Injected Stem Cells Improve Damaged Heart

These results were presented at the annual meeting of the American Association for Thoracic Surgery in Toronto (Canada).

The trial involved 20 patients with severe heart failure with ejection fractions less than 35%. Each patient was scheduled for off-pump cardiac bypass surgery. However, 10 were randomized to also receive stem cells during surgery. The other 10 patients underwent the bypass operation but received no stem cells. Each group consisted of eight men and two women.

After undergoing anesthesia, those selected to receive stem cells had bone marrow removed from their hipbones. While bypass surgery was taking place, the particular stem cells that influence blood vessel and heart muscle growth (CD34+ and CD45- cells) were isolated from other cells in the bone marrow. After completion of the bypass and in a process that took about 10 minutes, the surgeons injected the cell preparation into 25-30 sites where muscle damage was apparent. Prior imaging studies guided the team to the specific injection sites and helped them avoid injecting vessels or inserting the needle too far into the walls of the heart's chambers.

Before surgery, the average ejection fraction in the patients scheduled for bypass surgery alone was 30.7%, with a range of 26-34%. The patients who received the stem cells in addition to the bypass surgery had an average ejection fraction of 29.4%, with a range of 23-34%. After six months, the average ejection fraction rates were 46.1% for those who received the stem cells, with ranges of 44-50%, but only 37.2% in the bypass alone group, with ranges of 33-44%.

None of the patients experienced serious side effects or complications and there were no abnormal heart rhythms caused by the stem cells. Six months after the surgery, the researchers also found a notable increase in the marker Connexin 43 in the patients who received stem cells, which is typically reduced in patients with heart failure.

"We don't know if this increase was due to the growth of new heart muscle cells resulting from the stem cell injections or whether the stem cells coaxed existing cells to come out of hibernation,” explained Amit Patel, M.D., from the division of cardiac surgery at the University of Pittsburgh School of Medicine (PA, USA), who conducted the research along with colleagues from Baylor University (Dallas, TX, USA) and the department of cardiovascular surgery at the Benetti Foundation in Rosario, Argentina.