Colchicine for primary prevention of atrial fibrillation after open-heart surgery: Systematic review and meta-analysis

New-Onset Atrial Fibrillation in Adult Patients After Cardiac Surgery

Purpose of Review

An overview of recent literature regarding pathophysiology, risk factors, prophylaxis, and treatment of new-onset atrial fibrillation (AF) in post-cardiac surgical patients.

Recent Findings

AF is the most frequent adverse event after cardiac surgery with significant associated morbidity, mortality, and financial cost. Its causes are multifactorial, and models to stratify patients into risk categories are progressing but a consistent, evidence-based system has not yet been developed. Pharmacologic and surgical interventions to prevent and treat this complication have been an area of ongoing research and recent societal guidelines reflect this.

Summary

Inconsistencies remain surrounding how to best identify higher-risk AF patients, which interventions should be used to prevent and treat AF, and which patient groups should receive these interventions. The evidence for these available strategies and their place in contemporary guidelines are summarized.

Phospholipidic Colchicinoids as Promising Prodrugs Incorporated into Enzyme-Responsive Liposomes: Chemical, Biophysical, and Enzymological Aspects

Enzyme-responsive liposomes release their cargo in response to pathologically increased levels of enzymes at the target site. We report herein an assembly of phospholipase A2-responsive liposomes based on colchicinoid lipid prodrugs incorporated into lipid bilayer of the nanosized vesicles. The liposomes were constructed to addresses two important issues: (i) the lipid prodrugs were designed to fit the structure of the enzyme binding site; and (ii) the concept of lateral pressure profile was used to design lipid prodrugs that introduce almost no distortions into the lipid bilayer packing, thus ensuring that corresponding liposomes are stable. The colchicinoid agents exhibit antiproliferative activity in subnanomolar range of concentrations.

Immunopathogenesis and biomarkers of recurrent atrial fibrillation following ablation therapy in patients with preexisting atrial fibrillation

INTRODUCTION

Recurrent atrial fibrillation (RAF) following ablation therapy occurs in about 50% of patients. The pathogenesis of RAF is unknown, but is believed to be driven by atrial remodeling in the setting of background inflammation. Structural, electrophysiological and mechanical remodeling has been associated with atrial fibrillation (AF). Inflammation and fibrotic remodeling are the major factors perpetuating AF, as mediators released from the atrial tissues and cardiomyocytes due to mechanical and surgical injury could initiate the inflammatory process. In this article, we have critically reviewed the key mediators that may serve as potential biomarkers to predict RAF. Areas covered: Damage associated molecular patterns, heat shock proteins, inflammatory cytokines, non-inflammatory markers, markers of inflammatory cell activity, and markers of collagen deposition and metabolism are evaluated as potential biomarkers with molecular treatment options in RAF. Expert commentary: Establishing biomarkers to predict RAF could be useful in reducing morbidity and mortality. Investigations into the role of DAMPs participating in a sterile immune response may provide greater insight into the pathogenesis of RAF. Markers evaluating immune cell activity, collagen deposition, and levels of heat shock proteins show the greatest promise as potential biomarkers to predict RAF and develop novel therapies.

Cholinergic activity regulates the secretome of epicardial adipose tissue: Association with atrial fibrillation

Botulinum toxin injection on epicardial fat, which inhibits acetylcholine (ACh) release, reduced the presence of atrial fibrillation (AF) in patients after heart surgery. Thus, we wanted to study the profile of the released proteins of epicardial adipose tissue (EAT) under cholinergic activity (ACh treatment) and their value as AF predictors. Biopsies, explants, or primary cultures were obtained from the EAT of 85 patients that underwent open heart surgery. The quantification of muscarinic receptors (mAChR) by real-time polymerase chain reaction or western blot showed their expression in EAT. Moreover, mAChR Type 3 was upregulated after adipogenesis induction (p < 0.05). Cholinergic fibers in EAT were detected by vesicular ACh transporter levels and/or acetylcholinesterase activity. ACh treatment modified the released proteins by EAT, which were identified by nano-high-performance liquid chromatography and TripleTOF analysis. These differentially released proteins were involved in cell structure, inflammation, or detoxification. After testing the plasma levels of alpha-defensin 3 (inflammation-involved protein) of patients who underwent open heart surgery ( n = 24), we observed differential levels between the patients who developed or did not develop postsurgery AF (1.58 ± 1.61 ng/ml vs. 6.2 ± 5.6 ng/ml; p < 0.005). The cholinergic activity on EAT might suggest a new mechanism for studying the interplay among EAT, autonomic nervous system dysfunction, and AF.

Role of inflammatory signaling in atrial fibrillation

Atrial fibrillation (AF), the most prevalent arrhythmia, is often associated with enhanced inflammatory response. Emerging evidence points to a causal role of inflammatory signaling pathways in the evolution of atrial electrical, calcium handling and structural remodeling, which create the substrate of AF development. In this review, we discuss the clinical evidence supporting the association between inflammatory indices and AF development, the molecular and cellular mechanisms of AF, which appear to involve multiple canonical inflammatory pathways, and the potential of anti-inflammatory therapeutic approaches in AF prevention/treatment.

