SEVERE CONGENITAL MITRAL-STENOSIS IN INFANTS

Background Despite current medical and surgical therapy, infants with symptomatic congenital mitral stenosis (CMS) continue to have high rat es of morbidity and mortality. Catheter balloon dilation has been succ essful in relieving symptoms in a few older children with CMS but has not been evaluated in infants. Methods and Results We reviewed the rec ords of 85 infants with CMS to assess severity of CMS, associated card iac lesions, echocardiagraphic morphological appearance of the mitral valve, treatment, and outcome. There were five valve morphologies iden tified: ''typical'' hypoplastic mitral valve with symmetric papillary muscles (SYMM, 52%), supravalvar mitral ring (SVMR, 20%), double-orifi ce mitral valve (DOMV, 11%), hypoplastic mitral valve with asymmetric papillary muscles (ASYMM, 8%), and parachute mitral valve (PARA, 8%). Of the 85 infants, 31 (36%) were severely symptomatic, requiring inter vention within the first 2 years. Balloon dilation was performed in 18 infants (age, 8.7+/-5.7 months; weight, 5.9+/-1.9 kg) and valve surge ry in 13 (age, 10.9+/-5.9 months; weight, 6.7+/-2.1 kg). Balloon dilat ion decreased the peak transmitral gradient (LAa-LVED) >30% in 15 of i s initial attempts, from 20.3+/-8.2 to 10.9+/-4.9 mm Hg (P<.001), and the mitral valve area increased from 0.7+/-0.3 to 1.0+/-0.5 cm(2)/M(2) (n=10, P=.01). No infants died during the initial balloon dilation, a lthough 2 of 3 died during a repeat procedure for restenosis. Other co mplications included significant mitral regurgitation in 7 of 18 patie nts (39%), 4 of whom had SVMR. Of the 18 infants, 8 (44%) had persiste nt symptomatic improvement at a mean follow-up of 14 months (range, 2 to 32 months). The 2-year survival after balloon dilation was 70%; 40% remained free of repeat intervention. Mitral valve surgery in 13 infa nts consisted of SVMR resections in 7, mitral valve replacements in 4, and LA-to-LV aortic valved homografts in 2. The operative mortality w as 30%. Sustained improvement occurred in 8 (6 with SVMR) at 11 to 62 months of follow-up (mean, 30 months), with a 2-year survival of 60%. Conclusions Infants with severe CMS have 2-year mortality rates approa ching 40% regardless of treatment modality. Balloon dilation significa ntly reduces the transmitral gradient in the majority, but symptomatic improvement persists in only 40%. Procedure-related mortality was ass ociated with repeat balloon dilation in patients with left ventricular hypoplasia. Balloon dilation of ''typical'' CMS can provide symptomat ic relief in many infants, allowing postponement of valve replacement, although infants with SVMR do better with surgical management.