Objective To clarify the problems in angiographic diagnosis of major coronary arteries crossing the right ventricular outflow tract.

Design A retrospective study with clinicomorphological correlations to ascertain any aberrant coronary arteries and variations in distribution of the normal right coronary arterial branches.

Setting Tertiary referral centre.

Subjects 36 necropsy specimens together with the aortograms and surgical reports from 130 patients with tetralogy of Fallot.

Results A preventricular branch was found in 19% of cases with tetralogy of Fallot, but in none of 13 normal hearts. Aberrant origin of the anterior interventricular coronary artery was found in 14% of the specimens. The combination of “laid back” and straight lateral views, when reviewed retrospectively, identified this anomaly correctly in nine of 16 patients, with these findings confirmed at surgery in seven patients. A major branch initially thought to cross the outflow tract was shown retrospectively to be an infundibular artery in six, with surgical confirmation in four. It was a preventricular branch in another patient.

Conclusions Using the laid back view alone, infundibular and preventricular branches may be mistaken for a major aberrant artery. A combination of laid back and straight lateral views is needed to avoid false positive diagnosis.