Pharmacologic Strategies for Prevention of Atrial Fibrillation After Open Heart Surgery

Reducing New-Onset Atrial Fibrillation After Coronary Artery Bypass Graft Surgery

Postoperative atrial fibrillation is the most common dysrhythmia to occur after coronary artery bypass graft surgery. It develops in 10% to 40% of patients and can lead to complications such as hemodynamic instability, heart failure, and stroke. Risk factors include hypertension, diabetes, chronic kidney disease, and obesity. Patients who experience postoperative atrial fibrillation often have longer hospital stays, are at higher risk for readmission, and have increased mortality. Protocols designed to reduce the incidence of the condition can decrease hospital costs, improve patient outcomes, and increase overall quality of care. This quality improvement project took place in a tertiary care center located in southeastern Michigan and focused on the development and implementation of an evidence-based postoperative atrial fibrillation prophylaxis protocol using amiodarone. The outcomes of this project suggest that amiodarone prophylaxis can reduce the incidence of postoperative atrial fibrillation in patients with no previous history of atrial fibrillation undergoing coronary artery bypass graft surgery.

Simple Amiodarone Protocol Reduces Postoperative Atrial Fibrillation

Background

Incorporating amiodarone into an existing postoperative atrial fibrillation (AF) prevention pathway may reduce postoperative AF and length of stay (LOS).

Methods

From July 2002 through December 2002, 476 consecutive cardiac surgical patients were managed with an AF prevention protocol using aggressive potassium replacement, intraoperative/ postoperative magnesium supplementation, and postoperative resumption of β-blockers. From January 2003 through June 2003, 592 additional patients were subjected to the same protocol except amiodarone was initiated intraoperatively (150 mg intravenously) and continued postoperatively until discharge (200 mg orally three times daily). Incidence of AF, postoperative LOS, and AF risk factors were collected prospectively and compared using regression models with propensity scores to adjust for dissimilarities between groups.

Results

Incorporating amiodarone into an existing AF protocol resulted in a 45% reduction in postoperative AF (29% [136/476] versus 16% [94/592], P < 0.0001). After adjustment for covariates and propensity score, the relative risk reduction with amiodarone in this protocol remained significant (P = 0.001, RR 0.65, 95% CI 0.5–0.8). Multivariate risks for postoperative AF included no amiodarone (P = 0.0001), age (P < 0.0001), ejection fraction <40% (P = 0.0005), ventilator support >24 hours (P = 0.002), no postoperative β-blocker (P = 0.002), and mitral valve procedure (P = 0.03). When postoperative AF did occur, risk adjusted LOS was less in patients on the amiodarone protocol (mean 9.4 days versus 13.1 days, P = 0.06). Readmission after discharge for any reason (10% [49/476] versus 8% [45/592], P = 0.1) or for AF (1.1% [5/476] versus 0.7% [4/592], P = 0.5) was similar between groups.

Conclusion

Amiodarone initiated intraoperatively followed by oral dosing significantly reduces postoperative AF and tends to reduce LOS if AF occurs.

Magnesium status and magnesium therapy in cardiac surgery: A systematic review and meta-analysis focusing on arrhythmia prevention

PURPOSE

To investigate magnesium as prophylaxis or treatment of postoperative arrhythmias in cardiac surgery (CS) patients. To assess impact on biochemical and patient-centered outcomes.

MATERIALS AND METHODS

We searched MEDLINE, CENTRAL and EMBASE electronic databases from 1975 to October 2015 using terms related to magnesium and CS. English-Language RCTs were included involving adults undergoing CS with parenterally administered magnesium to treat or prevent arrhythmias, compared to control or standard antiarrythmics. We extracted incidence of postoperative arrhythmias, termination following magnesium administration and secondary outcomes (including mortality, length of stay, hemodynamic parameters, biochemistry).

