Post-operative atrial fibrillation is associated with a pre-existing structural and electrical substrate in human right atrial myocardium

Postoperative atrial fibrillation (POAF) after cardiac surgery: clinical practice review

Postoperative atrial fibrillation (POAF) after cardiac surgery is associated with elevated morbidity and mortality. Although current prediction models have limited efficacy, several perioperative interventions can reduce patients' risk of POAF. These begin with preoperative medications, including beta-blockers and amiodarone. Moreover, patients should be screened for preexisting atrial fibrillation (AF) so that concomitant surgical ablation and left atrial appendage occlusion can be performed in appropriate candidates. Intraoperative interventions such as posterior pericardiectomy can reduce mediastinal fluid accumulation, which is a trigger for POAF. Furthermore, many preventive strategies for POAF are implemented in the immediate postoperative period. Initiating beta-blockers, amiodarone, or both is reasonable for most patients. Overdrive atrial pacing, colchicine, and steroids have been used by some, although the evidence base is less robust. For patients with POAF, rate-control and rhythm-control strategies have comparable outcomes. Decision-making regarding anticoagulation should recognize that the stroke risk associated with POAF appears to be lower than that for general nonvalvular AF. The evidence that oral anticoagulation reduces stroke risk is less clear for POAF patients than for patients with general nonvalvular AF. Given that POAF tends to be shorter-lived and is associated with greater bleeding risks in the perioperative period, decisions regarding anticoagulation should be individualized. Finally, wearable technology and machine learning algorithms for better predicting and managing POAF appear to be coming soon. These technologies and a comprehensive clinical program could meaningfully reduce the incidence of this common complication.

Identification of Atrial Transmural Conduction Inhomogeneity Using Unipolar Electrogram Morphology

(1) Background: Structural remodeling plays an important role in the pathophysiology of atrial fibrillation (AF). It is likely that structural remodeling occurs transmurally, giving rise to electrical endo-epicardial asynchrony (EEA). Recent studies have suggested that areas of EEA may be suitable targets for ablation therapy of AF. We hypothesized that the degree of EEA is more pronounced in areas of transmural conduction block (T-CB) than single-sided CB (SS-CB). This study examined the degree to which SS-CB and T-CB enhance EEA and which specific unipolar potential morphology parameters are predictive for SS-CB or T-CB. (2) Methods: Simultaneous endo-epicardial mapping in the human right atrium was performed in 86 patients. Potential morphology parameters included unipolar potential voltages, low-voltage areas, potential complexity (long double and fractionated potentials: LDPs and FPs), and the duration of fractionation. (3) Results: EEA was mostly affected by the presence of T-CB areas. Lower potential voltages and more LDPs and FPs were observed in T-CB areas compared to SS-CB areas. (4) Conclusion: Areas of T-CB could be most accurately predicted by combining epicardial unipolar potential morphology parameters, including voltages, fractionation, and fractionation duration (AUC = 0.91). If transmural areas of CB indeed play a pivotal role in the pathophysiology of AF, they could theoretically be used as target sites for ablation.

Colchicine for prevention of post-operative atrial fibrillation: Meta-analysis of randomized controlled trials

Objective

This study intended to assess the efficacy of colchicine for prevention of post-operative atrial fibrillation (AF).

Background

Post-operative AF is a common complication of surgery operations. Inflammation plays a crucial role in the pathogenesis of post-operative AF. Colchicine, a potent anti-inflammatory drug, may have a role in mitigating the incidence of post-operative AF.

Methods

We searched Cochrane Library, Web of Science, PubMed, China National Knowledge Infrastructure (CNKI), Database of Chinese sci-tech periodicals (COVIP), and Wanfang Database for randomized controlled trials (RCTs) comparing colchicine versus placebo, or usual care for prevention of post-operative AF. The main outcome was the occurrence of AF post operation, which includes cardiac surgery, lung surgery, or pulmonary vein isolation. The estimated risk ratio (RR) for the occurrence of post-operative AF was evaluated using a random-effects model. The safety end point was the development of any side effects.

