The Changing Face of Postoperative Atrial Fibrillation Prevention

Factors Affecting Late Atrial Fibrillation and Its Association With Coronary Artery Bypass Outcomes

BACKGROUND

Although predictors and outcomes of postoperative atrial fibrillation (POAF) are well studied, evidence is lacking concerning postdischarge late/recurrent atrial fibrillation (AF). This study evaluated factors affecting late/recurrent AF and its association with coronary artery bypass grafting (CABG) outcomes in a real-world setting.

METHODS

From 2012 through 2016, 5175 patients were included. Independent factors associated with late/recurrent AF were identified in a competing risk setting. Cox proportional hazard regression was used to evaluate the association between late/recurrent AF and study outcomes, consisting of all-cause mortality, major adverse cardio-cerebrovascular events, acute coronary syndrome, cerebrovascular events, and heart failure admissions.

RESULTS

During a median follow-up of 60 months (quartile 1-quartile 3, 59.3-60.7 months), late/recurrent AF developed in 85 patients (1.64%). Independent factors associated with late/recurrent AF were age (subdistribution hazard ratio [sHR], 1.04; 95% CI, 1.02-1.07), left-ventricular ejection fraction (sHR, 0.97; 95% CI, 0.95-0.99), length of stay (sHR, 1.02; 95% CI, 1.01-1.04), and POAF (sHR, 4.02; 95% CI, 2.50-6.45). Late/recurrent AF was not significantly associated with all-cause mortality and major adverse cardio-cerebrovascular events at unadjusted or adjusted levels (adjusted hazard ratio, 0.80 [95% CI, 0.50-1.28] and 0.74 [95% CI, 0.48-1.13], respectively). Nevertheless, it significantly increased the unadjusted risk of cerebrovascular events (hazard ratio, 2.28; 95% CI, 01.07-4.87), which disappeared after adjustments.

CONCLUSIONS

Patients with advanced age, a lower left-ventricular ejection fraction, and POAF are more likely to have late/recurrent clinical AF. Albeit counterintuitive, late/recurrent AF was not independently associated with worse midterm post-CABG outcomes. These observations need to be further elucidated in larger-scale studies and interpreted in the context of a developing country with limited resources for late AF surveillance.

Exploring postoperative atrial fibrillation after non-cardiac surgery: mechanisms, risk factors, and prevention strategies

Atrial fibrillation (AF) stands as the most prevalent persistent arrhythmia and a common complication after surgical procedures. Although the majority of non-cardiac surgery patients experience postoperative AF (POAF) and the condition is typically self-limited and asymptomatic, its detrimental impact on patient outcomes, prolonged hospitalization, and heightened risk of stroke and overall mortality has become increasingly evident. Of significant concern, POAF emerges as a noteworthy risk factor for stroke, myocardial infarction, and mortality in comparison to patients with non-surgical atrial fibrillation. Multiple studies have corroborated the association between POAF and an elevated risk of stroke and mortality. The development of postoperative atrial fibrillation is multifactorial, with the inflammatory response being a primary contributor; additionally, factors such as hypovolemia, intraoperative hypotension, anemia, trauma, and pain can trigger POAF. Risk factors for POAF in non-cardiac surgery primarily relate to age, hypertension, obesity, prior cardiac disease, obstructive sleep apnea, and male sex. Prophylactic treatment with β-blockers, amiodarone, or magnesium has demonstrated efficacy, but further trials are warranted, especially in high-risk populations. This review provides an account of the incidence rate, pathophysiology, and prognosis of atrial fibrillation after non-cardiac surgery, elucidates the underlying mechanisms of its occurrence, and explores various preventive strategies investigated in this domain.

Preoperative Oral Magnesium loading to prevent postoperative Atrial Fibrillation following Coronary Surgery (POMAF-CS): A prospective randomized controlled trial

OBJECTIVES

Postoperative atrial fibrillation is common following coronary artery bypass grafting surgery. Hypomagnesemia is frequent after coronary artery bypass grafting surgery. No previous trials have assessed the effect of preoperative magnesium loading on postoperative atrial fibrillation incidence.

METHODS

Design: This was a single-center, double-blind, placebo-controlled, parallel-group trial, with balanced randomization [1:1]. Participants: were recruited from November 2018 until May 2019. Patients received either 3.2 g of magnesium daily (4 tablets of 0.4 g each twice daily) for 72 hours preoperatively and 1.6 g of magnesium (4 tablets) on the day of surgery, or placebo tablets.

RESULTS

The primary outcome was the incidence of postoperative atrial fibrillation. Secondary outcomes included time to extubation, transfusion rate, critical care unit and hospital length of stay. Of the 210 randomized participants, 200 (100 in each group) completed the study. 10 (10%) and 22(22%) subjects developed postoperative atrial fibrillation in the magnesium and placebo groups, respectively (RR = 0.45, 95% CI: 0.23 - 0.91). Hospital and critical care unit length of stay were comparable between the 2 groups. No side effect related to magnesium administration were documented.

CONCLUSION

In this randomized controlled trial, preoperative loading with oral administration of magnesium for 3 days in patients admitted for coronary artery bypass grafting surgery decreases the incidence of postoperative atrial fibrillation compared to placebo (NCT03703349).

CLINICAL TRIAL REGISTRY NUMBER

NCT03703349.