RESULTS

Thirty-five studies were included, with significant methodological heterogeneity. Atrial fibrillation (AF) was most commonly reported, followed by ventricular, supraventricular and overall arrhythmia frequency. Magnesium appeared to reduce AF (RR 0.69, 95% confidence interval (95%CI) 0.56-0.86, p=0.002), particularly postoperatively (RR 0.51, 95%CI 0.34-0.77, p=0.003) for longer than 24h. Maximal benefit was seen with bolus doses up to 60mmol. Magnesium appeared to reduce ventricular arrhythmias (RR=0.46, 95%CI 0.24-0.89, p=0.004), with a trend to reduced overall arrhythmias (RR=0.80, 95%CI 0.57-1.12, p=0.191). We found no mortality effect or significant increase in adverse events.

CONCLUSIONS

Magnesium administration post-CS appears to reduce AF without significant adverse events. There is limited evidence to support magnesium administration for prevention of other arrhythmias.

Pharmacogenomics in Anesthesia

A significant number of commonly administered medications in anesthesia show wide clinical interpatient variability. Some of these include neuromuscular blockers, opioids, local anesthetics, and inhalation anesthetics. Individual genetic makeup may account for and predict cardiovascular outcomes after cardiac surgery. These interactions can manifest at any point in the perioperative period and may also only affect a specific system. A better understanding of pharmacogenomics will allow for more individually tailored anesthetics and may ultimately lead to better outcomes, decreased hospital stays, and improved patient satisfaction.

Effect of ColchiciNe on the InciDence of Atrial Fibrillation in Open Heart Surgery Patients: END-AF Trial

BACKGROUND

Atrial fibrillation (AF) is a common arrhythmia in patients undergoing cardiac surgery and may result in significant morbidity and increased hospital stay. This study was conducted to determine if colchicine administered preoperatively to patients undergoing cardiac surgery and continued during hospitalization is effective in reducing the incidence of postoperative AF.

METHODS

In this multicenter prospective randomized open-label study, consecutive patients with no history of AF and scheduled to undergo elective cardiac surgery (n = 360) were randomized to colchicine (n = 179) or no-colchicine (n = 181). Main exclusion criteria were history of AF or supraventricular arrhythmias or absence of sinus rhythm at enrolment, and contraindications to colchicine. Colchicine was orally administered 12 to 24 hours preoperatively and continued until hospital discharge. The primary efficacy end point was documented AF lasting more than 5 minutes. Safety end point was colchicine adverse effects.

RESULTS

In-hospital mortality was 3.3%. The primary end point of AF occurred in 63 patients (17.5%): 26 (14.5%) in the colchicine group and 37 (20.5%) in the no-colchicine group (relative risk reduction 29.3% [P = .14]). Diarrhea occurred in 54 patients, 44 (24.6%) on colchicine and 10 (5.5%) on no-colchicine (P < .001). Diarrhea led to discontinuation of colchicine in 23 (52%) of the 44 patients.

CONCLUSION

Colchicine administered preoperatively to patients undergoing cardiac surgery and continued until hospital discharge failed to significantly reduce the incidence of early postoperative AF. Diarrhea was the most common adverse effect of colchicine leading to its discontinuation in more than half of the patients with this adverse effect.

Clinical effects of leukofiltration and surface modification on post-cardiopulmonary bypass atrial fibrillation in different risk cohorts

Objective. A manifestation of inflammatory injury to the heart, atrial fibrillation (AF), ranks among the most frequent and potentially life-threatening post-operative complications. Methods. In a prospective randomized study, 120 patients undergoing CABG were allocated into two groups (N = 60): Group 1- Polymethoxyethylacry late-coated circuits + Leukocyte filters (Terumo,USA); Group 2: Control:Uncoated circuits (Terumo,USA). Each group was further divided into three subgroups (N = 20) with respect to low (Euroscore 0—2), medium (3—5) and high (6+) risk patients. Results. Serum IL-2 levels were significantly lower in the study group at T4 and T5 (p < 0.01). C3a levels showed significant differences in the leukofiltrated group at T4 and T5 (p < 0.05). CPKMB levels demonstrated well-preserved myocardium in the leukofiltration group, post-operatively. AF incidence was 10% (2 patients) in the study and 35% (7 patients) in the control cohorts (p < 0.05). Phagocytic capacity on fibers in filtered patients was significantly lower. Conclusion: Leukofiltration and coating significantly reduce the incidence, ventricular rate, and duration of AF after CABG via modulation of systemic inflammatory response and platelet preservation in high risk groups. Perfusion (2007) 22, 279—288.

