Impact of the Right Ventricular Sokolow–Lyon Index in Children with Idiopathic Pulmonary Arterial Hypertension

Right ventricular (RV) hypertrophy is regarded as the adaptation on chronic RV pressure load in pulmonary hypertension. As the RV Sokolow–Lyon index (RVSLI) is an electrocardiographic marker of RV hypertrophy, we hypothesized that RVSLI might be able to reflect RV pressure load. Therefore, the purpose of this study was to characterize the diagnostic impact of the RVSLI in children with idiopathic pulmonary arterial hypertension (IPAH) in order to assess disease severity and to evaluate its value for the prediction of worse outcome. Forty-two children (aged 3–17 years) with IPAH were included in this retrospective study. The follow-up after baseline examination was 59 ± 17 months. Receiver-operating characteristic (ROC) curves and Kaplan–Meier analysis were used to discriminate a cut-off value of RVSLI and to assess its predictive value regarding morbidity and mortality. In 12/42 patients (29%) severe cardiovascular events (defined as death, lung transplantation, or Potts shunt) were observed (time to event 20 ± 22 months). Patients with an event showed higher RVSLI values (3.6 ± 1.2 mV vs. 2.6 ± 1.6 mV; p < 0.05). ROC analysis discriminated an RVSLI of 2.1 as the best cut-off value (area under the ROC curve: 0.79, sensitivity: 0.91, specificity: 0.70, p < 0.05) to detect patients with high-risk PAH (mPAP/mSAP ratio > 0.75). Relative risk for a severe event with an index > 2.1 mV was 1.76 (95% CI 1.21–3.20). Relative risk for death with RVSLI > 2.1 mV was 2.01 (95% CI 1.61–4.80). Our study demonstrates a strong relationship between RVSLI and disease severity in children with IPAH. An RVSLI > 2.1 mV at the time of first diagnosis is a predictor for patients at risk for cardiac events. As an adjunct to the usual diagnostic assessment this parameter may therefore contribute to the initial prognostic estimation.