Incidence, Risk Factors, and Outcomes of Perioperative Atrial Fibrillation following Noncardiothoracic Surgery: A Systematic Review and Meta-Regression Analysis of Observational Studies

Background

Atrial fibrillation (AF) occurs in 16-30% of patients after cardiac and thoracic surgery and can lead to serious complications like hypoperfusion of vital organs, pulmonary edema, and myocardial infarction. The evidence on risk factors and complications associated with perioperative AF after noncardiothoracic surgery is limited.

Methods

The primary objective was to determine demographic and clinical risk factors for new-onset atrial fibrillation associated with noncardiothoracic surgery. A secondary aim was to identify the incidence and odds of perioperative complications associated with the new-onset atrial fibrillation. A systematic search within multiple databases was conducted for studies that explicitly reported on new-onset atrial fibrillation after noncardiothoracic surgery. We reported data on demographics, comorbidities, and perioperative complications as mean difference (MD) or odds ratios (OR) and corresponding 95% confidence interval (CI) using random effects models. A two-sided P value of less than 0.05 was considered significant. We performed meta-regression and sensitivity analysis of various subgroups to confirm the inference of our findings.

Results

Eleven studies reporting on 121,517 patients were included, of whom 2,944 developed perioperative AF (incidence rate: 3.7%; 95% CI: 2.3%--6.2%). Advanced age (AF group versus control group: 69.36 ± 10.5 versus 64.37 ± 9.53 years; MD: 4.06; 95% CI: 1.67--6.44; P=0.0009), male gender (52.85% versus 43.59%; OR: 1.08; 95% CI: 0.54 to 1.62; I ²: 84%; P < 0.0001), preoperative hypertension (60.42% versus 56.51%; OR: 1.15; 95% CI: 1.08 to 1.23; I ²: 0%; P < 0.00001), diabetes mellitus (22.6% versus 23.04%; OR: 0.97; 95% CI: 0.89 to 1.05; I ²: 0; P < 0.00001), and cardiac disease (30.64% versus 8.49%; OR: 2.3; 95% CI: 0.28 to 4.31; I ²: 93%; P=0.03) were found to be significant predictors for perioperative AF. The AF group was at increased odds of developing postoperative cardiac complications (34.1% versus 5%; OR: 5.44; 95% CI: 0.49 to 10.39; I ²: 82%; P=0.03), postoperative stroke (0.5% versus 0.1%; OR: 3; 95% CI: 0.65 to 5.35; I ²: 0%; P=0.01), and mortality (7.40% versus 1.92%; OR: 3.58; 95% CI: 0.14 to 7.02; I ²: 0%; P=0.04). Study quality assessment by meta-regression and sensitivity analysis of the various subgroups did not affect the final inference of the results.

Conclusion

We identified advanced age, male gender, preoperative hypertension, diabetes mellitus, and cardiac disease as important risk factors for perioperative atrial fibrillation. The atrial fibrillation group was at increased odds for postoperative cardiac complications, stroke, and higher mortality, emphasizing the need for risk stratification and close monitoring.

Video-assisted Thoracoscopic Surgery versus Thoracotomy for Non-Small Cell Lung Cancer: A Meta-Analysis

BACKGROUND

Patients undergoing surgery for non-small cell lung cancer (NSCLC) are often elderly and have co-morbidity conditions and decreased performance status. Compared with open thoracotomy, video-assisted thoracoscopic lobectomy is associated with fewer postoperative complications. Despite encouraging results for patients with NSCLC who underwent VATS, the procedure is still not widely accepted, and large retrospective studies have yielded conflicting results.

OBJECTIVES

In video-assisted lobectomy for NSCLC, it has remained controversial whether mediastinal lymphadenectomy can be performed as effectively as an open procedure via thoracotomy. To deal with inherent biases in any non-randomized comparison, we analyzed propensity-matched studies and randomized controlled trials. The aim of this study was to evaluate the treatment outcomes of VATS and open thoracotomy for NSCLC patients.

METHODS

We collected publications on comparison of VATS versus open thoracotomy for NSCLC patients from 2007 to 2017. All trials analyzed the summary Hazard Ratios (HRs) of the endpoints of interest, including perioperative mortality and morbidity, and individual postoperative complications. Revman 5.3 software was used to analyze the combined pooled HRs using fixed- or random-effects models according to heterogeneity.

RESULTS

A systematic literature search was conducted including 15 studies. The results indicated that VATS was associated with lower postoperative morbidity and mortality, and significantly lower rates of prolonged pneumonia, atrial arrhythmias and renal failure.

CONCLUSIONS

Compared with lobectomy by thoracotomy, thoracoscopic lobectomy is associated with a lower incidence of major complications, including lower rates of prolonged pneumonia, atrial arrhythmias and renal failure. Lobectomy via VATs may be the preferred strategy for appropriately selected NSCLC patients. The determinants of this advantage should be analyzed to improve the safety and outcomes of other thoracic procedures.

Association Between Postoperative Dexmedetomidine Use and Arrhythmias in Infants After Cardiac Surgery

BACKGROUND

Dexmedetomidine has been suggested as an arrhythmia prophylactic agent after surgery for congenital heart disease due to its heart rate lowering effect, though studies are conflicting. We sought to study the effect of dexmedetomidine in infants that are at highest risk for arrhythmias.

