A minimally invasive model of myocardial infarction made by video-assisted thoracoscopic surgery

Abstract

The general myocardial infarction model was made by ligating the left anterior descending coronary artery through traditional large opening thoracotomy, although there were many drawbacks such as severe injuries and pain in this method. The present study tried to find a new method to establish a minimally invasive canine model of myocardial infarction that was less injurious and more accurate. Twelve mongrel dogs were used in this study. After three 10-mm-long incisions were made on the left thoracic wall, pericardium was cut, left anterior descending coronary artery was found and titanium nips were clamped through video-assisted thoracoscopy. Two or three titanium nips were used until ECG showed a definite ST-segment elevation more than 0.1 mV, then the thoracic wall was sutured. The survival time of the dogs was 4 weeks. During this period, a series of thoracoscopy were performed. White blood count, biochemical analysis of oxidatively modified proteins, creatine kinase and cardiac Troponin I were examined at the baseline and in the 1st and 6th hour, and 1st, 4th, 7th, 14th and 28th day after surgery. The dogs were then killed and the ratio of fibrosis area to whole left ventricular area was measured and calculated to assess the extent of fibrosis. The sections from different parts of the heart were stained with Masson trichrome stain to assess degree of fibrosis. In the model group we observed that ST-segment of ECG elevated more than 0.1 mV instantly when titanium nips were clamped and the elevation could last for 28 days after surgery. Significant difference between the model and control group was discerned in white blood count, the levels of oxidatively modified proteins, creatine kinase, cardiac Troponin I and the ratio of fibrosis area to whole left ventricular area. Masson trichrome staining showed a large amount of collagen deposition in the fibrosis area. All these results demonstrated that a new canine model of myocardial infarction could be established with a minimally invasive procedure through video-assisted thoracoscopy. This minimally invasive pharmacological animal model was perhaps a more promising animal model for some newly rising science fields such as the study of Metabonomics.