In vivo study of pulmonary artery remodeling and pulsatility in long Fontan patient
Authors: Belahnech Pujol Y , Marti Aguasca G , Domingo E , Dos L , Pijuan Domenech A , Miranda B , Gordon B , Gonzalez Fernandez V , Azpiroz M J , Rodenas Alesina E , Calabuig A , Garcia Del Blanco B , Ferreira Gonzalez I 
Published: October 2024

Abstract

Background
Pulmonary vasculopathy associated with Fontan circulation is a relatively unexplored entity that could have clinical and therapeutic implications.

Purpose
Our aim was to evaluate the physiology of the pulmonary artery in patients with Fontan circulation using conventional right heart catheterization (RHC) and intravascular ultrasound (IVUS).

Methods
From December 2022 to January 2024, data from all consecutive Fontan patients undergoing RHC were prospectively collected at a tertiary referral center for adult congenital heart disease. Pressures and pulmonary artery wall high-definition IVUS recordings (OptiCrossTM, 60 MHz, Boston Scientific) were recorded at rest and during apnea. Pathological Fontan pressure was defined when as exceeding 15 mmHg. IVUS pulsatility index was defined as [(systolic lumen area - diastolic lumen area)/(diastolic lumen area) ×100], Peterson's elastic modulus as (pulmonary pulse pressure/IVUS pulsatility index), and area of wall thickness as [(wall area - lumen area)/(lumen area) x100)].
In the literature, the mean ± standard deviation (SD) normal values of elastic modulus and wall thickness area have been reported as 21 ± 1.7 mmHg and 1.4 ± 1.3%, respectively, in healthy patients without pulmonary hypertension (1: doi: 10.1186/s12931-017-0568-z). We define an alteration in intrinsic pulmonary arterial wall viscoelastic properties as an elastic modulus &gt; 70 mmHg, and we define structural pulmonary wall remodeling as an increase in wall thickness area greater than 5%.

Results
13 patients were studied. Median age was 28.1 years interquartile range (IQR) (25.6- 41.4), 7 (53.9%) were female, and 4 (30,8%) were in functional New York Heart Associtation (NYHA) class I. RHC and pulmonary arterial wall IVUS values are presented in Figure 1. 6 (46.2%) had Fontan abnormal pressures at rest. All patients showed minimal pulse pressure in the pulmonary arteries synchronized with heart rate, median pulmonary pulse pressure (IQR) 3 (2-4) mmHg. This pulsatility was detected in the IVUS study in all patients, pulsatility index (median (IQR) 4.8 (3.3-10.1)) and elastic modulus (median (IQR) 51.5 (20.5-101.6) mmHg). All of them had some degree of structural pulmonary wall remodeling (&gt;5% wall thickness area), and 10 (76.9%) of them had marked remodeling (&gt; 10%). The median (IQR) of wall thickness area was 13.6 (10.5-18.3) % (Figure 2).
We think that the pseudo-normality of the elastic modulus is due to a low pulmonary pulse pressure, however, structural remodeling could be secondary to the endothelial dysfunction present and described in arteries with very low pulsatility.

Conclusions
The IVUS evaluation of the pulmonary artery in Fontan patients may be useful for revealing significant information regarding pulmonary physiology. Pulmonary wall thickening has been observed, providing insight into altered structural remodeling of the pulmonary arteries in this population.