The Index of Microcirculatory Resistance After Primary PCI: A Pooled Analysis of Individual Patient Data.

BACKGROUND: Despite treatment with primary percutaneous coronary intervention (PCI) in patients with ST-segment elevation myocardial infarction (STEMI), the risk of heart failure and late death remains high. Microvascular dysfunction, as assessed by the index of microcirculatory resistance (IMR), after primary PCI for STEMI has been associated with worse outcomes. It is unclear whether IMR after primary PCI predicts cardiac death. OBJECTIVES: The aims of this analysis were: 1) to determine if IMR is an independent predictor of cardiac death; 2) to assess the optimal cutoff value of IMR after STEMI; and 3) to compare IMR with several cardiac magnetic resonance parameters, including infarct size. METHODS: In a collaborative, pooled analysis of individual patient data from 6 cohorts that measured IMR directly after primary PCI, cardiac mortality up to 5 years was estimated using Kaplan-Meier analyses. The primary endpoint was cardiac death using the predefined IMR cutoff value of 40. RESULTS: In total, 1,265 patients were included in this study with a median follow-up of 2.8 years (IQR: 1.2-5.0 years). Cardiac death at 5 years occurred in 2.2% and 4.9% of patients (HR: 2.81; 95% CI: 1.34-5.88; P = 0.006) in the IMR ≤40 and IMR >40 groups, respectively. The composite of cardiac death or hospitalization for heart failure occurred in 4.9% and 8.9% (HR: 1.98; 95% CI: 1.20-3.29; P = 0.008) in the IMR ≤40 and IMR >40 groups, respectively. IMR was an independent predictor of cardiac death, whereas coronary flow reserve was not. The optimal cutoff value of IMR for the prediction of cardiac death in this cohort was 70 (HR: 4.73; 95% CI: 2.27-9.83; P < 0.001). Infarct size was 17.6% ± 13.3% and 23.9% ± 14.6% of the left ventricular mass in the IMR ≤40 and IMR >40 groups, respectively (P < 0.001). Microvascular obstruction and intramyocardial hemorrhage occurred more frequently in the IMR >40 group than in the IMR ≤40 group. CONCLUSIONS: In this large, pooled analysis of individual patient data, IMR measured directly after primary PCI in STEMI was an independent predictor of cardiac death. IMR may be used as a tool to identify patients at the time of primary PCI who are at highest risk for late cardiac mortality and who might benefit most from additional cardioprotective therapies and monitoring.

Near-infrared imaging of adoptive immune cell therapy in breast cancer model using cell membrane labeling.

The overall objective of this study is to non-invasively image and assess tumor targeting and retention of directly labeled T-lymphocytes following their adoptive transfer in mice. T-lymphocytes obtained from draining lymph nodes of 4T1 (murine breast cancer cell) sensitized BALB/C mice were activated in-vitro with Bryostatin/Ionomycin for 18 hours, and were grown in the presence of Interleukin-2 for 6 days. T-lymphocytes were then directly labeled with 1,1-dioctadecyltetramethyl indotricarbocyanine Iodide (DiR), a lipophilic near infrared fluorescent dye that labels the cell membrane. Assays for viability, proliferation, and function of labeled T-lymphocytes showed that they were unaffected by DiR labeling. The DiR labeled cells were injected via tail vein in mice bearing 4T1 tumors in the flank. In some cases labeled 4T1 specific T-lymphocytes were injected a week before 4T1 tumor cell implantation. Multi-spectral in vivo fluorescence imaging was done to subtract the autofluorescence and isolate the near infrared signal carried by the T-lymphocytes. In recipient mice with established 4T1 tumors, labeled 4T1 specific T-lymphocytes showed marked tumor retention, which peaked 6 days post infusion and persisted at the tumor site for up to 3 weeks. When 4T1 tumor cells were implanted 1-week post-infusion of labeled T-lymphocytes, T-lymphocytes responded to the immunologic challenge and accumulated at the site of 4T1 cell implantation within two hours and the signal persisted for 2 more weeks. Tumor accumulation of labeled 4T1 specific T-lymphocytes was absent in mice bearing Meth A sarcoma tumors. When lysate of 4T1 specific labeled T-lymphocytes was injected into 4T1 tumor bearing mice the near infrared signal was not detected at the tumor site. In conclusion, our validated results confirm that the near infrared signal detected at the tumor site represents the DiR labeled 4T1 specific viable T-lymphocytes and their response to immunologic challenge can be imaged in vivo.