abnormal conotruncal ridge morphology conotruncal ridge hypoplasia 2010-10-05T02:26:38Z MP:0010587 MPheno.ontology aortico-pulmonary spiral ridge hypoplasia bulbar ridge hypoplasia conotruncal cushion hypoplasia csmith outflow tract cushion hypoplasia underdevelopment or reduced size of the pair of spiral mesenchymal swellings in the primordial ventricular outflow tract, that eventually fuse to form the conotruncal septum, dividing the subvalvular outflow tract and contributing to the membranous interventricular septum