A New Examination For The Atrioventricular Conduction Axis In The Human Heart By The Stereomicrocope

The human cardiac conduction system (CCS) not only was small but also had not thich fibrous connective tissue sheath, so it was not easy to be identified under the naked eye. Although previous researchers had done a lot of study for the CCS, but they usually took comparative study by the hearts of experimental animal. And even more, there was seldom study about the dissection of the CCS in the human heart. Moreover, the cause of the sudden death in somebody (about 15%) couldn’t usually be found when the forensic pathological circles investigate the death cases by autopsy. But after checking their CCS, some important evidences might be found. Now, the lesions of CCS are admittedly important in sudden death cases. At present, the examination method of forensic medicine in the CCS is mainly to make many series tissue slices after direct drawing the materials from the regions of the sinoatrial node and atrioventricular node, and choose some slices to check intermittently. As the limitation and blindness of drawing materials, the CCS’s overall morphological structure couldn’t be observed systematically. Because of the inaccurate localization of the CCS, people couldn’t get any information of the CCS even if the tissue blocks were made into slices. So the cause of somebody’s death, Such as some pathological changes in the break, fibrosis and fatty degeneration or infiltration of the His bundle or left and right bundle branch, was very difficult to be found. More importantly, those methods could not be widely popularized in the all forensic department because they needed a lot of workload and the accurate localization of the CCS. Up to now, there is no perfect examinational method for the CCS on omni-directional three-dimensional level in world. In addition, the form and function of atrioventricular node (AVN) still need to be further determined. And the specialized conducting tissue of internodal tracts (the conduction bundle between the sinuatrial node and the AVN) is still controversial. Also, the atrioventricular ring that was founded in the tissue slices of animal hearts needs to be verified and researched on the human heart. Its function needs to be further defined. In short, the morphological examination of the atrioventricular conduction axis (ACA) is very important for the identification, inspecton, diagnosis of the CCS on anatomy and forensic pathology.A new set of examination method for the ACA designed by us was an integrated system. The method included the dissection of the ACA under a stereomicroscope after determining one or two starting-points of dissection on the human heart. It included observation, record and collection of the gross morphological characteristics of the ACA that was fully exposed. Then, we draw all dissected tissues of the ACA to make into myocardial sections that their cutting faces were parallel to the endocardium, and to observe the histological characteristics of the ACA after staining those sections. The feasibility of new method was validated by the experiment using 5 cases of human heart (3 male hearts,2 female hearts, age span of 17 years old to 71 years old, saved in formaldehyde solution) from the institute of pathology and forensic pathology, Zhejiang university and 3 cases of human heart (2 male hearts,1 female heart, age span of 28 years old to 70 years old, saved in formaldehyde solution) from the morphological center, Zhejiang medical college. Furthermore, the anatomic structure of ACA was explored in detail observation and study.The results showed as follows.1. the new method can accurately locate, successfully separate and check the tissue of ACA, obtain the groos pathological and stereo morphological data of the ACA which is unable to be obtained with the general inspection method, receive enough histology information by 1-2 tissue blocks (10 histological slices/tissue block), and significantly reduce the workload of the histological examination.2. No integral insulating membrane (membrane connective tissue intertwining myocardial tissue) was seen between the head and expanding area of AVN in all 8 samples, so that the head of AVN was not easy to be dissected.3. The AVN was flat and elliptical in all sample, that do not agree with other scholars point of view.4. Suspected special-organizations of atrioventricular ring and internodal tracts were reflected in the conventional histological examination of the heart. The mothod is helpful to check the CCS in the cardiac pathology and forensic medicine, but the form and function of the atrioventricular node area still need to be further researched.