METHODS

Retrospective cohort study of infants less than six months of age undergoing cardiopulmonary bypass for congenital heart disease. The arrhythmia incidence in the first 48 hours after surgery in infants receiving dexmedetomidine for sedation was compared to those that did not receive dexmedetomidine.

RESULTS

A total of 309 patients were included, 206 patients who did not receive dexmedetomidine and 103 patients who did. The incidence of tachyarrhythmias was similar between the non-DEX group and the DEX group (19% vs 15%, P = .34). When adjusted for baseline differences, the non-DEX group did not have an increased risk of postoperative tachyarrhythmias (odds ratio [OR]: 1.4, 95% confidence interval [CI]: 0.5-3.8). The non-DEX group had an increased need for treatment for arrhythmias (18% vs 8%, P = .012). The three lesions with baseline higher risk for arrhythmias (tetralogy of Fallot, transposition of the great arteries, and complete atrioventricular canal) had an increased incidence of tachyarrhythmias in the non-DEX group (34% vs 6%, P = .027). This risk was not significant in multivariate analysis (OR: 2.5, 95% CI: 0.4-15.5).

CONCLUSIONS

High-risk infants had decreased incidence of tachyarrhythmias when receiving dexmedetomidine, though this was not significant after accounting for baseline differences between groups.

Gastrointestinal complications following on-pump cardiac surgery-A propensity matched analysis

Background

Gastrointestinal complications following on-pump cardiac surgery are orphan but serious risk factors for postoperative morbidity and mortality. We aimed to assess incidence, perioperative risk factors, treatment modalities and outcomes.

Material and methods

A university medical center audit comprised 4883 consecutive patients (median age 69 [interquartile range IQR 60–76] years, 33% female, median logistic EuroScore 5 [IQR 3–11]) undergoing all types of cardiac surgery including surgery on the thoracic aorta; patients undergoing repair of congenital heart disease, implantation of assist devices or cardiac transplantation were excluded. Coronary artery disease was the leading indication for on-pump cardiac surgery (60%), patients undergoing cardiac surgery under urgency or emergency setting were included in analysis. We identified a total of 142 patients with gastrointestinal complications. To identify intra- and postoperative predictors for gastrointestinal complications, we applied a 1:1 propensity score matching procedure based on a logistic regression model.

Results

Overall, 30-day mortality for the entire cohort was 5.4%; the incidence of gastrointestinal complications was 2.9% and median time to complication 8 days (IQR 4–12). Acute pancreatitis (n = 41), paralytic ileus (n = 14) and acute cholecystitis (n = 18) were the leading pathologies. Mesenteric ischemia and gastrointestinal bleeding accounted for 16 vs. 18 cases, respectively. While 72 patients (51%) could be managed conservatively, 27 patients required endoscopic/radiological (19%) or surgical intervention (43/142 patients, 30%); overall 30-day mortality was 12.1% (p<0.001). Propensity score matching identified prolonged skin-to-skin times (p = 0.026; Odds Ratio OR 1.003, 95% Confidence Interval CI 1.000–1.007) and extended on-pump periods (p = 0.010; OR 1.006, 95%CI 1.001–1.011) as significant perioperative risk factors.

Comment

Prolonged skin-to-skin times and extended on-pump periods are important perioperative risk factors regardless of preoperative risk factors.

High risk for obstructive sleep apnea hypopnea syndrome predicts new onset atrial fibrillation after cardiac surgery: a retrospective analysis

PURPOSE

Obstructive sleep apnea hypopnea syndrome (OSAHS) is highly prevalent in patients undergoing coronary artery bypass surgery (CABG). OSAHS is a risk factor for the development of atrial fibrillation (AF), but the risk of AF in patients who are high risk for OSAHS is unclear.

METHODS

A retrospective study was conducted on consecutive patients undergoing CABG from 2013 to 2015 without AF pre-operatively. Patients were categorized as low risk for OSAHS, high risk for OSAHS, or diagnosed OSAHS based on medical records review. All diagnosed OSAHS patients were on active treatment with positive airway pressure. Outcomes assessed were postoperative AF (POAF), postoperative length of stay, re-intubation, in-hospital mortality, and cost of hospitalization.

RESULTS

Out of 209 eligible patients, 66.5% were low-risk for OSAHS, 18.7% high-risk for OSAHS, and 14.8% diagnosed/treated for OSAHS. POAF developed in 96 patients (45.9%) with greater frequency in high-risk OSAHS patients (69.2% high risk, 41.9% low risk, 40.3% diagnosed/treated, p = 0.01). In analyses adjusted for age, sex, ethnicity and comorbidities, high risk for OSAHS was associated with 2.9 greater odds (95% CI [1.2, 7.3], p = 0.02) for POAF while diagnosed/treated OSAHS was not associated with elevated risk (OR = 1.4, 95% CI [0.6, 3.6], p = 0.50) compared to patients at low risk for OSAHS.

CONCLUSIONS

High risk for OSAHS is an independent predictor for POAF in patients undergoing CABG. In contrast, patients diagnosed and treated for their OSAHS are not at elevated risk of POAF. These findings support evaluation of a standardized OSAHS screening and treatment program as part of the pre-operative evaluation for elective CABG.

Epidemiology of new-onset atrial fibrillation following coronary artery bypass graft surgery

OBJECTIVES

Postoperative atrial fibrillation (AF) following coronary artery bypass graft surgery (CABG) is significantly associated with reduced survival, but poor characterisation and inconsistent definitions present barriers to developing effective prophylaxis and management. We sought to address this knowledge gap.

