atrial arrhythmias.

Acupuncture for paroxysmal and persistent atrial fibrillation: An effective non-pharmacological tool?

In Traditional Chinese Medicine, stimulation of the Neiguan spot has been utilized to treat palpitations and symptoms related to different cardiovascular diseases. We evaluated whether acupuncture might exert an antiarrhythmic effect on patients with paroxysmal or persistent atrial fibrillation (AF). Two sets of data are reviewed. The first included patients with persistent AF who underwent electrical cardioversion to restore sinus rhythm. The second included patients with symptomatic paroxysmal AF. All subjects had normal ventricular function. Acupuncture treatment consisted of 10 acupuncture sessions on a once a week basis with puncturing of the Neiguan, Shenmen and Xinshu spots. In patients with persistent AF, the recurrence rate after acupuncture treatment was similar to that observed in patients on amiodarone, but significantly smaller than that measured after sham acupuncture treatment or in the absence of any antiarrhythmic drugs. In a small group of patients with paroxysmal AF, acupuncture resulted in a significant reduction in the number and duration of symptomatic AF episodes. In conclusion, we observed that acupuncture of the Neiguan spot was associated with an antiarrhythmic effect, which was evident in patients with both persistent and paroxysmal AF. These preliminary data, observed in 2 small groups of AF patients, need to be validated in a larger population but strongly suggest that acupuncture may be an effective non-invasive and safe antiarrhythmic tool in the management of these patients.

Novel Pharmacological Interventions to Maintain Sinus Rhythm after DC Cardioversion

Despite the availability of potentially curative interventions for atrial fibrillation, there remains an important role for conventional anti-arrhythmic therapy and anti-coagulation combined with direct current cardioversion. Unfortunately, the latter approach is disturbed by high recurrence rates of atrial fibrillation. In recent years, several adjunctive therapies have emerged which may facilitate the maintenance of sinus rhythm. These novel therapies and their potential mechanisms of action are reviewed in this article.

Noninvasive time and frequency predictors of long-standing atrial fibrillation early recurrence after electrical cardioversion

BACKGROUND

Several clinical factors have been studied to predict atrial fibrillation (AF) recurrence after electrical cardioversion (ECV) with limited predictive value.

METHODS

 A method able to predict robustly long-standing AF early recurrence by characterizing noninvasively the electrical atrial activity (AA) with parameters related to its time course and spectral features is presented. To this respect, 63 patients (20 men and 43 women; mean age 73.4 ± 9.0 years; under antiarrhythmic drug treatment with amiodarone) who were referred for ECV of persistent AF were studied. During a 4-week follow-up, AF recurrence was observed in 41 patients (65.1%).

RESULTS

 RR variability and the studied AA spectral features, including dominant atrial frequency (DAF), its first harmonic and their amplitude, provided poor statistical differences between groups. On the contrary, f waves power (fWP) and Sample Entropy (SampEn) of the AA behaved as very good predictors. Patients who relapsed to AF presented lower fWP (0.036 ± 0.019 vs 0.081 ± 0.029 n.u.(2) , P < 0.001) and higher SampEn (0.107 ± 0.022 vs 0.086 ± 0.033, P < 0.01). Furthermore, fWP presented the highest predictive accuracy of 82.5%, whereas SampEn provided a 79.4%. The remaining features revealed accuracies lower than 70%. A stepwise discriminant analysis (SDA) provided a model based on fWP and SampEn with 90.5% of accuracy.

CONCLUSIONS

 The fWP has proved to predict long-standing AF early recurrence after ECV and can be combined with SampEn to improve its diagnostic ability. Furthermore, a thorough analysis of the results allowed outlining possible associations between these two features and the concomitant status of atrial remodeling.

