James D. Rawn

Atrial Fibrillation after Cardiac Surgery

More than 200 000 patients undergo coronary artery bypass grafting (CABG) annually worldwide (1). Atrial fibrillation frequently occurs after cardiac surgery and has enormous cost implications (2-4). Management of atrial fibrillation in this setting is often frustrating, and strategies vary widely from institution to institution. Methods We searched the MEDLINE database for English-language reports published between 1966 and June 2000 by using the keywords atrial fibrillation, arrhythmia, coronary artery bypass, anti-arrhythmic agents, electrical countershock, anticoagulation, and complications. In addition, we searched references from relevant articles. Research studies relating to the epidemiology, mechanisms, complications, predictors, prevention, or treatment of atrial fibrillation after cardiac surgery were reviewed and relevant clinical information was extracted. Few articles from 1966 to 1979 are cited because the scientific methods of reports from this period were not well described or were not rigorous or because the reports seemed irrelevant to our current understanding of atrial fibrillation. Epidemiology Atrial arrhythmias occur after cardiac surgery in 10% to 65% of patients (2, 3, 5-25), depending on patient profile, type of surgery, method of arrhythmia surveillance, and definition of arrhythmia (Table 1). A meta-analysis of 24 trials (5) estimated the incidence at 26.7%. Patients undergoing CABG alone have a lower incidence of postoperative atrial fibrillation than patients undergoing valve surgery or combined CABGvalve operations (6, 11) (Table 1). Although the number of patients undergoing heart transplantation is relatively small, these patients appear to have the lowest incidence of postoperative atrial fibrillation (11). The highest incidence of atrial fibrillation is seen on postoperative days 2 to 3, with fewer patients developing atrial fibrillation either in the early postoperative period or 4 or more days after surgery (2, 9, 15, 19, 26). Table 1. Atrial Arrhythmias after Cardiac Surgery in Studies Involving 500 Patients: Incidence and Preoperative Risk Factors Mechanisms of Atrial Fibrillation after Cardiac Surgery Atrial fibrillation is usually attributed to reentry of multiple wavelets of excitation circulating throughout the atria. The exact electrophysiologic mechanisms causing atrial fibrillation after cardiac surgery are incompletely understood; however, episodes are probably initiated by triggers, such as atrial premature contractions, in patients with a susceptible underlying atrial substrate. Occasionally, atrial fibrillation may be caused by a rapidly firing atrial focus (27), although the importance of this mechanism among patients with postoperative atrial fibrillation has not yet been clarified (28). Reentry and atrial fibrillation are facilitated when adjacent atrial regions have widely disparate refractory periods (28-30). Slowed atrial conduction also facilitates reentry, and this probably explains the observed relation between a prolonged P-wave duration, as measured from a signal-averaged electrocardiogram, and the increased risk for atrial fibrillation following cardiac surgery (25). Atrial incisions, atrial ischemia, and associated cardiac disease contribute not only to abnormal atrial conduction and refractoriness but also to the increased frequency of triggering events. Atrial premature beats occur more often in the minutes (12) and hours (16) before onset of atrial fibrillation. Some (12) but not all (16) studies also provide evidence for increased sympathetic activation preceding atrial fibrillation. The role of atrial ischemia in the development of the underlying substrate and the triggering of atrial fibrillation after cardiac bypass operations has been studied. Although cardioplegia administered through the coronary circulation effectively arrests ventricular mechanical and electrical activity, the atrial septum remains significantly warmer than the ventricle (31) and usually retains electrical activity (32)a sign of inadequate myocardial protection (33). Persistence of atrial electrical activity during bypass is associated with postoperative atrial arrhythmias (32, 34). Poorer myocardial preservation, as measured by elevation of creatine kinaseMB, also correlates with postoperative atrial fibrillation (35). Not all evidence indicates that atrial ischemia plays a significant role in atrial fibrillation after cardiac surgery. The degree of atrial hypothermia has no effect on the atrial effective refractory period or on inducibility of atrial fibrillation in a canine model (29). The lower incidence of atrial fibrillation observed in pediatric cardiac surgery and in cardiac transplantation, situations in which atrial ischemia often occurs, suggests that atrial ischemia probably does not play the sole etiologic role. Complications of Atrial Fibrillation after Cardiac Surgery Many complications of coronary artery bypass surgery occur more often in patients who develop postoperative atrial fibrillation than in patients who do not (2, 3, 6, 10, 11, 17, 36-39). Because ill patients more commonly develop atrial fibrillation, it is not surprising that atrial fibrillation is more frequent in patients returning to the operating room for complications (2), patients who are readmitted to the intensive care unit in the postoperative period (6), and patients requiring prolonged ventilation or reintubation (2, 6). Atrial fibrillation also occurs more frequently in postoperative patients with pneumonia (2), perioperative myocardial infarction (6), congestive heart failure (3), cardiac arrest (2, 11), ventricular arrhythmias (2, 11), or renal failure (2, 10). Overall, patients who develop postoperative atrial fibrillation have significantly increased 30-day and 6-month mortality rates compared with patients who do not experience postoperative atrial fibrillation (6). Although atrial fibrillation is often a marker for severity of illness and not necessarily a cause of increased morbidity, some complications may be more directly a consequence of the arrhythmia. Patients with atrial fibrillation after cardiac surgery are more likely than patients who do not develop postoperative atrial fibrillation to have a cerebrovascular accident during hospitalization (2, 6, 11, 36, 37). Atrial fibrillation may cause hypotension or pulmonary edema (17), and stroke and cardiac index improve significantly in some patients after sinus rhythm is restored (38, 39). Patients with atrial fibrillation are also more likely to need a permanent pacemaker postoperatively (11). Even after adjustment for level of illness, patients with atrial fibrillation have longer stays in the intensive care unit (3, 6, 11) and in the hospital overall (2, 3). It has been estimated that hospital charges are

