Role of atrial electrophysiology and autonomic nervous system in patients with supraventricular tachycardia and paroxysmal atrial fibrillation

Ventricular response as a predictor of the termination of sustained paroxysmal atrial fibrillation

BACKGROUND

Atrial fibrillation (AF) is the most common sustained atrial arrhythmia. Accurate detection of the timing and possibility of AF termination is vital for optimizing rhythm and rate control strategies. The present study evaluated whether the ventricular response (VR) in AF offers a distinctive electrocardiographic indicator for predicting AF termination.

METHODS

Patients experiencing sustained paroxysmal AF for more than 3 h were observed using 24-h ambulatory Holter monitoring. VR within 5 min before AF termination (VR 0-5 min, BAFT) was compared with VR observed during the 60th to 65th min (VR 60-65 min, BAFT) and the 120th to 125th min (VR 120-125 min, BAFT) before AF termination. Maximum and minimum VRs were calculated on the basis of the average of the highest and lowest VRs across 10 consecutive heartbeats.

RESULTS

Data from 37 episodes of paroxysmal AF revealed that the minimum VR0-5 min, BAFT (64 ± 20 bpm) was significantly faster than both the minimum VR120-125 min, BAFT (56 ± 15 bpm) and the minimum VR60-65 min, BAFT (57 ± 16 bpm, p < .05). Similarly, the maximum VR0-5 min, BAFT (158 ± 49 bpm) was significantly faster than the maximum VR120-125 min, BAFT (148 ± 45 bpm, p < .05). In the daytime, the minimum VR0-5 min, BAFT (66 ± 20 bpm) was significantly faster than both the minimum VR60-65 min, BAFT (58 ± 17 bpm) and minimum VR120-125 min, BAFT (57 ± 15 bpm, p < .05). However, the mean and maximum VR0-5 min, BAFT in the daytime were similar to the mean and maximum VR120-125 min in the daytime, respectively. At night, the minimum, mean, and maximum VR0-5 min, BAFT were similar to the minimum, mean, and maximum VR120-125 min, respectively.

CONCLUSIONS

Elevated VR rates during AF episodes may be predictors for the termination of AF, especially during the daytime and in patients with nondilated left atria. These findings may guide the development of clinical approaches to rhythm control in AF.

Bereavement in childhood and young adulthood and the risk of atrial fibrillation: a population-based cohort study from Denmark and Sweden

BACKGROUND

Adverse childhood life events are associated with increased risks of hypertension, ischemic heart disease, and stroke later in life. Limited evidence also suggests that stress in adulthood may increase the risk of atrial fibrillation (AF). Whether childhood adversity may lead to the development of AF is unknown. We investigated whether the loss of a parent or sibling in childhood is associated with an increased risk of AF and compared this effect to that of similar losses in young adulthood.

METHODS

We studied 6,394,975 live-born individuals included in the Danish (1973-2018) and Swedish Medical Birth Registers (1973-2014). We linked data from several national registers to obtain information on the death of parents and siblings and on personal and familial sociodemographic and health-related factors. We analyzed the association between bereavement and AF using Poisson regression.

RESULTS

Loss of a parent or sibling was associated with an increased AF risk both when the loss occurred in childhood and in adulthood; the adjusted incident rate ratios and 95% confidence intervals were 1.24 (1.14-1.35) and 1.24 (1.16-1.33), respectively. Bereavement in childhood was associated with AF only if losses were due to cardiovascular diseases or other natural causes, while loss in adulthood was associated with AF not only in case of natural deaths, but also unnatural deaths. The associations did not differ substantially according to age at loss and whether the deceased was a parent or a sibling.

CONCLUSIONS

Bereavement both in childhood and in adulthood was associated with an increased AF risk.

Neuromodulation therapy for atrial fibrillation

Atrial fibrillation has a multifactorial pathophysiology influenced by cardiac autonomic innervation. Both sympathetic and parasympathetic influences are profibrillatory. Innovative therapies targeting the neurocardiac axis include catheter ablation or pharmacologic suppression of ganglionated plexi, renal sympathetic denervation, low-level vagal stimulation, and stellate ganglion blockade. To date, these therapies have variable efficacy. As our understanding of atrial fibrillation and the cardiac nervous system expands, our approach to therapeutic neuromodulation will continue evolving for the benefit of those with AF.

Neuromodulatory Approaches for Atrial Fibrillation Ablation

In this review, the authors describe evolving alternative strategies for the management of AF, focusing on non-invasive and percutaneous autonomic modulation. This modulation can be achieved – among other approaches – via tragus stimulation, renal denervation, cardiac afferent denervation, alcohol injection in the vein of Marshall, baroreceptor activation therapy and endocardial ganglionated plexi ablation. Although promising, these therapies are currently under investigation but could play a role in the treatment of AF in combination with conventional pulmonary vein isolation in the near future.

Correlation of heart rate recovery and heart rate variability with atrial fibrillation progression

Objective

To examine the combination of heart rate recovery (HRR) and heart rate variability (HRV) in predicting atrial fibrillation (AF) progression.

Methods

Data from patients with a first detected episode of AF who underwent treadmill exercise testing and 24-h Holter electrocardiography were retrospectively analysed. Autonomic dysfunction was verified using HRR values. Sympathetic and parasympathetic modulation was analysed by HRV. AF progression was defined as transition from the first detected paroxysmal episode to persistent/permanent AF.

Results

Of 306 patients, mean LF/HF ratio and HRR did not differ significantly by AF progression regardless of age (< or ≥65 years). However, when the LF/HF ratio was divided into tertiles, in patients aged <65 years, the mid LF/HF (1.60–2.40) ratio was significantly associated with lower AF progression rates and longer maintenance of normal sinus rhythm. For patients aged <65 years, less metabolic equivalents were related to higher AF progression rates. For patients aged ≥65 years, a low HRR was associated with high AF progression rates.

Conclusion

In relatively younger age, high physical capacity and balanced autonomic nervous system regulation are important predictors of AF progression. Evaluation of autonomic function assessed by age could predict AF progression.

The Clinical Application of the Deep Learning Technique for Predicting Trigger Origins in Patients With Paroxysmal Atrial Fibrillation With Catheter Ablation

Background:

Non–pulmonary vein (NPV) trigger has been reported as an important predictor of recurrence post–atrial fibrillation ablation. Elimination of NPV triggers can reduce the recurrence of postablation atrial fibrillation. Deep learning was applied to preablation pulmonary vein computed tomography geometric slices to create a prediction model for NPV triggers in patients with paroxysmal atrial fibrillation.

