THE EFFECT OF DEEP INBREATHING ON LEAD III OF THE ELECTROCARDIOGRAM

Abstract

This is a study of 200 healthy adults showing the effect of deep inspiration of Lead III (IIIR). The changes included occasional flattening to inversion of P, changing depth of Q (Q was never exaggerated), where R was absent it appeared and when small it increased in height, S if present became less deep or disappeared, T either became taller or less inverted, and S-T usually was unaltered. In left preponderance (hypertension without pain) there was,in some, de-pression of S-T and of T, in others there was no change. In hypertension with pain there was a deep Q and/or depression of S-T. Right ventricular preponderance caused no consistent change in IIIR. In left bundle branch block, R became taller, and there was depression of S-T. In right bundle branch block, R became lower and T if negative became less so. In arterior infarction there was no consistent change; in posterior infarction, a deep Q remained so and if Q was not present or slight, Q did not appear, nor was it produced. In a number of patients lowering of S-T and of T provided the only evidence of infarction. Lead IIIR should always be included in an electrocardiographic study.