Postoperative atrial fibrillation is not pulmonary vein dependent: results from a randomized trial

BACKGROUND

Although often short-lived and self-limiting, postoperative atrial fibrillation (POAF) is a well-recognized postoperative complication of cardiac surgery and is associated with a 2-fold increase in cardiovascular mortality and morbidity.

OBJECTIVE

Our aim was to determine whether intraoperative bilateral pulmonary vein radiofrequency ablation decreases the incidence of POAF in patients undergoing coronary artery bypass grafting (CABG).

METHODS

A total of 175 patients undergoing CABG was prospectively randomized to undergo adjuvant bilateral radiofrequency pulmonary vein ablation in addition to CABG (group A; n = 89) or CABG alone (group B; n = 86). Intraoperative pulmonary vein isolation was confirmed by the inability to pace the heart via the pulmonary veins after ablation. All patients received postoperative β-blocker.

RESULTS

There was no difference in the incidence of POAF in the treatment group who underwent adjuvant pulmonary vein ablation (group A; 37.1%) compared with the control group who did not (group B; 36.1%) (P = .887). There were no differences in postoperative inotropic support, antiarrhythmic drug use, need for oral anticoagulation, and complication rates. The mean length of postoperative hospital stay was 8.2 ± 6.5 days in the ablation group and 6.7 ± 4.6 days in the control group (P < .001).

CONCLUSION

Adjuvant pulmonary vein isolation does not decrease the incidence of POAF or its clinical impact but increases the mean length of stay in the hospital. The mechanism of POAF does not appear to depend on the pulmonary veins.

Landiolol hydrochloride for prevention of atrial fibrillation after cardiac surgery: a meta-analysis

BACKGROUND

Atrial fibrillation (AF) is the most common arrhythmic complication after cardiac surgery. Several studies have compared the efficacy of landiolol and placebo or other agents in preventing new-onset AF in patients after cardiac surgery. In this study, we conducted a meta-analysis to determine whether landiolol is effective in preventing new-onset AF after cardiac surgery.

METHODS AND RESULTS

Five randomized controlled trials and two retrospective analyses were included in this study. The clinical outcomes of interest were the occurrence of AF after cardiac surgery and major complications. Meta-analysis was performed using RevMan 5.0.18 software, and pooled estimates of the effect were reported as risk ratios (RR) with 95% confidence intervals (CI). The results of this meta-analysis indicate that landiolol is significantly associated with a decreased risk of occurrence of AF after cardiac surgery (RR = 0.33; 95% CI: 0.23-0.48; P < 0.00001) and is not associated with an increased risk of major complications (RR = 0.79; 95% CI: 0.43-1.45; P = 0.45) compared with the control group.

CONCLUSION

Landiolol administration in the perioperative period can reduce the occurrence of AF after cardiac surgery without increasing the risk of major complications. It can be used to prevent new-onset AF safely after cardiac surgery.

Postoperative atrial fibrillation in patients undergoing coronary artery bypass grafting or cardiac valve surgery: intraoperative use of landiolol

Background

Landiolol hydrochloride is a new β-adrenergic blocker with a pharmacological profile that suggests it can be administered safely to patients who have sinus tachycardia or tachyarrhythmia and who require heart rate reduction. This study aimed to investigate whether intraoperative administration of landiolol could reduce the incidence of atrial fibrillation (AF) after cardiac surgery.

