Early Tissue Distribution of Bone Marrow Mononuclear Cells After Transcoronary Transplantation in a Patient With Acute Myocardial Infarction
A 57-year-old man with no history of coronary artery disease was admitted for acute anterior ST-segment–elevation myocardial infarction caused by an occlusion of the proximal left anterior descending (LAD) coronary artery. The culprit artery was recanalized with direct stenting with an optimal result. Left ventricular ejection fraction was 40% with anteroapicoseptal akinesia. A positron-emission tomography study demonstrated reduced perfusion and borderline fluorine-18-fluorodeoxyglucose uptake in apical segments and adjacent anterior and septal wall, suggesting reduced viability in the distal LAD territory. Nine days after infarction, the patient underwent autologous bone marrow stem cell transplantation as a part of a research protocol. Bone marrow blood was aspirated under local anesthesia from both iliac crests. A total of 27.4×108 of mononuclear bone marrow cells (BMCs; 1.45×107 of CD34+ cells) were processed into a volume of 24 mL. Six milliliters of the cell suspension were separated, radiolabeled by 0.65 mL of 99mTc hexamethylpropylene amine oxime (Medi-Radiopharma LTD; radioactivity 700 MBq, physical half-life 6 hours), and mixed into a nonlabeled cell suspension. The BMC transplantation was performed on the same day. In brief, catheterization started with left ventricular and coronary angiography, which confirmed anterolateral akinesia with a left ventricular ejection fraction of 41% and no in-stent restenosis, respectively. Then, an over-the-wire balloon (same balloon diameter as implanted stent, shorter balloon length) was inflated in the proximal LAD inside the stent, and 4.5- to 5-mL portions of the cell suspension were injected through the central lumen. The balloon remained inflated for 3 minutes and then deflated for another 3 minutes to allow reflow. This maneuver was repeated 5 times. To monitor the fate of transplanted BMCs, nuclear imaging studies were performed at 2 and 18 hours after transplantation. The majority of transplanted BMCs were accumulated in spleen (Figure 1). The estimated radioactivity uptake by the heart was 5% of the injected radioactivity at 2 hours and 1% at 18 hours after transplantation. At 2 hours, transplanted cells occupied the whole LAD territory (Figure 2). At 18 hours, radioactivity was observed only in the apex and adjacent segments (Figure 3); in other words, in the region with reduced hypoperfusion and viability at PET.
This case points out the potential limitations of the transcoronary BMC transplantation in the setting of infarcted myocardium in humans. Additional research to increase the rate of cell engraftment and survival within the infarcted myocardial tissue is warranted.
Dr Penicka is the recipient of a research grant from the Czech Society of Cardiology.