Results

A total of 12 RCTs with 2274 patients were eventually included in this meta-analysis, where 1141 patients received colchicine and 1133 patients received placebo or usual care. Perioperative colchicine treatment was related to a decreased incidence of post-operative AF (RR: 0.65; 95% confidence interval [CI]: 0.56 to 0.75, p<0.001). Although the incidence of gastrointestinal side effects was increased with colchicine therapy when compared to placebo (RR = 2.49, 95% CI 1.85 to 3.34, p < 0.001), the incidence of major adverse events was not increased (RR = 0.86, 95% CI 0.46 to 1.60, p = 0.64).

Conclusion

In conclusion, the results of our meta-analysis suggest that colchicine treatment could lower the incidence of post-operative AF. Further studies are needed to determine the optimal colchicine treatment regime to minimize the incidence of adverse events.

Anti-Arrhythmic Effects of Sodium-Glucose Co-Transporter 2 Inhibitors

Arrhythmias are clinically prevalent with a high mortality rate. They impose a huge economic burden, thereby substantially affecting the quality of life. Sodium-glucose co-transporter 2 inhibitor (SGLT2i) is a new type of hypoglycemic drug, which can regulate blood glucose level safely and effectively. Additionally, it reduces the occurrence and progression of heart failure and cardiovascular events significantly. Recently, studies have found that SGLT2i can alleviate the occurrence and progression of cardiac arrhythmias; however, the exact mechanism remains unclear. In this review, we aimed to discuss and summarize new literature on different modes in which SGLT2i ameliorates the occurrence and development of cardiac arrhythmias.

Strain Echocardiography to Predict Postoperative Atrial Fibrillation

Postoperative atrial fibrillation (POAF) complicates 15% to 40% of cardiovascular surgeries. Its incidence progressively increases with aging, reaching 50% in octogenarians. This arrhythmia is usually transient but it increases the risk of embolic stroke, prolonged hospital stay, and cardiovascular mortality. Though many pathophysiological mechanisms are known, POAF prediction is still a hot topic of discussion. Doppler echocardiogram and, lately, strain echocardiography have shown significant capacity to predict POAF. Alterations in oxidative stress, calcium handling, mitochondrial dysfunction, inflammation, fibrosis, and tissue aging are among the mechanisms that predispose patients to the perfect “atrial storm”. Manifestations of these mechanisms have been related to enlarged atria and impaired function, which can be detected prior to surgery. Specific alterations in the atrial reservoir and pump function, as well as atrial dyssynchrony determined by echocardiographic atrial strain, can predict POAF and help to shed light on which patients could benefit from preventive therapy.

Neurological Complications of Cardiac Procedures

Neurological complications after cardiac surgery and percutaneous cardiac interventions are not uncommon. These include periprocedural stroke, postoperative cognitive dysfunction after cardiac surgery, contrast-induced encephalopathy after percutaneous interventions, and seizures. In this article, we review the incidence, pathophysiology, diagnosis, and management of these complications. Improved understanding of these complications could lead to their prevention, faster detection, and facilitation of diagnostic workup and appropriate treatment.

The isthmus characteristics of scar-related macroreentrant atrial tachycardia in patients with and without cardiac surgery

INTRODUCTION

Identifying the critical isthmus (CI) in scar-related macroreentrant atrial tachycardia (AT) is challenging, especially for patients with cardiac surgery. We aimed to investigate the electrophysiological characteristics of scar-related macroreentrant ATs in patients with and without cardiac surgery.

METHODS

A prospective study of 31 patients (mean age 59.4 ± 9.81 years old) with scar-related macroreentrant ATs were enrolled for investigation of substrate properties. Patients were categorized into the nonsurgery (n = 18) and surgery group (n = 13). The CIs were defined by concealed entrainment, conduction velocity less than 0.3 m/s, and the presence of local fractionated electrograms.

RESULTS

Among the 31 patients, a total of 65 reentrant circuits and 76 CIs were identified on the coherent map. The scar in the surgical group is larger than the nonsurgical group (18.81 ± 9.22 vs. 10.23 ± 5.34%, p = .016). The CIs in surgical group have longer CI length (15.27 ± 4.89 vs. 11.20 ± 2.96 mm, p = .004), slower conduction velocity (0.46 ± 0.19 vs. 0.69 ± 0.14 m/s, p < .001), and longer total activation time (45.34 ± 9.04 vs. 38.24 ± 8.41%, p = .016) than those in the nonsurgical group. After ablation, 93.54% of patients remained in sinus rhythm during a follow-up of 182 ± 19 days.

