Electrocardiography: A Technologist's Guide to Interpretation.

The nuclear medicine technologist works with electrocardiography when performing cardiac stress testing and gated cardiac imaging and when monitoring critical patients. To enhance patient care, basic electrocardiogram interpretation skills and recognition of key arrhythmias are essential for the nuclear medicine technologist. This article provides insight into the anatomy of an electrocardiogram trace, covers basic electrocardiogram interpretation methods, and describes an example case typical in the nuclear medicine environment.

Phenotypic and functional changes in blood monocytes following adherence to endothelium.

OBJECTIVE: Blood monocytes are known to express endothelial-like genes during co-culture with endothelium. In this study, the time-dependent change in the phenotype pattern of primary blood monocytes after adhering to endothelium is reported using a novel HLA-A2 mistyped co-culture model. METHODS AND RESULTS: Freshly isolated human PBMCs were co-cultured with human umbilical vein endothelial cells or human coronary arterial endothelial cells of converse human leukocyte antigen A2 (HLA-A2) status. This allows the tracking of the PBMC-derived cells by HLA-A2 expression and assessment of their phenotype pattern over time. PBMCs that adhered to the endothelium at the start of the co-culture were predominantly CD11b+ blood monocytes. After 24 to 72 hours in co-culture, the endothelium-adherent monocytes acquired endothelial-like properties including the expression of endothelial nitric oxide synthase, CD105, CD144 and vascular endothelial growth factor receptor 2. The expression of monocyte/macrophage lineage antigens CD14, CD11b and CD36 were down regulated concomitantly. The adherent monocytes did not express CD115 after 1 day of co-culture. By day 6, the monocyte-derived cells expressed vascular cell adhesion molecule 1 in response to tumour necrosis factor alpha. Up to 10% of the PBMCs adhered to the endothelium. These monocyte-derived cells contributed up to 30% of the co-cultured cell layer and this was dose-dependent on the PBMC seeding density. CONCLUSIONS: Human blood monocytes undergo rapid phenotype change to resemble endothelial cells after adhering to endothelium.

High-density lipoproteins enhance progenitor-mediated endothelium repair in mice.

OBJECTIVE: We quantified endothelial progenitor cell (EPC) engraftment into the endothelial layer as an index of progenitor-mediated endothelial repair. Studies were conducted in C57BL/6J and in apolipoprotein E-deficient (apoE(-/-)) mice. We also investigated the possibility that high-density lipoproteins (HDL) may promote progenitor-mediated endothelial repair. METHODS AND RESULTS: Thoracic aortic sections from C57BL/6J and apoE(-/-) mice were analyzed for evidence of progenitor-derived endothelium as determined by the number of stem cell antigen-1-positive (Sca-1+) cells in the endothelial layer. EPCs (Sca-1+ cells) were significantly increased after endothelial damage induced by lipopolysaccharide (LPS) administration in C57BL/6J mice. The number of EPCs was greater in the aortic endothelium of untreated apoE(-/-) than in untreated C57BL/6J mice and was similar to the number observed in LPS-treated C57BL/6J mice. The number of EPCs in the aortic endothelium of apoE(-/-) mice more than doubled after intravenous infusion of reconstituted HDL. CONCLUSIONS: EPCs are recruited into the aortic endothelial layer of mice in response to an inflammatory insult. EPCs are also increased in the aortic endothelium of untreated apoE(-/-) mice. The observation that number is further increased in apoE(-/-) mice after injection of HDL suggests a role for HDL in promoting progenitor-mediated endothelial repair.

Leukocyte recruitment and expression of chemokines following different forms of vascular injury.

UNLABELLED: Inflammation plays a central role in restenosis following coronary intervention. Recent human and animal data suggest important differences between the inflammatory responses to simple balloon angioplasty compared with stent implantation. To investigate the mechanisms of these differences, New Zealand white rabbits underwent bilateral iliac artery balloon denudation. Half received intravascular stents. Arteries were harvested at three, seven and 14 days for immunohistochemistry, and 4 hours, 8 hours and 14 days for chemokine mRNA analysis. Leukocyte content was quantified utilizing immunohistochemistry (RPN357, monoclonal antibody (mAb) against rabbit neutrophil; RAM-11, mAb against rabbit macrophage). We analyzed the mRNA levels of the chemokines monocyte chemoattractant protein 1 (MCP-1) and interleukin 8 (IL-8) through semi-quantitative polymerase chain reaction. We demonstrated the spatial pattern of MCP-1 mRNA levels through in situ mRNA hybridization. In balloon-injured arteries, leukocyte recruitment was confined to early neutrophil infiltration. IL-8 and MCP-1 mRNA levels peaked within hours and were undetectable at 14 days. In contrast, in stented arteries, early neutrophil recruitment was followed by prolonged macrophage accumulation. IL-8 and MCP-1 mRNA levels peaked within hours but were still detectable 14 days post injury. CONCLUSIONS: In contrast to balloon injury, stent-induced injury results in sustained chemokine expression and leukocyte recruitment. These data may have important implications for antirestenotic strategies.

Chronic Coronary Occlusions.

The goal of management of chronic coronary occlusions is primarily the relief of cardiac ischemic symptoms. This may be achieved through the use of medical therapy, recanalization by percutaneous endovascular intervention or coronary artery bypass grafting (CABG). Recanalization of the occluded vessel also may have the additional benefits of improved cardiac function and long-term survival.