Abstract
Methods of precordial counting of radio-active isotopes in the detection of left-to-right intracardiac shunts are presented. Both iodine-131 labelled albumin and technetium-99m were used but the latter is preferred, especially for children, since it has a short physical half-life and emits a single gamma ray. Investigations were done to establish normal values and those in patients who had either rheumatic or congenital heart disease. All left-to-right shunts were confirmed at cardiac catheterization. False negative results were rare but false positive results can occur in the presence of congestive cardiac failure. It is possible to detect left-to-right shunts with a pulmonary to systemic flow ratio as low as 1·2:1 and an estimate of this ratio can be made from the precordial curve. The main value of the method is as a preliminary investigation in the detection of intracardiac shunts.