# Retrograde Flow to Aortic Root Predicts Inferior Cardiopulmonary Performance and Restrictive Lung Physiology in Fontan Circulation

## TL;DR

Retrograde blood flow to the aortic root in certain heart defect patients is linked to worse physical performance and lung function.

## Contribution

Identifies retrograde aortic flow as a predictor of poor cardiopulmonary performance in Fontan circulation patients.

## Key findings

- HLHS-R patients reported less vigorous physical activity and had lower peak oxygen uptake.
- HLHS-R patients showed the most severe restrictive lung physiology.
- LV morphology patients had better cardiopulmonary performance than HLHS patients.

## Abstract

Cardiac output in Fontan circulation depends on systemic venous pressure, pulmonary vascular resistance, and ventricular function. Because myocardial function is dependent on coronary perfusion, we studied whether retrograde flow to aortic root in the mitral/aortic atresia subgroup of hypoplastic left heart syndrome (HLHS) affects cardiopulmonary performance.

We studied 26 stable Fontan patients (14.4 ± 2.4 years) with right (RV, n = 17) and left (LV, n = 9) systemic ventricle morphology. All RV patients had HLHS and were subdivided according to postnatal flow to the hypoplastic ascending aorta being antegrade (HLHS-A) or retrograde (HLHS-R) due to valve atresia. Physical activity was assessed by questionnaire (LASERI, a questionnaire for Finnish children regarding physical activity), cardiopulmonary exercise test (1-minute ramp protocol), body composition (Biacorpus RX 4000), and muscle fitness (EUROFIT). These data were correlated with the postnatal aorta size and current branch pulmonary artery size index (McGoon index).

Patients with HLHS-R seldom self-reported engagement in vigorous physical activity and had significantly lower cardiopulmonary performance (peak oxygen uptake [VO2peak]) than patients with LV morphology (P = 0.037), but not compared with patients with HLHS-A. Branch pulmonary artery size did not correlate with VO2peak. Patients with HLHS-R had most severe lung restrictions (forced vital capacity z-score –3 ± 0.9, P = 0.0073; forced expiratory volume in 1 second z-score –3.3 ± 1.1, P = 0.001).

Young Fontan patients with LV had better cardiopulmonary performance than patients with HLHS. Patients with HLHS-R were the least active and had the lowest VO2peak and most restrictive lungs. It is important to recognize postnatally single ventricle patients at high risk for inactivity to promote an active and healthy lifestyle.