Non-invasive atrial fibrillation organization follow-up under successive attempts of electrical cardioversion

The development of non-invasive tools able to provide valuable information about the effectiveness of a shock in external electrical cardioversion (ECV) is clinically relevant to enhance these protocols in the treatment of atrial fibrillation (AF). The present contribution analyzes the ability of a non-linear regularity index, such as sample entropy (SampEn), to follow-up non-invasively AF organization under successive attempts of ECV and to predict the effectiveness of every single shock. To this respect, the atrial activity (AA) preceding each delivered shock was extracted by using a QRST cancellation method. Next, the main atrial wave (MAW), which can be considered as the fundamental waveform associated to the AA, was obtained by applying a selective filtering centered on the dominant atrial frequency (DAF). Finally, the MAW organization was estimated with SampEn and two thresholds (Th1 = 0.1223 and Th2 = 0.0832) were established to predict the ECV outcome. Results indicated that, prior to the first attempt, all the patients who needed only one shock to restore NSR were below Th1. In addition, most of them were above Th2 in case of AF relapsing during the first month. Regarding several shocks, all the patients who maintained NSR more than one month were below Th2 after the first shock. Moreover, all the patients who relapsed to AF during the first month were between Th1 and Th2 and, finally, all the patients with ineffective ECV were above Th1. After each unsuccessful shock, a SampEn relative decrease was observed for the patients who finally reverted to NSR, but the largest variation took place after the first attempt, thus indicating that this shock plays the most important role in the procedure. Indeed, by considering jointly the patients who needed only one shock and the patients who needed several shocks, 91.67% (22 out of 24) of ECVs resulting in NSR, 93.55% (29 out of 31) of ECVs relapsing to AF during the first month and 100% (10 out of 10) of ECVs in which NSR was not restored were correctly classified. As conclusion, the MAW organization analysis via SampEn can provide useful information that could improve the effectiveness of conventional external ECV protocols used in AF treatment.

Relationship between the long-term preventive effect of combined treatment with antiarrhythmic drugs plus angiotensin-converting enzyme inhibitors and circadian variation in the onset of paroxysmal atrial fibrillation

We examined the relationship between the efficacy of combined treatment with antiarrhythmic drugs (AAD) plus enalapril for maintaining sinus rhythm and circadian variation in the onset of paroxysmal AF.Three hundred and forty-four patients with paroxysmal AF (239 men, mean age, 69 ± 11 years) who could be followed up ≥ 12 months were divided into 3 groups on the basis of circadian variation in the onset of AF: a diurnal group (7:00 AM-5:00 PM, n = 57), a nocturnal group (5:00 PM-7:00 AM, n = 108), and a mixed group (onset during both periods, n = 169). The maintenance rate of sinus rhythm during the follow-up period was compared between combined therapy (AAD plus enalapril) and AAD alone.In the diurnal group, the maintenance rates of sinus rhythm at 12, 36, 60, and 90 months were 100%, 100%, 100%, and 100%, respectively, for patients treated with AAD plus enalapril (n = 22) versus 97%, 91%, 89%, and 80% for patients treated with AAD alone (n = 35, P < 0.05). In the nocturnal group, the maintenance rates of sinus rhythm at 12, 36, 60, and 90 months were 96%, 96%, 96%, and 92%, respectively, in patients treated with AAD plus enalapril (n = 24) versus 100%, 100%, 100%, and 100% in patients treated with AAD alone (n = 84, P = NS). In the mixed group, maintenance rates of sinus rhythm at 12, 36, 60, and 90 months were 90%, 71%, 61%, and 57%, respectively, in patients treated with AAD plus enalapril (n = 49) versus 88%, 78%, 68%, and 61% in patients treated with AAD alone (n = 120, P = NS). Our findings suggest that the preventive efficacy of combined therapy with AAD plus enalapril is dependent on the timing of onset of paroxysmal AF, and this regimen seems to be most beneficial for the diurnal type of paroxysmal AF.

Complex interactions between the sinoatrial node and atrium during reentrant arrhythmias in the canine heart

BACKGROUND

Numerous studies implicate the sinoatrial node (SAN) as a participant in atrial arrhythmias, including atrial flutter (AFL) and atrial fibrillation (AF). However, the direct role of the SAN has never been described.

