Background-Radiofrequency (RF) catheter ablation is limited by thromboembolic complications. The objective of this study was to compare the incidence and characteristics of thrombi complicating RF and cryoenergy ablation, a novel technology for the catheter-based treatment of arrhythmias. Methods and Results-Ablation lesions (nϭ197) were performed in 22 mongrel dogs at right atrial, right ventricular, and left ventricular sites preselected by a randomized factorial design devised to compare RF ablation with cryocatheter configurations of varying sizes (7F and 9F), cooling rates (Ϫ1°C/s, Ϫ5°C/s, and Ϫ20°C/s) and target temperatures (Ϫ55°C and Ϫ75°C). Animals were pretreated with acetylsalicylic acid and received intraprocedural intravenous unfractionated heparin. Seven days after ablation, the incidence of thrombus formation was significantly higher with RF than with cryoablation (75.8% versus 30.1%, Pϭ0.0005). In a multiple regression model, RF energy remained an independent predictor of thrombus formation compared with cryoenergy (OR, 5.6; 95% CI, 1.7, 18.1; Pϭ0.0042).Thrombus volume was also significantly greater with RF than with cryoablation (median, 2.8 versus 0.0 mm 3 ; PϽ0.0001). More voluminous thrombi were associated with larger RF lesions, but cryolesion dimensions were not predictive of thrombus size. Conclusions-RF energy is significantly more thrombogenic than cryoenergy, with a higher incidence of thrombus formation and larger thrombus volumes. The extent of hyperthermic tissue injury is positively correlated with thrombus bulk, whereas cryoenergy lesion size does not predict thrombus volume, most likely reflecting intact tissue ultrastructure with endothelial cell preservation.
Abstract-The adhesion of neutrophils to damaged arterial surfaces is increased in the presence of platelets by a mechanism implicating platelet P-selectin. Such interactions may enhance thrombus formation and the vascular response to injury. In this study, we investigated the effects of a selectin blocker (CY-1503), an analogue of sialyl Lewis x , on platelet and neutrophil interactions after arterial injury produced by angioplasty in pigs.51 Cr-platelet deposition and 111In-neutrophil adhesion were quantified on intact, mildly and deeply injured carotid arterial segments, produced by balloon dilation, in control (saline, nϭ8) and treated (CY-1503, 15 mg/kg IV, nϭ7) pigs. The hematological parameters, the aggregation of whole blood in response to adenosine diphosphate, and the activating clotting time, as well as the heart rate and mean arterial blood pressure, were similar among groups and were not influenced significantly by CY-1503. The level of platelet and neutrophil adhesion increased significantly with the severity of arterial injury but was not influenced by CY-1503 on intact and mildly injured arterial segments. However, at the site of deep arterial injury, CY-1503 treatment was associated with a 58% reduction (PϽ0.01) in neutrophil adhesion, from 446.7Ϯ72.6ϫ10 3
Platelet and neutrophil interactions with injured vascular wall may contribute to restenosis. Their importance was mainly examined following balloon injury of intact arteries. However, dilation of diseased arteries is clinically more relevant and may elicit different responses. We investigated the relationship between platelets and neutrophil adhesion, neointima formation and P-selectin expression on damaged arteries after repeated balloon injury. In an acute single-injury model, 8 pigs were subjected to bilateral carotid angioplasty and sacrificed 1 h later. In a chronic model, 19 pigs were subjected to similar procedures and allowed to recover for 4 weeks; then 18 arteries were redilated at the same previously injured sites (double injury) while the remaining arteries were not redilated and used to investigate the extent and the adhesive properties of the neointima. After single injury, 51Cr-platelet adhesion (×106/cm2) increased significantly from 3.8 ± 0.6 to 45.9 ± 6.5 (p < 0.05) on mildly and deeply injured segments, respectively, and were statistically similar after double injury. After single injury, 111In-neutrophil adhesion (×103/cm2) increased from 226.6 ± 45.5 to 512.5 ± 70.3 (p < 0.05) on mildly and deeply injured segments, and were significantly higher (p < 0.05) after double injury (mild: 1,289.1 ± 227.9 and deep: 2,411.8 ± 333.9). As well, the neo-endothelium expresses P-selectin at 4 weeks and platelet and neutrophil adhesion was directly related to neointimal growth. These results, which indicate ongoing proinflammatory processes 1 month post-angioplasty, suggest that neutrophils may participate in the progression of restenosis.
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