Prophylactic ventral cardiac denervation: Does it reduce incidence of atrial fibrillation after coronary artery bypass grafting?

Partial CArdiac Denervation to Prevent Postoperative Atrial Fibrillation After Coronary Artery Bypass Grafting (pCAD-POAF): Study Protocol for a Randomized Controlled Trial

Postoperative atrial fibrillation (POAF) is commonly seen in patients who underwent coronary artery bypass grafting (CABG), increasing the risk of morbidity, mortality, and hospital expenses. This study aimed to evaluate the effect of partial cardiac denervation, which is achieved by cutting off the ligament of Marshall and resecting the fat pad along the Waterston groove, on the prevention of POAF after CABG. Patients planned for CABG at our center were screened for eligibility in this study. A total of 430 patients were randomized into the intervention (partial cardiac denervation) group and control group. Intraoperative high-frequency electrical stimulation and further histologic analysis were performed in a certain number of patients to confirm the existence of ganglia. All patients were continuously monitored for the incidence of POAF through an electrophysiologic device until the sixth day postoperatively, and required to complete a 30-day follow-up (12-lead electrocardiogram and echocardiogram assessment) after discharge. The primary end point is the incidence of POAF, whereas the secondary end points are the cost-effectiveness and safety outcomes. In conclusion, this trial will evaluate whether partial cardiac denervation through cutting off the ligament of Marshall and resecting the fat pad along the Waterston groove can reduce the incidence of POAF after CABG. If this procedure is revealed to be effective and safe, it may provide a potential therapeutic approach to prevent POAF in this group of patients.

The Significance of Systemic Inflammatory Markers in 'New-Onset Atrial Fibrillation' Following Cardiac Surgeries

Postoperative atrial fibrillation (AF) is a known complication of postoperative morbidity and mortality in cardiac surgery. The purpose of this retrospective study was to look into the association between the incidence of new-onset AF in patients undergoing cardiac surgery and preoperative systemic inflammatory markers. Patients were divided into two groups (Group A: new-onset AF, Group B: no AF) depending on the occurrence of AF in the postoperative period, and a retrospective analysis was performed to look for the association between the incidence of new-onset AF and levels of systemic inflammatory markers. Five hundred patients were enrolled in the study, and the duration was three years. One-hundred and fifty out of 500 patients who underwent cardiac surgeries between 2020 and 2023 had higher levels of preoperative inflammatory markers. The systemic immune inflammation index (SII), neutrophil scores, platelet counts, and C-reactive protein (CRP) levels were examined. Compared to patients without AF (Group B), those who developed AF (Group A) had significantly higher mean levels of CRP (6.2 ± 1.8 mg/L), platelet count (320 ± 50 x109/L), neutrophil scores (4.6 ± 0.9), and SII (650 ± 120) (p<0.05 for all). Higher thresholds of these inflammatory markers were related to a notable increase in the prevalence of AF, with odds ratios showing significantly higher risks associated with raised marker levels. In summary, there was a significant correlation found between an increased risk of new-onset AF after surgery and elevated preoperative inflammatory markers, such as CRP levels, platelet counts, neutrophil scores, and SII. These findings could be used as prognostic markers to identify patients who are more likely to experience postoperative AF. Further prospective studies will be required to analyze their predictive value. Limitations of our study include the relatively small sample size, potential bias from single-institutional data, and the retrospective nature of the study design.

Postoperative Atrial Fibrillation Following Cardiac Surgery: From Pathogenesis to Potential Therapies

Postoperative atrial fibrillation (POAF) is a major complication after cardiac surgery which can lead to high rates of morbidity and mortality, an enhanced length of hospital stay, and an increased cost of care. POAF is postulated to be a multifactorial phenomenon; however, some major pathogeneses have been proposed, including inflammatory pathways, oxidative stress, and autonomic dysfunction. Genetic studies also showed that inflammatory pathways, beta-1 adrenoreceptor variants, G protein-coupled receptor kinase 5 gene variants, and non-coding single-nucleotide polymorphisms in the 4q25 chromosomal locus are involved in this phenomenon. Moreover, several predisposing factors lead to the development of POAF, consisting of pre-, intra-, and postoperative contributors. The main predisposing factors comprise age, prior history of major cardiovascular risk factors, and ischemia-reperfusion injury during surgery. The management of POAF is based on the usual therapies used for non-surgical AF, including medications for either rate control or rhythm control in hemodynamically unstable patients. The perioperative administration of β-blockers and some antiarrhythmic agents has been recommended in major international guidelines. In addition, upstream therapies consisting of colchicine, magnesium, statins, and antioxidants have attenuated the incidence of POAF; however, some uncomfortable side effects developed in large randomized trials. The use of anticoagulation has also resulted in less mortality in patients with POAF at higher risk of thromboembolic events. Despite these recommendations, the actual regimen for the prevention of POAF remains controversial. In this review, we highlight the pathogenesis, predisposing factors, and potential therapeutic options for the management of patients at risk for or with POAF following cardiac surgery.

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.

Does Anterior Fat Pad Removal Reduce the Incidence of Atrial Fibrillation after CABG? A Meta-Analysis of Randomized Controlled Trials

BACKGROUND

Atrial fibrillation (AF) is a common complication after coronary artery bypass grafting (CABG). Several prospective randomized controlled trials (RCTs) have evaluated the effect of intact and removed anterior fat pads on the incidence of AF after CABG with conflicting results. We collected these RCTs and conducted a meta-analysis to determine whether anterior fat pad removal is effective in preventing the new onset of AF after CABG.

