Abnormal Pulmonary Artery Bending Correlates With Increased Right Ventricular Afterload Following the Arterial Switch Operation

Abstract

Purpose: In transposition of great arteries, increased right ventricular (RV) afterload is observed following arterial switch operation (ASO), which is not always related to pulmonary artery (PA) stenosis. We hypothesize that abnormal PA bending from the Lecompte maneuver may affect RV afterload in the absence of stenosis. Thus, we sought to identify novel measurements of three-dimensional cardiac magnetic resonance (CMR) images of the pulmonary arteries and compare with conventional measurements in their ability to predict RV afterload. Methods: Conventional measurements and novel measurements of the pulmonary arteries were performed using CMR data from 42 ASO patients and 13 age-matched controls. Novel measurements included bending angle, normalized radius of curvature ( Rc), and normalized weighted radius of curvature ( Rc- w). Right ventricular systolic pressures (as the surrogate for RV afterload) were measured by either recent echocardiogram or cardiac catheterization. Results: Conventional measurements of proximal PA size correlated with differential pulmonary blood flow ( r = 0.49, P = .001), but not with RV peak systolic pressures ( r = −0.26, P = .18). In ASO patients, Rc- w correlated with higher RV systolic pressures ( r = −0.57, P = .002). Larger neoaortic areas and rightward bending angles correlated with smaller right pulmonary artery Rc ( r = −0.48, P = .001; r = 0.41, P = .01, respectively). Finally, both pulmonary arteries had significantly smaller Rc compared to normal controls. Conclusions: Pulmonary arteries exhibit abnormal bends following ASO that correlate with increased RV afterload, independent of PA stenosis. Future work should focus on clinical and hemodynamic contributions of these shape parameters.

Blood Flow Dynamics at the Pulmonary Artery Bifurcation

“…This yields, at peak systole, De LPA = 1120 and De RPA = 1540. Physiological values of the Dean number have been very rarely reported in literature for the pulmonary artery bifurcation, one exception being a recent work by the current authors group [7]. The values obtained here are in line with those reported in that paper.…”

“…Deviations from this hemodynamically efficient configuration are common in post-surgical CHD geometries. Area obstructions (stenosis) of the proximal PAs, steeper branching angles and curvatures as well as other anatomic alterations can lead to a completely different flow morphology, as shown for instance in the case of TGA patients after the arterial switch operation [6,7]. Zhang et al computationally analyzed the effect of the LPA branching angle (i.e., the angle formed between the MPA and LPA centerlines) and found a dramatic decrease of the energy efficiency with decreasing angles (i.e., sharper bends) [21].…”

“…For instance, patients with repaired transposition of great arteries (TGA) can develop abnormal pulmonary artery morphology [5], with repercussions on haemodynamic efficiency. In recent studies, Capuano et al used image-driven computational fluid dynamics (CFD) on patient-specific TGA models and found that the curvature of the MPA bifurcation is a shape biomarker of clinical significance [6,7]. Steeper curvatures were found to increase the pressure load of the RV, with potentially adverse clinical outcomes [8].…”

Characterization of Flow Dynamics in the Pulmonary Bifurcation of Patients With Repaired Tetralogy of Fallot: A Computational Approach

“…The Womersley number reported in the pulmonary arteries of healthy volunteers is in the range of approximately 14–21 ( 42 ), which is in agreement with the range reported for the TOF population in this study. Recently, Loke et al ( 43 ) studied the pulmonary artery bending in healthy subjects and patients that have undergone arterial switch operation (ASO), and reported a Dean number in the range of 803 ± 280 in the RPA and 566 ± 140 in the LPA in the control group, and 1,902 ± 1,125 in the RPA and 1,067 ± 584 in the LPA of the ASO patients ( 43 ). These patients are often diagnosed with post-operative complications including right ventricular afterload and right ventricular hypertrophy, most commonly from left pulmonary arterial stenosis ( 44 ), similar to TOF patients.…”

Right ventricular afterload in repaired D-TGA is associated with inefficient flow patterns, rather than stenosis alone

“…The oldest ASO patients are reaching young adulthood, and while long-term consequences of repair are not yet fully realized [6], current evidence indicates that these patients can develop significant mid-term hemodynamic complications [7]. In particular, hemodynamic changes after ASO can include right ventricular (RV) diastolic dysfunction, hypertrophy, and increased afterload [7][8][9][10]. Importantly, the pulmonary artery (PA) is heavily manipulated in the ASO through the LeCompte maneuver, where the pulmonary trunk and its bifurcation are translocated anterior to the neoaorta [6].…”