METHODS

From 2002 to 2010, 11 239 consecutive patients without AF underwent isolated CABG at five sites. Clinical data collected for the Society of Thoracic Surgeons (STS) Database were augmented with details on AF detected via continuous in-hospital ECG/telemetry monitoring to assess new-onset post-CABG AF (adjusted for STS risk of mortality); time to first AF; durations of first and longest AF episodes; total in-hospital time in AF; number of in-hospital AF episodes; operative mortality; stroke; discharge in AF; and length of stay (LOS).

RESULTS

Unadjusted incidence of new-onset post-CABG AF was 29.5%. Risk-adjusted incidence was 33.1% and varied little over time (P=0.139). Among 3312 patients with post-CABG AF, adjusted median time to first AF was 52 (IQR: 48-55) hours; mean (SD) duration of first and longest events were 7.2 (5.3,9.1) and 13.1 (10.4,15.9) hours, respectively, and adjusted median total time in AF was 22 (IQR: 18-26) hours. Adjusted rates of operative mortality, stroke and discharge in AF did not vary significantly over time (P=0.156, P=0.965 and P=0.347, respectively). LOS varied (P=0.035), but in no discernible pattern.

CONCLUSIONS

Each year, ~800 000 people undergo CABG worldwide; >264 000 will develop post-CABG AF. Onset is typically 2-3 days post-CABG and episodes last, on average, several hours. Effective prophylaxis and management is urgently needed to reduce associated risks of adverse outcomes.

Atrial Fibrillation Is Associated With Increased Mortality in Patients Undergoing Transcatheter Aortic Valve Replacement: Insights From the Placement of Aortic Transcatheter Valve (PARTNER) Trial

BACKGROUND

This study sought to evaluate the impact of atrial fibrillation (AF) on clinical outcomes in patients undergoing transcatheter aortic valve replacement.

METHODS AND RESULTS

Data were evaluated in 1879 patients with baseline and discharge ECGs who underwent transcatheter aortic valve replacement in the Placement of AoRTic TraNscathetER Valve (PARTNER) trial. A total of 1262 patients manifested sinus rhythm (SR) at baseline/SR at discharge, 113 SR baseline/AF discharge, and 470 AF baseline/AF discharge. Patients who converted from SR to AF by discharge had the highest rates of all-cause mortality at 30 days (P<0.0001 across all groups; 14.2% SR/AF versus 2.6% SR/SR; adjusted hazard ratio [HR]=3.41; P=0.0002) and over 2-fold difference at 1 year (P<0.0001 across all groups; 35.7% SR/AF versus 15.8% SR/SR; adjusted HR=2.14; P<0.0001). The presence of AF on baseline or discharge ECG was a predictor of 1-year mortality (adjusted HR=2.14 for SR/AF group and HR=1.88 for AF/AF groups; P<0.0001 for both groups versus SR/SR). For patients discharged in AF, those with lower ventricular response (ie, <90 bpm) experienced less 1-year all-cause mortality (HR=0.74; P=0.04).

CONCLUSIONS

After transcatheter aortic valve replacement, the presence of AF at discharge, and particularly, the conversion to AF by discharge and higher ventricular response are associated with increased mortality. These data underscore the deleterious impact of AF, as well as the need for targeted interventions to improve clinical outcomes, in patients undergoing transcatheter aortic valve replacement.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00530894.

Rate Control versus Rhythm Control for Atrial Fibrillation after Cardiac Surgery

BACKGROUND

Atrial fibrillation after cardiac surgery is associated with increased rates of death, complications, and hospitalizations. In patients with postoperative atrial fibrillation who are in stable condition, the best initial treatment strategy--heart-rate control or rhythm control--remains controversial.

METHODS

Patients with new-onset postoperative atrial fibrillation were randomly assigned to undergo either rate control or rhythm control. The primary end point was the total number of days of hospitalization within 60 days after randomization, as assessed by the Wilcoxon rank-sum test.

RESULTS

Postoperative atrial fibrillation occurred in 695 of the 2109 patients (33.0%) who were enrolled preoperatively; of these patients, 523 underwent randomization. The total numbers of hospital days in the rate-control group and the rhythm-control group were similar (median, 5.1 days and 5.0 days, respectively; P=0.76). There were no significant between-group differences in the rates of death (P=0.64) or overall serious adverse events (24.8 per 100 patient-months in the rate-control group and 26.4 per 100 patient-months in the rhythm-control group, P=0.61), including thromboembolic and bleeding events. About 25% of the patients in each group deviated from the assigned therapy, mainly because of drug ineffectiveness (in the rate-control group) or amiodarone side effects or adverse drug reactions (in the rhythm-control group). At 60 days, 93.8% of the patients in the rate-control group and 97.9% of those in the rhythm-control group had had a stable heart rhythm without atrial fibrillation for the previous 30 days (P=0.02), and 84.2% and 86.9%, respectively, had been free from atrial fibrillation from discharge to 60 days (P=0.41).

CONCLUSIONS

Strategies for rate control and rhythm control to treat postoperative atrial fibrillation were associated with equal numbers of days of hospitalization, similar complication rates, and similarly low rates of persistent atrial fibrillation 60 days after onset. Neither treatment strategy showed a net clinical advantage over the other. (Funded by the National Institutes of Health and the Canadian Institutes of Health Research; ClinicalTrials.gov number, NCT02132767.).

