Doppler assessment of pulmonary artery flow patterns and ventricular function after the Fontan operation

Abstract

To assess the relation between ventricular systolic and diastolic function and pulmonary artery (PA) flow patterns after the Fontan operation, 15 postoperative patients were prospectively evaluated with echocardiography. Blood flow velocities in the PA were recorded with pulsed Doppler echocardiography. Ejection fraction was measured by 2-dimensional echocardiography using Simpson's rule. Indexes of diastolic function were measured from the systemic atrioventricular valve inflow Doppler and included peak E and A velocities, peak filling rate normalized for stroke volume, the fractions of filling in early and late diastole (E and A area fractions), and the E/A velocity and area ratios. Compared with 15 age-matched control subjects, the 15 patients who had undergone the Fontan procedure had decreased peak E velocity (0.65 ± 0.20 vs 0.87 ± 0.10 m/s), decreased $\text{E}\text{A}$ velocity ratio (1.29 ± 0.23 vs 1.98 ± 0.46), decreased normalized peak filling rate (6.09 ± 0.90 vs 6.81 ± 0.83 s⁻¹), decreased E area fraction (0.63 ± 0.09 vs 0.72 ± 0.07), increased A area fraction (0.37 ± 0.07 vs 0.24 ± 0.06), and decreased $\text{E}\text{A}$ area ratio (1.77 ± 0.45 vs 3.33 ± 1.15) (p < 0.05). These diastolic filling abnormalities are consistent with impaired ventricular relaxation and decreased early diastolic transvalvular pressure gradient. PA Doppler recordings showed 2 distinct patterns of flow. Pattern I, observed in 9 patients, showed biphasic forward flow with peak velocities in mid to late systole and middiastole. Pattern II, observed in the remaining 6 patients, showed decreased systolic forward flow, a late systolic to early diastolic flow reversal, and delayed onset of diastolic forward flow. Compared with pattern I patients, pattern II patients had no significant differences in any of the Doppler indexes of diastolic function; however, pattern II patients had a significantly tower ejection fraction (43 ± 9 vs 57 ± 5%). Thus, many patients undergoing the Fontan procedure have impaired ventricular relaxation, but, in the presence of a normal ejection fraction, biphasic forward PA flow is maintained. With the development of decreased ejection fraction, atrial systolic filling pressures are likely increased, the ventricular suction effect is decreased, and PA flow is diminished or absent in systole and early diastole.