The cause of tof remains largely unknown, but several genetic disorders and prenatal factors are thought to be associated with increased risks of this condition.

法四原因还不清楚，但是认为一些基因异和胎期因素与其有关。

Children with TOF may develop acute episodes of hypoxia, known as Tet spells, during activities that demand more oxygen.

法四在活动时，需氧增多，可出现急性缺氧发作，又称Tet spells。