Heart rate variability predicts outcome in children with pulmonary arterial hypertension

IntroductionObjective risk stratifiers are required to assess need for escalation of medical therapy or listing for transplantation in children with pulmonary arterial hypertension (PAH). We aimed to assess whether heart rate variability (HRV) predicts outcome in children with severe PAH.Patients and methodsParameters of HRV [SDNN = standard deviation of normal-to-normal intervals, SDANN = standard deviation of mean values for normal-to-normal intervals over 5 min, and RMSSD = square root of the mean square differences of successive RR intervals] were determined from Holter electrocardiograms of 47 patients (27 male; mean age 11.4 ± 5.5 years) with PAH (idiopathic PAH n = 21; associated PAH n = 26). HRV was assessed in relation to WHO Functional Class, six-minute-walk-test, echocardiographic and haemodynamic data, and as a predictor of death or lung transplantation.ResultsThe mean follow-up period was 19 ± 11.5 months (1.8–49.1 months). Ten patients died and 7 underwent transplantation and these children had significantly lower values of HRV [SDANN (70.7 ± 30.9 vs. 119.2 ± 57.2), SDNN (79.5 ± 30.5 vs. 129.9 ± 63.6), and RMSSD (22. ± 11.7 vs. 47.7 ± 34.5); p < 0.001 for all]. On univariate Cox-proportional-hazards analysis all parameters of HRV predicted death or transplantation (p < 0.05). SDANN and SDNN were also predictive of mortality alone (p < 0.05). On bivariate analysis SDANN and SDNN predicted outcome independently of functional status, syncope, right ventricular function, and haemodynamic parameters.ConclusionsHRV is a useful, non-invasive means of predicting a poor outcome and hence need to escalate therapy in children with PAH.