Author + information
- aDepartment of Cardiology, Southlake Regional Health Centre, Newmarket, Ontario, Canada
- bDepartment of Surgery, Li Ka Shing Knowledge Institute of St. Michael’s Hospital, Toronto, Canada
- cDepartment of Surgery, University of Toronto, Toronto, Canada
- dBrigham and Women’s Hospital Heart & Vascular Center, Harvard Medical School, Boston, Massachusetts
- eDivision of Cardiac Surgery, Keenan Research Centre for Biomedical Science and Li Ka Shing Knowledge Institute of St. Michael’s Hospital, Toronto, Canada
- fDepartment of Pharmacology and Toxicology, University of Toronto, Toronto, Canada
- ↵∗Address for correspondence:
Dr. Atul Verma, Southlake Regional Health Centre, Suite 602-581, Davis Drive, Newmarket, Ontario L3Y 2P6, Canada.
It is well known that coronary artery bypass graft surgery is associated with an increased risk of new onset post-operative atrial fibrillation (POAF). However, what remains unclear is the prognostic value of such POAF. POAF is often considered less worrisome because it is believed to be a self-limiting phenomenon secondary to inflammation. However, in this issue of the Journal, Kosmidou et al. (1) from the EXCEL (Evaluation of XIENCE Versus Coronary Artery Bypass Surgery for Effectiveness of Left Main Revascularization) trial provide insight into the poor outcomes associated with POAF. In their analysis, coronary artery bypass grafting was associated with an 18% incidence of new onset POAF. Most strikingly, POAF was associated with a 4-fold risk of stroke and a 3-fold increase in all-cause mortality after multivariable adjustment. These data highlight the need to understand better the true incidence of POAF in the medium and longer term to help develop effective surveillance and treatment approaches.
New onset POAF is an important cause of stroke in patients following cardiac surgery; it doubles the in-hospital risk (odds ratio: 2.23; 95% confidence interval: 1.78 to 2.80), according to a systemic review (2). However, POAF may also increase the risk of stroke at 1 year (3). Indeed, several risk factors have been identified for post-operative stroke in the cardiac surgical population including older age, renal insufficiency, diabetes, left ventricular dysfunction, and hypertension. Because many of these conditions are also risk factors for POAF, it is possible that POAF is just an incidental marker of other high-risk attributes that cause higher stroke and mortality rates. Although Kosmidou et al. (1) perform extensive multivariable adjustment, confounding linkage among these risk factors can never be completely eliminated. Ultimately, we need to determine whether POAF is truly a persistent problem after the post-operative period and whether treatment alters long-term prognosis (Figure 1).
There have been many studies describing the incidence of POAF in the post-cardiac surgical setting, with rates ranging from 15% to 48% (2,4–8), but most of these studies report on the risk during the hospital stay. There are very few data on the incidence of POAF in the subacute phase or in the longer term after hospital discharge. Some reports suggested that the incidence of POAF within 30 days after cardiac surgery is low, in the range of 2% to 5% (9,10). However, most of these studies assessed rhythm status with a single 12-lead electrocardiogram on post-operative day 30, which has very poor sensitivity compared with longer-term monitoring. Funk et al. (11), for example, used 14-day event recorders after hospitalization and found a much higher incidence of atrial fibrillation (AF): 14% within 2 weeks after discharge. Given that the monitors were patient triggered, it is quite possible that asymptomatic AF episodes were not detected. The true incidence of POAF in the subacute phase and beyond is not well defined and is arguably higher than we traditionally assume. Ongoing studies using continuous monitoring (e.g., SEARCH-AF [Detection of Atrial Fibrillation After Cardiac Surgery]; NCT02793895) will hopefully provide better data on the real incidence of subacute POAF.
