Combination therapy for prevention of atrial fibrillation after coronary artery bypass surgery: a randomized trial of sotalol and magnesium

Prevention of Atrial Fibrillation After Cardiac Surgery: A Review of Literature and Comparison of Different Treatment Modalities

Atrial fibrillation is the most common arrhythmia to occur after cardiac surgery, with an incidence of 10% to 50%. It is associated with postoperative complications including increased risk of stroke, prolonged hospital stays and increased costs. Despite new insights into the mechanisms of atrial fibrillation, no specific etiologic factor has been identified as the sole perpetrator of the arrhythmia. Current evidence suggests that the pathophysiology of atrial fibrillation in general, as well as after cardiac surgery, is multifactorial. Studies have also shown that new-onset postoperative atrial fibrillation following cardiac surgery is associated with a higher risk of short-term and long-term mortality. Furthermore, it has been demonstrated that prophylactic medical therapy decreases the incidence of postoperative atrial fibrillation after cardiac surgery. Of note, the incidence of postoperative atrial fibrillation has not changed during the last decades despite the numerous preventive strategies and operative techniques proposed, although the perioperative and postoperative care of cardiac patients as such has improved.

Cardiology: Post-Cardiothoracic Surgery Atrial Fibrillation: A Review of Preventive Strategies

Objective:

To review the available literature addressing preventive strategies of post-cardiothoracic surgery atrial fibrillation (post-CTS atrial fibrillation).

Data Sources:

Pertinent articles related to the etiology, risk factors, and preventive strategies were identified through a MEDLINE search (1966–March 2007) using the MeSH terms atrial fibrillation, cardiothoracic surgery, cardiac surgery, etiology, neurohormonal, sympathetic, volume, fluid, inflammation, risk factors, operative, pacing, β-adrenergic blockers, amiodarone, sotalol, calcium-channel blockers, magnesium, HMG-CoA reductase inhibitors, statins, fatty acids, PUFA, steroids, and nonsteroidal antiinflammatory drugs.

Study Selection and Data Extraction:

Articles evaluated were limited to human studies, published in the English language, with a Jadad score greater than 3. References of identified articles were reviewed for additional pertinent articles.

Data Synthesis:

Post-CTS atrial fibrillation most commonly occurs on the second or third postoperative day, with an incidence of 20–50%. Etiology theories include neurohormonal activation, volume overload, and inflammation. Studies examining nonpharmacologic therapies have shown that maintenance of the anterior epicardial fat pad is not a viable prophylactic strategy. Biatrial cardiac pacing, especially in combination with amiodarone, is a viable preventive option. Withdrawal of preoperative β-blockers places patients at higher risk for atrial fibrillation; these drugs should be continued postoperatively. Evidence exists supporting the use of amiodarone, sotalol, and magnesium in addition to β-blockers. Since most of these strategies work by attenuating neurohormonal activation, adverse events, including hypotension and bradycardia, are of concern. Adding agents with antiinflammatory properties, including hydroxymethylglutaryl coenzyme A reductase inhibitors or corticosteroids, may prove to be of benefit. Additional studies using novel therapies are needed in addition to established preventive strategies.

Conclusions:

Available evidence supports the continuation of preoperative β-blockers, as well as prophylactic amiodarone, sotalol, and magnesium. Other novel therapies, mostly targeting inflammation, are under investigation and may provide additional strategies.

Meta-analysis of randomized controlled trials on magnesium in addition to beta-blocker for prevention of postoperative atrial arrhythmias after coronary artery bypass grafting

Background

Atrial arrhythmia (AA) is the most common complication after coronary artery bypass grafting (CABG). Only beta-blockers and amiodarone have been convincingly shown to decrease its incidence. The effectiveness of magnesium on this complication is still controversial. This meta-analysis was performed to evaluate the effect of magnesium as a sole or adjuvant agent in addition to beta-blocker on suppressing postoperative AA after CABG.

Methods

We searched the PubMed, Medline, ISI Web of Knowledge, Cochrane library databases and online clinical trial database up to May 2012. We used random effects model when there was significant heterogeneity between trials and fixed effects model when heterogeneity was negligible.

Results

Five randomized controlled trials were identified, enrolling a total of 1251 patients. The combination of magnesium and beta-blocker did not significantly decrease the incidence of postoperative AA after CABG versus beta-blocker alone (odds ratio (OR) 1.12, 95% confidence interval (CI) 0.86-1.47, P = 0.40). Magnesium in addition to beta-blocker did not significantly affect LOS (weighted mean difference −0.14 days of stay, 95% CI −0.58 to 0.29, P = 0.24) or the overall mortality (OR 0.59, 95% CI 0.08-4.56, P = 0.62). However the risk of postoperative adverse events was higher in the combination of magnesium and beta-blocker group than beta-blocker alone (OR 2.80, 95% CI 1.66-4.71, P = 0.0001).