CONCLUSION

The characteristics of the isthmus in macroreentrant AT are diverse, especially for surgical scar-related AT. The identification of CIs can facilitate the successful ablation of scar-related ATs.

Post-Cardiac Surgery Atrial Fibrillation: Risks, Mechanisms, Prevention, and Management

Atrial fibrillation (AF) is the most common complication of cardiac surgery (CS). There are numerous risk factors, proposed mechanisms, and financial/clinical implications of post-CS AF (PCSAF). Management involves 2 arms: prevention and treatment. This review highlights and summarizes previous literature on PCSAF and challenges the standard dogma regarding anticoagulation, particularly in the short term.

Sarcolipin Exhibits Abundant RNA Transcription and Minimal Protein Expression in Horse Gluteal Muscle

Ca²⁺ regulation in equine muscle is important for horse performance, yet little is known about this species-specific regulation. We reported recently that horse encode unique gene and protein sequences for the sarcoplasmic reticulum (SR) Ca²⁺-transporting ATPase (SERCA) and the regulatory subunit sarcolipin (SLN). Here we quantified gene transcription and protein expression of SERCA and its inhibitory peptides in horse gluteus, as compared to commonly-studied rabbit skeletal muscle. RNA sequencing and protein immunoblotting determined that horse gluteus expresses the ATP2A1 gene (SERCA1) as the predominant SR Ca²⁺-ATPase isoform and the SLN gene as the most-abundant SERCA inhibitory peptide, as also found in rabbit skeletal muscle. Equine muscle expresses an insignificant level of phospholamban (PLN), another key SERCA inhibitory peptide expressed commonly in a variety of mammalian striated muscles. Surprisingly in horse, the RNA transcript ratio of SLN-to-ATP2A1 is an order of magnitude higher than in rabbit, while the corresponding protein expression ratio is an order of magnitude lower than in rabbit. Thus, SLN is not efficiently translated or maintained as a stable protein in horse muscle, suggesting a non-coding role for supra-abundant SLN mRNA. We propose that the lack of SLN and PLN inhibition of SERCA activity in equine muscle is an evolutionary adaptation that potentiates Ca²⁺ cycling and muscle contractility in a prey species domestically selected for speed.

Simultaneous Endo-Epicardial Mapping of the Human Right Atrium: Unraveling Atrial Excitation

Background The significance of endo-epicardial asynchrony (EEA) and atrial conduction block (CB), which play an important role in the pathophysiology of atrial fibrillation (AF) during sinus rhythm is poorly understood. The aim of our study was therefore to examine 3-dimensional activation of the human right atrium (RA). Methods and Results Eighty patients (79% men, 39% history of AF) underwent simultaneous endo-epicardial sinus rhythm mapping of the inferior, middle and superior RA. Areas of CB were defined as conduction delays of ≥12 ms, EEA as activation time differences of opposite electrodes of ≥15 ms and transmural CB as CB at similar endo-epicardial sites. CB was more pronounced at the endocardium (all locations P<0.025). Amount, extensiveness and severity of CB was higher at the superior RA. Transmural CB at the inferior RA was associated with a higher incidence of post-operative AF (P=0.03). EEA occurred up to 84 ms and was more pronounced at the superior RA (superior: 27 ms [interquartile range, 18.3-39.3], versus mid-RA: 20.3 ms [interquartile range, 0-29.9], and inferior RA: 0 ms [interquartile range, 0-21], P<0.001). Hypertension (P=0.009), diabetes mellitus (P=0.018), and hypercholesterolemia (P=0.015) were associated with a higher degree of EEA. CB (P=0.007) and EEA (P=0.037) were more pronounced in patients with a history of persistent AF compared with patients without AF history. Conclusions This study provides important insights into complex atrial endo-epicardial excitation. Significant differences in conduction disorders between the endo- and epicardium and a significant degree of EEA are already present during sinus rhythm and are more pronounced in patients with cardiovascular risk factors or a history of persistent AF.