Methods

Of the 200 consecutive patients whose records could be retrieved between October 2006 and September 2007, we retrospectively reviewed a total of 105 patients who met the inclusion criteria: no previous permanent/persistent AF, no permanent pacemaker, no renal insufficiency requiring dialysis, and no reactive airway disease, etc. Landiolol infusion was started after surgery had commenced, at an infusion rate of 1 μg/kg/min, titrated upward in 3–5 μg/kg/min increments. The patients were divided into 2 groups: those who received intraoperative β-blocker therapy with landiolol (landiolol group) and those who did not receive any β-blockers during surgery (control group). An unpaired t test and Fisher’s exact test were used to compare between-group differences in mean values and categorical data, respectively.

Results

Seventeen of the 105 patients (16.2%) developed postoperative atrial fibrillation: 5/57 (8.8%) in the landiolol group and 12/48 (25%) in the control group. There was a significant difference between the two groups (P=0.03). The incidence of AF after valve surgery and off-pump coronary artery bypass grafting was lower in the landiolol group, although the difference between the groups was not statistically significant.

Conclusions

Our retrospective review demonstrated a marked reduction of postoperative AF in those who received landiolol intraoperatively. A prospective study of intraoperative landiolol for preventing postoperative atrial fibrillation is warranted.

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.

Preoperative Statin use is not Associated with a Reduced Risk of Atrial Fibrillation After Cardiac Surgery

Introduction: Postoperative atrial fibrillation (POAF) is prevalent after cardiac surgery and associated with significant morbidity and costs. Statins are commonly used in this population and may be a preventative strategy for PAOF. We wished to examine the effect of preoperative statin use on the risk of POAF after cardiac surgery. Methods: A retrospective, observational study was conducted using data from 489 adult patients who underwent cardiac surgery at a single institution. Univariate analyses and unconditional logistic regression were used to determine the impact of preoperative statin use on the probability of developing POAF, while controlling for the baseline risk of POAF and the use of amiodarone prophylaxis (AMP). A baseline risk index was calculated for each patient using a previously validated model. Patients with chronic atrial fibrillation or missing data were excluded. Results: Mean patient age was 63 (SD=13) years, 73% were male, 68% underwent isolated coronary artery bypass grafting, 16% underwent isolated valve surgery, with 13% underwent combined CABG and valve surgeries, and 3% underwent other forms of cardiac surgery. POAF occurred in 27% of patients receiving statins and 24% of those not receiving statins (p=0.3792). After controlling for baseline risk of POAF and the use of AMP, we found that preoperative statins were not associated with reductions in POAF (OR=1.19, 95%CI=0.782-1.822, p=0.4118). Conclusions: Multiple factors impact the development of POAF after cardiac surgery including patient demographics, comorbidities, surgical type, and concomitant medications. In this study, after adjustment for these factors the preoperative use of statins did not significantly influence the development of POAF.

Drugs for the perioperative control of hypertension: current issues and future directions

The management of hypertension continues to pose important challenges. Recent developments have established the importance of more rigorous blood pressure control in the community. In the perioperative setting, hypertension has long been recognised as undesirable, although the adverse impact of high blood pressure on the acute risks of elective surgery may have been previously overstated.A number of agents and techniques are available to control blood pressure perioperatively. These include principally general and regional anaesthetics, alpha(2)-adrenoceptor agonists, peripheral alpha(1)- and beta-adrenoceptor antagonists, dihydropyridine calcium channel antagonists, dopamine D(1A)-receptor agonists (fenoldopam), and nitric oxide donors. Recent years have seen important developments in the receptor selectivity of new compounds and in pharmacokinetics, particularly esterase metabolism. The future study of genomics may enable us to identify patients at risk for hypertension-related adverse events and target therapies most effectively to these high-risk groups.

Potential Use of Statins to Prevent Atrial Fibrillation After Coronary Artery Bypass Surgery

Objective:

To review the published literature evaluating the effectiveness of statin therapy for preventing postoperative atrial fibrillation (POAF) after coronary artery bypass graft (CABG) surgery,

Data Sources:

A MEDLINE search was performed (1950–October 2007) using the search terms statins, HMG-CoA reductase inhibitors, coronary artery bypass graft, cardiac surgery, and atrial fibrillation,

Study Selection and Data Extraction:

All articles published in English describing or evaluating the use of statins in humans to prevent atrial fibrillation (AF) were included. Additional pertinent articles were identified from reference lists.

