Implantable devices increase the detection of silent atrial fibrillation in high-risk populations, being a useful tool in the early diagnosis of these patients, allowing monitoring for a longer time. Currently, these devices can be used for monitoring and possible early diagnosis of abnormalities in order to prevent health complications and bring about better outcomes, as well as monitor the user's progress and thus prevent more serious developments. Objective: to analyze, in patients with cardiovascular disease, the electrocardiographic aspects detected from the device in comparison to the conventional electrocardiogram, identifying aspects of similarity between the tracings obtained and automatic diagnostic accuracy by the device and by the visual assessment of the tracing. Method: a cross-sectional observational study of diagnostic accuracy will be carried out at the University Hospital of the Federal University of Piaui. The following parameters were considered: significance level of 95%, test power of 80%, value of the disease diagnosis rate of 84%, area under the receiver operating characteristic curve of 94% and an equal proportion of the number of positive and negative cases. The minimum sample size consisted of 100 patients, and an additional 10% will be added to compensate for possible losses. A total of 110 patients will be invited to participate in the study. Patients aged ≥ 18 years will be included, with the presence of one or more diagnoses below: systemic arterial hypertension, heart failure, valvular disease, coronary atherosclerotic disease, myocardial infarction, endocarditis, myocarditis, diabetes, cardiac arrhythmias and patients with cardiac pace or implantable automatic defibrillator. The variables analyzed will be: clinical-demographic data of the patients, including age, sex, race, socioeconomic profile; comorbidities and electrocardiographic findings as measured by the clock and conventional ECG. The data will be analyzed comparatively between the groups: 1 = EKG on the clock; 2 = 12-lead conventional EKG and DI (single lead). The primary outcome will be the positive diagnostic correlation of the data obtained in group 1 in relation to group 2. Secondary outcomes: successful measurement of the electrocardiographic record by the clock; diagnostic accuracy of atrial fibrillation and other heart rhythm disorders.