Methods:

We retrospectively analyzed 521 patients with paroxysmal atrial fibrillation who underwent catheter ablation of paroxysmal atrial fibrillation. Among them, pulmonary vein computed tomography geometric slices from 358 patients with nonrecurrent atrial fibrillation (1–3 mm interspace per slice, 20–200 slices for each patient, ranging from the upper border of the left atrium to the bottom of the heart, for a total of 23 683 images of slices) were used in the deep learning process, the ResNet34 of the neural network, to create the prediction model of the NPV trigger. There were 298 (83.2%) patients with only pulmonary vein triggers and 60 (16.8%) patients with NPV triggers±pulmonary vein triggers. The patients were randomly assigned to either training, validation, or test groups, and their data were allocated according to those sets. The image datasets were split into training (n=17 340), validation (n=3491), and testing (n=2852) groups, which had completely independent sets of patients.

Results:

The accuracy of prediction in each pulmonary vein computed tomography image for NPV trigger was up to 82.4±2.0%. The sensitivity and specificity were 64.3±5.4% and 88.4±1.9%, respectively. For each patient, the accuracy of prediction for a NPV trigger was 88.6±2.3%. The sensitivity and specificity were 75.0±5.8% and 95.7±1.8%, respectively. The area under the curve for each image and patient were 0.82±0.01 and 0.88±0.07, respectively.

Conclusions:

The deep learning model using preablation pulmonary vein computed tomography can be applied to predict the trigger origins in patients with paroxysmal atrial fibrillation receiving catheter ablation. The application of this model may identify patients with a high risk of NPV trigger before ablation.

Subclinical decrease in cardiac autonomic and diastolic function in patients with metabolic disorders: HSCAA study

Heart failure due to decreased diastolic function, HFpEF, is a growing health concern with rising prevalence. We examined subclinical cardiac autonomic and diastolic functions in 605 patients with metabolic diseases classified as pre-heart failure. Presence of glucose intolerance or diabetes, or visceral adiposity was significantly associated with reduced cardiac autonomic and diastolic functions. Higher autonomic functions were significantly associated with a parameter of better cardiac diastolic function (E/A) (SDNN: r = 0.306, p < 0.01; HF: r = 0.341, p < 0.01), with the association independent of diabetes, body mass index, visceral adiposity and insulin resistance index. Thus, reduced autonomic function may be a potential predictor for decreased cardiac diastolic functions in metabolic disorders.

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Metabolic disorders, including diabetes and obesity, are known risk factors for HFpEF.

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Reduced autonomic function may be involved in pathogenesis of HFpEF.

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Cardiac diastolic function in metabolic disorders in pre-HF phase is not well examined.

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In pre-HF subjects, reduced autonomic function is associated with lower cardiac diastolic functions.

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Our findings provide new insights into HFpEF etiology in metabolic disorders.

Role of Ganglionated Plexus Ablation in Atrial Fibrillation on the Basis of Supporting Evidence

The role of the autonomic nervous system (ANS) in the onset and maintenance of atrial fibrillation (AF) may be related to autonomic imbalance. The ANS may cause specific cellular electrophysiological phenomena, such as, shortening of the atrial effective refractory periods (ERPs) and ectopy based on firing activity in pulmonary vein myocytes. High frequency stimulation of atrial ganglionated plexi (GPs) may cause an increase in ERP dispersion and induce AF. Autonomic modification strategies by targeting GPs with catheter ablation have emerged as new targets. Various strategies have been used to detect location of GPs.However, it is still not clear which is the best method to localize GPs, how many GPs should be targeted, and what are the long-term consequences of these therapies. In this review, we discuss available evidence on the clinical impact of GP ablation to treat AF.

Autonomic modulation before and after paroxysmal atrial fibrillation events in patients with ischemic heart disease

BACKGROUND

The autonomic activity plays a critical role in generating paroxysmal atrial fibrillation (PAF). This study aimed to evaluate the changes in the autonomic nerve activity before and after PAF events in patients with and without ischemic heart disease (IHD).

METHODS

The study included 49 patients (71.43 ± 12.24 years old, 26 males) with PAF events lasting more than 30 s during 24-hr ambulatory Holter monitoring. The 20-min intervals before and after PAF events were divided into eight segments of 5 min each. Heart rate variability (HRV) analyses of the time and frequency domains were applied to each time segment.

RESULTS

Patients with IHD had significant increases in the root mean square successive differences (r-MSSD, p = .008) and HF component (p = .04), followed by a significant increase in the LF/HF ratio (p = .02) preceding the onset of PAF. Patients without IHD had only a significant increase in the r-MSSD (p = .045) preceding the onset of PAF. During the termination of PAF events, patients in both the IHD and control groups had a significantly decreased r-MSSD and HF, respectively.

CONCLUSION

Ischemic heart disease causes a sympathovagal imbalance in the initiation of PAF. Decreased parasympathetic activity regulated the termination of PAF in both the IHD and control groups. The modification of the autonomic nervous system (ANS) activity should be individualized due to the autonomic complexity in AF arrhythmogenesis and termination.

Heart rate increase after pulmonary vein isolation predicts freedom from atrial fibrillation at 1 year

INTRODUCTION

Ablation of atrial vagal ganglia has been associated with improved pulmonary vein isolation (PVI) outcomes. Disruption of vagal reflexes results in heart rate (HR) increase. We investigated the association between HR change after PVI and freedom from atrial fibrillation (AF) at 1 year.

METHODS AND RESULTS

Patients who underwent PVI for paroxysmal AF were identified from the Johns Hopkins Hospital AF registry. Electrocardiograms taken pre-PVI and post-PVI were used to determine the change in HR. Patients followed-up at 3, 6, and 12 months. Of 257 patients (66% male, age 59+/-11 years), 134 (52%) remained free from AF at 1 year. The average HR increased from 60.6 ± 11.3 beats per minute (bpm) pre-PVI to 70.7 ± 12.0 bpm post-PVI. Patients with recurrence of AF had lower post-PVI HR than those who remained free from AF (67.8 ± 0.2 vs 73.3 ± 13.0 bpm; P <.001). The probability of AF recurrence at 1-year decreased as the change in HR increased (estimated odds ratio [OR], 0.83; 95% confidence interval [CI, 0.74-0.93]; P = .002). HR increase more than 15 bpm was associated with the lowest odds of AF recurrence (estimated OR, 0.39; 95% [0.17-0.85]; P = .018) compared to HR decrease.

CONCLUSIONS

Resting HR was found to increase after PVI. Increase in HR more than 15 bpm has a positive association with remaining free from atrial fibrillation at 1 year.