Assessment of the Risk Factors and Outcomes for Postoperative Atrial Fibrillation Patients Undergoing Isolated Coronary Artery Bypass Grafting

BACKGROUND

Atrial fibrillation is the most common complication of cardiac surgery and is associated with significant morbidity and mortality. Recognizing patients at high risk for developing postoperative atrial fibrillation (POAF) may help identify those who could benefit from strategies to prevent POAF. This study was conducted to delineate outcomes and to assess risk factors for POAF among Taiwanese patients undergoing coronary artery bypass grafting (CABG).

METHODS

From January 2009 until February 2012, this prospective study included 266 consecutive patients admitted to our hospital with coronary artery disease. All patients underwent isolated CABG. Patients with preoperative permanent atrial fibrillation and concomitant surgery were excluded. Multiple risk factors associated with the incidence of POAF were collected and evaluated.

RESULTS

POAF occurred in 126 of 226 patients (47.37%). Univariate analysis revealed that significant risk factors for the condition were age, gender, diabetes, dyslipidemia, smoking, impaired renal function, impaired cardiac function, and increased serum electrolytes. Multivariate analysis showed dyslipidemia [hazard ratio (HR): 0.418; 95% confidence interval (Cl): 0.190-0.915, p = 0.029], impaired renal function as indicated by an estimated glomerular filtration rate < 60 mL/min/1.73 m(2) (HR: 3.174; 95% CI: 1.432-7.037, p = 0.004), and serum sodium (HR: 1.112; 95% Cl: 1.047-1.182, p = 0.001) prior to cardiopulmonary bypass as significant. Moreover, POAF was associated with lower 30-day, 1- and 3-year cumulative survival rates and higher early postoperative complications.

CONCLUSIONS

Patients with isolated CABG who were administered β-blockers, angiotensin converting enzyme inhibitor/angiotensin receptor blockers treatment, and lipid therapy before CABG were associated with reduced POAF, while those with impaired renal function and higher serum sodium before CABG predisposed POAF in a Taiwanese population.

KEY WORDS

Atrial fibrillation (AF); Coronary artery bypass grafting (CABG); Coronary artery disease (CAD); Postoperative atrial fibrillation (POAF).

Use of ivabradine and atorvastatin in emergent orthopedic lower limb surgery and computed tomography coronary plaque imaging and novel biomarkers of cardiovascular stress and lipid metabolism for the study and prevention of perioperative myocardial infarction: study protocol for a randomized controlled trial

Background

The incidence of perioperative myocardial infarction (PMI) globally is known to be around 2 to 3% and can prolong hospitalization, increased morbidity and mortality. Little is known about the pathophysiology and risk factors for PMI. We investigate the presence of elevated novel cardiac markers and preoperative coronary artery plaque through contemporary laboratory techniques to determine the correlation with PMI, as well as studying ivabradine and atorvastatin as protective pharmacotherapies against PMI in the context of orthopedic surgery.

Methods/Design

We aim to enroll 200 patients aged above 60 years who suffer from neck of femur fracture requiring surgery. Patients will be randomized to four arms (no study drugs, atorvastatin only, ivabradine only and ivabradine and atorvastatin). Our primary outcome is incidence of PMI. All patients will receive an electrocardiogram, cardiac echocardiography, measurement of novel cardiac biomarkers and computed tomography (CT) coronary angiography. A telephone interview post discharge will be conducted at 30 days, 60 days and 1 year.

Discussion

We postulate that ivabradine and atorvastatin will reduce the rate and magnitude of PMI following surgery by reducing heart rate and attenuating catecholamine-induced tachycardia postoperatively. Secondly, we postulate that postoperative reduction in heart rate and catecholamine-induced tachycardia with ivabradine will correlate with a reduction in cardiovascular novel biomarkers which will reduce atrial stretch and postoperative incidence of arrhythmia. We aim to demonstrate that treatment with ivabradine and atorvastatin will cause a reduction in the incidence and magnitude of PMI, the benefit of which is derived primarily in patients with greater atherosclerotic burden as measured by higher CT coronary calcium scores.

Trial registration

This study protocol has been listed in the Australia New Zealand Clinical Trial Registry (registration number: ACTRN12612000340831) on 23 March 2012.

A prospective randomized controlled trial on the incidence and predictors of late-phase postoperative atrial fibrillation up to 30 days and the preventive value of biatrial pacing

BACKGROUND

Postoperative atrial fibrillation (POAF) is considered to be a transient arrhythmia in the first week after cardiac surgery.

OBJECTIVE

To determine the 30-day incidence and predictors of POAF and the value of postoperative overdrive biatrial pacing in the prevention of POAF.

METHODS

Patients (n = 148) without a history of atrial fibrillation undergoing aortic valve replacement or coronary artery bypass graft (CABG) were randomized into a pacing group (n = 75) and a control group. Patients were treated with standardized sotalol postoperatively. Rhythm was continuously monitored for 30 days by a transtelephonic event recorder.