Conclusions

This meta-analysis offers the more definitive evidence against the prophylactic administration of intravenous magnesium for prevention of AA after CABG when beta-blockers are routinely administered, and shows an association with more adverse events in those people who received magnesium.

The efficacy of sotalol in preventing postoperative atrial fibrillation: a meta-analysis

OBJECTIVE

Supraventricular tachyarrhythmias including atrial fibrillation are common and troubling complications after cardiac surgery, and thus considerable interest in pharmacologic prophylaxis has developed. The aim of this study was to evaluate the efficacy of sotalol in the prevention of postoperative supraventricular tachyarrhythmias.

METHODS

Standard methods of meta-analysis were used. Randomized clinical trials published in English language were eligible for the meta-analysis.

RESULTS

A systematic review revealed 15 eligible publications that provided 20 comparisons of sotalol with a control group. The incidence and relative risk (RR) with 95% confidence interval (CI) of developing postoperative supraventricular tachyarrhythmias while taking sotalol were sotalol (n=489) versus placebo (n=499): 22.5% versus 41.5%, RR=0.55 (CI, 0.454-0.667, P<.001); sotalol (n=304) versus no treatment (n=311): 12% versus 39%, RR=0.329 (CI, 0.236-0.459, P<.001); sotalol (n=488) versus beta-blocker (n=555): 14% versus 23%, RR=0.644 (CI, 0.495-0.838, P<.001); sotalol (n=139) versus amiodarone (n=146): no significant differences in supraventricular tachyarrhythmia prevention; and sotalol (n=51) versus magnesium (n=54): no significant differences in supraventricular tachyarrhythmia prevention. Initiating sotalol orally or intravenously had no significant effect on efficacy. Initiating sotalol after surgery showed a trend toward less adverse events (before: RR=1.700 [CI, 0.903-3.200] and after: RR=0.767 [CI, 0.391-1.505]).

CONCLUSION

Sotalol is more effective in the prevention of supraventricular tachyarrhythmia than placebo or beta-blockers. Initiating sotalol before cardiac surgery has no advantage compared with initiating sotalol shortly after surgery. Starting sotalol intravenously after surgery may be a more reliable method than administering via a nasogastric tube or delaying treatment until the patient can take oral medication.

Nutritional challenges and outcomes after surgery for congenital heart disease

PURPOSE OF REVIEW

Adequate nutrition is crucial in children after surgery for congenital heart disease. We address selected nutritional and caloric requirements for children in the perioperative period before and after cardiac surgery and explore nutritional interdependence with other system functions. Recommendations based on our current practice are made at the end of each section.

RECENT FINDINGS

Early identification of deficient oropharyngeal motor skills and vocal cord dysfunction is crucial to establish enteral nutrition safely and has been demonstrated to improve clinical outcomes. The use of prealbumin as a marker of nutritional state should be accompanied by C-reactive protein given the influence of inflammation on its levels. Insulin infusions may improve outcomes in patients with postoperative hyperglycemia. Trace element abnormalities and early identification of immune-compromised states can aid in reducing morbidity in children after cardiac surgery. Use of feeding protocols and a home surveillance system for hypoplastic left heart syndrome improves outcomes.

SUMMARY

Adequate nutritional support in children after cardiac surgery is a challenge. Attention to lesion-specific feeding problems, supplementation of trace elements and minerals, and an organized approach to pace, timing, and type of feeding are beneficial.

Plasma magnesium should be monitored perioperatively in patients undergoing colorectal resection

OBJECTIVE

Hypomagnesemia has been shown to have several clinically important sequelae. The aims of this study were: to assess the impact of bowel preparation, with sodium picosulphate (Picolax), on plasma electrolytes, with particular regard to plasma magnesium, in patients undergoing bowel preparation for colonoscopy and colorectal resection and to evaluate the influence of perioperative magnesium levels on postoperative cardiac dysrhythmias.

METHOD

Sixty-one patients receiving sodium picosulphate (Picolax) bowel preparation were studied in two groups: Colonoscopy (31 patients) and Colorectal resection (30 patients). Plasma sodium, potassium, magnesium, calcium, urea, creatinine and blood haematocrit were measured in all patients prior to commencement of bowel preparation, at the time of colonoscopy or colorectal resection and 24 h postoperatively (surgery group only). Mean electrolyte and haematocrit levels were then compared. Postoperative cardiac dysrhythmias were recorded and analysed.

