Sunday, September 24, 2006
Stem Cells Show Little Heart-Attack Aid
Stem Cells Of Little Use In Damaged Hearts
Heart studies say stem cells failed to speed recovery
Marrow stem cells may help cardiac victims
Adult Stem Cells Help Weakened Hearts
Adult stem cells boost ailing hearts
There were three studies published in the Journal. All of them involved injecting patients' own bone marrow cells into a coronary artery that had become clogged and caused a heart attack. All of them measured the ejection fraction of the heart before and after stem cell injection to determine the extent of improvement. Two of them showed improvement in the hearts' function. One of them didn't. One would think that two out of three would weight the headlines toward the positive, but adult stem cells don't have the press relations that embryonic stem cells have.
First the study in which there was no improvement. In this study, all of the selected patients had heart attacks that involved the anterior wall of the heart, and which caused ST elevation on their EKG's. Both are associated with poorer prognosis in heart attack victims. All of the patients underwent angioplasty and stent placement. Half of them, that is 50, then received injections of their bone marrow cells into the affected coronary artery within a week of their heart attack. Six months later, their ejection fractions had increased to the same degree as the 50 patients who did not receive any injections, given the margin of error of the measurements.
The second study, which did show improvement, had the same sort of patients and control subjects with three exceptions - the heart attack did not have to involve the anterior wall, the control group received placebo injections rather than no injections, and the bone marrow cells were a heterogenous mix of different types rather than one isolated type (The unsuccessful study used only mononuclear bone marrow cells, which are one of many different types of stem cells found in the marrow). Four months later, there really wasn't much difference in the improvement of ejection fraction, again within the margin of error. However, after a year, there was substantial improvement in other measures - six percent of the controls died, for example, compared to only 2% of the stem cell treated patients. Forty percent of the controls had either died, had another heart attack, or required another angioplasty by the end of a year, compared to only 23% of the treated patients. Something went right there.
The last study was a little different. The patients in this study had heart attacks up to three months before the stem cell injections. They used the mononuclear stem cells, but from two different sources - bone marrow cells and circulating blood. They thus had three groups of patients for comparison - patients who received sham injections, patients who received bone marrow stem cells, and patients who received stem cells found in their circulatory system. After three months, the change in ejection fraction was about the same in the two groups given the margin of error in measurment. (Do you get the feeling that measuring the ejection fraction isn't the greatest gage?)
During that three month period, there were no deaths, heart attacks, or episodes of congestive heart failure in the bone marrow recipients compared to 4% of the controls and 9% of the peripheral blood recipients. (The sample size, however, was very small - only 23 in the control group, 34 in the peripheral blood group, and 35 in the bone marrow group.) They also measured how the patients felt by assessing what's known as the NYHA classification. The authors say that the bone marrow recipients had significant improvements in their NYHA classification compared to the other two groups, but when compared to the margin of error for the measurements, they didn't, really. The bone marrow recipients score dropped from 2.23+/-0.6 to 1.97+/-0.7. Compare that to the change for the placebo group - from 1.91+/-0.7 to 2.09+/-0.9. In other words, none of the groups had much of a change in their functional status after three months.
Interestingly, at the end of three months, this study did something different. The researchers injected the controls and the peripheral blood recipients with bone marrow cells to see if things would improve for them. They did. Both groups had absolute increases in their ejection fractions that exceeded those they had in the first three months of the study. They were very tiny increases, however, of only 2-4 percentage points.
So, what's the verdict? It certainly seems that the adult stem cells made some difference, especially in the second study, which was not only the longest period of observation, but also used the greatest mix of stem cells. There's something in that bone marrow that heals the ailing heart, we just aren't sure yet what it is, how it works, or how long it takes.
posted by Sydney on 9/24/2006 07:31:00 PM 0 comments