Atrial Myocyte NLRP3/CaMKII Nexus Forms a Substrate for Postoperative Atrial Fibrillation

RATIONALE

Postoperative atrial fibrillation (POAF) is a common and troublesome complication of cardiac surgery. POAF is generally believed to occur when postoperative triggers act on a preexisting vulnerable substrate, but the underlying cellular and molecular mechanisms are largely unknown.

OBJECTIVE

To identify cellular POAF mechanisms in right atrial samples from patients without a history of atrial fibrillation undergoing open-heart surgery.

METHODS AND RESULTS

Multicellular action potentials, membrane ion-currents (perforated patch-clamp), or simultaneous membrane-current (ruptured patch-clamp) and [Ca²⁺]_i-recordings in atrial cardiomyocytes, along with protein-expression levels in tissue homogenates or cardiomyocytes, were assessed in 265 atrial samples from patients without or with POAF. No indices of electrical, profibrotic, or connexin remodeling were noted in POAF, but Ca²⁺-transient amplitude was smaller, although spontaneous sarcoplasmic reticulum (SR) Ca²⁺-release events and L-type Ca²⁺-current alternans occurred more frequently. CaMKII (Ca²⁺/calmodulin-dependent protein kinase-II) protein-expression, CaMKII-dependent phosphorylation of the cardiac RyR2 (ryanodine-receptor channel type-2), and RyR2 single-channel open-probability were significantly increased in POAF. SR Ca²⁺-content was unchanged in POAF despite greater SR Ca²⁺-leak, with a trend towards increased SR Ca²⁺-ATPase activity. Patients with POAF also showed stronger expression of activated components of the NLRP3 (NACHT, LRR, and PYD domains-containing protein-3)-inflammasome system in atrial whole-tissue homogenates and cardiomyocytes. Acute application of interleukin-1β caused NLRP3-signaling activation and CaMKII-dependent RyR2/phospholamban hyperphosphorylation in an immortalized mouse atrial cardiomyocyte cell-line (HL-1-cardiomyocytes) and enhanced spontaneous SR Ca²⁺-release events in both POAF cardiomyocytes and HL-1-cardiomyocytes. Computational modeling showed that RyR2 dysfunction and increased SR Ca²⁺-uptake are sufficient to reproduce the Ca²⁺-handling phenotype and indicated an increased risk of proarrhythmic delayed afterdepolarizations in POAF subjects in response to interleukin-1β.

CONCLUSIONS

Preexisting Ca²⁺-handling abnormalities and activation of NLRP3-inflammasome/CaMKII signaling are evident in atrial cardiomyocytes from patients who subsequently develop POAF. These molecular substrates sensitize cardiomyocytes to spontaneous Ca²⁺-releases and arrhythmogenic afterdepolarizations, particularly upon exposure to inflammatory mediators. Our data reveal a potential cellular and molecular substrate for this important clinical problem.

Altered atrial cytosolic calcium handling contributes to the development of postoperative atrial fibrillation

Aims 

Atrial fibrillation (AF) is a commonly occurring arrhythmia after cardiac surgery (postoperative AF, poAF) and is associated with poorer outcomes. Considering that reduced atrial contractile function is a predictor of poAF and that Ca²⁺ plays an important role in both excitation–contraction coupling and atrial arrhythmogenesis, this study aims to test whether alterations of intracellular Ca²⁺ handling contribute to impaired atrial contractility and to the arrhythmogenic substrate predisposing patients to poAF.

Methods and results 

Right atrial appendages were obtained from patients in sinus rhythm undergoing open-heart surgery. Cardiomyocytes were investigated by simultaneous measurement of [Ca²⁺]_i and action potentials (APs, patch-clamp). Patients were followed-up for 6 days to identify those with and without poAF. Speckle-tracking analysis of preoperative echocardiography revealed reduced left atrial contraction strain in poAF patients. At the time of surgery, cellular Ca²⁺ transients (CaTs) and the sarcoplasmic reticulum (SR) Ca²⁺ content were smaller in the poAF group. CaT decay was slower in poAF, but the decay of caffeine-induced Ca²⁺ transients was unaltered, suggesting preserved sodium-calcium exchanger function. In agreement, western blots revealed reduced SERCA2a expression in poAF patients but unaltered phospholamban expression/phosphorylation. Computational modelling indicated that reduced SERCA activity promotes occurrence of CaT and AP alternans. Indeed, alternans of CaT and AP occurred more often and at lower stimulation frequencies in atrial myocytes from poAF patients. Resting membrane potential and AP duration were comparable between both groups at various pacing frequencies (0.25–8 Hz).