METHODS AND RESULTS

The SAN was optically mapped in coronary perfused preparations from normal canine hearts (n=17). Optical action potentials were recorded during spontaneous rhythm, overdrive atrial pacing, and AF/AFL induced by acetylcholine (ACh; 0.3 to 3 micromol/L) and/or isoproterenol (Iso; 0.2 to 1 micromol/L). An optical action potential multiple component algorithm and dominant frequency analysis were used to reconstruct SAN activation and to identify specialized sinoatrial conduction pathways. Both ACh and Iso facilitated pacing-induced AF/AFL by shortening atrial repolarization. The entire SAN structure created a substrate for macroreentry with 9.6+/-1.7 Hz (69 episodes in all preparations). Atrial excitation waves could enter the SAN through the sinoatrial conduction pathways and overdrive suppress the node. The sinoatrial conduction pathways acted as a filter for atrial waves by slowing conduction and creating entrance block. ACh/Iso modulated filtering properties of the sinoatrial conduction pathways by increasing/decreasing the degree of the entrance block, respectively. Thus, the SAN could beat independently from AF/AFL reentrant activity during ACh (49+/-39%) and ACh/Iso (62+/-25%) (P=0.38). Without ACh, the AF/AFL waves captured the SAN and overdrive suppressed it. Spontaneous SAN activity could terminate or convert AFL to AF during cholinergic withdrawal.

CONCLUSIONS

The specialized structure of the SAN can be a substrate for AF/AFL. Cholinergic stimulation not only can slow sinus rhythm and facilitate AF/AFL but also protects the intrinsic SAN function from the fast AF/AFL rhythm.

Psychological distress in patients diagnosed with atrial fibrillation: the state of the science

Atrial fibrillation (AF) is a life-complicating illness adversely affecting morbidity, health-related quality of life (HRQOL), and healthcare use. Studies using HRQOL instruments suggest that patients diagnosed with AF experience more psychological distress than do healthy controls. Psychological distress in forms of anxiety and depression in patients with heart failure or coronary artery disease is related to increased mortality, morbidity, and consumption of healthcare. However, there is a critical lack of knowledge regarding the type and extent of psychological distress and its consequences in patients diagnosed with AF. This article will review the current state of scientific knowledge regarding psychological distress in patients with AF and offer suggestions for future studies. Medline, CINAHL, PscyhInfo, and Psychology and Behavioral Sciences Collection databases up to June 2009 were reviewed for key terms atrial fibrillation, psychological distress, affective distress, mood, emotional distress, psychological stress, negative affect, anxiety, depression, anger, and hostility. Ten studies using tested instruments to measure psychological distress were retained. The prevalence of psychological distress was not consistently reported. Combined findings revealed that psychological distress in the form of depression and/or anxiety uniquely contributed to greater AF symptom severity, diminished HRQOL, and recurrence of AF. Studies describing interventions to address psychological distress were not found. Lack of conceptual clarity and diversity of study purposes, designs, participants, and instruments limit the ability to draw coherent conclusions from findings. Nevertheless, findings suggest that psychological distress is present in a substantial portion of patients diagnosed with AF and its presence is related to adverse outcomes. Further study to identify the prevalence, characteristics, and consequences of psychological distress in patients diagnosed with AF is required to extend our knowledge and provide a foundation for development of interventions to address psychological distress in this rapidly increasing population.

Low-Level Vagosympathetic Stimulation

Background— We used high-frequency stimulation delivered during the refractory period of the atrium and pulmonary veins (PVs) to induce focal firing and atrial fibrillation (AF). This study was designed to demonstrate that bilateral low-level vagosympathetic nerve stimulation (LL-VNS) could suppress high-frequency stimulation-induced focal AF at atrial and PV sites.

Methods and Results— In 23 dogs anesthetized with Na-pentobarbital, electrodes in the vagosympathetic trunks allowed LL-VNS at 1 V below that which slowed the sinus rate or atrioventricular conduction. Multielectrode catheters were fixed at the right and left superior and inferior PVs and both atrial appendages. LL-VNS continued for 3 hours. At the end of each hour, the high-frequency stimulation algorithm consisting of a 40-ms train of stimuli (200 Hz; stimulus duration, 0.1 to 1.0 ms) was delivered 2 ms after the atrial pacing stimulus during the refractory period at each PV and atrial appendages site. The lowest voltage of high-frequency stimulation that induced AF was defined as the AF threshold. Five dogs without LL-VNS served as sham controls. Six dogs underwent LL-VNS after transection of bilateral vagosympathetic trunks. LL-VNS induced a progressive increase in AF threshold at all PV and atrial appendages sites, particularly significant ( P <0.05) at the right superior PV, right inferior PV, left superior PV, and right atrial appendage. Bilateral vagosympathetic transection did not significantly alter the previous findings, and the 5 sham control dogs did not show changes in AF threshold at any site over a period of 3 hours.