RESULTS

POAF occurred in 73 (49.3%) patients, of whom 60 (40.5%) patients showed POAF during postoperative days (PODs) 0-5 and 37 (25%) patients during PODs 6-30. Prolonged aortic cross-clamp time was an important univariate predictor of 30-day and of late POAF (PODs 6-30; P = .017 and P = .03, respectively). Best-fit model analysis using 15 predetermined risk factors for POAF showed different positive interactive effects for early POAF (ie, baseline C-reactive protein levels with a history of myocardial infarction or low body mass index) and late POAF (ie, high body mass index, diabetes mellitus, baseline C-reactive protein, early POAF, creatinine levels, type of operation, smoking, and male gender). Biatrial pacing reduced the late POAF incidence in patients with aortic cross-clamp time >50 minutes (P = .006).

CONCLUSION

POAF is not limited to the first week after cardiac surgery but also occurs frequently in the postoperative month. It is desirable to regularly follow patients with POAF for atrial fibrillation recurrences after discharge.

Effect of preoperative obstructive sleep apnea on the frequency of atrial fibrillation after coronary artery bypass grafting

Patients with obstructive sleep apnea (OSA) have intermittent hypoxia leading to atrial remodeling and this has been associated with the development of atrial fibrillation (AF). Postoperative AF is a common complication of coronary artery bypass grafting (CABG). The aim of this prospective study was to determine whether the presence of OSA predicts the occurrence of post-CABG AF (PCAF). This was a prospective single-center study. Patients undergoing elective CABG were evaluated and categorized as confirmed, high-risk, or low-risk OSA according to a modified Berlin questionnaire. PCAF was evaluated by 24-hour cardiac monitoring strip or 12-lead electrocardiography during the postoperative period, and validated by an electrophysiologist. We included 277 patients. OSA prevalence was 47.7%, with body mass index (31.0 vs 26.9 kg/m(2), p ≤0.001), advanced age (63.7 vs 66.4 years, p = 0.031), hypertension (78.0% vs 64.8%, p = 0.015), and diabetes (45.5% vs 28.3%, p = 0.003) more prevalent in the OSA group. PCAF was found to occur in 37.2% of all patients and OSA was found to be a strong predictor of PCAF (45.5% vs 29.7%, p = 0.007). PCAF was also associated with continuous positive airway pressure use (12.6% vs 5.2%, p = 0.027). Increased length of stay was associated with PCAF (6.5 vs 5.3 days, p = 0.006), as was longer time from surgery to occurrence of PCAF (p = 0.001). In conclusion, OSA was found to be a strong predictor of PCAF, which in turn was found to be associated with increased length of stay.

Supraventricular arrhythmias after thoracotomy: is there a role for autonomic imbalance?

Supraventricular arrhythmias are common rhythm disturbances following pulmonary surgery. The overall incidence varies between 3.2% and 30% in the literature, while atrial fibrillation is the most common form. These arrhythmias usually have an uneventful clinical course and revert to normal sinus rhythm, usually before patent's discharge from hospital. Their importance lies in the immediate hemodynamic consequences, the potential for systemic embolization and the consequent long-term need for prophylactic drug administration, and the increased cost of hospitalization. Their incidence is probably related to the magnitude of the performed operative procedure, occurring more frequently after pneumonectomy than after lobectomy. Investigators believe that surgical factors (irritation of the atria per se or on the ground of chronic inflammation of aged atria), direct injury to the anatomic structure of the autonomic nervous system in the thoracic cavity, and postthoracotomy pain may contribute independently or in association with each other to the development of these arrhythmias. This review discusses currently available information about the potential mechanisms and risk factors for these rhythm disturbances. The discussion is in particular focused on the role of postoperative pain and its relation to the autonomic imbalance, in an attempt to avoid or minimize discomfort with proper analgesia utilization.

Glucocorticoids in adult cardiac surgery; old drugs revisited

Glucocorticoids can play a pivotal role in modulating different immune responses. The role of glucocorticoids in cardiac surgery is still controversial as many surgeons are concerned about the potential side effects.

In this review, we looked at the role of glucocorticoid administration in modulating postoperative inflammatory responses, atrial fibrillation (AF) and intimal hyperplasia and whether glucocorticoid use is associated with a significant increase in undesirable postoperative complication.

Post-operative Atrial Fibrillation - Pathophysiology, Treatment and Prevention

Atrial fibrillation occurring after cardiac surgery has been the subject of intensive research over the past decades. However, the incidence remains high, despite numerous preventive and treatment strategies. In addition, several reports show that the impact of post-operative atrial fibrillation (POAF) is high. It is an independent risk factor for mortality after several years. These findings make clear that the pathophysiology of POAF is not fully understood and POAF-associated risks to some extent might be underestimated. On the one hand, excessive triggers during the acute post operative phase after cardiac surgery might initiate AF even in atria with low vulnerability. On the other hand, many patients undergoing surgery have an atrial substrate at the time of operation promoting AF not only in the post-operative phase but also in the days and weeks thereafter. Progress in our understanding of the AF mechanisms in general has provided valuable insights into processes involved in atrial structural remodeling due to advanced age, hypertension, obesity, and congestive heart failure. These patient characteristics strongly contribute to cardiac disease, predict POAF and likely have an impact on the risk of thrombus formation in the weeks and months after cardiac surgery. For a better understanding of the mechanisms involved, it is important to not only recognize the occurrence of POAF by continuous monitoring after surgery, but also to identity the extent of atrial vulnerability to AF in these patients.