Conclusions 

Biochemical, functional, and modelling data implicate reduced SERCA-mediated Ca²⁺ reuptake into the SR as a major contributor to impaired preoperative atrial contractile function and to the pre-existing arrhythmogenic substrate in patients developing poAF.

Cardiomyocyte calcium handling in health and disease: Insights from in vitro and in silico studies

Calcium (Ca²⁺) plays a central role in cardiomyocyte excitation-contraction coupling. To ensure an optimal electrical impulse propagation and cardiac contraction, Ca²⁺ levels are regulated by a variety of Ca²⁺-handling proteins. In turn, Ca²⁺ modulates numerous electrophysiological processes. Accordingly, Ca²⁺-handling abnormalities can promote cardiac arrhythmias via various mechanisms, including the promotion of afterdepolarizations, ion-channel modulation and structural remodeling. In the last 30 years, significant improvements have been made in the computational modeling of cardiomyocyte Ca²⁺ handling under physiological and pathological conditions. However, numerous questions involving the Ca²⁺-dependent regulation of different macromolecular complexes, cross-talk between Ca²⁺-dependent regulatory pathways operating over a wide range of time scales, and bidirectional interactions between electrophysiology and mechanics remain to be addressed by in vitro and in silico studies. A better understanding of disease-specific Ca²⁺-dependent proarrhythmic mechanisms may facilitate the development of improved therapeutic strategies. In this review, we describe the fundamental mechanisms of cardiomyocyte Ca²⁺ handling in health and disease, and provide an overview of currently available computational models for cardiomyocyte Ca²⁺ handling. Finally, we discuss important uncertainties and open questions about cardiomyocyte Ca²⁺ handling and highlight how synergy between in vitro and in silico studies may help to answer several of these issues.

Cardiac autonomic regulation and PR interval determination for enhanced atrial fibrillation risk prediction after cardiac surgery

BACKGROUND

Changes in cardiac autonomic regulation and P-wave characteristics are associated with the occurrence of atrial fibrillation. The purpose of this study was to evaluate whether combined preoperative non-invasive determination of cardiac autonomic regulation and PR interval allows for the identification of patients at risk of new-onset atrial fibrillation after cardiac surgery.

METHODS

RR, PR and QT intervals, and linear and non-linear heart rate variability parameters from 20 min high-resolution electrocardiographic recordings were determined one day before surgery in 150 patients on chronic beta blockers undergoing elective coronary artery bypass grafting, aortic valve replacement, or both, electively.

RESULTS

Thirty-one patients (21%) developed postoperative atrial fibrillation. In the atrial fibrillation group, more arterial hypertension, a greater age, a higher EuroSCORE II, a higher heart rate variability index (pNN50: 9 ± 20 vs. 4 ± 10, p = 0.050), a short PR interval (156 ± 23 vs. 173 ± 31 ms; p = 0.011), and a reduced short-term scaling exponent of the detrended fluctuation analysis (DFA1, 0.96 ± 0.36 vs. 1.11 ± 0.30 ms; p = 0.032) were found compared to the sinus rhythm group. Logistic regression modeling confirmed PR interval, DFA1 and age as the strongest preoperative predictors of postoperative atrial fibrillation (area under the receiver operating characteristic curve = 0.804).

CONCLUSIONS

Patients developing atrial fibrillation after cardiac surgery presented with severe cardiac autonomic derangement and a short PR interval preoperatively. The observed state characterizes both altered heart rate regulation and arrhythmic substrate and is strongly related to an increased risk of postoperative atrial fibrillation.