The relationship among obesity, nutritional status, and mortality in the critically ill.

10 000 to

The silent risks of blood transfusion

11 000 more per patient with atrial fibrillation (2). Predictors of Atrial Fibrillation after Cardiac Surgery Several factors are associated with the development of atrial fibrillation after cardiac surgery. These factors can be classified as preoperative, intraoperative, or postoperative. Preoperative Factors Table 1 shows the preoperative factors associated with an increased incidence of atrial fibrillation after cardiac surgery. Older age has consistently predicted a higher incidence of postoperative atrial fibrillation (2-7, 9-12, 19, 25); incidence is increased by at least 50% per decade of older age (3, 6, 7, 10). Older age also predicts atrial fibrillation in the general population (40), possibly because of increased atrial fibrosis and dilation (41). Large, well-conducted observational studies have yielded conflicting results on the independent predictive value of other preoperative factors (Table 1). Hypertension, a predictor of atrial fibrillation in the general population (40), appears to predict atrial fibrillation after cardiac surgery (2, 6), and this may be related to associated fibrosis and dispersion of atrial refractoriness. Men appear more likely than women to develop post-CABG atrial fibrillation (2, 6, 7, 19, 25); sex differences in ion-channel expression and hormonal effects on autonomic tone may explain this disparity. Previous atrial fibrillation (3, 9) and previous congestive heart failure (3) are also predictors of postoperative atrial arrhythmias. An elevation in left ventricular end-diastolic pressure before surgery has been shown in some (9) but not all (3) studies to predict postoperative atrial fibrillation. Intraoperative Factors Some (3, 11, 15) but not all (2, 9, 19) studies show that aortic cross-clamp time correlates with postoperative atrial fibrillation, possibly because of the relation between cross-clamp time and atrial ischemia. Location of venous cannulation has also been related to the incidence of postoperative atrial fibrillation. Pulmonary vein venting has been associated with increased risk for postoperative atrial fibrillation (3, 6), while bicaval cannulation (which avoids incisions in the atria) has been associated with atrial fibrillation in some studies (3) but not others (42). Postoperative Factors Respiratory compromise, including pneumonia (2), chronic obstructive lung disease (6, 10, 11), and prolonged ventilation (2) are associated with atrial fibrillation after cardiac surgery. The need for postoperative atrial pacing is also associated with atrial fibrillation (3), and this probably reflects underlying sinus-node dysfunction and use of rate-controlling medications. Prophylaxis and Prevention Because of the high incidence of atrial fibrillation after cardiac surgery and the associated morbidity, mortality, and cost, much attention has focused on prevention of atrial fibrillation (Table 2). Table 2. Summary of Trials Investigating Prophylactic Drug Use for the Prevention of Atrial Arrhythmias in Patients Undergoing Cardiac Surgery Numerous randomized, controlled trials have demonstrated the benefit of prophylactic use of -adrenergic blockade in pat

Cumulative team experience matters more than individual surgeon experience in cardiac surgery.

