The time course and relation of positive signal-averaged electrocardiograms by time-domain and spectral temporal mapping analyses after infarction.

We evaluated the time course of development of positive signal-averaged electrocardiograms (SA-ECGs) by time-domain and Spectral Temporal Mapping (STM) analyses after myocardial infarction in 88 patients without bundle branch block. The incidence of positive SA-ECGs by time-domain analysis peaked at 4 to 8 weeks postinfarction whereas the peak incidence by STM analysis varied from 4 days to 4 to 10 months postinfarction. Positive time-domain SA-ECGs demonstrated a significantly reduced factor of normality (NF) compared with negative time-domain SA-ECGs by X, Z, or vector STM analyses, but marked overlap was present for the standard deviations of positive and negative SA-ECGs in all STM leads. Chi square analysis demonstrated a significant correlation only between X-lead STM analysis and time-domain analysis; however, the two methods were markedly discordant. Although there is a statistically significant relation between time-domain and STM analyses of SA-ECGs, the two analyses are not clinically interchangeable.

In vivo technetium-99m S12 antibody imaging of platelet alpha-granules in rabbit endothelial neointimal proliferation after angioplasty.

To examine the specificity of technetium-99m monoclonal antibody (S12) imaging for identifying activated platelets at interventional injury sites in atherosclerotic rabbit arteries, subgroups of unheparinized rabbits (n = 39) underwent serial percutaneous transluminal aortic angioplasty (PTA) procedures (with or without intravascular stent placement) followed by in vivo and then ex vivo gamma camera imaging, scanning, and immunoelectron microscopy to determine the intravascular loci of S12 Fab' antibody binding. Despite angiographic vessel patency, image-derived ratios of in vivo S12 binding in injured versus uninjured vascular segments were significantly increased (p less than 0.05) after one PTA (1.3 +/- 0.17, n = 7), PTA twice at 6-week intervals (1.4 +/- 0.22, n = 7), and PTA plus stent placement (1.6 +/- 0.28, n = 7) compared with control experiments (1.1 +/- 0.13, n = 7). Ex vivo imaging of blood-free excised aortas confirmed S12 localization at PTA (2 +/- 0.4, n = 3) and PTA plus stent placement (5 +/- 3.8, n = 7) sites (both p less than 0.05 versus controls). S12 antibody uptake decreased significantly (p less than 0.05) at 1 week after PTA plus stent placement in vivo (1.1 +/- 0.10, n = 4) and ex vivo (1.6 +/- 0.7, n = 3). Electron microscopic studies confirmed dense platelet, fibrin, and red blood cell deposition in regions of acute injury, with endothelial neointimal proliferation at 1 week after PTA. Immunoelectron microscopic studies confirmed specific in vivo S12 binding (22:1 versus nonrelevant IgG) at sites of alpha-granule GMP-140 expression in activated platelets. Therefore, S12 studies may be useful to localize sites of platelet-derived mitogen release at arterial PTA injury sites.