Cyanosis period: A key factor influencing exercise cardiac performance after Fontan procedure

Most patients with Fontan circulation struggle to increase cardiac output during exercise, affecting aerobic capacity and quality of life.

We sought to identify factors in the preFontan period and in management that influence their exercise cardiac performance.

We retrospectively collected anatomical, clinical and pre- and postFontan invasive haemodynamic data, including ventricular filling pressure in 57 consecutive Fontan patients who underwent cardiopulmonary exercise testing. Exercise cardiac performance was assessed by peak cardiac index measurement using a thoracic bioelectrical impedance device.

The median age at Fontan procedure was 6.3 (interquartile range 2.8) years, and 43 patients had concomitant fenestration. Age at cardiopulmonary exercise testing was 14.7 (interquartile range 5.4) years. In multivariable models, peak cardiac index was influenced by cyanosis duration (B=-0.272; P<0.0001) and by the Norwood procedure (-1.977; P=0.002). Peak indexed stroke volume was influenced by cyanosis duration (B=-1.109; P=0.0002), whereas peak heart rate was influenced by preFontan peripheral oxygen saturation (B=0.602; P=0.009). Cyanosis duration≤6.9 years predicted a peak indexed stroke volume≥45mL/m² (area under the curve=0.747; P=0.001). Furthermore, peak indexed stroke volume and peak heart rate were correlated with postFontan ventricular filling pressure: r_p=-0.539 (P=0.012) and r_p=-0.552 (P=0.010), respectively. PostFontan ventricular filling pressure was correlated with bidirectional cavopulmonary shunt duration (r_s=0.498; P=0.023).

Cyanosis duration and low preFontan peripheral oxygen saturation affect exercise cardiac performance after Fontan, partly through ventricular dysfunction. Early Fontan procedure and limited postFontan cyanosis could promote better long-term exercise cardiac performance.