Objective To compare the morphology of the pulmonary vessels in tetralogy of Fallot or pulmonary atresia–ventricular septal defect (PA–VSD) with (del22q) and without 22q11 deletion (non-del22q).

Patients 94 consecutive infants (54 with tetralogy of Fallot, 40 with PA–VSD) were studied using ultrasound and catheterisation.

Molecular investigations Identification of the 22q deletion was performed either by fluorescent in situ hybridisation or polymerisation chain reaction genotyping.

Results 25 patients were del22q (16/40 (40%) PA–VSD v 9/54 (17%) tetralogy of Fallot; p < 0.02). Major aortopulmonary collateral arteries was more common in patients with PA–VSD-del22q (p < 0.03). Such collaterals were identified in 13 patients: 10 del22q and three non-del22q (p < 0.001). The size of the right and left pulmonary arteries expressed as a standard deviation (SD) difference of the normal range was −4.2 (quartiles −5.3 and −2.9) for PA–VSD del22q, and −2.6 (−3.1 and −1.8) for PA–VSD non-del22q (p = 0.02). The mean (SD) difference between the measured and theoretical Nakata index was −373 (94) for PA–VSD del22q v−245 (93) in PA–VSD non-del22q (p = 0.0002). In tetralogy of Fallot patients with and without del22q, the size of the pulmonary arteries was similar (p = 0.6).

Conclusions A “specific” phenotype could be defined in patients with deletion: PA–VSD, major aortopulmonary collateral arteries with complex loop morphology, and small central pulmonary arteries. Differences in the morphology of the pulmonary vessels may indicate a different timing of the faulty developmental pathway in patients with and without 22q11 deletion.