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

法四的儿童在活动时，需增多，可出现急，又称Tet spells。

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.

法四的原因还不清楚，但是认为一些基因的异常和胎儿期的因素与其有关。