A good squeeze can definitely get the blood flowing. But the firm, rhythmic squeezes of an inflatable robot, can keep that blood flowing.

The device—a silicone sleeve ribbed with inflatable tubes—wraps around a waning heart and provides extra muscle-power to pump blood. In early tests, the heart-snuggling sleeve restored blood flow in six living pigs after they had suffered acute cardiac arrest, researchers reported Wednesday in Science Translational Medicine. If the thumping tech passes further testing, it could one day help prolong the lives of people with heart failure, an affliction that strikes around 40 million people worldwide.

It’s not the only device that helps weakened hearts to go on. But existing medical devices involve pumps and valves that carry risks of blood clotting and severe blood infections. So, an international team of researchers, headed by scientists at Harvard, set out to make a heart fortifier that doesn’t have to contact blood.

Their solution is the squishy silicone sleeve that blankets the whole heart and holds on with a suction device and a gripping gel. Embedded in the silicone are thin rings and spines of inflatable tubes, tethered to an external pump. The tubes inflate and collapse, causing the whole sleeve to contract and twist. The overall movement mimics the activity of the heart muscles and can be tuned to coordinate perfectly with each individual heart.

In experiments in pigs, the devices could almost completely restore blood flow following acute cardiac arrest. After the heart failure, the pigs' hearts pumped about 45 percent of the normal amount of blood. With the device, the blood output gushed up to 97 percent—around two liters per minute. The researchers also found that they could tweak the squeeze to compensate for different weaknesses in a heart, such as glitches with particular chambers.

Science Translational Medicine, 2017. DOI: 10.1126/scitranslmed.aaf3925 (About DOIs).