Washington DC, April 9 -- Smaller than a grain of rice, a new pacemaker is particularly suited to the small, fragile hearts of newborn babies with congenital heart defects.

A tiny pacemaker is paired with a small, soft, flexible wearable patch that sits on the patient's chest. The wearable patch detects irregular heartbeats and automatically emits pulses of light.

The light then flashes on and off at a rate that corresponds to the correct pacing. After the tiny pacemaker is no longer needed, it dissolves inside the body.

Northwestern University engineers have developed a pacemaker so tiny that it can fit inside the tip of a syringe -- and be non-invasively injected into the body.

Although it can work with hearts of all sizes, the pace...