In this study, we aimed to evaluate whether patients with left to right shunt coronary artery fistula (LRSCAF) are predisposed to developing pulmonary hypertension and right ventricular dysfunction compared with healthy individuals. The value of cardiac CT findings in determining the necessity of intervention for these patients was investigated. We retrospectively studied 19 patients with LRSCAF and 19 healthy patients. Several parameters were observed on cardiac CT by two radiologists, including pulmonary trunk diameter (PA diameter), right ventricular diameter (RVD), left ventricular diameter (LVD), RVD/LVD ratio, septal bowing and CT score of right ventricular dysfunction (CSRVD). Data from both groups were compared. The inter- and intra-observer variabilities and correlations were examined. The disease group was further divided into intervention (n = 9) and non-intervention (n = 10) groups, and their data were compared. All cardiac CT findings showed significant intra- and inter-observer correlation without significant variability. Mann–Whitney U tests and χ² analysis showed that PA diameter, RVD/LVD ratio acquired from two observers, and CSRVD were higher in the disease group than in the control group (all P values < 0.05 for χ² and almost all P values < 0.05 for Mann–Whitney U). The RVD/LVD ratio and CSRVD were higher in the intervention group than in the non-intervention group (all P values < 0.05). Receiver operating curve analysis identified RVD/LVD = 1.036 and CSRVD = 3.5 as the best cut-off values to determine the necessity of further intervention. Patients with LRSCAF are more predisposed to pulmonary hypertension and right ventricular dysfunction compared with the normal population. RVD/LVD > 1.0 and CSRVD ≥ 4.0 may determine the necessity of intervention for patients with LRSCAF.