Relationship between right-to-left shunt, hypoxia, and epilepsy

A right-to-left shunt (RLS) can mediate the hypoxic state, and hypoxemia is relevant for the development of drug-resistant epilepsy (DRE). The objective of this study was to identify the relationship between RLS and DRE and further investigate the contribution of RLS to the oxygenation state in patients with epilepsy (PWEs).

We performed a prospective observational clinical study of PWEs who underwent contrast medium transthoracic echocardiography (cTTE) between January 2018 and December 2021 at West China Hospital. The collected data included demographics, clinical features of epilepsy, antiseizure medications (ASMs), RLS identified by cTTE, electroencephalography (EEG), and magnetic resonance imaging (MRI). Arterial blood gas was also assessed in PWEs with or without RLS. The association between DRE and RLS was quantified using multiple logistic regression, and the parameters of oxygen levels were furtherly analyzed in PWEs with or without RLS.

A total of 604 PWEs who completed cTTE were included in the analysis, of which 265 were diagnosed with RLS. The proportion of RLS was 47.2% in the group of DRE, and the proportion of RLS was 40.3% in the group of non-DRE. Having RLS was associated with DRE in multivariate logistic regression analysis (adjusted OR = 1.53, P = 0.045). In the analysis of blood gas, the partial oxygen pressure in PWEs with RLS was lower than those without RLS (88.74 mmHg versus 91.84 mmHg, P = 0.044).

Right-to-left shunt could be an independent risk factor of DRE, and low oxygenation might be a possible reason.