P1395The role of hyponatremia in the development of atrial fibrillation after cardiac surgery

Predicting Postoperative Atrial Fibrillation: The Search Continues

Background To evaluate the influence of subclinical hypothyroidism (SCH) on the development of postoperative atrial fibrillation (AF) in patients undergoing aortic valve replacement surgery with extracorporeal circulation. Methods A prospective study in a tertiary hospital between July 2005 and December 2013 in which all patients undergoing aortic valve replacement with no other valve surgery were consecutively included. Patients who were in preoperative sinus rhythm were selected and they underwent thyroxine (T4) and thyroid-stimulating hormone determination in the month before surgery. Postoperative AF was defined as the development of AF during hospital admittance. Descriptive analysis and binary logistic regression were performed for the target variable. Results A total of 467 patients were studied, with 35 cases of SCH. The incidence of postoperative AF was 57% in the group with SCH versus 30.3% (p = 0.001) in the group without hypothyroidism, without significant differences in other postoperative complications. In the logistic regression analysis, the independent predictors of postoperative AF were SCH, age, and aortic clamping time. SCH multiplies the odds ratio of postoperative AF by 3.14 (95% confidence interval: 1.24-7.96). Conclusion SCH behaves like a risk factor for the development of postoperative AF in patients undergoing aortic valve replacement with extracorporeal circulation. Other studies are needed to determine whether preoperative T4 replacement therapy and/or more aggressive AF prophylaxis can prevent this complication in patients undergoing aortic valve replacement.

Postoperative atrial fibrillation (AF) is the most common arrhythmia that occurs after both cardiac and noncardiac surgery. It is associated with an increased morbidity, longer hospital stay and higher hospital costs. In addition, one of the most important clinical consequences of postoperative AF might be an increased incidence of perioperative stroke.1) There have been many investigations on the incidence, predictors, prophylactic strategies, and management of postoperative AF in patients undergoing cardiothoracic surgery. However, few studies have investigated the incidence and consequences of AF after noncardiothoracic surgery. Refer to the page 100-104 New onset AF after cardiac surgery has been reported to occur in 12 to 40 percent of patients after coronary artery bypass surgery, and the rate is even higher after valve replacement surgery, as high as 60%.2) Predictors associated with an increased risk of postoperative AF, after cardiac surgery, include advanced age, postoperative electrolyte shifts, pericarditis, a history of preoperative AF, a history of congestive heart failure, and chronic obstructive pulmonary disease. Focusing on the incidence and risk factors associated with new onset AF after thoracic (noncardiac) surgery, Vaporciyan and colleagues reported on 2,588 patients and found that the overall incidence of postoperative AF was 12.3%, somewhat lower than that with cardiac surgery; this is consistent with the results of previous reports.3),4) Significant multivariate predictors of AF after thoracic surgery include a male gender, older patient age, history of congestive heart failure, history of arrhythmias, and history of peripheral vascular disease.5) New onset AF, after cardiac and thoracic surgery, is likely triggered by direct intrathoracic stimulation or atrial irritation. It is, therefore, not surprising that the incidence of AF has been found to be lower when surgery does not involve the thorax. In one prospective series of 916 patients over 40 years of age undergoing major noncardiothoracic surgery, the incidence of AF was 2.5%;6) another more recently published study reported much lower incidence, 0.37%.7) Sohn and colleagues added and extended the observations on the topic of AF after noncardiothoracic surgery in this issue of the journal. They report the incidence of postoperative AF after noncardiothoracic surgery was 0.39%, and found that it was a relatively rare complication; it was associated with older age, and emergency surgery, and it extended the hospital stay. Their observations of significant multivariate predictors are different from those reported by Vaporciyan and colleagues. However, diverse patient groups were studied and different cardiac monitoring was used. Therefore, interpretation of the results should be made with consideration of the differences between the studies. The clinicians, especially cardiologists who are likely to care for patients prone to postoperative cardiac complications, consider which patients might benefit from prophylactic strategies. Prospective randomized trials have examined the utility of variety of pharmacological agents and nonpharmacological methods for prophylaxis in patients undergoing cardiothoracic surgery. Although the results have been conflicting, most investigators would agree that β-blockers can serve as effective prophylactic treatment with amiodarone and sotalol as alternative medications. It is uncertain whether such prophylactic medication would be effective in patients undergoing noncardiothoracic surgery because the mechanism of the postoperative AF might be somewhat different. If postoperative AF results from a preexisting electrophysiological substrate with a superimposed trigger, the latter factor might be more important in noncardiothoracic surgery. Therefore, extrapolation of the prophylactic strategies used in patients undergoing cardiothoracic surgery to the entire population of patients undergoing noncardiac surgery may not be warranted.8) Although most episodes of postoperative AF are self-limited, the natural course of postoperative AF after noncardiothoracic surgery should be defined. AF persisting for longer than 48 hours is associated with an increased risk of stroke or transient ischemic attack. Thus, after 48 hours of AF, anticoagulation should be considered, weighing the potential benefits against the risk of postoperative bleeding.9) The article reported by Sohn and colleagues raises concern with regard to postoperative AF after noncardiothoracic surgery; they suggest that it might be different from AF after cardiothoracic surgery in its pathogenesis, natural course and required management. To date, there have been no randomized controlled trials on new onset AF complicating noncardiothoracic surgery. Therefore, larger trials are needed to provide evidence based safe and effective strategies for the management of new onset AF in patients undergoing noncardiothoracic surgery.

