Amongst 22 patients with corrected left-to-right shunts, a diminution in heart size and reduction in central pulmonary arteries and pulmonary plethora was found in about half the patients. A good operative result can be expected, particularly in younger patients with less severe lesions, where the vessels had not been subjected to a high pressure for a long period. The failure of vessels to return to normal is assurmed to be due to changes in the vessel walls. Possible causes for persistent cardiomegaly are, in addition to persistent shunts, coronary artery disease, obesity, inadequate digitalisation and aortic and mitral insufficiency.