Data Synthesis:

POAF is a common complication following CABG surgery that is associated with significant morbidity. Current preventive strategies include the use of β-blockers and antiarrhythmic drugs such as amiodarono and Sotalol. Accumulating evidence suggests that statins may also reduce the risk of POAF. Numerous studies in nonsurgical cardiovascular patients have found reduced rates of AF with statins. In patients who have undergone CABG, several observational studies have also documented benefit. One randomized controlled trial reported a significant reduction in the risk of POAF and reduced length of hospital stay in patients given preoperative atorvastatin beginning 7 days before surgery. Ongoing research suggests that statins may reduce the risk of AF through pleiotropic effects independent of cholesterol lowering such as reductions in inflammation, oxidative damage, neurohormonal activation, and thrombosis.

Conclusions:

While the current evidence evaluating the use of statins to prevent POAF is encouraging, definitive conclusions cannot be drawn. However, because statins are widely used in cardiac patients for other indications and are not associated with the risks inherent to antiarrhythmic drugs, their value as an adjunct to current preventive strategies (or POAF deserves further study. Additional research is needed to examine the effectiveness of statins in risk-stratified patients undergoing CABG surgery and the impact on patient outcomes and attributed costs.

The Changing Face of Postoperative Atrial Fibrillation Prevention

Atrial fibrillation is the most common postoperative arrhythmia with significant consequences on patient health. Postoperative atrial fibrillation (POAF) complicates up to 8% of all noncardiac surgeries, between 3% and 30% of noncardiac thoracic surgeries, and between 16% and 46% of cardiac surgeries. POAF has been associated with increased morbidity, mortality, and longer, more costly hospital stays. The risk of POAF after cardiac and noncardiac surgery may be affected by several epidemiologic and intraoperative factors, as well as by the presence of preexisting cardiovascular and pulmonary disorders. POAF is typically a transient, reversible phenomenon that may develop in patients who possess an electrophysiologic substrate for the arrhythmia that is present before or as a result of surgery. Numerous studies support the efficacy of beta-blockers in POAF prevention; they are currently the most common medication used in POAF prophylaxis. Perioperative amiodarone, sotalol, nondihydropyridine calcium channel blockers, and magnesium sulfate have been associated with a reduction in the occurrence of POAF. Biatrial pacing is a nonpharmacologic method that has been associated with a reduced risk of POAF. Additionally, recent studies have demonstrated that hydroxymethylglutaryl-CoA reductase inhibitors may decrease the risk of POAF. Finally, based on recent evidence that angiotensin converting enzyme inhibitors and angiotensin receptor blockers reduce the risk of permanent atrial fibrillation, these medications may also hold promise in POAF prophylaxis. However, there is a need for further large-scale investigations that incorporate standard methodologies and diagnostic criteria, which have been lacking in past trials.

Amiodarone Prophylaxis: Impact on Atrial Fibrillation and Outcomes after Cardiac Surgery

This continuing feature will update readers on recent developments in cardiovascular pharmacotherapy. Cardiovascular disease remains the number one killer in the United States, and more clinical outcome trials have been conducted in cardiology than in any other field of medicine. Given this rapidly expanding knowledge base, pharmacists can have a significant impact on prevention and treatment—if they keep current with developments in drug therapy.

Preoperative beta-blocker use reduces atrial fibrillation in off-pump coronary bypass surgery

BACKGROUND

Atrial fibrillation (AF) after coronary artery bypass graft surgery constitutes the most common sustained arrhythmia and results in many complications. The purpose of this study was to assess the effects of prophylactic use of beta-blockers against atrial fibrillation in off-pump surgery patients in the early postoperative period.

METHODS

From 2002 to 2005, 78 patients were enrolled and 41 patients received 50 mg metoprolol succinate daily, which was initiated minimum four days before surgery. Preoperative beta-blocking therapy was continued until the morning of surgery. Thirty-seven patients were free of beta-blocker therapy. Esmolol was used within same range of doses in both groups during operations. Both groups received metoprolol succinate following operations. The frequency of AF occurrence was analysed from the operation time to the sixth postoperative day.