A minimally invasive monitoring system of cardiac output using aortic flow velocity and peripheral arterial pressure profile

BACKGROUND

In managing patients with unstable hemodynamics, monitoring cardiac output (CO) can provide critical diagnostic data. However, conventional CO measurements are invasive, intermittent, and/or inaccurate. The purpose of this study was to validate our newly developed CO monitoring system.

METHODS

This system automatically determines peak velocity of the ascending aortic flow using continuous-wave Doppler transthoracic echocardiography and estimates cardiac ejection time and aortic cross-sectional area using the pulse contour of the radial arterial pressure. These parameters are continuously processed to estimate CO (CO(est)). In 10 anesthetized closed-chest dogs instrumented with an aortic flowprobe to measure reference CO (CO(ref)), hemodynamic conditions were varied over wide ranges by infusing cardiovascular drugs or by random atrial pacing. Under each condition, CO(ref) and CO(est) were determined. Absolute changes of CO(ref) (ΔCOref) and CO(est) (ΔCO(est)), and relative changes of CO(ref) (%ΔCO(ref)) and CO(est) (%ΔCO(est)) from the corresponding baseline values were determined in each animal. We calibrated CO(est) against CO(ref) to obtain proportionally scaled CO(est) (CO(est)(N)).

RESULTS

A total of 1335 datasets of CO(ref) and CO(est) were obtained, in which CO(ref) ranged from 0.17 to 5.34 L/min. Bland-Altman analysis between CO(ref) and CO(est) indicated that the limits of agreement (the bias ± 1.96 × SD of the difference) and the percentage error (1.96 × [SD of the difference]/[mean CO] × 100) were from -1.01 to 1.13 L/min (95% confidence interval, -1.76 to 1.88 L/min) and 43%, respectively. The agreement between CO(ref) and CO(est)(N) was improved, with limits of agreement from -0.53 to 0.49 L/min (95% confidence interval, -0.62 to 0.59 L/min) and the percentage error of 20%. Polar plot analysis between ΔCO(ref) and ΔCO(est) indicated that mean ± 1.96 × SD of polar angle was -2° ± 22°. Four quadrant plot analysis indicated that %ΔCO(est) correlated tightly with %ΔCO(ref) (R(2) = 0.93). The %ΔCO(est) and %ΔCO(ref) changed in the same direction in 95% of the datasets. Reliability of this system was well preserved under conditions of random atrial pacing and also in a continuous manner.

CONCLUSION

Over a wide range of hemodynamic conditions, irrespective of cardiac beat irregularity, this system may allow minimally invasive monitoring of CO with a good trending ability. The present results warrant further research and development of this system for future clinical application.

[Anesthesia for geriatric patients. Part 1: age, organ function and typical diseases]

Due to demographic changes in the population of industrial nations the number of elderly patients undergoing elective or emergency procedures will rise significantly in the coming years. Anesthesia for geriatric patients is challenging for the anesthesiologist in many ways: with increasing age numerous physiological changes occur which all lead to a subsequent reduction of physical performance and compensatory capacity of the organism, in many cases additionally aggravated by chronic illness. Subsequently, these age-dependent changes (with or without chronic illness) increase the risk for admission to intensive care units, perioperative death, treatment costs and a prolonged length of hospital stay. Therefore, subtle preoperative assessment and tailored anesthetic management are essential in elderly patients. Part 1 of this continuous education article covers the influence of age on organ functions and describes typical comorbidities which are of high relevance for the perioperative care of geriatric patients. The special features of anesthetic agents and anesthesia management in the elderly will be presented in part 2.

Comparison of frequency of atrial fibrillation after coronary artery bypass grafting in African Americans versus European Americans

In the general population, African Americans experience atrial fibrillation (AF) less frequently than European Americans. This difference could also exist in the incidence of this arrhythmia after cardiac surgery, but this possibility has been insufficiently examined. To test the association of such an ethnic difference, we compared the incidence of postoperative AF in a consecutive series of 2,312 African Americans and 6,054 European Americans who underwent isolated coronary artery bypass grafting from July 2000 to June 2007. Raw differences between the cohorts in the incidence of new AF were adjusted to take into account the baseline differences. Postoperatively, new-onset AF developed in 504 (22%) of 2,312 African-American patients and in 1,838 (30%) of 6,054 European-American patients (p <0.01). After adjustment with logistic regression analysis for numerous baseline differences, African Americans remained less likely to develop AF (odds ratio 0.63, 95% confidence interval 0.55 to 0.72; p <0.001). Risk was also adjusted using propensity matching. In that analysis, 457 (22%) of 2,059 African-American patients had postoperative AF, as did 597 (29%) of 2,059 matched European-American patients (p <0.01). In conclusion, AF was significantly less common among African-American patients than among European-American patients after coronary artery bypass grafting.

Association of body mass index with new-onset atrial fibrillation after coronary artery bypass grafting operations

BACKGROUND

Postoperative atrial fibrillation (AF) frequently complicates coronary artery bypass grafting (CABG) operations. As the frequency of obesity has increased in the United States, the number of obese patients undergoing CABG has kept pace. This study sought to define the association between body mass index (BMI) and postoperative AF.

METHODS

We studied 12,367 consecutive patients with no history of AF who underwent isolated CABG operations. BMI was stratified according to Centers for Disease Control and Prevention criteria, and differences in baseline clinical and operative characteristics were adjusted through multivariate logistic regression models.