RESULTS

No significant changes following bowel preparation were observed in plasma sodium, potassium, calcium or creatinine. Plasma urea fell following bowel preparation (colonoscopy P < 0.001, resection P = 0.004) and rose following resection (P = 0.002). Magnesium levels increased following bowel preparation in both groups (colonoscopy P < 0.001, resection P = 0.007) and fell following resection (P < 0.001). Thirty-four per cent (21/60 patients) were hypermagnesemic following bowel preparation and 20% (6/30 patients) became hypomagnesemic following surgery. Postoperative cardiac dysrhythmias were associated with lower magnesium levels at induction and postoperatively (P = 0.022 and P = 0.033).

CONCLUSION

Bowel preparation with Picolax does not appear to cause significant electrolyte disturbance, except in elevating plasma magnesium. Postcolorectal resection plasma magnesium dropped significantly suggesting perioperative monitoring and replacement should be routine following colorectal surgery.

Clinical review: treatment of new-onset atrial fibrillation in medical intensive care patients--a clinical framework

Atrial fibrillation occurs frequently in medical intensive care unit patients. Most intensivists tend to treat this rhythm disorder because they believe it is detrimental. Whether atrial fibrillation contributes to morbidity and/or mortality and whether atrial fibrillation is an epiphenomenon of severe disease, however, are not clear. As a consequence, it is unknown whether treatment of the arrhythmia affects the outcome. Furthermore, if treatment is deemed necessary, it is not known what the best treatment is. We developed a treatment protocol by searching for the best evidence. Because studies in medical intensive care unit patients are scarce, the evidence comes mainly from extrapolation of data derived from other patient groups. We propose a treatment strategy with magnesium infusion followed by amiodarone in case of failure. Although this strategy seems to be effective in both rhythm control and rate control, the mortality remained high. A randomised controlled trial in medical intensive care unit patients with placebo treatment in the control arm is therefore still defendable.

Perioperative use of cardiac medical therapy among patients undergoing coronary artery bypass graft surgery: a systematic review

BACKGROUND

The use of perioperative cardiac medical therapy among patients undergoing coronary artery bypass graft surgery (CABG) has not been closely examined.

OBJECTIVES

The objective of this study was to systematically review the medical literature examining the effects of perioperative cardiac medical therapy on clinical outcomes among patients undergoing CABG.

METHODS

Using the Medline database and online clinical trial databases, we reviewed all randomized controlled trials (RCTs) and observational studies examining the effect of perioperative angiotensin-converting enzyme inhibitors, angiotensin II receptor blockers, antilipid agents (including statins), aspirin, beta-blockers, and calcium-channel blockers on clinical outcomes.

RESULTS

Our review identified 27 studies (6 RCTs, 21 observational studies), involving >700,000 patients, that examined the impact of perioperative medical therapy on clinical outcomes after CABG. Although studies provide conflicting results, the literature suggests that perioperative aspirin use may decrease inhospital mortality and myocardial infarction, whereas perioperative angiotensin-converting enzyme inhibitor use does not appear to be beneficial. Perioperative statin use reduces all-cause mortality at 30 days and cardiac death at 60 days and 1 year post-CABG but does not appear to reduce myocardial infarction or congestive heart failure rates. Multiple studies have demonstrated that pre- and postoperative beta-blockers are associated with a decrease in atrial fibrillation. In addition, beta-blockers may reduce inhospital and 30-day mortality, although these results are not consistent across all studies. Calcium-channel blockers do not appear to improve inhospital or 30-day mortality. No studies examined the perioperative use of angiotensin II receptor blockers or nonstatin antilipid agents among CABG patients.

CONCLUSIONS

The perioperative use of cardiac medical therapy among CABG patients remains understudied. Given their proven benefits among patients with cardiovascular disease and their potential to improve outcomes among CABG patients, further studies, particularly large RCTs, are needed.

Atrial fibrillation post-cardiac surgery: changing perspectives

Perioperative atrial fibrillation (AF) is one of the most frequent complications of cardiac surgery. Its development is associated with an increased morbidity and mortality, for example from perioperative stroke, as well as ventricular arrhythmias, postoperative myocardial infarction, congestive cardiac failure, renal failure, increased use of inotropic medications and the need for intra-aortic balloon pump. Furthermore, AF after cardiac surgery results in prolonged hospitalization after the procedure, as well as an excess utilization of hospital resources and increased hospital costs. Given the importance of AF for patient outcome, a wide variety of prophylactic pharmacologic strategies have been evaluated. The risk of post-operative AF should be reduced by the administration of amiodarone, a beta-blocker, sotalol or rate-limiting calcium antagonists. In addition, in patients undergoing cardiac surgery on pre-existing beta-blocker therapy, this treatment should be continued unless contraindications develop (such as post-operative bradycardia or hypotension). Unless contraindicated, a rhythm control strategy is recommended as the initial option for the treatment of post-operative AF following cardiothoracic surgery. More recently, some data regarding magnesium, statins and n-3 polyunsaturated fatty acids in reducing post-op AF are available. Clearly, perspectives are changing in our management of this common arrhythmia.

