Left ventricular ejection fraction was measured using the modified Simpson’s method on images of apical, 2- and 4-chamber views. Left atrial volume index was calculated by the prolate ellipsoid method. Two-dimensional transthoracic echocardiography was performed using an ultrasound machine (Vivid 7, GE Medical Systems, Horten, Norway and Sonos 5500, Philips Medical Systems, Andover, Massachusetts, USA) with a 2.5-MHz transducer. Transient ischemic attack (TIA) was defined as a neurologist-confirmed transient episode of neurologic dysfunction without a brain lesion on imaging studies. Beginning of follow-up was defined as time of acquisition of 2 nd ECG in JB group and acquisition of 1 st ECG in control group. Ischemic stroke was defined as symptomatic ischemic cerebral infarction with an apparent brain lesion on imaging studies. CHADS 2 score was calculated for each patient by assigning 1 point each for an age ≥75 years, history of heart failure, hypertension, and diabetes mellitus and 2 points for previous stroke or transient ischemic attack.

In addition, to minimize confounding factors, we matched age, gender, and CHADS 2 score, which are known as risk factors for stroke not only in patients with atrial fibrillation but also in patients without atrial fibrillation. Since the incidence of JB was very low we aimed for 1:2 matching.

For the controls, we excluded patients with a history of thromboembolic events, including ischemic stroke, and those lacking two-dimensional transthoracic echocardiographs. Additionally, patients who had been treated with implantation of a pacemaker or cardiac resynchronization therapy due to sick sinus syndrome or intractable heart failure were excluded from analysis.Īdditionally, we also included 138 age-, gender-, and CHADS 2 score-matched patients in sinus rhythm as a control group these patients had undergone minor surgery, including nasal septal deviation and cataract surgery, in the same period and at the same hospital. Patients with transient JB and those with hyperkalemia at the time of ECG recording, history of end-stage renal disease, paroxysmal atrial fibrillation, and only one recording of JB were excluded. Inclusion criteria for analysis comprised age older than 18 years and JB on multiple ECGs at an interval of at least 3 months. Respective ECGs with JB, with or without a retrograde P wave, were to be agreed upon by all three cardiologists. Retrograde P wave was defined as an inverted P wave after the QRS complex was noted. Then, three cardiologists reviewed the screened ECGs and finally selected those exhibiting JB in accordance with the following: JB was defined as a regular rhythm of less than 60 beats/min without a precedent P wave and a narrow QRS complex for a duration of less than 0.12 s. The algorithm for detecting JB is as follows: no P wave, a regular RR interval (i.e., an RR interval range that is less than 10 % of the average RR interval), narrow primary beat (<0.12 s for QRS duration), and a regular rate less than 60 beats/min. Initially, the ECGs were screened by an automated ECG analysis algorithm embedded in our system to detect for JB. The low and high cut-off frequencies were 0.5 and 100 Hz, respectively. The digital sampling rate was 500 samples per second. Twelve-lead ECGs were recorded by digital ECG instruments (General Electric Healthcare, Milwaukee, Wisconsin, USA). A total of 972,683 ECGs (mean of 2.55 ECGs per patient) stored in our electronic database system (Muse System, General Electric Healthcare, Milwaukee, Wisconsin, USA) were included in this study. We initially excluded patients who were admitted due to acute myocardial infarction or acute stroke and patients whose life expectancy is less than 6 months due to cancer. We screened consecutive patients who visited our outpatient center or were admitted to our hospital for ECG recording during the period. We retrospectively reviewed electrocardiograms (ECGs) for 380,682 patients (47.6 ± 19.9 years male, 49.3 %) from a single university hospital from January 2008 to December 2012.

Treatments for junctional escape rhythm