Infarct size determines myocardial uptake of CD34+ cells in the peri-infarct zone: results from a study of (99m)Tc-extametazime-labeled cell visualization integrated with cardiac magnetic resonance infarct imaging.

BACKGROUND: Effective progenitor cell recruitment to the ischemic injury zone is a prerequisite for any potential therapeutic effect. Cell uptake determinants in humans with recent myocardial infarction are not defined. We tested the hypothesis that myocardial uptake of autologous CD34(+) cells delivered via an intracoronary route after recent myocardial infarction is related to left ventricular (LV) ejection fraction (LVEF) and infarct size.

METHODS AND RESULTS: Thirty-one subjects (age, 36-69 years; 28 men) with primary percutaneous coronary intervention-treated anterior ST-segment-elevation myocardial infarction and significant myocardial injury (median peak troponin I, 138 ng/dL [limits, 58-356 ng/dL]) and sustained LVEF depression at ≤45% were recruited. On day 10 (days 7-12), 4.3×10(6) (0.7-9.9×10(6)) (99m)Tc-extametazime-labeled autologous bone marrow CD34(+) cells (activity, 77 MBq [45.9-86.7 MBq]) were administered transcoronarily (left anterior descending coronary artery). (99m)Tc-methoxyisobutyl isonitrile (99(m)Tc-MIBI) single-photon emission computed tomography before cell delivery showed 7 (2-11) (of 17) segments with definitely abnormal/absent perfusion. Late gadolinium-enhanced infarct core mass was 21.7 g (4.4-45.9 g), and infarct border zone mass was 29.8 g (3.9-60.2 g) (full-width at half-maximum, signal intensity thresholding algorithm). One hour after administration, 5.2% (1.7%-9.9%) of labeled cell activity localized in the myocardium (whole-body planar γ scan). Image fusion of labeled cell single-photon emission computed tomography with LV perfusion single-photon emission computed tomography or with cardiac magnetic resonance infarct imaging indicated cell uptake in the peri-infarct zone. Myocardial uptake of labeled cells activity correlated in particular with late gadolinium-enhanced infarct border zone mass (r=0.84, P<0.0001) and with peak troponin I (r=0.76, P<0.001); it also correlated with severely abnormal/absent perfusion segment number (r=0.45, P=0.008) and late gadolinium-enhanced infarct core (r=0.58 and r=0.84, P<0.0001) but not with echocardiography LVEF (r=-0.07, P=0.68) or gated single-photon emission computed tomography LVEF (r=-0.28, P=0.16). The correlation with cardiac magnetic resonance imaging-LVEF was weak (r=-0.38; P=0.04).

CONCLUSIONS: This largest human study with labeled bone marrow CD34(+) cell transcoronary transplantation after recent ST-segment-elevation myocardial infarction found that myocardial cell uptake is determined by infarct size rather than LVEF and occurs preferentially in the peri-infarct zone.