4 Should the normal range of pulmonary vascular resistance be re-defined in patients with fontan circulation?

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Abstract

Background

Creation of Fontan circulation helps establishing separating pulmonary and systemic circulation in patients born with anatomical/physiological single ventricle. These patients have significantly impaired exercise capacity, mainly due to limited augmentation of cardiac output, predominantly secondary to impaired venous return (pre-load). Studies have suggested that pulmonary vasodilator therapies improve cardiac output by augmenting venous return. Use of such vasodilator therapy is significantly sparse, as many of these patients are reported to have normal pulmonary vascular resistance (PVR). However, the normal range of PVR was defined only in those with subpulmonic ventricle and pulsatile pulmonary flow. Incorporating such an information into routine management of patients with Fontan circulation, who have passive venous filling and non-pulsatile flow is likely to mislead physicians, and delay appropriate therapy in many suitable candidate. We sought to evaluate observed PVR in this cohort.

Materials and methods

Retrospective review of data from a large tertiary adult congenital heart disease (ACHD) centre in the UK.

Results

From a cohort of 4454 patients with complex ACHD conditions, 154 had Fontan circulation; 70 patients with failing Fontan were investigated by cardiac catheterization. Thirty-four (48.6%) were male, mean age of 30.1±6.2 years (17–43), and mean body mass index of 24.1±5.3 kg/m2. Mean Fontan pressure was 16±4 mmHg (7–29), mean wedge capillary pressure was 11±3 mmHg (4–19), and mean trans-pulmonary gradient (TPG) was 5±3 mmHg (0–15). Mean cardiac output was 4.1±2.7 L/min and calculated PVR was 1.7±1.2 Wood units (0.25–5.3). Although cardiac output was well maintained, mean Fontan pressure significantly correlated with the mean capillary wedge pressure (p<0.0001) and PVR (p<0.0001). Rise in Fontan pressure was observed earlier than increase in PVR; however, 3/4th of patients with failing Fontan were noted to have normal PVR.

Conclusions

In patients with Fontan circulation, rise in PVR above the normal range was observed only after moderate rise in Fontan pressure. Such rise in PVR seems to be a very late phenomenon to occur. Acceptable range of PVR in patients with Fontan circulation should be re-defined, so that patients can be treated in a timely fashion. A large prospective trial or registry should be established to explore this subject further in details.

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