POSTER PRESENTATIONS

Funding Acknowledgements Type of funding sources: None. Background Approximately 1% of cardiac operations result in post-operative heart block (PoHB). Post -operative atrial fibrillation (PoAF) has been quoted as occurring in 40-50% of combined coronary artery bypass graft (CABG) and valvular procedures, 25% of CABG only and 30% of valve only procedures. The co-existence of PoAF in patients with PoHB, and the link to operation type is less well documented. Purpose To investigate characteristics predisposing patients post cardiac surgery for PoHB and PoAF. Methods We screened patients who had undergone CABG, aortic or mitral valve replacements (AVR and MVR respectively) or mitral valve repairs at Bristol Royal Infirmary between 1/1/2010 and 1/4/2020. We created a merged surgical and electrophysiological database identifying patients with permanent pacemakers inserted within 30 days of cardiac surgery for PoHB to create our final database. By reviewing electronic notes we identified patients in this cohort who developed PoAF prior to discharge. We excluded patients with congenital heart defects or known prior atrial fibrillation. We then analysed the incidence of both PoHB and PoAF for different operation subtypes. Results Of the 10779 operations, 6625 (61%) were CABG-Only, 4124 (38%) were Valve-Only and 1219 (11%) were combined CABG&Valve. In total 85 (0.8%) patients developed PoHB. There was a higher proportion of female patients in the PoHB group but no other demographic differences (See Table 1). In terms of operation type, the PoHB group contained a significantly higher proportion of patients who had undergone AVR (78% vs. 28%, p<0.001). There was also a significant association with operations performed on cardiopulmonary bypass and with longer cross clamp time however this did not remain statistically significant on multivariate analysis. Valve surgery was associated with a higher proportion of patients developing PoHB than CABG, with AVR relating to the highest PoHB rates (AVR 2.0%, MVR 0.9%, CABG 0.2%, p<0.0001). Both mechanical and bioprosthetic AVR were associated with a higher proportion of patients developing PoHB than MVR. In our cohort 34/85 (41%) patients with POHB developed post-operative AF. After univariate analysis of the patient and operation factors listed in Table 1, only age and body mass index were predictors of development of PoAF after multivariate analysis (age: odds ratio 1.81 (1.02-1.36), p=0.024, BMI: odds ratio 1.09 (1.02-1.17), p=0.01), with no association to surgical parameters. Conclusion PoHB occurs commonly following both CABG and valve procedures, with higher incidence in the setting of valve surgery, with our data showing a 2 fold higher chance of PoHB in patients undergoing aortic versus mitral valve replacements. In contrast, there is no clear relationship between type of surgery and development of postoperative atrial fibrillation in this cohort but larger studies are warranted.

The impact of obesity on early postoperative atrial fibrillation burden

Invited Commentary

Background Several drug therapies and perioperative techniques have been proposed to prevent episodes of atrial fibrillation (AF) after cardiac surgery. Preoperative preparation and evaluation by the anesthesiologist in conjugation with the cardiologist and the surgeon is a new important role. These conjugations augment preoperative treatment and reduce much of the perioperative morbidity and mortality.Aim The aim of this work was to assess preoperative use of two regimens of statins in minimizing the incidence of postoperative AF in patients undergoing coronary artery bypass grafting operation.Patients and methods Written informed consent was obtained from all patients before the operation as regards their acceptance to be subjected to the procedure after a full explanation of its benefits and potential risks. Diagnosis of unstable angina was confirmed and patients were randomly allocated into three equal groups using the closed envelop method, according to the statin management protocol. Group I (n=15) (the control group) included patients who did not receive any statins before the operation. Group II included (n=15) patients who received atorvastatin 80 mg orally once daily starting 7 days before operation (including the morning of the operation). Group III (n=15) included patients who received atorvastatin 80 mg orally once on the day before the operation and in the morning of the day of the surgery. On the first postoperative day, all patients received atorvastatin 40 mg orally once daily and continued for 30 days postoperatively. Incidence of postoperative in-hospital AF was assessed. AF is defined as episodes of AF that lasted more than or equal to 5 min that was registered by the monitoring system and/or on a rhythm strip or 12-lead ECG and the incidence of episodes that required intervention for angina or hemodynamic compromise.Results There was no significant difference between the three groups as regards the incidence, onset, and duration of in-hospital AF (P>0.05). There were no reported cases of AF after discharge from the hospital until day 30 postoperatively (12-lead ECG was performed during every outpatient visit and on day 30 postoperatively). Moreover, there was a significantly decreased incidence of AF on increasing the duration of preoperative statin use (studied using the Mann–Whitney test).Conclusion The incidence of postoperative AF reduced in patients who received atorvastatin 80 mg for 7 days before operation. However, two doses of atorvastatin 80 mg before operation failed to reduce the incidence of postoperative AF.

