A myocardial infarction, commonly known as a heart attack, occurs when blood flow through the coronary arteries is blocked. A heart attack usually happens to people with atherosclerotic coronary heart disease, which narrows one or more of the coronary arteries. A blood clot becomes lodged in the narrowed artery, preventing blood from reaching the heart muscle. Because the heart needs a virtually constant supply of oxygen-rich blood to survive, an interruption in blood flow to the heart can quickly cause muscle cells to die.
Dead heart muscle cells cannot help the heart pump blood. Thus, people who suffer a heart attack are often left with “weak” hearts. Instead of strongly squeezing blood out of the heart to the rest of the body, a larger portion of the blood remains in the heart (i.e. reduced ejection fraction). People who have had a heart attack that reduces ejection fraction commonly develop a condition known as congestive heart failure.
People with congestive heart failure often have difficult lives. Congestive heart failure patients periodically experience exacerbations that require hospitalization. They are put on restrictive diets; their salt and fluid intakes are limited. They must also take several different medications to help the heart pump blood through the arteries to the body and keep fluid levels in the body low. These medications do not heal or replace dead heart muscle cells. Instead, they make the remaining cells work harder (or decrease resistance in the arteries, or help the body eliminate fluid through urination).
What is needed is a way to regenerate dead heart muscle cells. Fortunately, several research groups are working on ways to use stem cells to regenerate heart muscle cells so that heart attack patients can regain heart muscle function.
There have been at least 11 clinical trials studying the effects of stem cells on patients with myocardial infarction. The trials show that stem cell infusion into the vein, the coronary artery, or the heart muscle itself is safe and well-tolerated by patients. Notably among the studies, patients with acute myocardial infarction who received allogeneic human mesenchymal cells intravenously had a better ejection fraction, better heart structure, and better lung function after six months than those who received a placebo. In the APOLLO trial, patients with acute myocardial infarction who received adipose-derived mesenchymal cells had half the dead heart muscle cells than those who received a placebo (i.e. lesion volume was 50% lower in treated patients).
Phase III clinical trials are considered definitive (pivotal) evidence of benefit. In phase III C-CURE trial, patients with heart failure due to coronary artery disease received autologous mesenchymal cells (i.e. their own cells, specially prepared). Treated patients enjoyed significantly increased ejection fraction (heart-pumping ability) and better functional capacity and quality of life. Other Phase II clinical trials (ADVANCE, CONCERT-CHF, TRIDENT, POSEIDON-DCM) are ongoing.
These results are welcome news for patients who suffer—or will one day suffer—from a heart attack, an event that happens in 735,000 Americans every year.
Reference: Golpanian, S. et al. (2016). Rebuilding the Damaged Heart: Mesenchymal Stem Cells, Cell-Based Therapy, and Engineered Heart Tissue. Physiological Reviews. 2016 Jul; 96(3): 1127–1168