“…(4,6,10) Fisher et al suggested that some patients may tolerate very high pulmonary arterial pressure for long periods without deterioration of their clinical status. (9) However, unrepaired PDA in these asymptomatic patients may eventually become clinically significant, particularly in conjunction with an acquired physiological insult from recurrent pneumonia, development of chronic obstructive pulmonary disease, ischaemic heart disease or calcific aortic stenosis. (2,3) In addition, there is an associated risk of infective endarteritis, even in small PDAs, estimated to be up to 0.45% per year after the second decade of life.…”