Illustration of the heart muscle patchEva Meyer-Besting/UNIVERSITTSMEDIZIN GTTINGENA muscle patch crafted from stem cells has improved cardiac function in monkeys with heart disease. It is now being tested in a small number of people, with early results from the first recipient suggesting it could treat advanced heart failure.Heart failure when the heart cant pump enough blood to meet the bodys demands usually occurs after a heart attack permanently damages or weakens the organ. Short of receiving a transplant or fitting a pump, no treatment can fully restore cardiac function, only slow its decline.