The Role of Colchicine in Treating Postoperative and Post-catheter Ablation Atrial Fibrillation

PURPOSE

The goal of this review was to summarize, analyze, and compare trials studying the efficacy of colchicine in the prevention of atrial fibrillation (AF) post-operatively (POAF) and post-catheter ablation. Ongoing studies and current guidelines are also presented and reviewed.

METHODS

Published studies on the field were identified through a literature search of the PubMed and clinicaltrials.gov databases.

FINDINGS

Four original studies regarding POAF, two original studies regarding post-catheter ablation AF, and six meta-analyses were identified. In addition, the 3 most recent guidelines/expert consensus documents were scrutinized.

IMPLICATIONS

AF occurs frequently after cardiac surgery (POAF) and catheter pulmonary vein isolation (postablation AF) and is associated with increased cardiovascular morbidity. A number of trials over the last few years have investigated the role of colchicine in the prevention of POAF and postablation AF targeting the local and systemic inflammatory process that leads to initiation and maintenance of AF. Available data imply that colchicine may have a preventive role in POAF and/or postablation AF. However, certain limitations of these studies underline the need for further investigation.

Inflammation and atrial fibrillation: A comprehensive review

Atrial fibrillation (AF) has different underlying substrates. Atrial remodeling involves electrophysiological and structural abnormalities that promote the development and perpetuation of AF. Experimental and clinical data indicate that inflammation is implicated in the pathophysiology of atrial remodeling. The mechanistic links between atrial remodeling and inflammation are complex while diverse underlying diseases and conditions may affect these pathways. Inflammatory markers have also been associated with AF development, recurrence, perpetuation, total AF burden as well as with thromboembolic complications. The development of specific anti-inflammatory interventions in this setting seems to be challenging and complicated. Several agents with pleiotropic properties, including anti-inflammatory, have been tested in experimental and clinical settings with variable results. This updated review provides a concise overview of all available data regarding the role of inflammation in AF including the predictive role of inflammatory markers. Also, current knowledge and future directions on anti-inflammatory strategies are critically discussed.

Colchicine, a microtubule-disassembling drug, in the therapy of cardiovascular diseases

Colchicum autumnale, from which colchicine has been isolated more than 100 years ago, has been used as a treatment for pain and swelling for thousands of years. It is one of the few drugs known from that time period whose use has survived to modernity. Over the past decades, advances in the knowledge of (i) cytoskeletal microtubules (МТ), and (ii) anti-inflammatory and anti-fibrotic effects of colchicine, a classical MT-disassembling (tubulin-targeting) agent, have led to potential new uses for this very old drug extended beyond acute gouty arthritis and familial Mediterranean fever. Here, in brief, I present the Bulgarian contribution to possible potential of colchicine in the therapy of cardiovascular diseases that has emerged in the early 1970s in the Laboratory of Electron Microscopy, Medical Institute, Varna, Bulgaria, studying the secretory function of vascular smooth muscle cells. From this time onward, low-dose colchicine (0.5-1.0 mg/daily) was increasingly administered orally for therapy of cardiovascular diseases such as acute coronary syndromes, postoperative atrial fibrillation (in cardiac surgery), pericarditis, cardiac hypertrophy-associated heart failure, restenosis after angioplasty, and systemic necrotizing vasculitis. Thus, colchicine might be a new tool in the present therapeutic armamentarium for cardiovascular diseases. It is simply an example of MT-disassembling drugs. Further studies will definitely be required before gaining real confidence in this kind of antitubulin pharmacology and therapy. This may lead to developing new and more specific antitubulins for cardiovascular diseases.

Cost-effectiveness of colchicine treatment on post-operative atrial fibrillation events in patients of major cardiac surgery

Aims

Post-operative atrial fibrillation (POAF) occurs in 20-50% of patients amid post-operative stay after Cardiac Surgery. We intend to determine whether colchicine therapy in patients undergoing cardiac surgery is a cost-effective strategy for prevention of POAF. To undertake cost utility analysis and calculate incremental cost utility ratio (ICUR) for colchicine therapy in these subgroup of patients.

Methods and results Design

Decision tree model to calculate the ICUR comparing two treatment strategies in patients undergoing cardiac surgery. One wherein patients received colchicine along with usual care and second where they received placebo or just usual care. Cost utility analysis was undertaken using relevant data from the systematic review and meta-analysis of the available randomized controlled trials till June 2016 and mean cost calculations from validated available sources across various jurisdictions.

Results

Colchicine treatment based on mean costs for life expectancy calculated at 10 years' post-surgery using recommended discounting rates of 3.5% was € 17544.80 cheaper per quality-adjusted life-year (QALY) gained. The incremental cost is negative and the incremental effect (QALY) is positive (South East quadrant), Hence the intervention of colchicine treatment is unequivocally cost-effective, meaning it is dominant and achieves better outcomes at a lower cost.

Conclusion

Our findings provide a benchmark for current and future analyses relating to effectiveness of colchicine on POAF events after cardiac surgery. Currently, there are few reports that provide cutting edge estimates of the higher expenses associated with POAF. Future analyses should likewise explore the impact of added costs from using pharmacologic efforts to prevent and treat POAF after cardiac surgery.