CME model is suitable for evaluating the therapeutic effects of intravenous diltiazem; intravenous diltiazem treatment significantly improved cardiac function through alleviating inflammatory responses and microvascular thrombotic injury

The aim of this study was to assess the feasibility of evaluating the therapeutic effects of intravenous diltiazem in a newly established rat model of coronary thrombotic microembolism (CME). CME was induced by injecting 0.199 ml saline containing 5 mg of automicrothrombotic particulates (~10 μm) into the aorta of Sprague Dawley rats. The injection was carried out over 10 sec using a tuberculin syringe with a 28-gauge needle. The CME model rats were randomly divided into untreated (CME, n=38) and diltiazem-treated (CME+DIL, n=38) groups. Diltiazem (1 mg/ml, 50 μg/min/kg) was intravenously injected using an infusion pump through the tail vein for 175 min, 5 min following the injection of the automicrothrombotic particulates. Hemodynamic measurements, echocardiography and pathohistological examinations were performed at various time-points (3 h, 24 h and 7 and 28 days) postoperatively. Arteriolar thrombosis, multifocal myocardial necrosis, inflammatory cell infiltration with markedly increased myocardial tumor necrosis factor α (TNF-α) and interleukin-6 (IL-6) expression, reduced left ventricular (LV) systolic function and increased plasma von Willebrand factor (vWF), endothelin-1 (ET-1) and serum c-troponin I (c-TnI) levels (indicating vascular endothelial injury and myocardial necrosis) were observed in the CME model rats. These pathological responses in CME rats were partly attenuated by intravenous diltiazem treatment. The present CME model is suitable for evaluating the therapeutic effects of intravenous diltiazem; intravenous diltiazem treatment significantly improved cardiac function through alleviating inflammatory responses and microvascular thrombotic injury in this rat model of CME. Introduction Coronary thrombotic microembolism (CME) may be induced by spontaneous plaque rupture and disrupted plaque components produced during coronary interventions. CME has been shown to lead to myocardial microinfarcts, as reflected by elevated creatine kinase (CK) and troponin I (TnI) (1-7), which may partly contribute to impaired microvascular perfusion and result in the ‘slow’ or ‘no-reflow’ phenomenon (6-10). A number of efforts, including intravascular thrombolysis drug application and thrombosis suction, have been attempted for the prevention and treatment of CME and CME-induced myocardial impairment (11-16). Previous studies have demonstrated that calcium antagonists are capable of relieving microvascular spasm (17,18) and that the intravascular application of diltiazem may attenuate coronary artery spasms in patients with microvascular angina or acute myocardial infarction with ‘no-reflow’ phenomenon (19,20). In our previous experimental study, a rat CME model was established by the aortic injection of automicrothrombotic particulates (9). In the present study, we examined whether this model is suitable for testing and reflecting the therapeutic effects of drugs that may be capable of attenuating coronary microembolization. It was hypothesized that intravenous diltiazem, an agent with proven clinical effectiveness in reducing coronary microembolization, may attenuate the cardiac dysfunction and pathological changes in the rat CME model. Materials and methods Animals. A total of 152 adult male Sprague Dawley rats (weight, 250-350 g; age, 12 weeks) were used in the present study. Thirty-two rats were used for the dose-finding pilot study. Forty rats were subjected to an aortic saline injection (sham group, n=40) and 80 rats underwent procedures to induce CME, as described previously (9). Briefly, blood (0.5 ml) was obtained from the ventral tail artery of all rats 1 day prior to surgery (21). The blood was left to clot for 1 h and then dried overnight at 37 ̊C (9,22). The dried blood was fragmented into thrombotic particulates with a Sabi Crush Easy Pill Smasher (SABI Co., Palo Alto, CA, USA) for 5 min. Subsequently, 5 mg thrombotic particulates were dissolved in 0.2 ml saline and filtered through a 45-μm metal filter. The filtrates were collected and the mixed solution (1 μl) was utilized for a Effects of intravenous diltiazem in a rat model of experimental coronary thrombotic microembolism YUPENG BAI1*, LIQUN HU2*, JIE WU2, YE GU2, LUN LI2, BO GAO2 and HONG JIANG1 1Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan 430060; 2Department of Cardiology, Puai Hospital, Huazhong University of Science and Technology, Wuhan 430030, P.R. China Received April 4, 2013; Accepted August 5, 2013 DOI: 10.3892/etm.2013. 1263 Correspondence to: Professor Hong Jiang, Department of Cardiology, Renmin Hospital of Wuhan University, 238 Jiefang Road, Wuhan, Hubei 430060, P.R. China E-mail: jianghong58@gmail.com *Contributed equally