Conclusions— LL-VNS may prevent episodic AF caused by rapid PV and non-PV firing.

Electrophysiological characteristics associated with symptoms in pacemaker patients with paroxysmal atrial fibrillation

PURPOSE

The purpose of this study is to identify the electrophysiological factors affecting symptoms in paroxysmal atrial fibrillation (PAF) using patients with paroxysmal atrial fibrillation and pacemakers with advanced atrial fibrillation (AF) diagnostics.

METHODS

Seventy-nine patients (age 71.0 +/- 8.2, 54.4% male) with symptomatic PAF and AF burden of 1% to 50% with DDDRP pacemakers implanted were assessed for 6 months. Patients recorded symptom onset and duration and these were correlated with device-derived electrophysiological data.

RESULTS

Of 2,638 AF episodes, 333 were symptomatic and 2,305 asymptomatic, with 194 non-atrial tachyarrhythmia symptomatic episodes giving a sensitivity of 12.6% and a positive predictive value of 63.2% for specific AF symptoms. Symptomatic AF episodes were 3.8 times more common diurnally than nocturnally (p < 0.001). Diurnally, symptomatic AF was significantly associated with a shorter AF cycle length (CL; p = 0.04), faster ventricular rate (p = 0.004), shorter PR interval (p < 0.001), faster preceding heart rate (p = 0.001) and increased early recurrence of AF (p < 0.04). Nocturnally, a significantly longer AF CL (p = 0.04) and PR interval (p < 0.001) prior to AF onset predicted symptomatic AF.

CONCLUSIONS

Symptoms in PAF are predicted by changes in AF episode duration, ventricular rate during AF, preceding sinus heart rate, AV nodal conduction and AF cycle length but not ventricular irregularity. Excess diurnal sympathetic tone and excess nocturnal vagal tone predispose to symptomatic PAF. These findings may have relevance for therapies for symptom control of PAF.

The effect of pretreatment with renin-angiotensin-aldosterone system blockers on cardioversion success and acute recurrence of atrial fibrillation

BACKGROUND

Renin-angiotensin-aldosterone system (RAS) may be activated during atrial fibrillation (AF). It is unclear whether RAS inhibition may facilitate cardioversion from AF and may prevent acute recurrence of AF (ARAF). We thus investigated the effect of pretreatment with RAS blockers on cardioversion success and ARAF in patients with AF scheduled for elective cardioversion.

METHODS

This observational study included 356 patients with AF undergoing elective pharmacological or electrical cardioversion. Of these patients, 135 were not included based on exclusion criteria and the remaining 221 patients were divided into RAS group (n = 116, 69 male) or non-RAS group (n = 105, 58 male) based on precardioversion use of any RAS blocker.

RESULTS

Hypertension, coronary heart disease and heart failure were more frequent in the RAS group. Cardioversion from AF was more successful in the RAS group than in the non-RAS group (%92 vs. %82, p = 0.026). The rate of ARAF was lower in RAS group compared with that in non-RAS group (17% vs. 31%, p = 0.026). In multivariate analysis, pretreatment with RAS blockers in addition to shock number and enlarged left atrium, independently predicted ARAF (OR: 0.33, 95% CI: 0.15-0.75, p = 0.008). Independent predictors of cardioversion success were shock number and left atrial dilatation, but not use of RAS blocker.

CONCLUSION

Precardioversion use of RAS blockers may reduce ARAF following successful cardioversion of AF, but did not improve electrical cardioversion.

