Soon, sensors that can track heart-attack damage

London: In what could revolutionise the treatment of heart patients, scientists have developed tiny implantable magnetic sensors which they say can accurately indicate the severity of a cardiac attack.

Developed by a team from the Massachusetts Institute of Technology, the sensors can even read the severity of a heart attack days after the damage happened.

These sensors, the researchers said, could soon be used to monitor people at high risk of having a heart attack, the NewScientist reported.

According to scientists, following a heart attack, some biomarkers, unique proteins released by heart cells as they die, remain in the blood.

Some hang around for a day, while others remain for a week. So a blood sample drawn days after a suspected heart attack contains only a partial collection of these proteins, complicating diagnosis.

To examine this theory, the MIT researchers used three disc-shaped magnetic sensors implanted under the skin of a mouse and tracked the total amount of biomarkers released over a 72-hour period following an induced heart attack.

Each 8-millimetre-wide sensor is a porous plastic bag filled with nanoparticles of iron oxide. The nanoparticles are coated with antibodies to the proteins released by dying heart cells. The bag is supported by a ring doughnut shaped piece of hard plastic internally.

After an induced heart attack, proteins leak into the fluid underneath the mouse's skin and diffuse into the three sensors.

The antibodies in each sensor grab their target protein, creating clumps of iron particles that "light up" in an MRI scanner in a characteristic way.

The MRI scan determines the amount of captured protein that has been attracted to its equivalent antibody, which reflects the amount of injured heart tissue.

"This is the first time these things have been used to detect a clinical event," said Michael Cima, a materials engineer at MIT, who led the study.

The clumps grow larger as more protein enters the sensor, increasing the MRI signal. From the signal strength, "not only could we tell (a mouse) had had a heart attack, but we could estimate the size", Cima said.

"This caught us totally by surprise. This information could help doctors quantify the amount of heart muscle damaged after a second heart attack," he added.

Currently doctors inject dye to enhance images of the heart. But scar tissue from previous attacks prevents dye transport, creating incomplete pictures, said the researcher who detailed their work in the journal Nature Biotechnology.

Cima hoped that by implanting these sensors, people who are at high risk of a heart attack can monitor themselves.

But, these devices are years in the future, he said.