Association of Autoantibodies against M2-Muscarinic Acetylcholine Receptor with Atrial Fibrosis in Atrial Fibrillation Patients

Objectives

To investigate the association of serum autoantibodies against M2-muscarinic acetylcholine receptor (anti-M2-R) with atrial fibrosis in long-standing persistent atrial fibrillation (AF) patients.

Methods

Twenty-four long-standing persistent AF patients, scheduled to undergo hybrid ablation surgery, were enrolled in the study. Twenty-six patients with sinus rhythm, scheduled to undergo coronary artery bypass grafting surgery, were enrolled into the non-AF group. We detected serum anti-M2-R levels. Left atrial appendages were subjected to histological and molecular biological assays. Patients in the AF group received follow-up for two years.

Results

The AF group showed significantly higher serum anti-M2-R levels compared to the non-AF group (496.2 ± 232.5 vs. 86.3 ± 25.7 pmol/L, p < 0.001). The AF group exhibited severe fibrosis in the left atrial appendages, as indicated by increased collagen volume fraction (45.2 ± 4.7% vs. 27.6 ± 8.3%, p < 0.001), and higher levels of collagen I (0.52 ± 0.04 vs. 0.24 ± 0.06, p < 0.001) and collagen III (0.51 ± 0.07 vs. 0.36 ± 0.09, p < 0.001). TGF-β1 and CTGF were also upregulated in the AF group. A positive correlation between serum anti-M2-R levels and fibrosis of the left atrial appendage and fibrogenic indexes was observed.

Conclusions

Serum anti-M2-R levels are higher in AF patients and are associated with the severity of atrial fibrosis. In addition, serum anti-M2-R levels are positively correlated to TGF-β1 and CTGF expression in the left atrial appendage.

Histone deacetylase inhibition attenuates atrial arrhythmogenesis in sterile pericarditis

Cardiac surgery is complicated with atrial fibrillation (AF). Histone deacetylase (HDAC) inhibition reduces AF occurrence. In pericarditis, HDAC inhibition may modulate AF trigger and substrate. We recorded electrocardiograms in control and pericardiotomic (op) rabbits without and with an intraperitoneal injection of MPT0E014 (HDAC inhibitor). Conventional microelectrodes recorded action potentials (APs) in pulmonary veins (PVs), the right and left atrium (LA). Masson's trichrome was used to identify collagen fibers in PVs and the LA. Electrocardiograms showed frequent atrial premature contractions in op rabbits, but not in the other 3 groups. The beating rates in PVs and opPVs were decreased by MPT0E014 treatment. Spontaneous burst firings occurred in opPVs (36.4%), but not in control PVs. H₂O₂ induced greater burst firings in opPVs (72.7%) than in control PVs (11.1%), MPT0E014-treated PVs (16.7%), and MPT0E014-treated opPVs (12.5%). The AP duration at a repolarization extent of 90% (APD₉₀) was shorter in the opLA than that in the control LA. In the presence of isoproterenol (1 μM), rapid atrial pacing (RAP, 20 Hz) induced a higher incidence of burst firings in the opLA (90%) than in the other groups. In contrast, acetylcholine (5 mM) and RAP induced a lower incidence of burst firing in the MPT0E014-treated LA (33.3%) than in the other groups. Fibrosis prevailed in opPVs and the opLA compared to the respective control PVs and LA, which was attenuated in those that received MPT0E014. In conclusion, a pericardiotomy increased fibrosis and arrhythmogenesis in PVs and the LA, which were prevented by HDAC inhibition.

The ambiguity of physical activity, exercise and atrial fibrillation

Although commonly associated with cardiovascular disease or other medical conditions, atrial fibrillation may also occur in individuals without any known underlying conditions. This manifestation of atrial fibrillation has been linked to extensive and long-term exercise, as prolonged endurance exercise has shown to increase prevalence and risk of atrial fibrillation. In contrast, more modest physical activity is associated with a decreased risk of atrial fibrillation, and current research indicates a J-shaped association between atrial fibrillation and the broad range of physical activity and exercise. This has led to the hypothesis that the mechanisms underlying an increased risk of atrial fibrillation with intensive exercise are different from those underlying a reduced risk with moderate physical activity, possibly linked to distinctive characteristics of the population under study. High volumes of exercise over many years performed by lean, healthy endurance trained athletes may lead to cardiac (patho)physiological alterations involving the autonomic nervous system and remodelling of the heart. The mechanisms underlying a reduced risk of atrial fibrillation with light and moderate physical activity may involve a distinctive pathway, as physical activity can potentially reduce the risk of atrial fibrillation through favourable effects on cardiovascular risk factors.

Association of SCN10A Polymorphisms with the Recurrence of Atrial Fibrillation after Catheter Ablation in a Chinese Han Population

The nonsynonymous SCN10A single nucleotide polymorphism (SNP) rs6795970 has been reported to associate with PR interval and atrial fibrillation (AF) and in strong linkage disequilibrium (LD) with the AF-associated SNP rs6800541. In this study, we investigated whether rs6795970 polymorphisms are associated with AF recurrence after catheter ablation. A total of 502 consecutive patients with AF who underwent catheter ablation were included. AF recurrence was defined as a documented episode of any atrial arrhythmias lasting ≥30 s after a blanking period of 3 months. AF recurrence was observed between 3 and 12 months after catheter ablation in 24.5% of the patients. There was a significant difference in the allele distribution (p = 7.86 × 10⁻⁵) and genotype distribution (p = 1.42 × 10⁻⁵) of rs6795970 between the AF recurrence and no recurrence groups. In a multivariate analysis, we identified the following independent predictors of AF recurrence: the rs6795970 genotypes in an additive model (OR 0.36, 95%CI 0.22~0.60, p = 7.04 × 10⁻⁵), a history of AF ≥36 months (OR 3.57, 95%CI 2.26~5.63, p = 4.33 × 10⁻⁸) and left atrial diameter (LAD) ≥40 mm (OR 1.85, 95%CI 1.08~3.19, p = 0.026). These data suggest that genetic variation in SCN10A may play an important role in predicting AF recurrence after catheter ablation in the Chinese Han population.