I read with interest the recent article in EJCTS by Enc and colleagues [1] in which they have attempted to tackle the controversial issue of impact of off-pump coronary artery bypass surgery (OPCAB) on the incidence of postoperative atrial fibrillation (AF). Based on the results of their retrospective study they have concluded that there is no reduction of AF rate with OPCAB. Interestingly, their study is conspicuous not because they have attempted to verify a hypothesis with a study design marred with inherent weaknesses but because they have ignored the current best available evidence while trying to justify their conclusion. OPCAB is fast becoming a safe alternative to conventional myocardial revascularization. By avoiding cardiopulmonary bypass (CPB), OPCAB is a potentially more physiologic method to maintain the functional integrity of major organ systems with the possibility of reducing mortality and morbidity [2]. In recent years a large body of evidence has been presented in the medical literature on the safety and efficacy of OPCAB. We are currently practicing in an era of evidence-based medicine where a logical and comprehensive approach to evaluating clinically relevant research incorporates many different types of evidence including randomised clinical trials (RCTs), nonrandomised clinical trials, and experimental data and analyses the information’s content for its consistency, coherence and clarity [2]. In this era of evidence-based medicine double-blinded RCTs have been allotted the highest level of evidence [3]. Any research that ignores current best available evidence can only be termed biased. I shall further take this opportunity to inform Enc and colleagues [1] and general readership of EJCTS that we have recently evaluated the current best available evidence on this topic taking into account all the published meta-analyses (Level Ia) as well as performed a metaanalysis of six RCTs published after these several metaanalyses [4]. The findings of our meta-analysis corroborated the findings of the already performed meta-analyses that found significant differences in the incidence of AF after OPCAB and conventional myocardial revascularization [2,5]. The skeptics might say that a meta-analysis is however only as good as the studies it includes and the factors it takes into account. Well if that’s the case then perhaps it is time to undertake a large-scale multi-center RCT of OPCAB versus CPB with the development of postoperative AF as a primary endpoint. This may be the only definitive way to answer the question of whether OPCAB reduces the incidence of post-operative AF in patients undergoing coronary artery bypass surgery.

Literature review

BackgroundFew studies have focused on new-onset postoperative atrial fibrillation in patients with hypertrophic obstructive cardiomyopathy who have undergone septal myectomy. Therefore, we investigated the incidence and prognosis effects of postoperative atrial fibrillation following septal myectomy in patients with hypertensive obstructive cardiomyopathy. Additionally, we investigated the relationship of estimated glomerular filtration rate and postoperative atrial fibrillation.MethodsData from 300 patients with hypertrophic obstructive cardiomyopathy who underwent isolated surgical septal myectomy were collected from January 2012 to March 2018.ResultsThe overall incidence of postoperative atrial fibrillation during hospitalization was 22.67% (68 of 300 patients). Patients with postoperative atrial fibrillation were older (P<0.001), had lower preoperative estimated glomerular filtration rate (P<0.001), and a larger preoperative left atrial diameter (P=0.038) compared to patients without. The preoperative estimated glomerular filtration rate predicted postoperative atrial fibrillation with sensitivity and specificity of 0.824 and 0.578 (P<0.001), respectively. Multivariate regression analyses showed that age [odds ratio (OR) =1.090, 95% confidence interval (CI): 1.034–1.110], an New York Heart Association functional class ≥ III (OR =2.985, 95% CI: 1.349–6.604), hypertension (OR =2.212, 95% CI: 1.062–4.608), a history of syncope (OR =3.890, 95% CI: 1.741–8.692), and the preoperative estimated glomerular filtration rate (OR =0.981, 95% CI: 0.965–0.996) were independent risk factors associated in the development of postoperative atrial fibrillation. Survival analysis showed that the incidence of long-term cardiovascular events was higher in the patients with postoperative atrial fibrillation than that in the patients without the condition (P<0.001).ConclusionsThe preoperative estimated glomerular filtration rate was a moderate predictor of postoperative atrial fibrillation after septal myectomy. Postoperative atrial fibrillation affected the early recovery and the long-term prognoses of patients with hypertrophic obstructive cardiomyopathy who underwent septal myectomy.

Does Continuing Cardiac Drugs Until the Morning of Surgery Reduce the Incidence of Postoperative Atrial Fibrillation After Coronary Artery Bypass Graft Surgery?

Postoperative atrial fibrillation and total dietary antioxidant capacity in patients undergoing cardiac surgery: The Polyphemus Observational Study

No decrease in incidence of atrial fibrillation in patients undergoing off-pump coronary artery bypass grafting

Anti-Inflammatory Role of Statins in Preventing Postoperative Atrial Fibrillation