Epi-aortic Doppler measurement of cardiac output in univentricular connection

BACKGROUND In the initial postoperative period after a Fontan-type operation for a univentricular circulation, cardiac output information is important, but cannot be provided by conventional methods due to the surgical reconstruction of the heart. In this regard we investigated the feasibility of epi-aortic Doppler measurements in order to calculate cardiac output. METHODS : Epi-aortic cardiac output measurement was compared with Fick measurements as the gold standard in eight patients with a univentricular circulation after a Fontan-type operation. RESULTS The mean diameter of the aorta by epi-aortic measurement was 18 mm (range 14 to 25), by angiography 17 mm (range 10 to 24), correlation coefficient 0.88 (p < 0.05). The mean cardiac output by epi-aortic measurement was 2.8 l.min(-1) (range 1.2 to 6.3), by the Fick calculations 1.8 l.min(-1) (range 0.8 to 5.0). The correlation coefficient for cardiac output data in aortic diameters up to 20 millimeter in diameter was 0.55 (p < 0.05). CONCLUSIONS Epi-aortic Doppler measurement of cardiac output after Fontan type reconstructions could be applied in aortas up to 20 millimeter in diameter. A reasonable correlation with Fick calculations was found. This was supported by Bland-Altman plotting. The method is intrinsically invasive, but application and removal of the device were easy and no complications related to the system were observed. An important restriction is the often present abnormal anatomy, either congenitally or after surgery.