Introduction:The association between obesity and mortality in critically ill patients is unclear based on the current literature. To clarify this relationship, we analyzed the association between obesity and mortality in a large population of critically ill patients and hypothesized that mortality would be impacted by nutritional status. Methods:We performed a single-center observational study of 6,518 adult patients treated in medical and surgical ICUs between 2004 and 2011. All patients received a formal, in-person, and standardized evaluation by a registered dietitian. Body mass index was determined at the time of dietitian consultation from the estimated dry weight or hospital admission weight and categorized a priori as less than 18.5 kg/m2 (underweight), 18.5–24.9 kg/m2 (normal/referent), 25–29.9 kg/m2 (overweight), 30–39.9 kg/m2 (obesity class I and II), and more than or equal to 40.0 kg/m2 (obesity class III). Malnutrition diagnoses were categorized as nonspecific malnutrition, protein-energy malnutrition, or well nourished. The primary outcome was all-cause 30-day mortality determined by the Social Security Death Master File. Associations between body mass index groups and mortality were estimated by bivariable and multivariable logistic regression models. Adjusted odds ratios were estimated with inclusion of covariate terms thought to plausibly interact with both body mass index and mortality. We utilized propensity score matching on baseline characteristics and nutrition status to reduce residual confounding of the body mass index category assignment. Results:In the cohort, 5% were underweight, 36% were normal weight, 31% were overweight, 23% had class I/II obesity, and 5% had class III obesity. Nonspecific malnutrition was present in 56%, protein-energy malnutrition was present in 12%, and 32% were well nourished. The 30-day and 90-day mortality rate for the cohort was 19.1 and 26.6%, respectively. Obesity is a significant predictor of improved 30-day mortality following adjustment for age, gender, race, medical versus surgical patient type, Deyo-Charlson index, acute organ failure, vasopressor use, and sepsis: underweight odds ratio 30-day mortality is 1.09 (95% CI, 0.80–1.48), overweight 30-day mortality odds ratio is 0.93 (95% CI, 0.80–1.09), class I/II obesity 30-day mortality odds ratio is 0.80 (95% CI, 0.67–0.96), and class III obesity 30-day mortality odds ratio is 0.69 (95% CI, 0.49–0.97), all relative to patients with body mass index 18.5–24.9 kg/m2. Importantly, there is confounding of the obesity-mortality association on the basis of malnutrition. Adjustment for only nutrition status attenuates the obesity–30-day mortality association: underweight odds ratio is 0.74 (95% CI, 0.54–1.00), overweight odds ratio is 1.05 (95% CI, 0.90–1.23), class I/II obesity odds ratio is 0.96 (95% CI, 0.81–1.15), and class III obesity odds ratio is 0.81 (95% CI, 0.59–1.12), all relative to patients with body mass index 18.5–24.9 kg/m2. In a subset of patients with body mass index more than or equal to 30.0 kg/m2 (n = 1,799), those with either nonspecific or protein-energy malnutrition have increased mortality relative to well-nourished patients with body mass index more than or equal to 30.0 kg/m2: odds ratio of 90-day mortality is 1.67 (95% CI, 1.29–2.15; p < 0.0001), fully adjusted. In a cohort of propensity score matched patients (n = 3,554), the body mass index–mortality association was not statistically significant, likely from matching on nutrition status. Conclusions:In a large population of critically ill adults, the association between improved mortality and obesity is confounded by malnutrition status. Critically ill obese patients with malnutrition have worse outcomes than obese patients without malnutrition.

Surgical Embolectomy for Acute Massive and Submassive Pulmonary Embolism in a Series of 115 Patients

Purpose of review Clinical research has identified blood transfusion as an independent risk factor for immediate and long-term adverse outcomes, including an increased risk of death, myocardial infarction, stroke, renal failure, infection and malignancy. New findings have called into question the traditional assumptions clinicians utilize in evaluating the risks and benefits of blood transfusion. Appreciation of newly recognized risks is important for conserving scarce resources and optimizing patient outcomes. Recent findings Recent clinical outcomes research has examined the impact of blood transfusion on critically ill patients, trauma patients, patients undergoing cardiac surgery, patients experiencing acute coronary syndromes, oncology patients and others. These studies provide additional evidence of adverse outcomes associated with blood transfusion in a wide variety of clinical contexts. Summary The benefits of blood transfusion have never been conclusively demonstrated, but evidence of transfusion-related harm continues to accumulate. Given the transfusion triggers that currently predominate in clinical practice it appears that clinical outcomes could improve significantly with more widespread adoption of restrictive transfusion strategies.

