Characterizing Patients With Post-operative Atrial Fibrillation in Relation to Cardiac Surgery by Signal Processed Surface Electrocardiogram (wavECG) and Transthoracic Echocardiography A LAACS-2 Sub-study

Introduction: Post-operative atrial fibrillation (POAF) is frequently observed after open-heart surgery,1-3 and atrial fibrillation (AF) is frequently complicated by stroke.4-6 During AF, the electrical activity is uncoordinated and the atrial contraction is reduced, increasing the risk of thrombi formation. Subsequently, the thrombi can enter the general circulation, reach the small intracerebral arteries and block blood flow resulting in ischaemic damage.5,7 Anti-coagulant medicines efficiently prevent ischaemic strokes,8 however many patients are asymptomatic or have vague symptoms why diagnosis can be difficult to obtain.5 Furthermore, AF that occurs secondarily to surgery is currently considered self-limiting and continuous anti-coagulation is not necessarily recommended.4,9 However, cumulating evidence suggest that secondary AF in patients with known heart disease increases the long-term risk of stroke and transitory ischaemic attack, recurrent AF and mortality.10-15 In patients undergoing coronary artery bypass grafting (CABG) new-onset AF is associated with increased long-term risk of stroke and mortality compared to patients without AF.14,15 Though there are well-established risk factors for AF, such as age, arterial hypertension, heart failure, myocardial infarction, heart valve disease and diabetes mellitus, the pathophysiology of AF is complex and not fully understood.6,16,17 Both structural remodelling of the atria and electrical pathways, as well as oxidative stress, calcium overload, myofibroblast activation, microRNAs and inflammation, are mentioned as possible factors involved in initiation and progression of AF.6,16-18 Attempts to create and improve risk stratification models for AF and stroke has previously been done, both in community based cohorts and patients undergoing cardiac surgery, e.g. CHA2DS2-VASC, FHS AF risk score, ARIC risk prediction tool, CHARGE-AF risk model, HAVOC score, SYNTAX score, POAF score and POAF prediction model.19-27 However, it remains challenging to accurately predict occurrence of AF both perioperatively and in the subsequent years.28,29

A recent systematic review and meta-analysis concluded that p-wave terminal force in lead V1 (PTFV1), p-wave duration and maximum p-wave area, are all correlated with stroke,30 and a recent review similarly suggest that short and prolonged p-wave and PTFV1 is correlated with AF.31 sp-ECG by Myovista (Southlake, Texas, USA) is a novel advanced ECG utilizing continues wavelet transform signal processing and can detect left ventricular diastolic dysfunction (LVDD) which is associated with AF and post-operative heart failure in other studies.17,32-35 LA strain and E/LA strain indices predicted new cardiovascular events including strokes, in a stroke population36 In patients undergoing catheter ablation for AF, LA strain can identify patients at risk of AF recurrence37,38 POAF has furthermore been predicted in a cohort of patients with severe aortic stenosis by LA strain indexes.39

Aim: We aim at characterizing patients with AF occurrence by novel, easy, and accessible methods such as electrocardiogram (ECG), signal processed surface ECG (Myovista, wavECG) and transthoracic echocardiography (TTE).

Methods: Explorative, prospective cohort study of adult patients undergoing first-time elective open-heart surgery at Department of Cardiothoracic Surgery at Copenhagen University Hospital, Rigshospitalet. One hundred consecutive patients enrolled in the Left Atrial Appendage Closure by Surgery-2 (LAACS-2) trial (NCT03724318) fulfilling the inclusion/exclusion criteria are included in the current study.

The study is approved by the Regional Committee on Health Research Ethics and all procedures followed are in accordance with the ethical standards of the responsible committee on human experimentation and with the Helsinki Declaration. All patients have signed informed consent prior to study enrolment.