P-wave dispersion in patients with Guillain-Barré syndrome

Cardiac autonomic dysfunction assessed by the presence of arrhythmia, by the methods, such as heart rate variability or blood pressure variability, and by the electrocardiographic abnormalities is common in Guillain-Barré syndrome (GBS). The goal of present study was to analyze the P-wave dispersion (PWD), which is the non-invasive marker of atrial arrhythmia, in GBS patients and to compare those with healthy individuals. Thirty-five patients with GBS (mean age 53.6 ± 15.5 years) and 35 healthy controls (mean age 49.2 ± 14.1 years) were included to this study. Demographic and clinical information of the patients with GBS were assessed retrospectively. A 12-lead surface electrocardiogram was acquired from all participants. Minimum and maximum P-wave duration and PWD were measured in the patients with GBS and healthy controls. Maximum P-wave duration and PWD were significantly longer, and minimum P-wave duration was significantly lower in the patients with GBS rather than the control group (p = 0.037, p < 0.001, p = 0.007, respectively). GBS disability scores were positively correlated with the maximum P-wave duration (p = 0.015, r = 0.406) and PWD (p = 0.001, r = 0.525). We found that PWD was significantly prolonged in GBS patients compared with the controls. The increased PWD which is cheap, quick, non-invasive and feasible electrocardiographic marker may be related to increased risk for atrial fibrillation in patients with GBS.

Modulation of Autonomic Nervous Activity in the Termination of Paroxysmal Atrial Fibrillation

BACKGROUND

Autonomic nervous activity plays a critical role in the genesis of paroxysmal atrial fibrillation (AF, PAF). However, the role of autonomic nervous activity on AF termination has not been elucidated. Heart rate variability (HRV) is widely used to evaluate autonomic nervous activity in humans. The purpose of this study was to assess whether autonomic nervous activity assessed by HRV contributes to AF termination.

METHODS

Electrocardiograms (ECGs) and HRV were studied in patients with termination of sustained (>30 s) PAF by 24-hour ambulatory Holter monitoring. The 20-minute interval after termination of AF was divided into four segments of 5 minutes each, and a frequency analysis was applied to each 5-minute segment.

RESULTS

In 52 AF episodes, the ultra-low-frequency power, very-low-frequency power, low-frequency power (LF), high-frequency power (HF), and total power significantly decreased with time after episodes of AF termination. The LF/HF (L/H) ratio, normalized LF (LFnu), and normalized HF (HFnu) significantly changed after AF termination. Eighteen (35%) episodes had decreased LFnu and increased HFnu (sympathetic withdrawal and vagal activation), which had slower average AF ventricular responses (92 ± 16 beats/min vs 105 ± 24 beats/min, P < 0.05) than the AF termination episodes (n = 34, 65%) with increased LFnu and decreased HFnu (sympathetic activation and vagal withdrawal). Moreover, older patients (aged >65 years) had a higher incidence (n = 27, 75%) of AF termination with increased LFnu and decreased HFnu than did younger patients (aged ≤65 years, n = 7, 44%, P < 0.05).

CONCLUSION

Autonomic changes critically regulate termination of PAF, which is modulated by aging.

Different Impacts of Atrial Fibrillation and Cardiac Premature Contractions on the Health-Related Quality of Life in Elderly People: The Yilan Study

Atrial fibrillation (AF) is currently recognized as one of the most common cardiac arrhythmias worldwide, with the increasing prevalence that has been estimated to be as high as 9% among the elderly. Health-related quality of life (HRQoL) has become an important patient-centered health outcome measurement, but the impacts created by AF and other arrhythmias with similar symptoms, such as frequent atrial and ventricular premature contractions (APCs and VPCs, defined as ≥ 3 beats/5 minutes), have not been extensively evaluated. The Yilan Study is a population-based community health survey, which in part aims to evaluate the prevalence and impacts of these arrhythmias on the HRQoL in a community dwelling elderly population. A total of 1,732 citizens from the Yilan, Taiwan, aged 65 years or older (45.8% male) were enrolled and visited at their homes, where HRQoL was measured utilizing the Short Form-12 Health Survey. Each participant's heart rhythm was recorded with an electrocardiographic monitor for 5 minutes. The results disclosed that the prevalence of AF of this aged population was 5.8%, similar to the mean global prevalence. Besides, the prevalence of frequent APCs and frequent VPCs in these elderly people were 7.1% and 5.5%, respectively. After multiple regression analysis, elderly people with AF had lower scores in the physical component of HRQoL, while those elderly people with frequent VPCs had lower scores in the mental component. Ultimately, these findings can provide additional useful and population-specific information about AF, and assist medical professionals in designing more effective strategies for cardiac arrhythmia treatments.

Novel Percutaneous Epicardial Autonomic Modulation in the Canine for Atrial Fibrillation: Results of an Efficacy and Safety Study

BACKGROUND

Endocardial ablation of atrial ganglionated plexi (GP) has been described for treatment of atrial fibrillation (AF). Our objective in this study was to develop percutaneous epicardial GP ablation in a canine model using novel energy sources and catheters.

METHODS

Phase 1: The efficacy of several modalities to ablate the GP was tested in an open chest canine model (n = 10). Phase 2: Percutaneous epicardial ablation of GP was done in six dogs using the most efficacious modality identified in phase 1 using two novel catheters.

RESULTS

Phase 1: Direct current (DC) in varying doses (blocking [7-12 μA], electroporation [300-500 μA], ablation [3,000-7,500 μA]), radiofrequency ablation (25-50 W), ultrasound (1.5 MHz), and alcohol (2-5 mL) injection were successful at 0/8, 4/12, 5/7, 3/8, 1/5, and 5/7 GP sites. DC (500-5,000 μA) along with alcohol irrigation was tested in phase 2. Phase 2: Percutaneous epicardial ablation of the right atrium, oblique sinus, vein of Marshall, and transverse sinus GP was successful in 5/6 dogs. One dog died of ventricular fibrillation during DC ablation at 5,000 μA. Programmed stimulation induced AF in six dogs, preablation and no atrial arrhythmia in three, flutter in one, and AF in one postablation. Heart rate, blood pressure, effective atrial refractory period, and local atrial electrogram amplitude did not change significantly postablation. Microscopic examination showed elimination of GP, and minimal injury to atrial myocardium.

CONCLUSION

Percutaneous epicardial ablation of GP using DC and novel catheters is safe and feasible and may be used as an adjunct to pulmonary vein isolation in the treatment of AF in order to minimize additional atrial myocardial ablation.

