QT interval in children with sensory neural hearing loss

Long QT syndrome was first described in children with congenital sensory neural hearing loss (SNHL). The deafness was attributed to abnormalities in potassium ion channels of the inner ear. Similar channels are present in the heart and its dysfunction causes long QT syndrome. Whether congenital SNHL is associated with prolonged QT is unknown. This study examined 52 patients (median age 8.35 years, range 0.21-17.42 years) with SNHL and compared them to 63 healthy children (median age 10.2 years; range 0.67-19 years). An observer, who was blinded from the presence or absence of SNHL, measured QT, QTc intervals and dispersions from a standard 12-lead electrocardiogram. To assess the cardiac autonomic enervation, power spectral analysis of heart rate variability was determined using a 24-hour ambulatory heart rate monitor and was expressed as high (HF) to low frequency (LF) ratio. Left ventricular size and functions were evaluated by using two-dimensional echocardiography. The medians (and ranges) of QT intervals were 340 ms (230-420 ms) in patients and 320 ms (240-386 ms) in the control group (P < 0.01). The QTc was longer in patients with SNHL (median 417 ms, range 384-490 ms) than in controls (median 388 ms, range 325-432 ms, P < 0.001). QT dispersions in SNHL were higher (median .038 ms, range 00-11 ms) than controls (median 27 ms, range 00-52 ms, P < 0.001). T wave inversion (n = 16) and alternans (n = 3) occurred in patients with SNHL. Heart rates were similar in both groups. Some deaf patients (n = 8) had dizzy episodes with a QTc > 440 ms. The HF:LF ratio was 1.32 (0.516-2.33) in deaf patients and 1.428 (0.67-2.3) in the control group (P > 0.1). Left ventricular size and functions were similar and normal in deaf patients and controls. In children, congenital SNHL is associated with a prolonged QT interval.