A calcium transport mechanism for atrial fibrillation in Tbx5-mutant mice

Risk for Atrial Fibrillation (AF), the most common human arrhythmia, has a major genetic component. The T-box transcription factor TBX5 influences human AF risk, and adult-specific Tbx5-mutant mice demonstrate spontaneous AF. We report that TBX5 is critical for cellular Ca²⁺ homeostasis, providing a molecular mechanism underlying the genetic implication of TBX5 in AF. We show that cardiomyocyte action potential (AP) abnormalities in Tbx5-deficient atrial cardiomyocytes are caused by a decreased sarcoplasmic reticulum (SR) Ca²⁺ ATPase (SERCA2)-mediated SR calcium uptake which was balanced by enhanced trans-sarcolemmal calcium fluxes (calcium current and sodium/calcium exchanger), providing mechanisms for triggered activity. The AP defects, cardiomyocyte ectopy, and AF caused by TBX5 deficiency were rescued by phospholamban removal, which normalized SERCA function. These results directly link transcriptional control of SERCA2 activity, depressed SR Ca²⁺ sequestration, enhanced trans-sarcolemmal calcium fluxes, and AF, establishing a mechanism underlying the genetic basis for a Ca²⁺-dependent pathway for AF risk.

The human heart contains four distinct chambers that work together to pump blood around the body. In individuals with a condition called atrial fibrillation, two of the chambers (known as the atria) beat irregularly and are unable to push all the blood they hold into the other two chambers of the heart. This can cause heart failure and increases the likelihood of blood clots, which may lead to stroke and heart attacks.

Small molecules called calcium ions play a crucial role in regulating how and when the atria contract by driving electrical activity in heart cells. To contract the atria, a storage compartment within heart cells known as the sarcoplasmic reticulum releases calcium ions into the main compartment of the cells. Calcium ions also enter the cell from the surrounding tissue. As the atria relax, calcium ions are pumped back into the sarcoplasmic reticulum or out of the cell by specific transport proteins.

Individuals with mutations in a gene called Tbx5 are more likely to develop atrial fibrillation than other people, but it was not clear how such gene mutations contribute to the disease. Here, Dai, Laforest et al. used mice with a mutation in the Tbx5 gene to study how defects in Tbx5 affect electrical activity in heart cells.

The experiments found that the Tbx5 gene was critical for calcium ions to drive normal electrical activity in mouse heart cells. Compared with heart cells from normal mice, the heart cells from the mutant mice had decreased flow of calcium ions into the sarcoplasmic reticulum and increased flow of calcium ions out of the cell.

These findings provide a direct link between atrial fibrillation and the flow of calcium ions in heart cells. Together with previous work, these findings indicate that multiple different mechanisms could lead to atrial fibrillation, but that many of these involve changes in the flow of calcium ions. Therefore, personalized medicine, where clinicians uncover the specific mechanisms responsible for atrial fibrillation in individual patients, may play an important role in treating this condition in the future.

Entropy Mapping Approach for Functional Reentry Detection in Atrial Fibrillation: An In-Silico Study

Catheter ablation of critical electrical propagation sites is a promising tool for reducing the recurrence of atrial fibrillation (AF). The spatial identification of the arrhythmogenic mechanisms sustaining AF requires the evaluation of electrograms (EGMs) recorded over the atrial surface. This work aims to characterize functional reentries using measures of entropy to track and detect a reentry core. To this end, different AF episodes are simulated using a 2D model of atrial tissue. Modified Courtemanche human action potential and Fenton–Karma models are implemented. Action potential propagation is modeled by a fractional diffusion equation, and virtual unipolar EGM are calculated. Episodes with stable and meandering rotors, figure-of-eight reentry, and disorganized propagation with multiple reentries are generated. Shannon entropy (ShEn), approximate entropy (ApEn), and sample entropy (SampEn) are computed from the virtual EGM, and entropy maps are built. Phase singularity maps are implemented as references. The results show that ApEn and SampEn maps are able to detect and track the reentry core of rotors and figure-of-eight reentry, while the ShEn results are not satisfactory. Moreover, ApEn and SampEn consistently highlight a reentry core by high entropy values for all of the studied cases, while the ability of ShEn to characterize the reentry core depends on the propagation dynamics. Such features make the ApEn and SampEn maps attractive tools for the study of AF reentries that persist for a period of time that is similar to the length of the observation window, and reentries could be interpreted as AF-sustaining mechanisms. Further research is needed to determine and fully understand the relation of these entropy measures with fibrillation mechanisms other than reentries.

