Calcification Scarcely Occurs in Human Atrioventricular Nodal Arteries in Old Age

To elucidate age-related changes of the Atrioventricular Nodal (AVN) artery, the authors investigated age-related changes of elements in the AVN artery by direct chemical analysis. In addition, the effects of different arterial origins, arterial sizes, and genders on element accumulation were investigated in the AVN arteries. Sixty-two formalin-fixed adult Thai hearts were dissected, and the following two types of the AVN artery were found: The first type was a single AVN artery arising from the Right Coronary Artery (RCA). The second type was a single AVN artery arising from the terminal part of the Left Circumflex Artery (LCX). For element analysis, both 55 and 7 AVN arteries arising from the RCA and the LCX, respectively, were used. After the arteries were incinerated with nitric acid and perchloric acid, element contents were determined by inductively coupled plasma-atomic emission spectrometry. It was found that the Zn content decreased significantly in the AVN arteries with aging, but six element contents such as Ca, P, S, Mg, Fe, and Na did not change significantly with aging. Regarding the relationships among seven elements in the AVN arteries, extremely significant direct correlations were found both between Ca and Mg contents and between P and S contents, and a significant direct correlation was found between S and Mg contents. However, no significant correlation was found between Ca and P contents in the AVN arteries. To examine an effect of the different arterial origins on element accumulation, the AVN arteries were separated into the RCA and the LCX groups by the arterial origin and age-related changes of element contents were compared between two groups. It was found that there were no significant differences between the RCA and LCX groups in age-related changes of Ca and P contents. No gender differences and effect of arterial size were found in age-related changes of Ca and P contents in the AVN arteries. To elucidate whether calcification occurred in the AVN arteries in old age, both the mass ratios of Ca/P and Mg/Ca were estimated in the AVN arteries. The mass ratio of Ca/P increased progressively in the AVN arteries with Ca increase, being not constant. The mass ratio of Mg/Ca decreased gradually in the AVN arteries with Ca increase, but the average mass ratio of Mg/Ca was moderate, being 8.9% ± 0.9%. These results indicated that calcification scarcely occurred in the AVN arteries in old age, independently of the arterial origin, arterial size and gender.