How many versus how much: comprehensive haemodynamic evaluation of partial anomalous pulmonary venous connection by cardiac MRI

Objectives: The objective of this study was to investigate the effect of location and number of anomalously connected pulmonary veins and any associated atrial septal defect (ASD) on the magnitude of left-to-right shunting in patients with partial anomalous pulmonary venous connection (PAPVC), and how that influences right ventricular volume loading. Methods and results: The cardiac magnetic resonance (CMR) and echocardiography examinations of 26 paediatric patients (mean age, 11.2 ± 5.1 years) with unrepaired PAPVC were analysed. Fourteen patients had right-sided, 11 left-sided and 1 patient bilateral PAPVC. An ASD was present in 11 patients, of which none had a Qp/Qs < 1.5 and 8 had a Qp/Qs≥ 2.0. No patient with isolated left upper PAPVC experienced a Qp/Qs ≥ 2.0 compared to 9/12 patients with right upper PAPVC. Qp/Qs correlated with indexed right ventricle (RV) end-diastolic volume (RVEDVi, r = 0.59, p = 0.002) by CMR and with echocardiographic right ventricular end-diastolic dimension (RVED) z-score (r = 0.68, p = 0.003). A RVEDVi >124 ml/m² by CMR and a RVED z-score >2.2 by echocardiography identified patients with a Qp/Qs ≥1.5 with good sensitivity and specificity. Conclusions: An asymptomatic patient with a single anomalously connected left upper pulmonary vein and without an ASD is unlikely to have a significant left-to-right shunt. On the other hand, right-sided PAPVC is frequently associated with a significant left-to-right shunt, especially when an ASD is present. Key Points: • Patients with PAPVC and ASD routinely have a significant left-to-right shunt. • Patients with right PAPVC are likely to have a significant left-to-right shunt. • Patients with left PAPVC are unlikely to have a significant left-to-right shunt. • CMR is helpful in decision-making for patients with PAPVC.