The electrocardiogram in hypertension with especial reference to Lead IV

Abstract In hypertension the extremity leads may show: 1. 1. Left axis deviation alone; 2. 2. Left axis deviation, with a negative T 1 and a positive T 3 —usually in cases with myocardial damage; 3. 3. Left axis deviation, with a negative T 1 , a positive T 3 , a convex S-T 1 interval and a concave S-T 3 interval. In such cases the heart usually shows pronounced dilatation; 4. 4. Absence of left axis deviation, as a consequence of factors mentioned below. Lead IV shows usually the following characteristics: P-wave diphasic; Q, shallow or absent; a normally wide ventricular complex; R-wave, high; T-wave, rather low, negative and of normal shape; no notches usually. When, however, the hypertension is due to aortic insufficiency, the S-T segment has a long, convex descending limb and a short ascending one. When the hypertension is complicated by coronary sclerosis, then instead of a small or an absent Q-wave, this wave is usually deep; the R-wave, low; the S-T interval, isoelectric in its first portion; and the T-wave, negative and deep. However, many variable forms are seen. In a few cases of hypertension associated with nephrosclerosis we found a deep S-wave (−5 to −7 mm.) continuing into a distinctly convex S-T interval which, after returning to the isoelectric level, ended in a deep, negative T. Ziskin concludes his paper, published in 1928, with the words: “Other factors, besides those enumerated, and at present unknown, are involved in the production of left ventricle preponderance.” Since then eight years have passed in which extensive research work has been done to investigate the condition of the myocardium and the coronary vessels by means of the electrocardiogram. Using as routine a thoracic lead in addition to the standard leads, we were able to draw conclusions not only from the similarities, but especially from the differences between them. This brought out the fact that in hypertension left axis deviation is present in 83 per cent of the cases in standard or chest leads, for which in our opinion not only the clockwise rotation in the longitudinal axis, but especially the enlargement of the heart must be held responsible. We based our experiments on the assumption that left axis deviation, when absent in marked cardiac dilatation, is obscured by interfering factors. Certain factors were found to cause this absence; e.g., in youth, the longitudinal position of the heart, notwithstanding dilatation; the enlargement in a sagittal plane only, in incipient cases; and finally, in advanced age, coronary sclerosis. Therefore the absence of left axis deviation in a case of marked enlargement of the heart should lead one to suspect some of the above mentioned conditions. A negative T 1 and a positive T 3 were found to imply an involvement of the myocardium. The convex S-T 1 interval and concave S-T 3 interval, which in our opinion are caused by the pronounced cardiac dilatation accompanying these cases, should therefore suggest, usually, a doubtful prognosis. We have drawn attention to a special type of the ventricular complex in lead IV, in which an S-wave and an extremely convex S-T interval are conspicuous; in these cases serious kidney damage was found (nephrosclerosis, chronic nephritis). Finally, we have described in detail the electrocardiogram in cases of hypertension and its differential diagnostic difficulties, giving the chest lead especial attention.