Prevalence and risk factors of atrial fibrillation during lung and esophageal surgery: A Prospective observational study

The aim of this prospective observational study was to screen for risk factors of intraoperative atrial fibrillation (AF) during noncardiac thoracic surgery. The study was conducted as a single-institution study in Zhejiang Cancer Hospital, Hangzhou, China. All the participants were patients with cancer scheduled for thoracotomy.This study was conducted from July 2013 to August 2016 and included 144 patients scheduled for thoracotomy under general anesthesia. We collected the patients' demographic and perioperative medical data in our hospital. AF was diagnosed using electrocardiography (ECG), on the basis of the presence of characteristic ECG features of AF by one or more ECG leads for at least 30 seconds.Of the participants, 144 completed the study and 18 developed intraoperative AF. Higher percentages of subjects in the AF group than in the non-AF group had histories of chemotherapy (P = .014) and alcohol consumption (P = .034) before surgery. The AF group had a lower mean body mass index (P = .019), significantly higher mean heart rate (P < .001), and lower tidal volume (P = .01) than the non-AF group. After the logistic regression analysis, only alcohol consumption (odds ratio [OR] = 5.279; 95% confidence interval [CI]: 1.432-19.467), history of chemotherapy (OR = 4.019; 95% CI: 1.504-15.334), and high heart rate (OR = 1.093; 95% CI: 1.033-1.156) during 1-lung ventilation were identified as the risk factors of AF during lung and esophageal surgeries.The incidence of intraoperative AF during noncardiac thoracic surgery was 12.5%. Alcohol consumption, history of chemotherapy, and high heart rate during 1-lung ventilation were the risk factors related to intraoperative AF.

Colchicine for prevention of post-cardiac procedure atrial fibrillation: Meta-analysis of randomized controlled trials

BACKGROUND

Development of atrial fibrillation after certain cardiac procedures is a common medical problem. The inflammatory process plays an important role in the pathogenesis of post-cardiac procedure atrial fibrillation (PCP-AF). Colchicine, a potent anti-inflammatory agent, has been used in several studies to reduce the risk of PCP-AF. This meta-analysis of randomized controlled trials (RCTs) was conducted to assess the efficacy of colchicine in prevention of PC-PAF.

METHODS

We searched PubMed, EMBASE, Web of Science, Cochrane Library database and Google Scholar for RCTs, using terms "Atrial fibrillation, atrial, or fibrillation and colchicine". The primary end-point was the occurrence of AF post cardiac procedure, which includes cardiac surgery or pulmonary vein isolation. The safety end point was the occurrence of any side effects. Estimated odds ratios (OR) and 95% confidence intervals (CI) were evaluated.

RESULTS

A total of six RCTs were included in this meta-analysis, enrolling a total of 1257 patients. Colchicine significantly reduced the odds of PCP-AF (OR 0.52; 95% CI, 0.40-0.68, P<0.001, I²=0%). However, occurrence of side effects was significantly higher with colchicine when compared to placebo (OR 2.10; 95% CI, 1.34-3.30, P<0.001, I²=0%). The number needed to treat is 7 and the number needed to harm is 11.2. The proportion of patients discontinuing treatment was 16%.

CONCLUSION

This meta-analysis shows that colchicine is an effective drug for prevention of PCP-AF. Colchicine could be considered as a prophylaxis to reduce PCP-AF, with some risk of treatment discontinuation due to the poor gastrointestinal tolerance (diarrhea).

Intraoperative Inducibility of Atrial Fibrillation Does Not Predict Early Postoperative Atrial Fibrillation

Background

Early postoperative atrial fibrillation (EPoAF) is associated with thromboembolic events, prolonged hospitalization, and development of late PoAF (LPoAF). It is, however, unknown if EPoAF can be predicted by intraoperative AF inducibility. The aims of this study are therefore to explore (1) the value of intraoperative inducibility of AF for development of both EPoAF and LPoAF and (2) the predictive value of de novo EPoAF for recurrence of LPoAF.

