abnormal conotruncal ridge morphology absent conotruncal ridges 2010-10-05T02:26:19Z MP:0010586 MPheno.ontology absence 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 absent aortico-pulmonary spiral ridges absent bulbar ridges absent conotruncal cushion absent conotruncal cushions absent endocardial ridges absent outflow tract cushions csmith