Studies on the Duration of the Electrical Systole of the Heart (II) : CLINICAL INVESTIGATION ON THE RELATION BETWEEN : THE HEART AREA AND THE QT INTERVAL

Abstract

The author analysed the relationship of the QT interval to the heart area in 122 cases which were considered under no influence of digitalis, quina alkaloid and abnormal conditions of any electrolyte, including heart disease, tuberculous disease, and others. The size of the heart was measured by a planimeter on the teleroentgenogram. The measured heart area divided by the normal heart area was termed the enlargement rate of heart area. The measured QT interval divided by the normal QT interval reported in the preceding article was termed the prolongation rate of QT interval. The results are as follows.(1) In 45 cases without myocardial damage demonstrable by clinical examinations, on the average, the prolongation rate of QT interval was about linearly proportional to the enlargement rate of heart area.(2) In 66 cases with myocardial damage without heart failure, on the average, the prolongation rate of QT interval was fairly proportional to the enlargement rate of heart area. But, as compared with in the cases without myocardial damage, the prolongation rate of QT interval to the enlargement rate of heart area was scattered more broadly, and the QT interval was prolonged to a lesser degree(3) In 11 cases with heart failure, the prolongation rate of QT interval to the enlargement rate of heart area was markedly decreased.(4) The above-mentioned date can be clearly interpreted from the standpoint of the law of the heart (Starling) and "Chain doublets Theory (Maekawa)". And it may be concluded that, the QT interval is prolonged proportionally to the increased quantity of the heart work and that, when the heart performs less work than that reguired, the prolongation of QT interval is in a lesser degree according to the decreased work.(5) Consequently, the clinical value of the QT interval lies in the deviation not from the normal QT interval, but from the QT interval which the healthy heart would show when it would work out the load required for that examined heart to do so.Therefore, clinically, the duration of the QT interval should be judged from the viewpoint of the heart work by putting something proportional to the quantity of the load required for the examined heart to work out, for instance the heart area, as a indicator.