RESULTS

Sixteen patients developed AF with an overall incidence of 22.5%. Four patients from the study group and three patients from the control group were excluded from the study because of transfer to on-pump surgery. There was no difference with regard to the number of grafts carried out, duration of operations and ventilation, intensive care unit stay and inotropic need among groups. Length of hospital stay did not differ among groups either. There was a higher incidence of postoperative AF in patients without beta-blocker prophylaxis (11.7-32.4% P=0.049).

CONCLUSION

Low-dose postoperative beta-adrenergic blockade is valuable for patients who receive these medications before off-pump coronary artery bypass grafting procedures and may be beneficial against AF in all patients.

Practical regimen for amiodarone use in preventing postoperative atrial fibrillation

BACKGROUND

Postoperative atrial fibrillation occurs in 5% to 65% of patients undergoing cardiac surgery. Although postoperative atrial fibrillation is often regarded as a temporary, benign, operation-related problem, it is associated with a twofold to threefold increase in risk of adverse events, including permanent or transient stroke, acute myocardial infarction, and death.

METHODS

This randomized, controlled, double-blinded trial included 250 eligible consecutively enrolled patients undergoing coronary artery bypass grafting (CABG). They received 300 mg of amiodarone/placebo administered intravenously over 20 minutes on the first postoperative day and an oral dose of 600 mg of amiodarone or placebo twice daily for the first 5 postoperative days.

RESULTS

The patients in amiodarone prophylaxis experienced a reduction in risk of atrial fibrillation of 14% (95% confidence interval [CI], 5.0% to 24%), with the number needed to treat at 6.9 (95% CI, 4.2 to 20), and the results for symptomatic atrial fibrillation showed a risk reduction of 18% (95% CI, 9.4% to 26), with the number needed to treat at 5.7 (95% CI, 3.9 to 11). Of the patients who developed atrial fibrillation in the placebo group, 84% experienced a symptomatic attack versus only 43% in the amiodarone group.

CONCLUSIONS

Postoperative prophylaxis with a high dose of oral amiodarone after an intravenous bolus infusion is a safe, practical, feasible, and effective regimen for CABG patients. It significantly diminishes the occurrence of postoperative atrial fibrillation.

Risk-Stratified Evaluation of Amiodarone to Prevent Atrial Fibrillation After Cardiac Surgery

BACKGROUND

Amiodarone prophylaxis (AMP) reduces the prevalence of postoperative atrial fibrillation (POAF) after cardiac surgery. We investigated the impact of AMP on the frequency and duration of POAF, the intensive care unit and hospital length of stay, and its cost-effectiveness in a risk-stratified cohort.

METHODS

A retrospective, observational analysis of 509 patients who underwent cardiac surgery in 2003 was performed. Data sources included The Society of Thoracic Surgeons national database; medical and medication administration records; and the activity-based cost data from our institution. Risk stratification for POAF was determined using a validated risk index. Cost-effectiveness was determined from the hospital's perspective.

RESULTS

The mean patient age was 63 years, 27% were female, 80% underwent coronary artery bypass grafting, and 29% underwent valve surgery. When a risk-stratified evaluation was made, 50% of patients were at an elevated risk for having POAF develop. When compared with nonprophylaxed patients, those receiving AMP (59%) experienced less POAF (31% vs 22%; p = 0.027) and shorter durations of POAF (4.7 vs 2.7 days; p = 0.025). In the elevated-risk group, AMP clinically (but not significantly) reduced length of stay in the intensive care unit (101 vs 68 hours; p > 0.05) and post-procedural hospital length of stay (9.7 vs. 7.9 days, p > 0.05). In the elevated-risk group, AMP was robustly cost-effective in reducing POAF.

