A 72-year-old patient has been hospitalized with complaints of intense palpitations. The symptoms started suddenly, approximately 40 minutes ago. The patient denies chest pain or dizziness. He has a history of arterial hypertension, for the treatment of which he regularly takes medicines, but does not know their name. Objectively, the patient is conscious and oriented, verbal contact with him is productive. Blood pressure 104/55 mm Hg. SpO2 shows 97% on room air. ECG registers a rhythm of 190/min with a regular rhythm, the width of the QRS complexes is 0.09 seconds, a negative P wave is registered after each ventricular complex. What drug should be used to start the treatment of this patient?