Introduction: Obstructive sleep apnea is an independent cardiovascular risk factor which can be diagnosed by means of a portable device (WatchPAT ® ) capable to perform automatic analysis of the peripheral artery tonometry, its amplitude and variability, with a high grade of correlation to polysomnography.Objective: To describe the use of WatchPAT ® for diagnosing obstructive sleep apnea in patients with cardiovascular disease.Methods: A case series study of patients evaluated in cardiovascular consultation who underwent to home sleep monitoring using the WatchPAT ® 200U system between February 1, 2017 to February 1, 2018, due to suspected obstructive sleep apnea.Results: 37 patients were included, with an average age of 57.6 years, most of whom were male.Cardiovascular diseases were: uncontrolled or predominantly nocturnal hypertension (37.8%), recurrent palpitations and/or chronic fatigue (21.6%); sleep disturbances were informed only in 27% of the patients.Obstructive sleep apnea was identified in 97.3% of the patients (29.7% moderate and 56.8% severe), 37.8% had high blood pressure, 49.5% had established heart disease, and 18.9% were diabetic.Only, fifty percent of the patients with severe obstructive sleep apnea and 45% with moderate obstructive sleep apnea snored.Conclusion: Cardiovascular disease specialists should participate more actively in the search and diagnosis of obstructive sleep apnea; it is highly prevalent in patients with nocturnal or resistant high blood pressure, heart rhythm disorders or myocardial structural damage.Obstructive sleep apnea can be diagnosed using portable devices such as WatchPAT ® .