CONCLUSIONS

Amiodarone prophylaxis reduced the prevalence and duration of POAF. Baseline risk for POAF was a major determinant of the overall cost-effectiveness of AMP. The greatest cost savings with AMP was seen in patients at an elevated risk for POAF. These findings suggest the need for risk stratification when prescribing AMP.

Effect of Low-Dose Amiodarone and Magnesium Combination on Atrial Fibrillation After Coronary Artery Surgery

BACKGROUND

To evaluate whether postoperative administration of intravenous low-dose amiodarone and magnesium sulfate (MgSO(4)) combination would reduce the incidence of atrial fibrillation following coronary artery bypass grafting (CABG) in normomagnesemic high-risk patients for postoperative atrial fibrillation (POAF).

METHODS

A total of 136 patients undergoing elective CABG and had > or =3 risk factors for POAF were prospectively randomized to one of three groups, to receive a single dose of amiodarone (5 mg/kg) and MgSO(4) (1.5 g) (combination group, n = 44), or an equal dose of amiodarone (amiodarone group, n = 44) or equal volumes of saline (control group, n = 48) at early postoperative period. Continuous electrocardiographic (ECG) monitoring was performed for the first 48 hours and an ECG was recorded every 8 hours later. POAF longer than 30 minutes or for any length requiring treatment, and the drug-related side effects were recorded.

RESULTS

The study population showed a homogeneous distribution regarding risk factors for POAF and there was no significant difference in patient characteristics, echocardiographic variables, or operative variables among three groups. POAF developed in 4 patients in combination group, in 16 patients in amiodarone group and in 16 patients in control group, representing a 24% relative risk reduction between the combination group and control group (p = 0.023). No statistically significant difference regarding incidence of POAF was observed between amiodarone and control groups.

CONCLUSIONS

Combined prophylactic therapy with amiodarone and MgSO(4) at the early postoperative period without a maintenance phase is an effective, simple, well-tolerated, and possibly cost-effective regimen to prevent POAF in normomagnesemic, high-risk patients.

Synthesis and biological evaluation of benzopyran analogues bearing class III antiarrhythmic pharmacophores

We have synthesized a series of compounds combining the hydroxy-benzopyran ring of vitamin E with the methylsulfonylaminophenyl group of class III antiarrhythmic drugs, connected through tertiary amine moieties. Evaluation of the antiarrhythmic and antioxidant activity of the new compounds was carried out on isolated rat heart preparations using the non-recirculating Langendorff mode. The new analogues were present, at 10 microM concentration, during ischemia and reperfusion. Selected compounds were further studied by a conventional microelectrode method in order to get insight into their cellular mode of action. The most active compound, N-[4-[2-[[2-(3,4-dihydro-6-hydroxy-2,2,7,8-tetramethyl-2H-1-benzopyran-5-yl)ethyl] methylamine]ethyl]phenyl]methanesulfonamide (19a), reduces premature beats, prolongs QT and QRS intervals during ischemia and reperfusion, and reduces MDA content, leading to a fast recovery of the heart. In addition, it exhibits moderate class III antiarrhythmic action.

Multifactor dimensionality reduction for detecting gene-gene and gene-environment interactions in pharmacogenomics studies

In the quest for discovering disease susceptibility genes, the reality of gene-gene and gene-environment interactions creates difficult challenges for many current statistical approaches. In an attempt to overcome limitations with current disease gene detection methods, the multifactor dimensionality reduction (MDR) approach was previously developed. In brief, MDR is a method that reduces the dimensionality of multilocus information to identify polymorphisms associated with an increased risk of disease. This approach takes multilocus genotypes and develops a model for defining disease risk by pooling high-risk genotype combinations into one group and low-risk combinations into another. Cross-validation and permutation testing are used to identify optimal models. While this approach was initially developed for studies of complex disease, it is also directly applicable to pharmacogenomic studies where the outcome variable is drug treatment response/nonresponse or toxicity/no toxicity. MDR is a nonparametric and model-free approach that has been shown to have reasonable power to detect epistasis in both theoretical and empirical studies. This computational technology is described in detail in this review, and its application in pharmacogenomic studies is demonstrated.