Nutritional Status and Mortality in the Critically Ill.

OBJECTIVES Individual surgeon experience and the cumulative experience of the surgical team have both been implicated as factors that influence surgical efficiency. We sought to quantitatively evaluate the effects of both individual surgeon experience and the cumulative experience of attending surgeon-cardiothoracic fellow collaborations in isolated coronary artery bypass graft (CABG) procedures. METHODS Using a prospectively collected retrospective database, we analyzed all medical records of patients undergoing isolated CABG procedure at our institution. We used multivariate generalized estimating equation regression models to adjust for patient mix and subsequently evaluated the effect of both attending cardiac surgeon experience (since fellowship graduation) and the number of previous collaborations between attending cardiac surgeons and cardiothoracic fellow pairs on cardiopulmonary bypass and crossclamp times. RESULTS From 2001 to 2010, 4068 consecutive patients underwent isolated CABG procedure at our institution performed by 11 attending cardiac surgeons and 73 cardiothoracic fellows. Mean attending experience after fellowship graduation was 10.9 ± 8.0 years and mean number of cases between unique pairs of attending cardiac surgeons and cardiothoracic fellows was 10.0 ± 10.0 cases. After patient risk adjustment, both attending surgical experience since fellowship graduation and the number of previous collaborations between attending surgeons and cardiothoracic fellows were significantly associated with a reduction in cardiopulmonary bypass and crossclamp times (P < .001). The influence of attending-fellow pair experience far exceeded the influence of surgical experience with beta estimates for attending-fellow pair experience nearly three times that of attending surgeon experience. CONCLUSIONS Cumulative experience of attending cardiac surgeons and cardiothoracic fellows has a dramatic effect on both cardiopulmonary bypass and crossclamp times, whereas attending cardiac surgeon learning curves following fellowship graduation are clinically insignificant. Taken together, these findings suggest that the primary driver of operative efficiency in CABG procedure is the collaborative experience of the attending surgeon-cardiothoracic fellow operative team, rather than the individual experience of the attending surgeon.

Long and short-term outcomes following coronary artery bypass grafting in patients with and without chronic kidney disease

BACKGROUND Pulmonary embolectomy is often indicated for central pulmonary embolism (PE) with hemodynamic instability, but remains controversial for hemodynamically stable patients with signs of right ventricular dysfunction. Because thrombolytic therapy is often contraindicated postoperatively, we reviewed risk factors and outcomes of pulmonary embolectomy for stable and unstable central PE, particularly in the early postoperative period. METHODS Between October 1999 and September 2013, 115 patients underwent pulmonary embolectomy for central, hemodynamically unstable PE (49 of 115, 43%) or hemodynamically stable PE (56 of 115, 49%). Ten operations for alternate indications (right atrial mass, endocarditis) were excluded for comparison analysis, leaving 105 patients. RESULTS Mean age was 59 ± 13 years; 46 of 105 patients (44%) had recent surgery (within 5 weeks): orthopedic (12 of 46, 25%), neurosurgery (11 of 46, 24%), or general surgery (10 of 46, 22%). Preoperative demographics did not differ between groups, except for the frequency of cardiopulmonary resuscitation among unstable patients (11 of 49, 22%) versus stable patients (0 of 56, 0%; p < 0.001). Operative mortality for the combined groups was 6.6% (7 of 105): unstable 10.2% (5 of 49) versus stable 3.6% (2 of 56; p = 0.247). Of 11 patients requiring preoperative cardiopulmonary resuscitation, 4 died. Six-month, 1-year, and 3-year survival rates were, respectively, 75%, 68.4%, and 65.8% for unstable PE, and 92.6%, 86.7%, and 80.4% for stable PE (p = 0.018). CONCLUSIONS This large series of pulmonary embolectomies demonstrates excellent early and late survival rates for patients with stable PE and unstable PE. These findings confirm pulmonary embolectomy as a beneficial therapeutic option for central PE, especially during the postoperative period when thrombolytic therapy is often contraindicated.