Head-Up Tilt

Autonomic dysfunction has been associated with paroxysmal atrial fibrillation (PAF). The head-up tilt test (HUTT) is an important diagnostic tool for autonomic dysfunction. The aim of this study was to examine atrial fibrillation recurrence after RFCA by performing HUTT. A total of 488 consecutive patients with PAF who underwent RFCA were prospectively enrolled. HUTT was positive in 154 (31.6%) patients after a mean follow-up of 22.7 ± 3.5 months, and 163 (33.4%) had a recurrence. HUTT positive was significantly higher in PAF patients with recurrence compared to those without (68 (41.7%) versus 86 (26.5%), P < 0.001). Multivariate Cox regression analysis revealed that HUTT positive (HR: 1.96; 95% CI: 1.49-2.48, P < 0.001), left atrial diameter (HR: 1.77; 95%CI: 1.15-2.11, P = 0.004), AF duration (HR: 1.27; 95%CI: 0.98-1.83, P = 0.014), and sleep apnea (HR: 1.02; 95%CI: 0.81-1.53, P = 0.032) were independent predictors of clinical recurrence after RFCA. The success rate of ablation was 70.4% in patients in the HUTT negative group compared with 58.4% in patients in the HUTT positive group (log-rank P = 0.006). Patients with a positive headup tilt test were at an increased risk of AF recurrence after catheter ablation. Our results suggest that HUTT was a significant predictor for AF recurrence after catheter ablation for PAF.

Arrhythmia risk associated with sleep disordered breathing in chronic heart failure

The intersecting relationships of sleep disordered breathing (SDB), arrhythmogenic risk and chronic heart failure (HF) are complex and most likely multi-directional and synergistic. Autonomic dysfunction is a common pathophysiological feature of each of these entities. Intermittent hypoxia, hypercapnia, mechanical cardiac influences due to upper airway obstruction and rostral fluid shifts are SDB-specific mechanisms which may trigger, perpetuate and exacerbate HF and arrhythmogenesis. Specific pathophysiological mechanisms will vary according to the predominance of central as compared to obstructive sleep apnea. The risk of cardiac arrhythmias and HF attributable to SDB may be considerable given the high prevalence of SDB and its likely physiologic burden. The current review focuses on the data, which have accrued elucidating the specific contributory mechanisms of SDB in cardiac arrhythmias and HF, highlighting the clinical relevance and effects of standard SDB treatment on these outcomes, and describing the role of novel therapeutics.

Effect of pulmonary vein isolation on atrial fibrillation recurrence after ablation of paroxysmal supraventricular tachycardia in patients with high dispersion of atrial refractoriness

PURPOSE

This study aimed to assess pulmonary vein isolation (PVI) efficacy on atrial fibrillation (AF) recurrence and to determine a predictive dispersion of atrial refractoriness (dERP) value for performing PVI in paroxysmal supraventricular tachycardia (PSVT) patients.

METHODS

Of 67 PSVT patients with past AF episodes who underwent accessory pathway (AP) or slow pathway of atrioventricular node ablation, 63 (4 lost to follow-up or death) were assigned into two groups (A and B; 29 and 34 patients, respectively) based on whether they underwent or not subsequent PVI, and all were followed-up up to 3 years. Atrial effective refractory period (AERP) and dERP were measured during the ablation procedure.

RESULTS

In receiver operating characteristic (ROC) curve analysis, dERP = 74.5 ms effectively predicted AF recurrence in PSVT patients (p = 0.003). Difference in AF recurrence rate between groups did not reach statistical significance (17.2%, 5/29 vs. 29.4%, 10/34, p = 0.203). AF recurrence rate was lower in patients with dERP >74.5 ms who underwent AP or slow-pathway ablation with vs. without PVI (18.2%, 2/11 vs. 77.8%, 7/9, p = 0.012).

CONCLUSIONS

PVI addition after successful AP or slow pathway of atrioventricular node ablation significantly reduced AF recurrence in PSVT patients with high atrial vulnerability (dERP >74.5 ms).

Nav1.8 channels in ganglionated plexi modulate atrial fibrillation inducibility

AIMS

Emerging evidences indicate that SCN10A/NaV1.8 is associated with cardiac conduction and atrial fibrillation, but the exact role of NaV1.8 in cardiac electrophysiology remains poorly understood. The present study was designed to investigate the effects of blocking NaV1.8 channels in cardiac ganglionated plexi (GP) on modulating cardiac conduction and atrial fibrillation inducibility in the canine model.

METHODS AND RESULTS

Thirteen mongrel dogs were randomly enrolled. Right cervical vagus nerve stimulation (VNS) was applied to determine its effects on the sinus rate, ventricular rate during atrial fibrillation, PR interval, atrial effective refractory period, and the cumulative window of vulnerability. The NaV1.8 blocker A-803467 (1 μmol/0.5 mL per GP, n = 7) or 5% DMSO/95% polyethylene glycol (0.5 mL per GP, n = 6, control) was injected into the anterior right GP and the inferior right GP. The effects of VNS on the sinus rate, ventricular rate, PR interval, atrial effective refractory period, and the cumulative window of vulnerability were significantly eliminated at 10, 35, and 90 min after A-803467 injection. In separate experiments (n = 8), A-803467 blunted the slowing of sinus rate with increasing stimulation voltage of the anterior right GP at 10 min after local injection.

CONCLUSIONS

Blockade of NaV1.8 channels suppresses the effects of VNS on cardiac conduction and atrial fibrillation inducibility, most likely by inhibiting the neural activity of the cardiac GP.

Supraventricular arrhythmias after thoracotomy: is there a role for autonomic imbalance?

Supraventricular arrhythmias are common rhythm disturbances following pulmonary surgery. The overall incidence varies between 3.2% and 30% in the literature, while atrial fibrillation is the most common form. These arrhythmias usually have an uneventful clinical course and revert to normal sinus rhythm, usually before patent's discharge from hospital. Their importance lies in the immediate hemodynamic consequences, the potential for systemic embolization and the consequent long-term need for prophylactic drug administration, and the increased cost of hospitalization. Their incidence is probably related to the magnitude of the performed operative procedure, occurring more frequently after pneumonectomy than after lobectomy. Investigators believe that surgical factors (irritation of the atria per se or on the ground of chronic inflammation of aged atria), direct injury to the anatomic structure of the autonomic nervous system in the thoracic cavity, and postthoracotomy pain may contribute independently or in association with each other to the development of these arrhythmias. This review discusses currently available information about the potential mechanisms and risk factors for these rhythm disturbances. The discussion is in particular focused on the role of postoperative pain and its relation to the autonomic imbalance, in an attempt to avoid or minimize discomfort with proper analgesia utilization.

