Heart Attack (Myocardial Infarction)

A heart attack, also called a myocardial infarction, occurs when vessels that supply oxygenated blood to the heart become blocked. The part of the heart muscle starved for oxygen may die or become permanently damaged.

Most heart attacks are caused by a blood clot that forms a blockage in the coronary arteries. Blood clots are often the result of coronary artery disease (CAD), also called atherosclerosis, in which hardened fat deposits called plaques build up inside blood vessels. The plaque may cause fissures, or tiny tears, causing blood clots to form. A piece of plaque may also break loose and lodge in a small blood vessel, blocking blood flow.

How does molecular imaging help people who have experienced a heart attack?

Following a heart attack, heart function is assessed using either echocardiography or nuclear imaging.

Molecular and functional imaging procedures assess heart function and provide valuable information on specific biochemical and structural changes in heart tissue including:

• the extent of scarring
• degree of coronary artery disease
• left ventricle remodeling (changes in the size, shape, and function of the heart after injury)
• the development of congestive heart failure.

Images and information provided by myocardial perfusion imaging, nuclear functional heart studies and other molecular imaging procedures help physicians:

• assess the potential for sudden cardiac death and other cardiac events in patients who have suffered a heart attack or who have chronic heart failure
• select patients for automatic internal cardiac defibrillators (AICDs)

Research

Molecular imaging is already playing an important role in the diagnosis, management and risk stratification of patients with heart disease. However, we have only seen the beginning of a new and ever expanding frontier using targeted molecular imaging.

Molecular imaging approaches not only complement existing imaging technology, but will also permit the early detection of disease — before changes in physiological function or anatomical structure occur. Molecular imaging will enhance the development and application of truly personalized treatment. Molecular imaging will affect clinical care indirectly by facilitating faster and better drug development and improving the basic understanding of cardiovascular disease.

There are many new and emerging molecular imaging technologies that may help patients with heart disease. In addition to using myocardial perfusion imaging and nuclear functional studies, physicians are using new radiotracers such as  I-123-metaiodobenzylguanidine (MIBG) with SPECT and carbon-11-meta-hydroxyephedrine or carbon-11-mHED with PET to assess the potential for sudden cardiac death and other cardiac events in patients who have suffered a heart attack or who have chronic heart failure.

Other molecular imaging procedures and technologies under development include:

• fusion imaging, also called co-registration or hybrid imaging, which allows information from two different studies to be viewed on one image.
• the use of imaging biomarkers
• the use of cardiovascular molecular imaging to monitor genetic or stem cell therapy
• nanomedicine, including the use of laser-activated nanoparticles to destroy atherosclerotic plaque and adult stem cells to rejuvenate arteries.