Apparent Aortic Stiffness in Children With Pulmonary Arterial Hypertension

Abstract

Background Left ventricular (LV) dysfunction, mediated by ventricular interdependence, has been associated with negative outcomes in children with pulmonary arterial hypertension (PAH). Considering the dilation of the pulmonary arteries as a paramount sign of PAH, we hypothesized that the ascending aorta will present signs of apparent stiffness in children with PAH, and that this effect may be due to mechanical interaction with the dilated main pulmonary artery (MPA). Methods and Results 42 children with PAH and 26 age- and size-matched controls underwent comprehensive CMR evaluation. Assessment of aortic stiffness was evaluated by measuring pulse wave velocity (PWV), aortic strain, and distensibility. Children with PAH had significantly increased PWV in the ascending aorta (3.4 vs. 2.3 m/s for PAH and controls, respectively; p = 0.001), and reduced aortic strain (23 vs. 29%, p < 0.0001) and distensibility (0.47 vs. 0.64 %/mmHg, p = 0.02). Indexed MPA diameter correlated with PWV (p = 0.04) and with aortic strain (p = 0.02). The ratio of MPA to aortic size correlated with PWV (p = 0.0098), strain (p = 0.0099), and distensibility (p = 0.015). Furthermore, aortic relative area change was associated with LV ejection fraction (p = 0.045) and ventricular-vascular coupling ratio (p = 0.042). Conclusions Pediatric PAH patients have increased apparent ascending aortic stiffness, which was strongly associated with the degree of MPA distension. We speculate that distension of the MPA may play a major role in limiting full aortic expansion during systole, which modulates LV performance and impacts systemic hemodynamics in pediatric PAH.

Children with kawasaki disease present elevated stiffness of great arteries: Phase‐contrast MRI study

“…Furthermore, tonometric studies do not take into account pulse wave reflections and bifurcation morphology, which can significantly alter PWV measurements . Reported PWV values for the ascending and descending aorta were in agreement with previously reported studies considering a flow‐area and wave‐propagation method . In this study, we found elevated PWV in ascending and descending aorta using a PC‐MRI‐derived technique, which is arguably the gold standard noninvasive technique for assessment of central aortic stiffness .…”

“…In this study, we found elevated PWV in ascending and descending aorta using a PC‐MRI‐derived technique, which is arguably the gold standard noninvasive technique for assessment of central aortic stiffness . We specifically applied the flow‐area method, which can be reliably applied to investigate stiffness in discrete vascular segment when sufficient temporal resolution is guaranteed . Additional studies are required to explore the status of thoraco‐abdominal and abdominal aorta to better understand the extracardiac inflammatory processes in KD.…”

“…The follow‐up risk stratification of all KD patients was performed according to coronary artery abnormalities, as proposed by recent American Heart Association (AHA) guidelines . All volunteers provided consent for participation in a prior study investigating aortic–MPA interactions in pulmonary hypertension, and we received a waiver to use these data as a comparison group with the current study . This study was part of the Colorado Multi‐Institutional Review Board‐approved imaging protocol.…”

“…This approach required carefully segmented tissue and phase images using a previously described algorithm applying semiautomatic active contour model, which tracks the edges of the vessel wall initialized by a manual delineation in a single time frame . Segmented tissue and phase contours were then transferred into the custom MatLab program (MathWorks, Natick, MA) for further PWV calculations as shown in our previous studies . We derived PWV using a flow‐area (QA) method that enables regionally specific assessment of vascular stiffness by calculating dQ/dA of the flow‐area loop at the early systolic phase under assumption of a backward reflection free environment .…”

“…21 Segmented tissue and phase contours were then transferred into the custom MatLab program (MathWorks, Natick, MA) for further PWV calculations as shown in our previous studies. 20 We derived PWV using a flow-area (QA) method that enables regionally specific assessment of vascular stiffness by calculating dQ/dA of the flow-area loop at the early systolic phase under assumption of a backward reflection free environment. 16,22 To meet this assumption, we considered data points at the early systolic phase without signs of plateauing or upstroke notch, which commonly signify the presence of impeding backward wave reflection.…”