fail to muscularise. Such deviation, however, can be found
in the absence of subpulmonary obstruction, as in the socalled
Eisenmenger ventricular septal defect [4]. So as to
produce the features of tetralogy of Fallot, therefore, it is
also necessary to have abnormal morphology of the septoparietal
trabeculations that encircle the subpulmonary
outflow tract [5]. The combination of the deviated outlet
septum and the hypertrophied septoparietal trabeculations
produce the characteristic right ventricular outflow
tract obstruction of tetralogy of Fallot (Figure 1). The deviation
of the muscular outlet septum is also responsible for
creating the malalignment type ventricular septal defect,
and results in the aortic override. The associated hypertrophy
of the right ventricular myocardium is the haemodynamic
consequence of the anatomical lesions created by
the deviated outlet septum.