Usefulness of severe cardiac sympathetic dysfunction to predict the occurrence of rapid atrial fibrillation in patients with Wolff-Parkinson-White syndrome

Atrial fibrillation (AF) can be a potentially life-threatening arrhythmia when it conducts rapidly through the accessory pathway, which was not predicted by the noninvasive method. We evaluated the cardiac sympathetic activity for predicting the occurrence of AF in patients with Wolff-Parkinson-White (WPW) syndrome. Iodine-123 metaiodobenzylguanidine scintigraphy was performed under stable sinus rhythm conditions at rest <1 week before an electrophysiologic study (EPS) to assess the sympathetic activity using the heart/mediastinum (H/M) ratio in 45 consecutive patients with WPW who had a history of supraventricular tachycardia (mean ± SD, age: 47 ± 17 years, 42.2% women). The study also included 15 normal healthy volunteers (56 ± 17 years, 40% women). The H/M ratio was lower in patients with WPW syndrome than in the normal control group, and in the 15 patients with AF induced during EPS than in the 30 patients without AF (p <0.0001). The sensitivity of H/M ratio ≤2.8 for predicting the AF induced during EPS was 75% in 12 of 16 patients, and the specificity was 89.7% in 26 of 29 patients. The H/M ratio was positively correlated with anterograde effective refractory period (r = 0.514, p <0.0001). The sensitivity of H/M ratio ≤2.75 for predicting the AF with a short anterograde effective refractory period (≤250 ms) was 91.7% in 11 of 12 patients, and the specificity was 90.9% in 30 of 33 patients. In conclusion, the severe cardiac sympathetic dysfunction was associated with the occurrence of AF, particularly in those with rapid AF and in patients with WPW syndrome.

Role of Stress in Cardiac Arrhythmias

Stress is a major trigger of cardiac arrhythmias; it exerts profound effects on electrophysiology of the cardiomyocytes and the cardiac rhythm. Psychological and physiological stressors impact the cardiovascular system through the autonomic nervous system (ANS). While stressors vary, properties of the stress response at the level of cardiovascular system (collectively referred to as the autonomic cardiovascular responses) are similar and can be studied independently from the properties of specific stressors. Here, we will review the clinical and experimental evidence linking common stressors and atrial arrhythmias. Specifically, we will describe the impact of psychological and circadian stressors on ANS activity and arrhythmogenesis. We will also review studies examining relationships between autonomic cardiovascular responses and cardiac arrhythmias in ambulatory and laboratory settings.

Psychological distress and arrhythmia: risk prediction and potential modifiers

The connection between the heart and the brain has long been anecdotally recognized but has systematically been studied only relatively recently. Cardiac arrhythmias, especially ventricular arrhythmias that can lead to sudden cardiac death, remain a major public health concern and there is mounting evidence that psychological distress plays a critical role both as a predictor of high-risk cardiac substrate and as an inciting trigger. The transient, unpredictable nature of emotions and cardiac arrhythmias has made their study challenging, but evolving technologies in monitoring and imaging along with larger epidemiological data sets have encouraged more sophisticated studies examining this relationship. Here we review the research on psychological distress including anger, depression and anxiety on cardiac arrhythmias, insights into proposed mechanisms, and potential avenues for future research.

Predictive value of pre-procedural autoantibodies against M2-muscarinic acetylcholine receptor for recurrence of atrial fibrillation one year after radiofrequency catheter ablation

Background

Increasing evidences have suggested that autoantibodies against muscarinic-2 acetylcholine receptor (anti-M₂-R) may play an important role in the development of atrial fibrillation (AF). Predictive value of pre-procedural anti-M₂-R for the recurrence of AF after radiofrequency catheter ablation is still unclear.

Methods

Totally 76 AF patients with preserved left ventricular systolic function were prospectively enrolled and subjected to ablation after the detection of serum anti-M₂-R by enzyme linked immunosorbent assay. These patients were given follow-up examination for one year after ablation. Risk estimation for the recurrence of AF was performed using the univariate and multivariate logistic regression.

Results

In AF group, serum anti-M₂-R was significantly higher than that in the control group in terms of frequency (40.8% versus 11.7%; p < 0.001) and titer (1:116 versus 1:29; p < 0.001). Compared with paroxysmal AF patients, persistent AF patients had higher frequency (57.6% versus 27.9%; p = 0.009) and titer (1:132 versus 1:94; p = 0.012) for autoantibodies. During one-year follow-up examination after ablation, the recurrence of AF was observed in 25 (32.9%) patients. Multivariate analysis showed that pre-procedural serum anti-M₂-R was an independent predictor for the recurrence of AF at the time point of 12 months after ablation (odds ratio: 4.701; 95% confidence interval: 1.590-13.894; p = 0.005).

Conclusions

In AF patients, the frequency and titer of serum anti-M₂-R were significantly higher than those in the control group with sinus rhythm. Pre-procedural serum anti-M₂-R was an independent predictor for the recurrence of AF one year after radiofrequency catheter ablation.

P-wave dispersion by 12-lead electrocardiography in carotid artery stenting

OBJECTIVE

Although carotid artery stenting (CAS) is an effective treatment for severe carotid stenosis, it has been associated with alterations in autonomic functions during or shortly after the procedure. And, autonomic functions influence P-wave durations. In this study, our aim was to investigate P-wave durations on 12-lead surface electrocardiography after CAS.

METHODS

Patients (19 male, 8 female) who are suitable for CAS, without a history of hypertension, diabetes mellitus, severe coronary artery or valvular heart disease, were enrolled in our study. 12-lead surface electrocardiography recordings were obtained at the beginning, immediately after and at the 24 h of the procedure. P-wave maximum, minimum and dispersion durations were analyzed by double-blinded observers. Results were statistically analysed using Friedman and Wilcoxon tests.

RESULTS

The P maximum and P dispersion values were significantly increased immediately after the procedure and continued with high levels at 24-h recordings, respectively (128 ± 10/19 ± 7, 143 ± 14/37 ± 11, and 137 ± 11/30 ± 7 ms, p value <0.05). The P minimum value was significantly decreased immediately after the procedure (109 ± 11/105 ± 10 ms, p value <0.05). At 24-h recordings, a nonsignificant increase occured in P minimum values (106 ± 8 ms).

CONCLUSIONS

P maximum and dispersion durations were significantly increased after the CAS and continued with high levels at 24-h recordings, which may be associated with the alterations in autonomic functions via augmented parasympathetic activity by vagally mediated stimulus. Overall, these findings suggest that decline in cardiovascular activity is prolonged at least 24 h after CAS.

Global Psychological Distress and Risk of Atrial Fibrillation Among Women: The Women's Health Study

Background

Symptoms of psychological distress and depression have been associated with risk of ventricular arrhythmias and sudden cardiac death. Their relationship with atrial arrhythmias, however, is less well studied.