Methods and Results

Patients (N=496, 75% male) undergoing cardiothoracic surgery for coronary and/or valvular heart disease were included. AF induction was attempted by atrial pacing, before extracorporeal circulation. All patients were on continuous rhythm monitoring until discharge to detect EPoAF. During a follow‐up period of 2 years, LPoAF was detected by ECGs and Holter recordings. Sustained AF was inducible in 56% of patients. There was no difference in patients with or without AF before surgery (P=0.159), or between different types of surgery (P=0.687). In patients without a history of AF, incidence of EPoAF and LPoAF was 37% and 2%, respectively. EPoAF recurred in 58% patients with preoperative AF, 53% developed LPoAF. There were no correlations between intraoperative inducibility and EPoAF or LPoAF (P>0.05). EPoAF was not correlated with LPoAF in patients without a history of AF (P=0.116), in contrast to patients with AF before surgery (P<0.001).

Conclusions

Intraoperative AF inducibility does not predict development of either EPoAF or LPoAF. In patients with AF before surgery, EPoAF is correlated with LPoAF recurrences. This correlation is absent in patients without AF before surgery.

Preclinical efficacy and safety of KCNH2-G628S gene therapy for postoperative atrial fibrillation

BACKGROUND

Postoperative atrial fibrillation (POAF) is the most common complication occurring after cardiac surgery. Multiple studies have shown significantly increased risks of stroke, myocardial infarction, and death associated with POAF. Current prophylaxis strategies are inadequate to eliminate this problem. We examined the preclinical efficacy and safety of KCNH2-G628S gene transfer to prevent POAF.

METHODS

Domestic pigs received AdKCNH2-G628S by epicardial atrial gene painting and atrial pacemaker implantation for continuous-burst pacing to induce atrial fibrillation. In an initial dose-ranging evaluation, 3 pigs received 5 × 1010 to 5 × 1011 virus particles. In the formal study, 16 pigs were randomized to 3 groups: 5 × 1011 virus particles of AdKCNH2-G628S with 20% Pluronic P407 in saline, 20% Pluronic P407 in saline with no virus, and saline alone. Animals were followed with daily efficacy and safety evaluations through the period of peak adenovirus-mediated transgene expression. After 14 days, pacing was discontinued, and the animals were followed in sinus rhythm for an additional 14 days to assess any longer-term toxicity.

RESULTS

In the primary efficacy analysis, the G628S animals exhibited a significant increase in the average time in sinus rhythm compared with the Pluronic control group (59 ± 7% vs 14 ± 6%; P = .009). There was no significant difference between the Pluronic and saline controls (14 ± 6% vs 32 ± 12%; P = .16). Safety assessment showed improved left ventricular function in the G628S animals; otherwise there were no significant differences among the groups in any safety measure.

CONCLUSIONS

These data indicate that KCNH2-G628S gene therapy can successfully and safely reduce the risk of AF.

Spatial distribution of conduction disorders during sinus rhythm

BACKGROUND

Length of lines of conduction block (CB) during sinus rhythm (SR) at Bachmann's bundle (BB) is associated with atrial fibrillation (AF). However, it is unknown whether extensiveness of CB at BB represents CB elsewhere in the atria. We aim to investigate during SR 1) the spatial distribution and extensiveness of CB 2) whether there is a predilection site for CB and 3) the association between CB and incidence of post-operative AF.

METHODS

During SR, epicardial mapping of the right atrium (RA), BB and left atrium was performed in 209 patients with coronary artery disease. The amount of conduction delay (CD, Δlocal activation time ≥7ms) and CB (Δ≥12ms) was quantified as % of the mapping area. Atrial regions were compared to identify potential predilection sites for CD/CB. Correlations between CD/CB and clinical characteristics were tested.

RESULTS

Areas with CD or CB were present in all patients, overall prevalence was respectively 1.4(0.2-4.0) % and 1.3(0.1-4.3) %. Extensiveness and spatial distribution of CD/CB varied considerably, however occurred mainly at the superior intercaval RA. Of all clinicalcharacteristics, CD/CB only correlated weakly with age and diabetes (P<0.05). A 1% increase in CD or CB caused a 1.1-1.5ms prolongation of the activation time (P<0.001). There was no correlation between CD/CB and post-operative AF.

CONCLUSION

CD/CB during SR in CABG patients with electrically non-remodeled atria show considerable intra-atrial, but also inter-individual variation. Despite these differences, a predilection site is present at the superior intercaval RA. Extensiveness of CB at the superior intercaval RA or BB does not reflect CB elsewhere in the atria and is not associated with post-operative AF.