Surgery for Anomalous Origin of the Right Coronary Artery From the Left Aortic Sinus

Objectives:The association between nutritional status and mortality in critically ill patients is unclear based on the current literature. To clarify this relation, we analyzed the association between nutrition and mortality in a large population of critically ill patients and hypothesized that mortality would be impacted by nutritional status. Design:Retrospective observational study. Setting:Single academic medical center. PatientsSix thousand five hundred eighteen adults treated in medical and surgical ICUs between 2004 and 2011. Interventions:None. Measurements and Main Results:All cohort patients received a formal, in-person, standardized evaluation by a registered dietitian. The exposure of interest, malnutrition, was categorized as nonspecific malnutrition, protein-energy malnutrition, or well nourished and determined by data related to anthropometric measurements, biochemical indicators, clinical signs of malnutrition, malnutrition risk factors, and metabolic stress. The primary outcome was all-cause 30-day mortality determined by the Social Security Death Master File. Associations between nutrition groups and mortality were estimated by bivariable and multivariable logistic regression models. Adjusted odds ratios were estimated with inclusion of covariate terms thought to plausibly interact with both nutrition status and mortality. We used propensity score matching on baseline characteristics to reduce residual confounding of the nutrition status category assignment. In the cohort, nonspecific malnutrition was present in 56%, protein-energy malnutrition was present in 12%, and 32% were well nourished. The 30-day and 90-day mortality rates for the cohort were 19.1% and 26.6%, respectively. Nutritional status is a significant predictor of 30-day mortality following adjustment for age, gender, race, medical versus surgical patient type, Deyo-Charlson index, acute organ failure, vasopressor use, and sepsis: nonspecific malnutrition 30-day mortality odds ratio, 1.17 (95% CI, 1.01–1.37); protein-energy malnutrition 30-day mortality odds ratio, 2.10 (95% CI, 1.70–2.59), all relative to patients without malnutrition. In the matched cohort, the adjusted odds of 30-day mortality in the group of propensity score-matched patients with protein-energy malnutrition was two-fold greater than that of patients without malnutrition. Conclusion:In a large population of critically ill adults, an association exists between nutrition status and mortality.

Transcriptional profiling and growth kinetics of endothelium reveals differences between cells derived from porcine aorta versus aortic valve

BACKGROUND Improved understanding of the incidence and risk factors for operative complications and long-term mortality following coronary artery bypass grafting (CABG) is needed to better define the optimal role for CABG in patients with chronic kidney disease (CKD). METHODS We analysed 2438 patients who underwent CABG at a single centre between 2005 and 2008. Multivariable regression was used to analyse associations and to generate a CKD-specific predictive tool. RESULTS Operative mortality was 4.8% in individuals with stage 3 CKD, 7.1% in individuals with stage 4-5 CKD and 2.2% in those without significant CKD (P < 0.001). CKD was associated with post-operative blood transfusion, acute kidney injury, myocardial injury and cardiac arrest, and use of exogenous blood and acute kidney injury were strongly associated with in-hospital death in CKD patients. Patients with stage 3 (HR 1.64, 95% CI 1.30-45.94) and stage 4-5 CKD (HR 2.77, 95% CI 1.00-2.68) were more likely to die during follow-up than those without CKD, but mortality rates were low among patients who survived to discharge-stage 3 (0.006 deaths/year) and stage 4-5 CKD (0.009/year). A scoring system including urgent or emergent surgery (OR 2.30), prior cardiac surgery (OR 3.06), concurrent valve surgery (OR 2.06), preoperative shock (OR 6.18), and prior stroke (OR 1.98) had 96.4% percent specificity for the detection of in-hospital death in patients with CKD. CONCLUSIONS Perioperative mortality and morbidity remain more frequent in patients with stage 3-5 CKD than patients with preserved renal function, but long-term outcomes in patients surviving hospitalization are favourable. We have developed a predictive tool that holds promise as a means of identifying CKD patients most likely to survive surgery and benefit from CABG.

Are homografts superior to conventional prosthetic valves in the setting of infective endocarditis involving the aortic valve

This case report illustrates the presentation, diagnosis, and surgical management of an anomalous origin of the right coronary artery from the left coronary sinus in a young adult in whom the right coronary artery was reimplanted directly onto the aorta, rather than bypassed, as is typically done.