The utility of wall stress (using 4D flow) in a patient with percutaneous occlusion of the ductus arteriosus.

Description of Clinical Presentation: A 42-year-old patient with newly diagnosed heart failure underwent physical examination, which revealed a continuous left infraclavicular murmur. Transthoracic echocardiography demonstrated a reduced ejection fraction (LVEF 33%) and a large patent ductus arteriosus (PDA). Initial medical management was instituted. Subsequent cardiac catheterization identified a large Krichenko type C PDA with reversible pulmonary vascular resistance. Percutaneous closure was performed with a 35-mm Amplatzer™️ device, achieving complete occlusion without residual shunt.

Diagnostic Techniques and Their Most Important Findings: At two-year follow-up, echocardiography showed improvement in left ventricular function (LVEF 43%), reduction of pulmonary artery systolic pressure to 47 mmHg, and no residual ductal flow. The patient later developed exertional angina, prompting cardiac magnetic resonance (CMR) to exclude ischemic cardiomyopathy. CMR (Figure 1) revealed the occluder protruding into the aortic lumen without obstruction but producing vortex and helical flow on 4D flow assessment, associated with increased posterior wall shear stress (WSS) and slight focal dilation (Figures 2–3). Moderate left ventricular systolic dysfunction persisted (LVEF 35%), with preserved right ventricular function (RVEF 53%). Linear septal intramyocardial late gadolinium enhancement was noted. T1 mapping demonstrated prolonged inversion recovery times and an elevated extracellular volume fraction (36%), consistent with diffuse myocardial fibrosis. No ischemic enhancement or regional wall motion abnormalities were detected.

Cardiac MRI provides accurate quantification of ventricular function and enables tissue characterization through parametric mapping and late gadolinium enhancement. The addition of 4D flow allows direct visualization and quantification of intracardiac and vascular hemodynamics; in this case, the impact of an occluder device on aortic flow. The device produced localized vortex and helical flow as welll as increased WSS, correlating with area of focal aortic dilation.

Learning Points from this Case: Abnormal flow dynamics are recognized contributors to the initiation and progression of aortic disease, including atherosclerosis, aneurysm formation, and dissection, although direct measurement of their effects has historically been limited¹. In this patient, device protrusion generated turbulent flow and increased aortic wall stress.

Elevated WSS is a known predictor of ascending aortic dilation in bicuspid aortic valve disease¹-². We propose that it may also serve as a predictor in patients with large occluder devices that alter aortic flow patterns. Progressive increases in WSS over time may predispose to aortic dilation, aortopathy, or device-related complications, highlighting the importance of quantifying and reporting these findings in longitudinal studies³.

Future research should aim to clarify the complex interplay between anatomy, physiology, and pathological remodeling on WSS, employing 4D flow to better define risk and guide management¹–³.

Fig. 1 Magnetic resonance imaging study. A) Left 2-chamber view showing the ductal occluder device (red arrows) with slight protrusion into the origin of the left pulmonary artery. B) Right ventricular outflow tract demostrating the position of the occluder device. C) Distal aortic arch and decending aorta with the device partially protuding into the aortic lumen. D) Dimensions of the occluder device. E) Four-chamber view demostrating left ventricular dilation.
Fig. 2 4D Flow in the pulmonary artery: A) Pathline visualization demostrating flow acceleration along the anterior wall of the main pulmonary artery and turbulent flow at the origin of the left pulmonary artery (LPA). B) Regions of increased shear wall stress highlighted (red arrows). C) Quantitive analysis in pascals (Pa) comparing both pulmonary branches. D-F) Multiplanar reconstructions depicting the site of device protrusion into the proximal LPA.
Fig. 3 4D Flow in the aorta: A) Pathline visualization demostrating flow acceleration in the ascending aorta and turbulent flow at the site of device protusion. B) Regions of increased wall shear stress (red arrows). C) Quantification in pascals (Pa) comparing wall shear stress before the device and at the device site. D-F) Multiplanar reconstructions illustrating the location and extent of the device protrusion within the aortic lumen.