In vivo effects of contrast media on coronary thrombolysis

AbstractObjectives. The aim of the present study was to evaluate the influence of radiographic contrast media (CM) on alteplase-induced coronary thrombolysis.Background. Contrast media inhibit fibrinolysis in vitro and interact with endothelial cells, platelets and the coagulation system. The in vivo effects of CM on thrombolysis are not known.Methods. Occlusive coronary artery thrombosis was induced in 4 groups of 10 dogs by the copper coil technique. After 70 min of occlusion the dogs were randomized to intracoronary injection of 2 ml kg−1of either saline, a low-osmolar ionic CM (ioxaglate), a low-osmolar nonionic CM (iohexol) or a high-osmolar ionic CM (amidotrizoate). Thrombolysis with alteplase and co-therapy with aspirin and heparin was initiated after 90 min of occlusion. The coronary artery flow was monitored with an electromagnetic flowmeter throughout the experiment.Results. Iohexol and amidotrizoate, but not ioxaglate, were associated with longer reperfusion delays (time to optimal reperfusion: 67 ± 48 min and 65 ± 49 min, respectively, vs. 21 ± 11 min after placebo; p < 0.05) and shorter periods of coronary perfusion (optimal perfusion time: 21 ± 26 min and 21 ± 28 min, respectively, vs. 58 ± 40 min after placebo; p < 0.05). No significant differences were observed between groups with regard to activated partial thromboplastin times, circulating thrombin-antithrombin III complex concentrations and fibrinogen.Conclusions. In this animal model administration of iohexol and amidotrizoate before thrombolysis significantly delayed reperfusion. This interaction should be considered in the design of clinical trials of thrombolytic therapy that evaluate coronary artery patency and in patients receiving local infusions of fibrinolytic agents

Sonoporation: Mechanical DNA Delivery by Ultrasonic Cavitation

Development of nonviral gene transfer methods would be a valuable addition to the gene-therapy armamentarium, particularly for localized targeting of specific tissue volumes. Ultrasound can produce a variety of nonthermal bioeffects via acoustic cavitation including DNA delivery. Cavitation bubbles may induce cell death or transient membrane permeabilization (sonoporation) on a single cell level, as well as microvascular hemorrhage and disruption of tissue structure. Application of sonoporation for gene delivery to cells requires control of cavitation activity. Many studies have been performed using in vitro exposure systems, for which cavitation is virtually ubiquitous. In vivo, cavitation initiation and control is more difficult, but can be enhanced by cavitation nucleation agents, such as an ultrasound contrast agent. Sonoporation and ultrasonically enhanced gene delivery has been reported for a wide range of conditions including low frequency sonication (kilohertz frequencies), lithotripter shockwaves, HIFU, and evendiagnostic ultrasound (megahertz frequencies). In vitro, a variety of cell lines has been successfully transfected, with concomitant cell killing. In vivo, initial applications have been to cancer gene therapy, for which cell killing can be a useful simultaneous treatment, and to cardiovascular disease. The use of ultrasound for nonviral gene delivery has been demonstrated for a robust array of in vitro and mammalian systems, which provides a fundamental basis and strong promise for development of new gene therapy methods for clinical medicine.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45550/1/11188_2004_Article_457016.pd

Contribution of Ventricular Diastolic Dysfunction to Pulmonary Hypertension Complicating Chronic Systolic Heart Failure

ObjectivesThe aim of the study is to clarify the clinical role of Doppler-echocardiographic parameters of left ventricular diastolic dysfunction (LVDD) as determinants of pulmonary hypertension in patients experiencing left ventricular systolic dysfunction (LVSD) with and without the presence of functional mitral valve regurgitation (FMR).BackgroundPulmonary hypertension (pulmonary venous or mixed pulmonary venous-arterial hypertension) complicating LVSD is associated with poor outcomes beyond that of LVSD alone. The view of the contribution of LVDD as a determinant of pulmonary hypertension is controversial and not well defined as a tool in clinical practice.MethodsData from patients with LVEF ≤40% undergoing Doppler-echocardiography evaluations during the period from August 2001 to December 2004 were analyzed. Pulmonary systolic pressure (PSP), parameters of diastolic function (mitral valve [MV] transmitral flow velocity [E]/mitral annular diastolic velocity [e′] ratio, MV deceleration time [DT]), quantitated effective regurgitant orifice area (EROA) of FMR, and clinical characteristics were evaluated. Pulmonary hypertension was defined as an estimated PSP ≥45 mm Hg.ResultsCriteria were met in 1,541 patients; one-third (n = 533) demonstrating PSP ≥45 mm Hg (58 ± 10 mm Hg, range 45 to 102 mm Hg). Patients with pulmonary hypertension were older with higher E/e′ ratio, EROA, and lower DT and LVEF. In multivariate analysis, pulmonary hypertension was independently predicted not only by severity of FMR (EROA ≥20 mm2, odds ratio: 3.8, p < 0.001) but also by parameters of LVDD (E/e′ ratio ≥15, odds ratio: 3.31, p < 0.001; DT ≤150 ms, odds ratio: 3.8, p < 0.001). Receiver-operating characteristics curve analysis showed that EROA, E/e′ ratio, and DT provided significant incremental value in predicting pulmonary hypertension (c-statistic 0.830, p < 0.001).ConclusionsPatients with LVSD commonly have secondary pulmonary hypertension, which is largely determined by the severity of LVDD even with adjustment for FMR and low LVEF. Thus, measures of LVDD in routine clinical practice where PSP may not be estimated are important physiologic descriptors of hemodynamic status and are cumulatively linked in the prediction of pulmonary hypertension

Magnetically Targeted Endothelial Cell Localization in Stented Vessels

ObjectivesA novel method to magnetically localize endothelial cells at the site of a stented vessel wall was developed. The application of this strategy in a large animal model is described.BackgroundLocal delivery of blood-derived endothelial cells has been shown to facilitate vascular healing in animal models. Therapeutic utilization has been limited by an inability to retain cells in the presence of blood flow. We hypothesized that a magnetized stent would facilitate local retention of superparamagnetically labeled cells.MethodsCultured porcine endothelial cells were labeled with endocytosed superparamagnetic iron oxide microspheres. A 500:1 microsphere-to-cell ratio was selected for in vivo experiments based on bromo-deoxyuridine incorporation and terminal deoxynucleotidyl transferase mediated dUTP nick end labeling assays. Stents were magnetized and implanted in porcine coronary and femoral arteries using standard interventional equipment. Labeled endothelial cells were delivered locally during transient occlusion of blood flow.ResultsThe delivered cells were found attached to the stent struts and were also distributed within the adjacent denuded vessel wall at 24 h.ConclusionsMagnetic forces can be used to rapidly place endothelial cells at the site of a magnetized intravascular stent. The delivered cells are retained in the presence of blood flow and also spread to the adjacent injured vessel wall. Potential applications include delivering a cell-based therapeutic effect to the local vessel wall as well as downstream tissue