Tetralogy of fallot: Underdevelopment of the pulmonary infundibulum and its sequelae

Abstract

It is proposed that the tetralogy of Fallot basically is a “monology”, just 1 anomaly, namely, underdevelopment of the subpulmonary infundibulum and its sequelae. The parietal band (crista supraventricularis) and the adjacent infundibular free wall together form an abnormally small cone (conus) of muscle beneath the pulmonary artery, whereas the septal band is normally formed. The hypothesis that the essence of tetralogy is an abnormally small subpulmonary conus is illustrated by angiocardiographic and anatomic findings in typical tetralogy compared with the normal. This unifying concept, which needs experimental embryologic assessment, facilitates angiocardiographic diagnosis of “masked” tetralogy in which the presence of this anomaly may be obscured by associated malformations. To demonstrate this, a rare case is presented, the fourth known patient with coexisting tetralogy and cor triatriatum. This 20 year old man also had a patent ductus arteriosus and a right pulmonary sequestration. The resulting systemic level of pulmonary hypertension “masked” the coexistence of tetralogy, which angiocardiography made evident. Despite the absence of a pulmonary outflow tract gradient due to the association of severe pulmonary hypertension, autopsy confirmed that this patient displayed the angiocardiographic hallmark of tetralogy: an abnormally small subpulmonary infundibulum.