Methods and Results
In the study, 611 patients were included after CABG. All patients had echocardiograms performed preoperatively and LA functional measurements were assessed. These measurements were LA maximum volume index (LAVmax), LA minimum volume index (LAVmin) and LA emptying fraction (LAEF). The endpoint was AF occurring >14 days after surgery.
During the follow-up period of a median of 3.7 years, 52 (9%) developed AF. The mean age was 67 years, 84% were male and the average left ventricle ejection fraction was 50 %. No differences were observed between the patients developing AF and those who did not develop AF. No functional LA measurements were significant predictors of AF in the whole CABG population. However, in patients with normal-sized LA (n=532, events: 49), both LAEF and LAVmin were univariable predictors of AF. When the functional measurements were adjusted for the CHADS2 score, both LAVmin (HR=1.07 (1.01-1.13), p=0.014 ) and LAEF (HR: 1.02 (1.00-1.03, p= 0.023)), remained significant predictors.
ConclusionNo echocardiographic measurements were significant predictors of AF after CABG. In patients with a normal LA size, LAVmin as well as LAEF were significant predictors of AF.
Keywords: atrial fibrillation; cardiac surgery; left atrium; echocardiography
Introduction
Coronary artery bypass grafting (CABG) is the most performed major cardiovascular surgery procedure in the US, constituting half of all major cardiovascular procedures (1). The most common postoperative arrhythmia following CABG is atrial fibrillation (AF) (2) (3). AF is also the most common cardiac arrhythmia overall with increased risk of stroke (4). Hence, being able to identify patients at risk of AF is key to prescribing anticoagulants and preventing ischemic strokes. With correct screening, the risk of post-operative complications can be reduced as the treatment and monitoring of the patient can be individually tailored. Currently, congestive heart failure, hypertension, age >75 years, diabetes, and previous stroke/transient ischemic attack (CHADS2) are used to determine the appropriate anticoagulant treatment for patients to prevent strokes. This scoring system is associated to the development of post-operative AF (POAF) and is also used to predict AF (5). However, an improved model for predicting AF in patients with a CABG may decrease mortality due to a decrease in the number of patients experiencing stroke. Patients are routinely examined before CABG with an echocardiogram to identify valvular disease and to evaluate the systolic function. Currently, the most widely used echocardiographic measurement in the clinic for predicting AF is the maximal volume of the left atrium (LAVmax) (6). Several studies have found that functional measurements of the left atrium (LA), such as the LA emptying fraction (LAEF) and the LA minimum volume index (LAVmin), are useful in predicting AF (7,8). Since it seems that the LA functional measures can play a role in predicting AF, we hypothesized that: 1. The LA functional measurements would be better predictors than LAVmax for AF following CABG. Furthermore, we hypothesized that: 2. LA functional measurements would be significant predictors of AF even in patients with a normal LA size.