BRIEF RESEARCH COMMUNICATIONS • Serial Assessment of Tricuspid Annular Plane Systolic Excursion Is Associated with Death or Lung Transplant in Children with Pulmonary Arterial Hypertension (PAH)

Pulmonary arterial hypertension (PAH) in the pediatric population may be classified as primary/idiopathic or may be associated with congenital heart (CHD) or lung disease. Over time, right ventricular (RV) function determines morbidity and mortality.

In adults with PAH, outcome is associated with tricuspid annular plane systolic excursion (TAPSE) – a measure of RV longitudinal function.

The aim of this study was to investigate the association of serial assessment of TAPSE with death or lung transplant in pediatric patients with PAH.

The authors retrospectively studied serial echocardiograms in 48 children (ages 0-18 years) with PAH (mean pulmonary artery pressures > 20 mm Hg; indexed pulmonary vascular resistance [PVRi] > 3 Woods units) and > 1-year follow-up. The first echocardiogram constituted the presentation time point. Participants underwent annual echocardiography as per clinical routine, including measurement of RV fractional area change (FAC) and TAPSE, which was measured by two-dimensional or M-mode echocardiogram and expressed as a Z score.

Associations between TAPSE or FAC and time-dependent outcomes were modeled in an extended Cox regression model through which each echocardiogram in a given patient is modeled as a new observation with censoring at the next echocardiogram (unless an event happens, in which case the event is assigned to the previous echocardiogram).

18 patients had primary/idiopathic PAH, 25 had PAH-CHD, and five had PAH associated with lung disease. The median age at presentation was 7.7 years and median follow-up duration was 4.4 years. Ten participants (21%) experienced the primary endpoint of death or lung transplantation.

Participants experiencing death or transplant had a significantly lower FAC and TAPSE in comparison with transplant-free survivors. An increase in TAPSE Z score and a decrease in FAC conferred a decreased risk for the primary outcome, although this was not statistically significant (hazard ratio of 0.56 per Z score unit of TAPSE and 0.46 per 10% change in FAC).

A TAPSE Z score of <–4 at 1 year after presentation was associated with increased hazard of death or transplant. The FAC at 1 year after presentation was lower in the primary-endpoint group with marginal statistical significance (p=0.07). Calcium channel blockers were associated with an improved TAPSE Z score.

The author concluded that while values at presentation were similar between PAH transplant-free survivors and nonsurvivors, TAPSE Z score and, to a lesser extent, FAC at 1-year follow-up were associated with poor outcomes, with serial measurements showing a diverging trajectory over time. They also commented that the decline in TAPSE prior to worsening FAC may arise from an earlier decrease in longitudinal versus circumferential/radial function. Therefore, they believe that TAPSE may be a sensitive indicator of RV efficiency in PAH. However, despite this, they still advocate to assess FAC, which incorporates apical and radial shortening.

Few more comments were made by the authors:

• First, they suggest that since TAPSE reflects RV coupling to its load, it is valuable to assess responses to treatment, as suggested by the current and prior studies.
• Second, in prior studies, a TAPSE < 12 mm was associated with worse outcome, especially if low values persisted after initiating therapy.
• Finally, they suggest that the use of Z scores, rather than absolute values, may be more appropriate in children.