The impact of statin use on atrial fibrillation

The aim of the present systematic review is to present an overview of the evidence linking atrial fibrillation (AF), inflammation and oxidative stress, with emphasis on the potential of statins to decrease the incidence of different types of AF, including new-onset AF, after electrical cardioversion (EC) and after cardiac surgery. Observational and clinical trials have studied the impact of statin therapy on new-onset, post-EC or postoperative AF. Data from different observational trials have shown that treatment with statins significantly reduces the incidence of new-onset AF in the primary and secondary prevention. The data are insufficient to recommend the use of statins before EC. Finally, perioperative statin therapy may represent an important non-antiarrhythmic adjunctive therapeutic strategy for the prevention of postoperative AF.

[Atrial fibrillation and the autonomous nervous system]

The autonomic nervous system has a crucial role in the genesis, maintenance and abruption of atrial fibrillation. The substrate and trigger mechanism of atrial fibrillation can be influenced by the changing autonomic tone. The authors summarize the current knowledge on the relationship between autonomic nervous system and atrial fibrillation. The special neuroanatomical status and the role of autonomic reflexes and baroreflex in the initiation, maintenance, and termination of arrhythmia are reviewed. Furthermore, the mechanism and consequences of autonomic effect of the curative radiofrequency catheter ablation of pulmonary vein with atrial vagal neuroablation are discussed. At the end we also summarize the pharmacologic therapy of atrial fibrillation. Classification of atrial fibrillation, as either vagal or adrenergic, has only limited impact on current management.

Heart rate variability explored in the frequency domain: a tool to investigate the link between heart and behavior

The neural regulation of circulatory function is mainly effected through the interplay of the sympathetic and vagal outflows. This interaction can be explored by assessing cardiovascular rhythmicity with appropriate spectral methodologies. Spectral analysis of cardiovascular signal variability, and in particular of RR period (heart rate variability, HRV), is a widely used procedure to investigate autonomic cardiovascular control and/or target function impairment. The oscillatory pattern which characterizes the spectral profile of heart rate and arterial pressure short-term variability consists of two major components, at low (LF, 0.04-0.15Hz) and high (HF, synchronous with respiratory rate) frequency, respectively, related to vasomotor and respiratory activity. With this procedure the state of sympathovagal balance modulating sinus node pacemaker activity can be quantified in a variety of physiological and pathophysiological conditions. Changes in sympathovagal balance can be often detected in basal conditions, however a reduced responsiveness to an excitatory stimulus is the most common feature that characterizes numerous pathophysiological states. Moreover the attenuation of an oscillatory pattern or its impaired responsiveness to a given stimulus can also reflect an altered target function and thus can furnish interesting prognostic markers. The dynamic assessment of these autonomic changes may provide crucial diagnostic, therapeutic and prognostic information, not only in relation to cardiovascular, but also non-cardiovascular disease. As linear methodologies fail to provide significant information in conditions of extremely reduced variability (e.g. strenuous exercise, heart failure) and in presence of rapid and transients changes or coactivation of the two branches of autonomic nervous system, the development of new non-linear approaches seems to provide a new perspective in investigating neural control of cardiovascular system.

Depressive symptoms predict recurrence of atrial fibrillation after cardioversion

OBJECTIVE

The aim of this study was to evaluate whether depressive symptoms and the type-D personality are predictive of early recurrence of atrial fibrillation (or atrial flutter; AF) after successful electrical cardioversion (CV).

BACKGROUND

Depressive symptoms are associated with an adverse prognosis in patients with coronary artery disease, congestive heart failure, and ventricular arrhythmias. Anger and hostility have been shown to be predictive of development of AF. However, little is known about the effects of depression on AF.

METHODS

Fifty-four patients with persistent AF completed the Hospital Anxiety and Depression Scale (HADS) and the Type D Scale (DS-14) prior to elective electrical CV. Patients with a successful CV were followed for 2 months.

