Three main techniques have been used to deliver stem cells to the heart. The simplest technique to introduce stem cells intravenously and hope that they will home to the heart and stay there. A more technically demanding way to introduce stem cells to the heart is to inject them into the wall of the heart. This method is called transendocardial cell injection, and it requires electromechanical mapping guidance (NOGA) in order to direct the surgeon to the site where the stem cells should be injected. Finally, stem cells are introduced to hearts by means of intracoronary delivery. Intracoronary delivery takes advantage of angioplasty technology to deliver stem cells through the coronary arteries where they move across the blood vessels and enter the heart.
Stem cell delivery by means of intravenous introduction has been shown in several studies to be extremely inefficient. The vast majority of the stem cells end up in the lungs, liver and the spleen and only a tiny, insignificant fraction goes to the heart.
The transendocardial injection method is the most difficult of the three methods, but it is also the most direct, since it deposits the stem cells directly into the cardiac muscle . This method requires special equipment and also increases the risk of rupture of the heart wall.
The intracoronary method was adapted from the same procedure that cardiologists use to implant stents. This procedure, known as percutaneous infusion (PCI), uses an over-the-wire technique to inflate the coronary artery nearest the damage, and then deposits the stem cells into the artery (see this video here). Because PCI has been used so much recently and because the technique has been greatly refined, stem cell delivery with this technology is second nature to many cardiologists. However, it does have some risk of causing narrowing of the artery (stenosis).
Which technique is better, transendocardial injection or intracoronary delivery? While some papers have compared the two procedures, there has been no randomized comparison with blinded endpoint analysis of the two techniques; until now.
In a paper published in the Journal of Cellular and Molecular Medicine by a Dutch lab at the University of Utrecht in the Netherlands, these two techniques were used to deliver stem cells to the hearts of pigs that had suffered heart attacks. The number of stem cells delivered in both cases were exactly the same, and the outcomes were compared and statistically compared. The stem cells were also labeled with a low-energy radioactive isotope so that they could be easily visualized in imaging experiments.
The results showed that both sets of pigs, which were given the stem cell treatments four weeks after the heart attack, improved about the same. Also the retention of stem cells in the heart was the same for both groups. The only difference was that the cells delivered by transendocardial injection tended to be clustered near the border of the infarct, but in the case of intracoronary delivery, the cells were spread throughout the heart muscle.
Also the safety profiles of both techniques were about the same, with the exception that the intracoronary delivery technique was easier and did not show the variation of the transendocardial technique, which is a much more difficult technique.
The authors conclude that both of these delivery techniques are feasible and safe. Furthermore, the conditions and cost of the techniques should determine which is used, since the safety and efficacy of the two is essentially the same.