Methods and Results

We sought to assess the long-term relations between psychological distress and risk of atrial fibrillation (AF) in the Women's Health Study of female health professionals. We measured psychological symptoms with the Mental Health Inventory-5. Incident AF was assessed annually and verified through medical records. Among 30 746 women without history of cardiovascular disease or AF, 771 cases of AF occurred during a median follow-up of 125 months (interquartile range, 117–130 months). Global psychological distress was not associated with AF risk in age-stratified (P=0.61 for linear trend) or multivariable proportional-hazards models that included antidepressant use (P=0.34). A proxy measure for depression, consisting of Mental Health Inventory-5 score <53, antidepressant use, or both, was also not associated with AF risk in multivariable models (hazard ratio=0.99; 95% confidence interval, 0.78–1.25; P=0.93). In post hoc analyses of individual symptoms from the Mental Health Inventory-5, positive affect, “feeling happy some/a good bit of the time,” was associated with reduced risk of AF (hazard ratio=0.69; 95% confidence interval, 0.49–0.99; P=0.04); other depressive and anxious symptoms were not.

Conclusions

In this prospective study of women without known cardiovascular disease, global psychological distress and specific depressive symptoms were unrelated to AF risk. (J Am Heart Assoc. 2012;1:e001107 doi: 10.1161/JAHA.112.001107.)

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.

Preoperative left atrial dysfunction and risk of postoperative atrial fibrillation complicating thoracic surgery

OBJECTIVE

Postoperative atrial fibrillation complicating general thoracic surgery increases morbidity and stroke risk. We aimed to determine whether preoperative atrial dysfunction or other echocardiographic markers are associated with postoperative atrial fibrillation.

METHODS

In 191 patients who had undergone anatomic lung or esophageal resection, preoperative clinical and echocardiographic data were compared between patients with and without postoperative atrial fibrillation. Presence of postoperative atrial fibrillation lasting more than 5 minutes during hospitalization was detected using continuous telemetry or 12-lead electrocardiography. Maximal left atrial volume and indices of left atrial function were assessed.

RESULTS

Patients with postoperative atrial fibrillation (33/191, 17%) were older (71 ± 5 years vs 64 ± 12 years, P < .0001), were taking β-blockers more often, had greater left atrial volume, had decreased left atrial emptying fraction, and had lower E' and A' septal velocities compared with patients without postoperative atrial fibrillation. The incidence of postoperative atrial fibrillation in patients with left atrial volume 32 mL/m(2) or greater was 37% (11/30) and greater than in those with left atrial volume less than 32 mL/m(2) (14%, 22/160, P = .002). Length of hospital stay was significantly increased in patients with postoperative atrial fibrillation compared with patients without (P = .04). Older age was significantly associated with greater β-blocker use and left atrial volume and lower left atrial emptying fraction. On multivariate analysis, lower left atrial emptying fraction (odds ratio, 1.03 per unit decrement; 95% confidence interval, 1.002-1.065; P = .04) and preoperative use of β-blockers (odds ratio, 2.82; 95% confidence interval, 1.18-6.77; P = .02) were the only independent risk factors associated with postoperative atrial fibrillation.

CONCLUSIONS

These data show that an echocardiogram before major thoracic surgery, increased use of preoperative β-blockers, and decreased left atrial emptying fraction were associated with postoperative atrial fibrillation. Echocardiographic predictors of left atrial mechanical dysfunction may prove clinically useful in risk stratifying patients in whom postoperative atrial fibrillation is more likely to develop and to benefit from prevention strategies aimed at mitigating atrial function before surgery.

Effects of the novel amiodarone-like compound SAR114646A on cardiac ion channels and ventricular arrhythmias in rats

Amiodarone is the "gold standard" for current antiarrhythmic therapy because it combines efficacy with good hemodynamic and electrophysiological tolerance. Amiodarone is effective against both atrial and ventricular arrhythmias by intravenous (i.v.) or oral route. However, the i.v. formulation has limitations. Therefore, we identified SAR114646A, an amiodarone-like antiarrhythmic agent with good aqueous solubility suitable for i.v. application. Patch-clamp experiments were performed with isolated cardiomyocytes from guinea pigs and rats. In guinea pig ventricular cardiomyocytes, the fast Na(+) channel and the L-type Ca(2+) channels were blocked by SAR114646A with half-maximal concentrations (IC(50)) of 2.0 and 1.1 μM, respectively. The tail current of the fast activating rectifying potassium channel I(Kr) was blocked with an IC(50) value of 0.6 μM, whereas the IC(50) values for inhibition of the I(Ks) and I(K1) channels was >10 μM. ATP-sensitive K(+) channels were evoked by application of the channel opener rilmakalim (3 μM). SAR114646A blocked this current with an IC(50) value of 2.8 μM. In guinea pig atrial cardiomyocytes, carbachol (1 μM) was used to activate the I(KACh) and SAR114646A inhibited this current with IC(50) of 36.5 nM. The transient outward current I(to) and the sustained current I(sus) were investigated in rat ventricular myocytes. SAR114646A blocked these currents with IC(50) of 1.8 and 1.2 μM, respectively. When expressed in Chinese hamster ovary cells, the currents hKv1.5 and hHCN4 were inhibited with IC(50) values of 1.1 and 0.4 μM, respectively. Micropuncture experiments in isolated rabbit left atria revealed that SAR114646A prolonged the 50% repolarization significantly at 3 and 10 μM. In guinea pig papillary muscle, the APD at 90% of repolarization was slightly prolonged at 3 and 10 μM. SAR114646A demonstrates antiarrhythmic activity in anaesthetised rats, subjected to 5 min ischemia followed by 10 min reperfusion, where 1 mg/kg of SAR114646A applied as i.v. bolus 5 min prior to ischemia, decreased mortality to 0% compared to 80% under control conditions. In conclusion, SAR114646A is a multichannel blocker with improved water solubility, compared to amiodarone. In contrast to amiodarone, SAR114646A also blocks the K(+) channels I(to) and I(sus). A potent antiarrhythmic effect as observed in rats can also be expected in other animal models.

