Abstract 16192: Exercise Stress Response of Myocardial Velocities in 11 Children with Fontan Physiology versus 33 Normal Controls - a Color Tissue Doppler Study

Abstract

Background: Exercise capacity is diminished after Fontan palliation for complex congenital heart defects and (in adults) permitted risk stratification for adverse events. It is controversial how the right ventricle (RV) adjusts to systemic work load. This study used tissue Doppler imaging (TDI) stress echocardiography in 11 children with Fontan (SV) to study segmental wall motion patterns.

Methods: 11 children with Fontan physiology and 33 normal controls were recruited at routine stress echocardiography. Groups were matched for age (13.7±2.8 v. 14.1±2.8y; NS), height and weight. Color TDI cine loops were acquired as digital raw data before and right after Bruce treadmill maximum exercise test. Peak systolic (S) velocity was measured in the basal posterior wall (LV short axis) and in the basal lateral, basal septal and basal RV free wall near the ring (long axis).

Results: Exercise times were similar for SV and control at 12.8±2.5 v.11.2±1.6 min (NS). SV had lower baseline and peak heart rates than controls (Table) and only reached 87±8% of predicted HR v. 93±7% in controls (p<0.05). On TDI, long axis baseline and peak TDI velocities were markedly lower in SV than in controls (Table). Yet the relative increase of S velocity over baseline was comparable between groups and still followed the same heterogeneous segmental pattern (Table). Short axis S velocities were preserved.

Conclusions: Quantitative stress echocardiography with tissue Doppler imaging is feasible in children with Fontan physiology. Despite normal exercise times, Fontan patients had diminished longitudinal S velocities pre and post exercise stress. However, segmental variation was similar to controls: Right ventricular myocardium still showed a lower ability to augment S velocities than LV segments. This suggests that the different substructure in RV and LV may be the chief determinant of wall motion patterns. TDI stress imaging is useful to better understand myocardial mechanics in Fontan patients.