Audiological evaluation and associated clinical characteristics of hearing impairment in young infants with congenital cyanotic heart disease: a cross-sectional study

Abstract Background Infants with congenital cyanotic heart disease (CCHD) are at increased risk of click-ABR-defined hearing impairment due to chronic hypoxemia, altered hemodynamics, and exposure to ototoxic medications associated with intensive medical care, although infants with documented ototoxic exposure were excluded from the present study. Early detection of auditory dysfunction is essential to prevent long-term developmental delays. This study aimed to determine the prevalence of hearing impairment before cardiac surgery and its associated clinical factors in infants with CCHD. Methods This cross-sectional study included 51 infants aged 6–24 months with CCHD at the Pediatric Cardiology and Audiology Units of Tanta University Hospital. Audiological assessment included otoscopy, tympanometry, and auditory brainstem response (ABR). Hearing impairment detected by ABR was classified as unilateral or bilateral, with severity graded as normal (≤ 30 dBnHL), mild (31–40 dBnHL), or moderate-to-severe (≥ 41 dBnHL) based on the wave V threshold. Results The mean age was 14.9 ± 4.96 months, and 26 (51%) were female. Tetralogy of Fallot (37.3%) and transposition of the great arteries (33.3%) were the most frequent diagnoses. Bilateral normal click-ABR thresholds were observed in 29 infants (56.9%), whereas 22 (43.1%) demonstrated click-ABR wave V threshold elevations > 30 dBnHL on single-assessment testing, including bilateral elevations in 10 (19.6%) and unilateral elevations in 12 (23.5%). Mean ABR wave V thresholds were 36.5 ± 10.7 dBnHL in the left ear and 35.5 ± 10.6 dBnHL in the right ear. Only four infants (7.8%) had moderate-to-severe bilateral threshold elevations (≥ 41 dBnHL). Lower baseline oxygen saturation (SpO₂) was independently associated with click-ABR-defined threshold elevation on multivariable analysis (OR = 0.534, 95% CI: 0.367–0.776, p = 0.001). Conclusion Hearing impairment identified by click-evoked ABR was relatively common in infants with CCHD, predominantly mild and often unilateral. Lower measured baseline SpO₂ was associated with click-ABR-defined hearing impairment; however, this finding should be interpreted cautiously given the variability of oxygen saturation measurements and the chronic hypoxemia characteristic of CCHD. The observed association does not establish a clinically meaningful oxygen saturation threshold or a causal relationship between hypoxemia and hearing impairment. Larger prospective longitudinal studies using repeated or continuous measures of oxygenation are needed to clarify the relationship between chronic hypoxemia and auditory function. Preoperative audiological evaluation using ABR may facilitate early detection and timely intervention in this high-risk population.