RESULTS

During the follow-up period, 27 patients (50%) had recurrence of the arrhythmia. Depressive mood (HADS depression scale >7) was the only significant nonsomatic predictor of recurrence, which was observed in 85% of depressed versus 39% of nondepressed patients [odds ratio=8.6; 95% confidence interval (CI)=1.7-44.0, P=.004]. HADS anxiety scores and the presence of the type-D personality pattern were not associated with recurrence of AF. On multivariate Cox regression analysis, including variables with a prevalence >10% of the total study population and a univariate discriminative effect yielding a P value of <.2, a HADS depression score >7 was found to be the only independently predictive variable of arrhythmia recurrence (hazard ratio=2.7; 95% CI=1.05-7.2; P=.046).

CONCLUSIONS

Our results indicate that depressive mood is a major risk factor for recurrence of AF after electrical CV. Heightened adrenergic tone and a proinflammatory state are possible mechanisms responsible for the observed association. Identification of depression may be of value prior to the decision to perform electrical CV.

Exercise testing for non-invasive assessment of atrial electrophysiological properties in patients with persistent atrial fibrillation

AIMS

Experimental studies suggest that the autonomic nervous system modulates atrial refractoriness and conduction velocity in atrial fibrillation (AF). These modulatory effects are, however, difficult to assess in the clinical setting. This study sought to non-invasively characterize in patients with persistent AF, the influence of autonomic modulation induced by exercise on atrial fibrillatory rate as marker of atrial refractoriness and to identify clinical and electrocardiographic predictors of atrial rate response.

METHODS AND RESULTS

In 24 patients (16 males, mean age 60 +/- 13 years) with persistent AF (16 +/- 25 months), continuous ECGs were recorded during bicycle exercise testing. Fibrillatory rate (in fibrillations per minute, fpm) was assessed at baseline and immediately after termination of exercise with spatiotemporal QRST cancellation and time-frequency analysis. Ventricular response was characterized by time-domain HRV indices. Exercise had no influence on mean fibrillatory rate (409 +/- 42 vs. 414 +/- 43 fpm, P = NS). Seven patients responded to exercise with an increase in fibrillatory rate (26 +/- 10 fpm, P < 0.001 and three with a decrease (-21 +/- 8 fpm, P < 0.001), while the remaining 14 patients did not show a response. Responders' HRV indices changed in response to exercise similarly to that of non-responders. Their baseline fibrillatory rate was, however, lower than that of non-responders (387 +/- 18 vs. 425 +/- 48 fpm, P = 0.028). No other clinical or echocardiographic variable was associated with fibrillatory rate response. Twelve weeks after cardioverson, responders were more likely to remain in sinus rhythm than non-responders (88 vs. 46 %, P = 0.04).

CONCLUSIONS

Exercise-induced autonomic activation produces changes in atrial electrophysiological properties that can be detected by time-frequency analysis. Higher baseline fibrillatory rates are associated with an impaired atrial response to exercise that suggests advanced electrical remodelling and reduced sensitivity to autonomic stimuli.

Atrial premature complexes and heart rate have prognostic significance in 1-month atrial fibrillation recurrence after electrical cardioversion

AIMS

The aim of this study was to investigate the significance of simple 24-h Holter (24H) data after electrical cardioversion (CV) for atrial fibrillation (AF) recurrence.

METHODS

We prospectively studied 47 consecutive patients subjected to CV, who successfully converted to sinus rhythm. All underwent echocardiography and 24H after CV. AF recurrence was studied at 14 days and 1 month by second 24H or by interim report of AF.

RESULTS

About 53.2% remained in sinus rhythm (group I) and the rest recurred to AF (group II). Group I had fewer atrial premature complexes per hour (APC/h) (P = 0.002) and lower maximum (max HR), average, and minimum heart rates compared with group II (all Ps < 0.05). The optimal value of APC/h and max HR with best sensitivity and specificity was 32 APC/h and 90 bpm, respectively. These findings were the predictors of AF recurrence [hazard ratio (HR) = 4.5 with 95% CI = 1.7-11.7 and HR = 4.3 with 95% CI = 1.7-10.9, respectively]. Patients with the combination of both predictors had greater HR of AF recurrence compared with those with < 32 APC/h and max HR < 90 bpm (HR = 8.8 with 95% CI = 2.5-31.4).

CONCLUSION

Patients with frequent APC/h and high max HR are at high risk for 1-month AF recurrence after electrical CV.