Atrial fibrillation following cardiac surgery: a retrospective cohort series

Atrial fibrillation (AF) is a common postoperative complication of cardiac surgery, yet the prevention and treatment of postoperative AF remains controversial and varies among practitioners. The purpose of this study was to document the incidence and time of onset of postoperative AF in a cardiac surgical cohort, examine risk factors implicated in the occurrence of postoperative AF, and assess effectiveness of current treatment strategies implemented for postoperative AF. A retrospective health record review was conducted on 1078 adults following cardiac surgery. Data on demographic, preoperative, perioperative, and postoperative risk factors for postoperative AF, documented episodes of AF, and clinical outcomes were recorded. Overall incidence of postoperative AF was 39.6%: 57.6% after cardiac valve surgery, 69.3% after combined coronary artery bypass graft and valve surgery, and 33% after bypass graft surgery alone. The peak onset of postoperative AF occurred on the second postoperative day. Advancing age, history of AF, combined cardiac valve and coronary artery bypass graft surgery, and high Mg+2 levels on the third postoperative day were significant predictors of postoperative AF in this cohort. Length of hospitalization increased with the presence of postoperative AF. Findings corroborate that multiple factors play a role in the development of AF following cardiac surgery.

Pharmacological study of BRS, a new bicarbonated Ringer's solution, in haemorrhagic shock dogs

BACKGROUND AND OBJECTIVES

Sodium bicarbonate is the most physiological alkalinizing agent. The effect of a new bicarbonated Ringer's solution (BRS) containing Mg2+, on metabolic acidosis and serum magnesium abnormality were evaluated and compared with those of acetated Ringer's (ARS), lactated Ringer's (LRS) and Ringer's (RS) solutions in an experimental haemorrhagic shock model with dogs.

METHODS

Animals were randomly divided into six groups (n = 6 in each group), a sham-operated group, an operated group without infusion, and 4 operated groups with infusion (BRS, ARS, LRS and RS groups). Each RS was intravenously administered at 60 mL kg(-1) h(-1) for 1.5 h. Arterial blood gases, plasma electrolytes and cardiovascular parameters were analysed.

RESULTS

BRS significantly improved blood base excess values, which were decreased by blood-letting, faster and more markedly than did LRS and RS (BRS--6.3 +/- 0.5 mEq L(-1); LRS--9.2 +/- 1.1 mEq L(-1); RS--12.4 +/- 1.0 mEq L(-1) at the end of infusion). The alkalinizing effect of BRS tended to be better than that of ARS but not significantly so. The serum Mg2+ concentration was well-maintained by BRS as compared to other RS (BRS 1.5 +/- 0.0 mgdL(-1); ARS 1.2 +/- 0.0mgdL(-1); LRS 1.1 +/- 0.0mgdL(-1); RS 1.3 +/- 0.1 mgdL(-1), at the end of infusion).

CONCLUSIONS

These results suggest that BRS is a suitable perioperative solution for metabolic acidosis and serum electrolyte balance among RS tested.

Pharmacological study of BRS, a new bicarbonated Ringer's solution, in partially hepatectomized rabbits

BACKGROUND AND OBJECTIVE

The effects of bicarbonated Ringer's solution were evaluated and compared with those of acetated Ringer's, lactated Ringer's and Ringer's solutions in partially hepatectomized rabbits.

METHOD

Animals were randomly divided into six groups (n = 6 in each group): a sham-operated group, an operated group without infusion, and four operated groups with infusions of each of the four Ringer's solutions. Each Ringer's solution was intravenously administered at 40 mL kg(-1) h(-1) for 1.5 h. Arterial blood gases, plasma magnesium concentrations and cardiovascular parameters were analysed.

RESULTS

The partial hepatectomy-induced decrement of base excess was inhibited by bicarbonated Ringer's solution more remarkably than by either lactated or plain solutions (P < 0.01). The alkalinizing effect of bicarbonated Ringer's solution tended to be more marked than that of the acetated solution but not significantly so. Plasma magnesium concentrations were well maintained by bicarbonated solution as compared to the other solutions (P < 0.01).

CONCLUSIONS

These results suggest that bicarbonated Ringer's solution is the most suitable perioperative solution for metabolic acidosis and plasma electrolyte balance among the Ringer's solutions tested.