Implication of aneurysmal transformation in isolated perimembranous ventricular septal defect.

Defects on the membranous ventricular septum (perimembranous ventricular septal defect [VSD]) may spontaneously close or diminish in size by "aneurysmal transformation" (i.e., adherence of the tricuspid valve or adjacent tissue onto the VSD). It was recently shown that the appearance of aneurysmal transformation may be associated with subaortic ridges, as well as left ventricular (LV)-to-right atrial (RA) shunts. In all, 877 consecutive patients with isolated perimembranous VSD were retrospectively studied. Results of actuarial analysis showed that patients with a perimembranous VSD had a 98% probability of aneurysmal transformation by the age of 240 months. Of these patients, the expected probabilities of developing LV-RA shunt, spontaneous closure and subaortic ridge were 45, 35 and 6%, respectively. Patients with LV-RA shunts had higher probabilities of developing infective endocarditis (p = 0.002) and persistent left-to-right shunts (p < 0.001). The presence of a subaortic ridge may be accompanied by LV outflow tract obstruction (10 of 25 patients), infundibular pulmonary stenosis (n = 3), or aortic valve deformity or aortic regurgitation (n = 5), and none of those with a subaortic ridge closed spontaneously. It was confirmed that a substantial proportion of aneurysmal transformation of isolated perimembranous VSD is associated with LV-RA shunts and subaortic ridges.