Atrial strain: an important addition to the armamentarium of non-invasively assessing Fontan function?

Abstract

Patients with univentricular hearts are being palliated mostly with the total cavopulmonary connection, either by an extracardiac conduit (ECC) or an intra-atrial lateral tunnel (ILT). Despite the excellent results with regard to volume unloading and oxygen saturation, Fontan patients on the long-term are at high risk of reduced exercise capacity, clinical deterioration and premature death [1]. Although many Fontan patients deteriorate over time it is difficult to identify which patients are at most risk and much effort has therefore been undertaken to search for predictive variables. Contributing factors leading to adverse outcomes are multiple and include diastolic and systolic ventricular dysfunction, rhythm disturbances including bradyand tachy-arrhythmias, atrioventricular valve regurgitation, increased pulmonary artery pressure, complex anatomy leading to inflow or outflow obstructions and thrombo-embolic events [2]. Currently, the role of atrial function in the (failing) Fontan circulation is being increasingly studied. The present study of Veldtman et al. contributes importantly to this expanding knowledge [3]. In the Fontan circulation, the maximum cardiac output is often limited to the ventricular preload. As a result, in Fontan patients with impaired ventricular diastolic function, which is frequently encountered, the atria may play an important role in maintaining adequate ventricular filling [4]. Atrial function can be divided in atrial reservoir function (during ventricular systole), atria conduit function (during early diastole) and atrial contraction function (during late diastole). Novel post-processing applications after echocardiography as well as cardiac MRI have enabled non-invasive assessment of these different components of atrial function using strain, as explained in the present issue by Veldtman et al. [3]. In healthy adults, atrial function as assessed by echocardiographic strain has been shown to relate to exercise capacity [5]. In children, Khoo et al. [6] studied the development of the various atrial functions in healthy hearts as well as in univentricular hearts at the age of 0 to 6.5 years using echocardiographic strain measurements. In healthy growing children, atrial reservoir function increased with age, whereas the contribution of atrial contraction function became less important over time. In single ventricle patients, during the same period in different stages of their palliative trajectory (pre-Glenn, post-Glenn, pre-Fontan completion and postFontan completion) the increase in atrial reservoir function was absent, and this observed difference between normal children and children with single ventricles increased over time, already being significantly different before any surgical intervention. In contrast, the atrial contractile function was consistently higher in the patients as compared to controls in all stages. This finding suggests that adequate diastolic function in the Fontan patient relies more on atrial contraction function for ventricular filling as compared to normal controls. This is especially of importance in Fontan patients without adequate sinus rhythm, which frequently occurs. Various authors studied the relation among atrial strain measurements in Fontan patients and clinical relevant outcome parameters, yielding conflicting results. Van der Ven et al. [7] assessed the role of atrial function, as assessed with atrial feature tracking strain with cardiac MRI, on exercise capacity and clinical events in 95 Fontan patients. In this study, atrial function did not predict exercise capacity or events during follow up. In contrast, two other recent studies did find correlations between reduced echocardiographic This comment refers to the article available online at https:// doi. org/ 10. 1007/ s1055402102298-w.