POAF occurring in the longer term would certainly require action. Gialdini et al. (3) studied 11,837 cardiac surgical patients with new onset POAF and found that 86.0% and 38.5% of them had a CHA2DS2-VASC (congestive heart failure, hypertension, age ≥75 years, diabetes mellitus, and stroke, transient ischemic attack, or thromboembolism; vascular disease, age 65 to 74 years, and female sex) score of ≥2 and ≥4, respectively. If POAF persists post-hospitalization, then most if not all of these patients at high risk of stroke would warrant long-term oral anticoagulation (OAC). However, OAC is often underprescribed for cardiac surgical patients with POAF. In the analysis by Kosmidou et al. (1), only 10.1% of patients with POAF were sent home with OAC, and in the Perioperative Cardiovascular Surgical Care (CAPS-Care) registry, only 39% were discharged with warfarin therapy even though 80% of these patients had a CHADS2 (congestive heart failure, hypertension, age ≥75 years, diabetes mellitus, and stroke, transient ischemic attack, or thromboembolism) score of ≥2 (12). OAC has proven very effective in stroke reduction and may even reduce mortality rates, as evidenced by the trials of non–vitamin K oral anticoagulant agents versus warfarin in chronic nonvalvular AF (13). However, the potential benefits must be weighed against the risks of post-operative and longer-term bleeding. If we believe that POAF may continue well beyond hospitalization and lead to long-term morbidity and mortality, as suggested by the current EXCEL analysis, then randomized trials on the benefits of OAC in this population must be undertaken (14).
In conclusion, we congratulate Kosmidou et al. (1) for an excellent analysis highlighting the grievous long-term risk linked with new POAF following coronary artery bypass grafting. POAF developed in almost 1 in 5 patients, and this occurrence was associated with a marked increase in stroke and death. Future randomized trials will need to determine how best to decrease this risk. Only then will we have a sense of whether POAF, and for that matter other “situational” AF, is only associated with future stroke or is truly causative and thus guilty as charged.
The authors acknowledge the editorial assistance provided by Hwee Teoh, PhD, St. Michael’s Hospital, Toronto, Canada.
↵∗ Editorials published in the Journal of the American College of Cardiology reflect the views of the author and do not necessarily represent the views of JACC or the American College of Cardiology.
Dr. Bhatt is on the advisory boards of Cardax, Elsevier Practice Update Cardiology, Medscape Cardiology, and Regado Biosciences; is on the Board of Directors of the Boston VA Research Institute and the Society of Cardiovascular Patient Care; is the Chair of the American Heart Association Quality Oversight Committee; is on the data monitoring committees of the Cleveland Clinic, Duke Clinical Research Institute, Harvard Clinical Research Institute, Mayo Clinic, Mount Sinai School of Medicine, and Population Health Research Institute; has received honoraria from the American College of Cardiology (Senior Associate Editor, Clinical Trials and News, acc.org), Belvoir Publications (Editor in Chief, Harvard Heart Letter), Duke Clinical Research Institute (clinical trial steering committees), Harvard Clinical Research Institute (clinical trial steering committee), HMP Communications (Editor in Chief, Journal of Invasive Cardiology), Journal of the American College of Cardiology (Guest Editor; Associate Editor), Population Health Research Institute (clinical trial steering committee), Slack Publications (Chief Medical Editor, Cardiology Today’s Intervention), Society of Cardiovascular Patient Care (Secretary and Treasurer), WebMD (CME steering committees), Clinical Cardiology (Deputy Editor), NCDR-ACTION Registry Steering Committee (Chair), and VA CART Research and Publications Committee (Chair); has received research funding from Amarin, Amgen, AstraZeneca, Bristol-Myers Squibb, Chiesi, Eisai, Ethicon, Forest Laboratories, Ironwood, Ischemix, Lilly, Medtronic, Pfizer, Roche, Sanofi, The Medicines Company; has received royalties from Elsevier (Editor, Cardiovascular Intervention: A Companion to Braunwald’s Heart Disease); has been a site co-investigator for Biotronik, Boston Scientific, and St. Jude Medical (now Abbott); has been a trustee of the American College of Cardiology; and has conducted unfunded research for FlowCo, Merck, PLx Pharma, and Takeda. Dr. A. Verma has received research grants from Bayer, Biosense Webster, and Medtronic; and serves on the advisory boards of Bayer, Biosense Webster, and Medtronic. Dr. S. Verma has received research grants from Boehringer Ingelheim and Bristol-Myers Squibb-Pfizer; and has received speaker’s honoraria from Bayer Healthcare, Boehringer Ingelheim, Bristol-Myers Squibb, Pfizer, and Servier.
- 2018 American College of Cardiology Foundation
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