Original article
Cardiovascular
Caval Blood Flow During Supine Exercise in Normal and Fontan Patients

https://doi.org/10.1016/j.athoracsur.2007.08.062Get rights and content

Background

Extracardiac total cavo-pulmonary connection (TCPC) bypasses the right atrium and has in theory better hemodynamics than intraatrial TCPC repair. Both are thought to have inferior hemodynamics compared with a normal circulation. Direct comparison of flow rates at rest and during exercise with magnetic resonance imaging technique have not been performed.

Methods

The study comprised 20 children. Six children (median age, 9.3 years; interquartile range, 2.2) had undergone extracardiac TCPC. Eight children (median age, 8.9 years; interquartile range, 5.0) had an intraatrial TCPC, and 6 children (median age, 10.3 years; interquartile range, 2.6) were healthy control subjects. Blood flows in the aorta, inferior vena cava, and superior vena cava were measured at rest and during two levels of submaximal supine bicycle exercise (0.5 W/kg and 1.0 W/kg) using a magnetic resonance imaging scanner mounted with a bicycle.

Results

Heart rate, respiratory rate, inspiratory fraction, and blood flow rates in the aorta and inferior vena cava increased equally in all three groups. If patients were grouped together, flow rates were significantly lower, and the inspiratory flow fraction in the inferior vena cava was significantly higher, than in control subjects. Retrograde flows were observed in all three groups at rest but tapered off with exercise.

Conclusions

At submaximal levels of lower limb exercise, patients with extracardiac as well as intraatrial TCPC showed a similar increase in respiration, heart rate, and aortic and caval flow rates as healthy control subjects. This is in accordance with the observation that many patients with TCPC perform well during daily life activities.

Section snippets

Study Group

Three groups of children were investigated. Group A comprised 6 children with an extracardiac TCPC, group B, 8 children with an intraatrial TCPC, and group C, 6 healthy control subjects. Seven of the patients in group B were studied as part of a previously reported study [5]. Compared with the previous study, this study adds a control group and a group of children with an extracardiac TCPC operation. Baseline data are shown in Table 1. The operations included a two-stage procedure with an

Results

All children completed the protocol. One of the control subjects was moving excessively during exercise and it was not possible to achieve valid IVC flow measurements in that specific child. Age, height, weight, and body surface area did not differ between the three groups (Table 1).

Comment

This study compares real-time blood flow during exercise in children undergoing intraatrial and extracardiac TCPC operations with that of healthy children. The overall result was that both patient groups were able to respond to a submaximal lower limb exercise with a similar increase in heart rate and respiration and in IVC and aortic flows, which did not differ from the response in healthy children. The IVC flow in the two patient groups varied more with respiration than in the age-matched

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