Prevalence and extent of right-to-left shunt on contrast-enhanced transcranial Doppler in patients with chronic hyperventilation syndrome: results of a case-control study.

AIM

Chronic hyperventilation syndrome (CHVS) represents a frequent but poorly understood breathing pattern disorder. In a previous small pilot study, we reported a higher prevalence of right-to-left shunt (RLS) in CHVS patients than in healthy subjects. The aim of this study was to confirm those previous results from this larger and matched case-control study, and to evaluate the prevalence and grade of RLS in patients with CHVS in whom organic and psychiatric causes were excluded.

CLINICAL RATIONALE FOR THE STUDY

Determining other types of CHVS triggers not related to organic or psychiatric causes which could be clinically useful.

MATERIAL AND METHODS

100 subjects (mean age 34 ± 6 years; 80% females), including 50 patients with CHVS and 50 age- and sex-matched healthy controls (CG), were prospectively recruited into this single-centre study. Vascular RLS was diagnosed using contrast-enhanced transcranial Doppler (c-TCD).

RESULTS

RLS prevalence significantly increased in the CHVS group (n = 23) compared to the CG group (n = 8) (46% vs 16%; p < 0.01). Patients with CHVS and RLS tended to have more frequent permanent shunts compared to the CG (60% vs 25%; p = 0.08), but there was no difference regarding RLS grading between the groups.

CONCLUSIONS AND CLINICAL IMPLICATIONS

This study confirmed our previous findings in which the prevalence of RLS in patients with CHVS was significantly higher than in an age- and sex-matched healthy control group. However, we could not confirm the results of our prior study, where RLS was larger in CHVS than in CG. The tentative association between RLS and CHVS needs to be further examined.