ER provides the clinician with a rapid and accurate

ER-2000® provides the clinician with a rapid and accurate assessment of a patient׳s arrhythmia, improving clinical decision making and clinical outcomes. Further large-scale study is warranted to confirm the accuracy of ER-2000®. Furthermore, the efficacy and usefulness of ER-2000® should be examined under specific conditions, such as in patients with stroke or transient ischemic attack suspected to have paroxysmal AF, in diagnosing asymptomatic episodes of AF recurrence after catheter ablation, or for the diagnosis of arrhythmia causing syncope.
Conflict of interest
Acknowledgments This study was supported by a research grant from Boryung Soo & Soo Ltd., Seoul, Korea.
Introduction The association between influenza-like illness and adverse cardiac events has been reported in several observational studies [1,2], prompting the American Heart Association and Canadian Cardiovascular Society to recommend annual influenza calcium ionophore for patients with cardiac disease [3,4]. However, there has been no study on the association between influenza vaccination and cardiac arrhythmia, an underappreciated contributor of cardiac morbidity and mortality. In this exploratory retrospective study of 229 patients, we assessed the association between influenza vaccination and implantable cardioverter defibrillator (ICD) therapies in the six months before and the three months during the 2010–2011 influenza season.
Materials and methods Patient demographics, co-morbidities, and medication use were ascertained from responses to survey questions and a review of each patient׳s hospital chart. Each patient׳s ICD chart was reviewed to confirm the incidence of any ICD therapy (appropriate and inappropriate shock or antitachycardia pacing) for an arrhythmic event between June 1st, 2010 and March 1st, 2011. Inappropriate ICD therapies secondary to lead or device malfunctions were excluded, as they do not reflect arrhythmic events. The type of each ICD therapy was adjudicated by two individuals (R.K. and S.M.S.). December 1st, 2010–March 1st, 2011 was considered influenza season, consistent with the peak of influenza season in Canada [5], whereas June 1st, 2010–November 30th, 2010 was deemed “pre”-influenza season. Of note, a good match between the influenza vaccine and globally circulating influenza strains was noted during this influenza season [6]. Patients were divided into two groups: those that received the influenza vaccine and those that did not. Patient characteristics for each group were reported as proportions, mean±standard deviation or median with range where appropriate. Student׳s t-, Fisher׳s exact, and Wilcoxon Rank-Sum tests were used to assess differences between the two groups. Possible endpoints that may differ between vaccinated vs. unvaccinated individuals were considered to be a reduction in the number of vaccinated individuals receiving any ICD therapy compared to unvaccinated individuals or a reduction in the total number of arrhythmic events requiring ICD therapies in vaccinated individuals, the latter of which accounts for clustering of arrhythmia during the winter months [7]. A binomial test for proportions was performed to assess differences in the total number of ICD therapies between the groups during “pre”- and influenza season. The “pre”-influenza season was divided into two 3 month periods for comparison with the 3 month influenza period. Poisson regression analysis [8] was employed to assess differences between groups in the number of ICD therapies received during influenza season. The analysis was repeated for appropriate ICD shocks during influenza season. Results were reported as an incident rate ratio (IRR) comparing the incidence of ICD therapies in unvaccinated vs. vaccinated patients. Since the patient cohort in this study was small, thereby impacting the validity of multivariate analysis, our primary evaluation of ICD therapy incidence was unadjusted for differences between the two study groups with regard to factors known to impact cardiac arrhythmia, such as patient age, co-morbidity, or history of ventricular arrhythmias. Secondary analyses adjusted for these factors. Finally, when comparing the number of ICD therapies during influenza season between patients who were or were not vaccinated, an adjustment was made for the number of ICD therapies received in the “pre”-influenza period. We repeated the above analysis after restricting the cohort to those with a left ventricular ejection fraction ≤35% to understand the impact of influenza vaccination on all ICD therapies and appropriate ICD shocks in patients with left ventricular systolic dysfunction.