健常高齢者の体表面電位図の検討 ―QRS・T波について―

体表面上に多数の誘導点を設け,それらの各瞬時の電位を求めて等電位線を作成したものが体表面電位図(以下,電位図)である.従来から心起電力を記録する方法として,標準十二誘導心電図やベクトル心電図が臨床上広く用いられているが,標準十二誘導心電図は胸壁上の誘導点が6ヵ所と少いことに問題があり,またベクトル心電図は心起電力を固定した単一双極子であると仮定すること自体にその限界がある.電位図は多数の誘導点を有し心臓の電気現象に関してより多くの情報を得ることができ,また単極誘導心電図から構成されるため,心筋の局所電位の把握にも優れているという特徴を有している.そこで電位図は,虚血性心疾患,心室肥大,心室内伝導傷害部位の同定や心性不整脈の発生源の診断などに応用される様になってきている.ところでわが国は高齢化社会への急激な移行に伴い高齢者の循環器疾患の発症率はますます高くなった.そこで電位図の虚血性心疾患などへの臨床応用が盛んになる中で,まず基礎となる健常高齢者について検討がなされなければならないが,多数の健常高齢者を対象に検討した報告は少なく1),高齢者の心疾患患者の電位図を検討する場合には問題がある.そこで60歳以上の健常高齢者の電位図を,当教室の木村ら2)が報告した60歳未満の健常成人例のそれと比較し,性差,年齢差につき検討した.

To examine the changes in the body surface isopotential maps (maps) with the increase of age, recorded maps at 87 lead points of 296 normal healthy adults, and I analyzed maps comparatively among six groups. On mean maps at the time of 10msec from the QRS initial, the position of the maximum (the greatest positive potential at a certain time point) shifted lower on the anterior chest, and that of the minimum (the greatest negative potential at a certain time point) shifted higher on the back with increasing age. At 30 msec the potential of the maximum decreased on the left anterior chest surface in males, while it increased in females with increasing age. The maximum potential of QRS on each lead (Rmax V) slightly decreased on the antero-superior chest in males, while it clearly increased from the left anterior chest to the left back in females with increasing age. The value of % VC decreased with age in both sexes. These data suggested that the potential of Rmax V was affected by heart size and lung impedance. However in females, changes in the breast might have a greater influence on the changes in Rmax V. The sex difference in Rmax V became smaller with age. The minimum potentials of QRS (Smax V) decreased on the upper anterior chest and back surface. No sex or age differences were found in the ratio of the breakthrough recognition, although the time of the breakthrough tended to increase in both sexes. On ST and T maps, there were few changes with age, but significant sex differences were observed among every age group. These were significant differences in maps between the aged and younger groups. Careful attention should be paid to age and sex differences, when analyzing maps of aged persons.