RESULTS

The unadjusted incidence of new-onset postoperative AF demonstrated a U-shape with regard to BMI. The highest incidence (34%) was found in the "lean" stratum (BMI<18.5 kg/m2), followed by 32% in the "severely obese" (BMI≥40 kg/m2) stratum. Lower incidences were found in the "normal" stratum (30%), in the "obese" stratum (28%), and the lowest incidence (26%) was in the overweight stratum. Observed incidence was 50% greater than the expected incidence in the "severely obese" stratum (32% vs 21%). In multivariate regression analysis adjusted for age and other covariates, BMI remains a strong risk factor for new-onset postoperative AF. Compared with normal BMI, obesity (odds ratio, 1.24; 95% confidence interval, 1.08 to 1.42) and severe obesity (odds ratio, 2.00; 95% confidence interval, 1.54 to 2.57) both emerged as strong risk factors for postoperative AF. No association was found between a lean BMI and postoperative AF (odds ratio, 1.14; 95% confidence interval, 0.66 to 1.98).

CONCLUSIONS

After adjusting for potential confounders, obesity, as reflected by the body mass index, remains an independent predictor of postoperative AF.

Postoperative atrial fibrillation

Postoperative atrial fibrillation (POAF) is common among surgical patients and associated with a worse outcome. Pathophysiology of POAF is not fully disclosed, and several perioperative factors could be involved. Direct cardiac stimulation from perioperative use of catecholamines or increased sympathetic outflow from volume loss/anaemia/pain may play a role. Metabolic alterations, such as hypo-/hyperglycaemia and electrolyte disturbances, may also contribute to POAF. Moreover, inflammation, both systemic and local, may play a role in its pathogenesis. Strategies to prevent POAF aim at reducing its incidence and ameliorate global outcome of surgical patients. Nonpharmacological prophylaxis includes an adequate control of postoperative pain, the use of thoracic epidural analgesia, optimization of perioperative oxygen delivery, and, possibly, modulation of surgery-associated inflammatory response with immunonutrition and antioxidants. Perioperative potassium and magnesium depletion should be corrected. The impact of those interventions on patients outcome needs to be further investigated.

Myocardial extraction of intracellular magnesium and atrial fibrillation after coronary surgery

BACKGROUND

The effects of magnesium loading on the incidence of atrial fibrillation following coronary artery bypass graft surgery (CAGB) are equivocal. None of the previous studies assessed the influence of myocardial extraction of magnesium in these settings. The current trial aims to elucidate whether the incidence of atrial fibrillation following CABG is affected by the preoperative rate of myocardial extraction of magnesium.

METHODS

The ethical committee approved the study protocol. 113 patients (94 male, mean age 63 ± 11 years) planned for elective CABG surgery under normothermic cardiopulmonary bypass were prospectively included. Preoperative independent variables included preoperative treatment, electrocardiographic abnormalities, left ventricular ejection fraction estimation, left atrial size, creatinine clearance and assays of plasma and intracellular magnesium, calcium, albumin, potassium and ionized calcium, drawn preoperatively from the coronary sinus and the aortic root. The covariates - including the rate of myocardial extraction of magnesium - were entered in a logistic regression model to predict the odds of atrial fibrillation.

RESULTS

The incidence of post operative atrial fibrillation was 16%. A rate of myocardial extraction of intracellular magnesium ≥ 7% increases fivefold the multivariate risk of postoperative atrial fibrillation (p < .01). Advanced age was also significantly associated to postoperative atrial fibrillation.

CONCLUSIONS

This study suggests that a preoperative rate of myocardial extraction of intracellular magnesium ≥ 7% could be a new and a potent predictive factor for postoperative atrial fibrillation.

Effect of Statins in Preventing Postoperative Atrial Fibrillation Following Cardiac Surgery

Background: Postoperative occurrence of AF has been associated with less favorable outcomes in patients undergoing cardiac surgery and may result in increased postoperative morbidity and mortality. Objectives: A focused clinical question was designed and a Meta-analysis of published studies was performed to identify the effect of preoperative use of statins on the occurrence of AF after cardiac surgery. Methods: Using the Medline database, the Cochrane clinical trials database and online clinical trial databases, we reviewed all RCTs and observational studies examining the effect of statins on AF occurrence following cardiac surgery. We searched for literature published before April 2009 and earlier. Results: This analysis identified 6 studies (observational studies) which examined the effect of preoperative use of statins on AF occurrence following cardiac surgery, involving 10165 patients. Contradictory to most of previous studies, the overall outcomes suggested that the statins group did not have a significant decrease in AF occurrence following cardiac surgery comparing to control group (P = 0.19). Conclusions: The preoperative medication of statins showed no significant decrease in AF occurrence following cardiac surgery in this Meta-analysis result. More prospective studies and researches are needed to explore and demonstrate the accurate mechanism and effect of statins on postoperative AF.

A practical approach to the management of patients with atrial fibrillation

Atrial fibrillation is the most commonly encountered clinical arrhythmia and continues to grow in incidence. Current management involves highly individualised therapies based on underlying concomitant disease processes and symptoms. Moreover, there are numerous therapeutic permutations involving anticoagulation, rate-limitation and antiarrhythmic strategies. This review serves to update the clinician with a practical approach to each patient population and on current advances in management.