Telegram Messenger Support for Smoking Cessation After Heart Attack

Inclusion Criteria: * Willing and able to provide written informed consent. * Age 18 years or older. * Hospitalization with a confirmed diagnosis of acute myocardial infarction (MI), including both ST-elevation MI (STEMI) and non-ST-elevation MI (NSTEMI). * Current smoker at the time of index MI: self-reported smoking of at least one cigarette per day in the month prior to hospitalization. * Regular user of the Telegram messenger application (app installed on a personal smartphone). * Possession of a smartphone with internet access and a valid phone number. * Ability and willingness to provide contact information for a close relative or cohabiting person who can verify smoking status at follow-up. Exclusion Criteria: * Smoking cessation more than 1 month prior to the index MI hospitalization. * Physical or cognitive impairment that prevents the use of a smartphone (e.g., severe visual/hearing impairment, inability to read or respond to messages). * Inability to read and understand the Russian language fluently. * Comorbid condition with a life expectancy of less than 1 year. * Active severe mental illness (e.g., psychosis, severe untreated depression) that would impede understanding of the protocol or adherence. * Unwillingness or inability to provide contact details for a close relative for outcome verification.