The study is a two-arm, parallel, randomized clinical trial. The purpose of the study is to evaluate the effectiveness of automated mobile phone text message-based intervention for secondary prevention after acute coronary syndrome hospitalization. Text messages will include information about lifestyle modifications, medication adherence and cardiovascular risk factor control. The participants will be randomized into intervention and control groups in a 1:1 ratio. The intervention group will receive 4 pre-designed and semi-personalized text messages per week in addition to usual care for 6 months, while the control group will receive usual care.

Purpose of the trial: The purpose of the study is to evaluate the effectiveness of automated mobile phone text message-based intervention for secondary prevention after acute coronary syndrome hospitalization.

Trial design: Two-parallel arm, single-blind, block randomization.

Primary endpoint: The proportion achieving guideline levels of modifiable risk factors (LDL-C <70mg/dL, blood pressure <140/90 mm Hg, exercising regularly [≥5 d/wk × 30minutes of moderate exercise per session], nonsmoker status, and BMI <25). The investigators prespecified in the statistical analysis plan the efficacy variable of proportion achieving combined risk factor control (achieving risk factor targets in 4 or more of the 5 modifiable risk factors listed above) as a measure of a multiple risk factor effect.

Secondary endpoints: The plasma LDL-C level at 6 months, Level of physical activity, Blood Pressure, Medication adherence measured via Morisky scale, Proportion of non-smokers, Body mass index (BMI), Rates death and hospitalization up to 6 months.

Duration of follow-up: 6 months

Trial treatment:

Intervention: The treatment group will receive the usual discharge treatment, instructions and information for acute coronary syndrome patients as well as the text-messaging intervention. The program will include a variety of topics such as standard follow-up care reminders as well as general self-management and healthy living habits texts. There will be four streams: one for patients who are non-smokers and are free of diabetes; one for current/recent smokers; one for diabetic patients; and one for smoker and diabetic patients. Texts will be sent out 4 times per week for 180 days. All participants in the same stream will receive the same texts in the same order.

Control: The usual care group will receive standard discharge treatment, instructions, and information for patients with acute coronary syndrome. The participants will also receive SMS thanking for their participation in the trial, reminders of trial appointment and informing if they have changed contact details. The frequency of this SMS will be monthly.

Expected sample size, enrollment and expected number of centers:

Sample size = 160 Recruitment start date: November, 2017 Recruitment end date: May, 2019 Follow-up end date: November, 2019 Number of centers: 1

Statistical considerations:

• Intention to treat analysis
• The trial has >90% power (2 sided alpha = 0.05) to detect 15% difference in achieving risk factor targets in 4 or more of the 5 modifiable risk factors listed.

Inclusion Criteria:

• Consecutive patients who have been hospitalized at the UFMG's University Hospital with primary or secondary diagnosis of Acute Coronary Syndrome and are discharged for outpatient follow-up;
• Age ≥ 18 years, of both sexes;
• Patients who are able to receive text messages by their own mobile phone.

Exclusion Criteria:

• Refusal or inability to sign the Informed Consent.
• Complete illiteracy.