Remodeling of atrial ATP-sensitive K⁺ channels in a model of salt-induced elevated blood pressure

Hypertension is associated with the development of atrial fibrillation; however, the electrophysiological consequences of this condition remain poorly understood. ATP-sensitive K(+) (K(ATP)) channels, which contribute to ventricular arrhythmias, are also expressed in the atria. We hypothesized that salt-induced elevated blood pressure (BP) leads to atrial K(ATP) channel activation and increased arrhythmia inducibility. Elevated BP was induced in mice with a high-salt diet (HS) for 4 wk. High-resolution optical mapping was used to measure atrial arrhythmia inducibility, effective refractory period (ERP), and action potential duration at 90% repolarization (APD(90)). Excised patch clamping was performed to quantify K(ATP) channel properties and density. K(ATP) channel protein expression was also evaluated. Atrial arrhythmia inducibility was 22% higher in HS hearts compared with control hearts. ERP and APD(90) were significantly shorter in the right atrial appendage and left atrial appendage of HS hearts compared with control hearts. Perfusion with 1 μM glibenclamide or 300 μM tolbutamide significantly decreased arrhythmia inducibility and prolonged APD(90) in HS hearts compared with untreated HS hearts. K(ATP) channel density was 156% higher in myocytes isolated from HS animals compared with control animals. Sulfonylurea receptor 1 protein expression was increased in the left atrial appendage and right atrial appendage of HS animals (415% and 372% of NS animals, respectively). In conclusion, K(ATP) channel activation provides a mechanistic link between salt-induced elevated BP and increased atrial arrhythmia inducibility. The findings of this study have important implications for the treatment and prevention of atrial arrhythmias in the setting of hypertensive heart disease and may lead to new therapeutic approaches.

Respiratory cycle-dependent atrial tachycardia: prevalence, electrocardiographic and electrophysiologic characteristics, and outcome after catheter ablation

BACKGROUND

Little is known about the tachyarrhythmias relating to respiration. Case reports presented patients with respiratory cycle-dependent atrial tachycardias (RCATs), which cyclically emerge after starting inspiration and cease during expiration.

OBJECTIVE

The aim of the present study was to elucidate the prevalence, characteristics, and long-term outcome after radiofrequency catheter ablation (RFCA) of RCATs.

METHODS

The electrocardiographic and electrophysiologic properties and results of RFCA were analyzed in 60 patients with a total of 71 focal atrial tachycardias (ATs).

RESULTS

Nine RCATs (13%) were observed in 7 patients (12%). RCATs were irregular, with a mean cycle length ranging from 220 to 650 ms, and developed incessantly accounting for 32% ± 14% of the 24-hour heartbeats. The P-wave morphology was positive or biphasic (positive to negative) in V1, and positive in I and II. The electroanatomical mapping demonstrated a centrifugal activation pattern, with the earliest site located at the antrum of the right superior pulmonary vein (RSPV), inside the RSPV, and inside the superior vena cava (SVC) in 4, 2, and 3 RCATs, respectively. Radiofrequency energy delivery at the earliest site or the electrical isolation of the RSPV and SVC suppressed all RCATs. During a follow-up of 25 ± 15 months, 1 RCAT recurred and was eliminated in a second procedure.

CONCLUSION

RCATs were observed in 13% of the focal ATs. As presumed from the P-wave morphologies, their foci converged around the RSPV or inside the SVC. RFCA was effective to eliminate RCATs.

Autonomic remodeling in the left atrium and pulmonary veins in heart failure: creation of a dynamic substrate for atrial fibrillation

BACKGROUND

Atrial fibrillation (AF) is commonly associated with congestive heart failure (CHF). The autonomic nervous system is involved in the pathogenesis of both AF and CHF. We examined the role of autonomic remodeling in contributing to AF substrate in CHF.

METHODS AND RESULTS

Electrophysiological mapping was performed in the pulmonary veins and left atrium in 38 rapid ventricular-paced dogs (CHF group) and 39 control dogs under the following conditions: vagal stimulation, isoproterenol infusion, β-adrenergic blockade, acetylcholinesterase (AChE) inhibition (physostigmine), parasympathetic blockade, and double autonomic blockade. Explanted atria were examined for nerve density/distribution, muscarinic receptor and β-adrenergic receptor densities, and AChE activity. In CHF dogs, there was an increase in nerve bundle size, parasympathetic fibers/bundle, and density of sympathetic fibrils and cardiac ganglia, all preferentially in the posterior left atrium/pulmonary veins. Sympathetic hyperinnervation was accompanied by increases in β(1)-adrenergic receptor R density and in sympathetic effect on effective refractory periods and activation direction. β-Adrenergic blockade slowed AF dominant frequency. Parasympathetic remodeling was more complex, resulting in increased AChE activity, unchanged muscarinic receptor density, unchanged parasympathetic effect on activation direction and decreased effect of vagal stimulation on effective refractory period (restored by AChE inhibition). Parasympathetic blockade markedly decreased AF duration.

CONCLUSIONS

In this heart failure model, autonomic and electrophysiological remodeling occurs, involving the posterior left atrium and pulmonary veins. Despite synaptic compensation, parasympathetic hyperinnervation contributes significantly to AF maintenance. Parasympathetic and/or sympathetic signaling may be possible therapeutic targets for AF in CHF.

Left atrial pressure and dominant frequency of atrial fibrillation in humans

BACKGROUND

Atrial stretch is thought to play a role in the development of atrial fibrillation (AF). However, the precise mechanism by which stretch contributes to AF maintenance in humans is unknown.

OBJECTIVE

The purpose of this study was to determine the impact of left atrial (LA) pressure on AF frequency in patients undergoing catheter ablation of AF.

METHODS

The subjects of this study were 58 consecutive patients with persistent AF (n = 40) or paroxysmal AF (n = 18) undergoing LA ablation. LA pressure was measured before ablation. Both atria and the coronary sinus were mapped, and regional dominant frequency (DF) was determined.

RESULTS

Mean LA pressure in the persistent AF group was significantly higher than in the paroxysmal AF group (18 ± 5 vs 10 ± 4 mmHg, P <.0001). Mean DF in the persistent AF group was also higher than in the paroxysmal AF group (6.36 ± 0.51 Hz and 5.83 ± 0.54 Hz, P = .0006). In patients with persistent AF, there was a significant correlation between LA pressure and DF at the LA appendage (r = 0.55, P = .0002). DF(max) was found at the LA appendage region in 24 (60%) of the 40 patients with persistent AF (P = .0006). In multivariate analysis, LA pressure was the only independent predictor of DF(max) in the LA appendage (P = .04, odds ratio 1.41, 95% confidence interval 1.02-1.94).

CONCLUSION

Higher LA pressure in patients with persistent AF implies that these patients are more vulnerable to stretch-related remodeling than are patients with paroxysmal AF. The DF of AF was directly related to LA pressure in patients with persistent AF. This finding suggests that atrial stretch may contribute to the maintenance of AF in humans by stabilizing high-frequency sources.