ABC | Volume 111, Nº2, August 2018

Original Article Sampaio et al Monitoring of rhythm, atrial fibrillation and stroke Arq Bras Cardiol. 2018; 111(2):122-131 Exclusion criteria were previous AF or AFL or admission electrocardiogram showing any of these conditions, hemorrhagic stroke, age younger than 18 years, residence in areas with no mobile phone coverage, need for intensive care due to severity of disease or difficult management of disease, sequela of neurologic injury, and patients with important cognitive impairment that could negatively affect the ability to understand the instructions related to the use of the devices. Patients with suspected stroke/TIA were seen at two medium-sized public hospitals in the city of Curvelo, Minas Gerais, Brazil, between August 2016 and April 2017. Control patients were enrolled during outpatient visits. Patients’ follow-up and therapeutic approach were left to the assistant physicians’ discretion. Patients or legal caregivers were invited to participate in the study, which was approved by the research ethics committee of University Hospital of São José/FELUMA, and all participants signed an informed form. Measurement tools: the diagnosis of stroke/TIA was confirmed by computed tomography (CT) and/or magnetic resonance imaging (MRI), and classified for etiologies using the TOAST 14 criteria. CT and MRI tests were performed by radiologists experienced in the Siemens Somatom Spirit or Toshiba Asteion4 CT scanners and the GE Optima MR360 1.5T. Demographic and clinical data: data of age, sex, skin color, place of residence, anamnesis, previous diseases, family history, weight, height, traditional cardiovascular risk factors, and CHADS 2 and CHA 2 DS 2 -VASc scores were collected, and cardiologic and neurologic tests were also performed. Complementary tests: 12-lead ECG, transthoracic echocardiography, Doppler examination of carotid and vertebral arteries, chest X-ray (posterior-anterior and lateral views), laboratory tests including complete blood test, urea, creatinine, glucose, transaminases, GGT, potassium, sodium, TSH, free T4, cholesterol (total and fractions), triglycerides, prothrombin time (PT) and partial thromboplastin time (PTT). Heart rhythmmonitoring: during the first week after clinical diagnosis and notification of cryptogenic ischemic stroke or TIA, heart rhythm was monitored by three-channel Holter 24h recorders (DMS 300-8 and DMS 300-9) and analyzed simultaneously with the DMS CardioScan II software (DM Software Inc. Stateline, NV, USA) and electrocardiography (Policardiógrafo IP®, PoIP) (eMaster, BeloHorizonte, MG, Brazil). PoIP monitoring: PoIP monitors independently collect and transmit electrocardiographic data at real time using the General Packet Radio Services/ Enhanced Date Rates  for GSM Evolution  ( GPRS/ EDGE); data are then stored in the cloud. We used the Brazilian cell phone provider Vivo for transmission of the data to the PoIP web portal, and the Mozilla Firefox was used as the web browser for analysis of the data. PoIP offers a “Portal de Exames”, an app that enables monitoring of different PoIP devices as well as the access to laboratory tests by individual access credentials (Figure 1). Six electrodes were arranged so that frontal plane leads could be monitored beyond V 1 -V 2 . Patients and family members were instructed and trained for the monitoring technique, quality of transmission signal, battery charge and charging of the lithium-based batteries. The monitoring was closely controlled via internet by the responsible staff members for the correct use of the device, and quality of the electrode contacts; if necessary, family or caregivers were informed about inadequate system operation or the quality of data transmission. Procedures: Each participant received an electrode pack and a leaflet with a thorax illustration indicating electrodes’ colors and correct positioning for replacement. All electrocardiographic recordings were analyzed by the same investigator (RSF), a cardiologist experienced in ambulatory electrocardiography, and all electrocardiographic tracings considered indicative of AF or tachycardia were reviewed by a second investigator (EBS), a cardiac electrophysiologist. For analysis of PoIP findings, the results were accessed via internet and examined for AF/AFL every 12 hours or every time the monitor button was pressed by the patient/caregiver. Every 24-hour period, all data transmitted by PoIP were exported and reviewed offline, and quantitative analysis of arrhythmias registered. In this analysis, we considered – number of (single or in pairs) SVES, number of nonsustained atrial tachycardia (AT) episodes greater than three consecutive premature atrial complexes and shorter than 30 seconds, sustained AT longer than 30 seconds and number of AF episodes longer or shorter than 30 seconds. Statistical analysis : categorical variables were expressed as counts and percentages and numerical variables as mean ± standard deviation (SD). Data normality assumptions were verified with the Shapiro-Wilk test. Associations between categorical variables were assessed by Fisher’s exact test or the chi-square test of independence. Comparisons of two groups between independent samples were made by the Wilcoxon test, the Mann-Whitney test or the Student’s t-test, as appropriate. Analyses were performed using the free R software version 3.3.2 at 5% level of significance. Initial cohort was composed of 58 patients with stroke/acute TIA and 26 controls. For selection of patients with similar characteristics for the groups of interest, we used the propensity scorematching (PSM)method. A logistic regression was constructed to estimate the probability of belonging to the stroke/TIA group, considering the following predicting variables – sex, age and CHADS 2 corrected by subtracting two points in patients with stroke/TIA. PSM enabled the selection of 26 patients with stroke/TIA matched with controls by the probabilities obtained from the logistic model, so that the analysis of the cohort yielded 52 patients (26 with stroke/TIA and 26 controls) (Figure 2). Sample power to verify the difference between the recording period on the first day of Holter and PoIP use (23.7 ± 1 and 20 ± 3.2h, respectively) was greater than 80%. Results Our sample was composed of 52 patients, equally allocated into stroke/TIA and control groups (Figure 2). More than half of patients (51.9%) were men, mean age was 70.7 ± 10.5 years, with 73.1% of patients aged 65 years or older. Mean BMI was 25.5 ± 5.6 kg/m 2 , 21.2% were smokers and 19.2% alcohol consumers. Mean corrected CHADS2 and CHA2DS2-VASc scores were 1.8 ± 0.8 and 3.3 ± 1.2, respectively. 123