Systolic Function in the Fontan Circulation Is Exercise, but Not Preload, Recruitable.

BACKGROUND

Fontan circulatory failure with impaired systolic function is well documented; however, its mechanisms are not fully understood. The aim of this study was to explore myocardial functional reserve in adolescent patients with Fontan circulation in response to exercise or acute preload increase.

METHODS

The study included 32 patients (median age, 16.7 years; range, 15.4-17.9 years; 12 female patients) with Fontan circulation. Echocardiographic imaging was performed during exercise using a recumbent cycle ergometer and during heart catheterization with a rapid infusion of 0.9% saline infusion at 5 mL/kg body weight. Myocardial peak longitudinal strain (LS) was measured in a four-chamber view during specific time intervals before, during, and after exercise (LSstress) and volume load (LScath). During catheterization, central venous pressure and ventricular end-diastolic pressure were simultaneously recorded. A control group of 16 healthy individuals participated in the exercise test.

RESULTS

Mean LSstress was less negative for patients than for control subjects (P ≤ .001 at all stages); however, it significantly improved from -18.4 ± 5.5% at baseline to -22.0 ± 6.5% (P = .004) at maximal loading. LSstress at maximal loading did not correlate with changes in heart rate. During catheterization, mean LScath was -19.6 ± 6.0% at baseline and did not improve significantly at 1.00 to 2.00 minutes and at 4.00 to 6.00 minutes after saline infusion. In more than half of the patients, LScath worsened or improved by less than -2% after saline infusion. Worsening of LScath correlated with central venous pressure and ventricular end-diastolic pressure in all conditions (P ≤ .017). There was no difference in LSstress or LScath between the morphologic right ventricle and the morphologic left ventricle.

CONCLUSIONS

Patients with Fontan circulation demonstrate systolic myocardial functional reserve that can be recruited with exercise stress but not with an acute increase in preload.