Cell infusions boost heart function, revive damaged heart muscle
American Heart Association
Infusing a patient's own cells into a heart artery several days after a heart attack speeds the healing process and strengthens the heart's pumping power, researchers report in today's rapid access issue of Circulation: Journal of the American Heart Association.
In a small study of heart attack patients, German researchers extracted progenitor cells from patient's blood or bone marrow and infused them into an artery. Progenitor cells are derived from stem cells, which have the potential to develop into any cell in the body. Progenitor cells are already on their way to becoming a specific type of cell.
"The infusion of progenitor cells was associated with a reduction in the size of muscle damage, a significant improvement in pumping function, and less enlargement of the heart within four months after a heart attack," said co-author Andreas M. Zeiher, M.D., chairman of the department of internal medicine at the University of Frankfurt in Germany.
The small study corroborates previous research that indicates stem and progenitor cells can reduce heart attack damage, and thus, the heart enlargement and failure that often follows. The findings indicate that progenitor cell therapy enhances regeneration of the left ventricle after heart attack.
"Our findings suggest that progenitor-cell infusion may, in part, restore heart function even after damage to the heart muscle has already occurred," said co-author Stefanie Dimmeler, Ph.D., head of the division of molecular cardiology at the University of Frankfurt.
"Heart failure – the failure of the heart to pump an adequate blood supply to the body – is the major, long-term consequence of a heart attack," Dimmeler noted. "It reduces not only quality of life but also life expectancy, despite optimal treatment with drugs."
About 4.9 million Americans live with heart failure and more than 51,500 will die of the debilitating condition this year.
The researchers enrolled 28 acute heart attack patients (88 percent men; average age 51). They were randomly assigned to receive either their own blood- or bone marrow-derived progenitor cells. Cells from both sources proved equally effective in improving the heart's functioning, researchers said.
The patients had been treated with angioplasty – a balloon catheter procedure that included placing a metal-mesh stent in the artery where the heart attack occurred to help keep it open. They were also treated with an anti-clotting drug to prevent blood clots.
Using a catheter, the researchers infused the cells into the stented part of the artery an average of 4.7 days after a heart attack. All patients underwent a dye-enhanced magnetic resonance imaging (MRI) examination a few days after their cell infusions to assess their heart damage and again four months later. Two patients who showed a narrowing of the infused artery that restricted blood flow were excluded from the study's final analysis.
Among the remaining 26 patients, the researchers found significant improvement in the heart's overall pumping strength and the areas damaged by the heart attack.
The average amount of blood ejected from the left ventricle, the heart's main pumping chamber, increased from 44.1 percent to 48.9 percent. The amount of blood ejected from a normal ventricle is about 60 percent, researchers said.
The researchers also examined the volume of dead heart muscle at each MRI exam. The average volume of the dead tissue decreased by about 20 percent during the four-month follow up. Cell therapy appeared to rescue irreversibly dysfunctional heart tissue, researchers said.
Neither the improvements in heart functioning nor the decrease in dead muscle correlated with the number of cells infused into a patient. Instead, the team's analysis indicated that the key to the improvements was the ability of cells to migrate from the artery into the heart muscle.
Two natural growth factors known as VEGF and SDF-1 increase after heart muscle is damaged. The researchers suggested that these growth factors act as homing signals to draw the progenitor cells to injured heart tissue to repair it.
Despite the study's promising findings, Zeiher noted the importance of confirming its results.
"Randomized, placebo-controlled studies that include a large number of patients are required to prove that this treatment reduces the occurrence of heart failure," he said.
Other co-authors are M. B. Britten, M.D.; N. D. Abolmaali, M.D.; B. Assmus, M.D.; R. Lehmann, M.D.; J. Honold, M.D.; J. Schmitt, M.D.; T. J. Vogl, M.D.; H. Martin, M.D. and V. Schächinger, M.D.
For more information, or to contact American Heart Association, see their website at: www.americanheart.org
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