Doctors use magnetic resonance imaging (MRI) to obtain detailed pictures of the inside of the body. This study will evaluate a new MRI technique in people who have recently had a heart attack. Researchers will also examine the effect of fish oil supplementation on heart health in study participants.

A new MRI technique to examine the heart was recently developed. In this study, researchers will use this new technique to evaluate the heart in people who have recently had a heart attack to determine whether a specific pattern of heart muscle damage is related to sudden cardiac death. This fatal condition, also known as cardiac arrest, occurs when the heart abruptly stops pumping blood to the body, resulting in loss of consciousness, absence of pulse, and a stop in breathing. The most common cause of sudden cardiac death is a heart attack.

In addition to evaluating the new heart MRI technique, this study will also examine the effects of fish oil supplementation in people who have recently had a heart attack. Recent research has shown that omega-3 fatty acids, commonly found in fish oil, may be beneficial for people with heart conditions. Lastly, the study will determine whether specific biomarkers and genetic factors can help predict the likelihood of a person dying from sudden cardiac death after previously experiencing a heart attack.

Apart from studying the likelihood of sudden cardiac death, This study will measure the change in structure and pumping function of the heart (known as ventricular remodeling) and this study will determine if the high dose of fish oil treatment will result in an improvement of the heart.

This study will enroll people who have had a heart attack in the 2 to 4 weeks before study entry. At a baseline study visit, participants will undergo an MRI of their heart and complete an exercise stress test on a treadmill. A blood sample will be collected, and women will provide a urine sample for a pregnancy test. Questionnaires asking about diet, medical history, and emotions will also be completed. Participants will then be randomly assigned to receive either fish oil supplements or placebo on a daily basis for 6 months. Every 2 to 3 months, study researchers will call participants to check on their health and progress. At a study visit at Month 6, participants will undergo repeat baseline testing. After this visit, study researchers will call participants every 6 months for 3 years to follow up on participants' health status.

Inclusion Criteria:

• Experienced a heart attack in the 2 to 4 weeks before study entry
• Lives in the greater Boston area or adjacent regions (within a 50-mile radius of Boston)

Exclusion Criteria:

• Unable to undergo an MRI because of metallic implants (e.g., pacemakers, an implantable cardioverter defibrillator [AICD]) at time of study entry
• Active cancer or any other terminal illness with an expected survival rate of less than 6 months after study entry
• Significant kidney dysfunction with a glomerular filtration rate (GFR) of less than 60 mL/min in the 2 weeks before study entry
• Inability to follow study procedures
• Pregnant
• Hemodynamic instability
• Urgent clinical need for a pacemaker or AICD
• Inaccessibility of medical records

Plan to share data with GISSI Heart Failure group for pooling and meta-analysis

Measured in the 3-year follow-up period after participant's last study visit

Adverse events were evaluated every 2 months during the 6-month study drug period by an investigator with conducted scripted telephone interviews with each patient. Tolerance to study drug, adverse events, and pill counts were also evacuated during these interviews.

The study was not powered to evaluate for clinical heart failure and hard cardiac outcomes. A prospective trial would be necessary to determine the effect of earlier and high-dose omega-3 fatty acid therapy on improving clinical outcomes.