METHODS AND RESULTS

Prospective RCTs were collected for analysis and the main outcomes include the occurrence of AF after CABG, total hospital stay, and major complications. Statistical analysis was conducted using RevMan 5.0.18 software (The Cochrane Collaboration), and pooled estimates of the effect were reported as risk ratios (RRs) or mean differences (MDs) with their 95% confidence intervals (CIs). The results of this meta-analysis indicate that anterior fat pad removal was not associated with a decreased risk of occurrence of AF after CABG (RR = 1.34, 95% CI: 0.88-2.03; P = 0.18), and it also did not increase the risk of major complications (RR = 1.05, 95% CI: 0.75-1.47; P = 0.79) or lengthen total hospital stay (MD = 0.06, 95% CI: -0.46 to 0.58; P = 0.83) compared with the control group.

CONCLUSION

Anterior fat pad removal did not decrease the risk of the occurrence of AF after CABG despite its safety and convenience, and it should not be used to prevent new-onset AF after CABG unless new evidence is provided.

Outcome Reporting in Cardiac Surgery Trials: Systematic Review and Critical Appraisal

Background

There is currently no accepted standard for reporting outcomes following cardiac surgery. The objective of this paper was to systematically review the literature to evaluate the current use and definition of perioperative outcomes reported in cardiac surgery trials.

Methods and Results

We reviewed 5 prominent medical and surgical journals on Medline from January 1, 2010, to June 30, 2014, for randomized controlled trials involving coronary artery bypass grafting and/or valve surgery. We identified 34 trials meeting inclusion criteria. Sample sizes ranged from 57 to 4752 participants (median 351). Composite end points were used as a primary outcome in 56% (n=19) of the randomized controlled trials and as a secondary outcome in 12% (n=4). There were 14 different composite end points. Mortality at any time (all-cause and/or cardiovascular) was reported as an individual end point or as part of a combined end point in 82% (n=28), myocardial infarction was reported in 68% (n=23), and bleeding was reported in 24% (n=8). Patient-centered outcomes, such as quality of life and functional classification, were reported in 29% (n=10). Definition of clinical events such as myocardial infarction, stroke, renal failure, and bleeding varied considerably among trials, particularly for postoperative myocardial infarction and bleeding, for which 8 different definitions were used for each.

Conclusions

Outcome reporting in the cardiac surgery literature is heterogeneous, and efforts should be made to standardize the outcomes reported and the definitions used to ascertain them. The development of standardizing outcome reporting is an essential step toward strengthening the process of evidence-based care in cardiac surgery.

Abnormal heart rate variability and atrial fibrillation after aortic surgery

Introduction

Complete denervation of transplanted heart exerts protective effect against postoperative atrial fibrillation; various degrees of autonomic denervation appear also after transection of ascending aorta during surgery for aortic aneurysm.

Objective

This study aimed to evaluate if the level of cardiac denervation obtained by resection of ascending aorta could exert any effect on postoperative atrial fibrillation incidence.

Methods

We retrospectively analysed the clinical records of 67 patients submitted to graft replacement of ascending aorta (group A) and 132 with aortic valve replacement (group B); all episodes of postoperative atrial fibrillation occurred during the 1-month follow-up have been reported. Heart Rate Variability parameters were obtained from a 24-h Holter recording; clinical, echocardiographic and treatment data were also evaluated.

Results

Overall, 45% of patients (group A 43%, group B 46%) presented at least one episode of postoperative atrial fibrillation. Older age (but not gender, abnormal glucose tolerance, ejection fraction, left atrial diameter) was correlated with incidence of postoperative atrial fibrillation. Only among a subgroup of patients with aortic transection and signs of greater autonomic derangement (heart rate variability parameters below the median and mean heart rate over the 75^th percentile), possibly indicating more profound autonomic denervation, a lower incidence of postoperative atrial fibrillation was observed (22% vs. 54%).

Conclusion

Transection of ascending aorta for repair of an aortic aneurysm did not confer any significant protective effect from postoperative atrial fibrillation in comparison to patients with intact ascending aorta. It could be speculated that a limited and heterogeneous cardiac denervation was produced by the intervention, creating an eletrophysiological substrate for the high incidence of postoperative atrial fibrillation observed.

Post-operative atrial fibrillation: a maze of mechanisms

Post-operative atrial fibrillation (POAF) is one of the most frequent complications of cardiac surgery and an important predictor of patient morbidity as well as of prolonged hospitalization. It significantly increases costs for hospitalization. Insights into the pathophysiological factors causing POAF have been provided by both experimental and clinical investigations and show that POAF is ‘multi-factorial’. Facilitating factors in the mechanism of the arrhythmia can be classified as acute factors caused by the surgical intervention and chronic factors related to structural heart disease and ageing of the heart. Furthermore, some proarrhythmic mechanisms specifically occur in the setting of POAF. For example, inflammation and beta-adrenergic activation have been shown to play a prominent role in POAF, while these mechanisms are less important in non-surgical AF. More recently, it has been shown that atrial fibrosis and the presence of an electrophysiological substrate capable of maintaining AF also promote the arrhythmia, indicating that POAF has some proarrhythmic mechanisms in common with other forms of AF. The clinical setting of POAF offers numerous opportunities to study its mechanisms. During cardiac surgery, biopsies can be taken and detailed electrophysiological measurements can be performed. Furthermore, the specific time course of POAF, with the delayed onset and the transient character of the arrhythmia, also provides important insight into its mechanisms.

This review discusses the mechanistic interaction between predisposing factors and the electrophysiological mechanisms resulting in POAF and their therapeutic implications.