4D Flow CMR Assessment of Ventricular Dyssynchrony and Intracardiac Flow Alterations in an Infant with Wolff–Parkinson–White Syndrome

Description of Clinical Presentation: A 5-month-old boy with an unremarkable perinatal history was referred to our hospital after poor weight gain was noted during a routine health check-up. His body weight was 6.1 kg, and although his growth rate was within normal limits, echocardiography suggested left ventricular (LV) enlargement. He was referred to pediatric cardiology section for further evaluation. Electrocardiography revealed sinus rhythm at 127 bpm, left bundle branch block, and a delta wave, leading to the diagnosis of Wolff–Parkinson–White (WPW) syndrome type B. Holter monitoring showed no episodes of tachyarrhythmia. Echocardiography demonstrated an LV end-diastolic diameter of 26.8 mm (108% of normal) and an LV ejection fraction of 42%. The parasternal long-axis view demonstrated paradoxical contraction of the basal interventricular septum. LV enlargement and dyssynchrony were attributed to conduction via the accessory pathway. Flecainide therapy was initiated, and the patient is currently under follow-up.

Diagnostic Techniques and Their Most Important Findings: To evaluate the hemodynamic impact of ventricular dyssynchrony in WPW syndrome, 4D flow cardiac MRI (CMR) was performed. It revealed clear asynchronous ejection between the aorta and pulmonary artery, with an ejection onset time difference of 51 ms. Intracardiac flow analysis showed flow stagnation at the aneurysmal dilation of the basal interventricular septum, identified as residual volume. The LV flow component ratios were: direct flow 17.9%, delayed ejection flow 31.7%, retained inflow 27.2%, and residual volume 23.2% , among which the direct flow was decreased. At the 3-month follow-up after initiation of medical therapy, residual volume persisted in the dilated basal interventricular septum, while the intracardiac flow component ratios had improved (direct flow 21.6%, delayed ejection flow 37.5%, retained inflow 22.6%, and residual volume 18.3%).

Learning Points from this Case: To our knowledge, this is among the first cases to use 4D flow CMR to quantitatively assess ventricular dyssynchrony by measuring ejection timing differences between the aorta and pulmonary artery, while also revealing changes in intracardiac blood flow patterns.


Flow stagnation was observed at the aneurysmal dilation of the basal interventricular septum, appearing as residual volume on intracardiac flow analysis.


Intracardiac flow component ratios may serve as a useful imaging biomarker for assessing treatment response.

Asynchronous ejection between the aorta and pulmonary artery.
Flow stagnation identified as residual volume (arrow). At the 3-month after flecainide therapy, residual volume persisted, while the intracardiac flow had improved.