Int J Clin Pract. 2017;71:e12949. wileyonlinelibrary.com/journal/ijcp | 1 of 9 https://doi.org/10.1111/ijcp.12949 © 2017 John Wiley & Sons Ltd Received: 30 September 2016 | Accepted: 12 March 2017 DOI: 10.1111/ijcp.12949 ORIGINAL ARTICLE Age- and sex-based reference ranges for non-invasive ventricular repolarisation parameters Annabella Braschi 1 | Maurizio G. Abrignani 2 | Vincenzo C. Francavilla 1 | Vincenzo Abrignani 3 | Giuseppe Francavilla 1 1 Department of Internal and Specialistic Medicine, Palermo University Hospital, Palermo, Italy 2 Operative Unit of Cardiology, S. Antonio Abate Hospital, Trapani, Italy 3 University of Bologna, Medicine and Surgery School, Bologna, Italy Correspondence Annabella Braschi, Department of Internal and Specialistic Medicine, Palermo University Hospital, Palermo, Italy. Email: annabellabraschi@alice.it Summary Background: Some electrocardiographic parameters are able to assess indirectly ven- tricular repolarisation homogeneity. It is consequently essential to discriminate be- tween normal and abnormal values in clinical decision-making. Considering there is still not a consensus about normal cut-off values, the aim of this study was to docu- ment reference intervals in all age groups of a healthy population, providing for age- and sex-percentile tables, which can be used easily and quickly in clinical practice. Methods: We evaluated repolarisation markers in 606 sex-matched participants aged 1 day–94 years. Each subject underwent a 12-lead electrocardiogram at rest, and the following parameters were measured: QT, corrected QT, QTpeak, Tpeak-Tend, Tpeak- Tend dispersion, Tpeak-Tend/QT and QTpeak/QT ratio. Results: A relationship was demonstrated between age and QTpeak, Tpeak-Tend, QT and QTc. In children, QTpeak, Tpeak-Tend and QT intervals increased linearly with age. In adolescents, all the three parameters remained stable. In adults, QTpeak and QT showed a further significant increase. On the contrary, Tpeak-Tend interval was longer in adults aged between 20 and 64 years than in participants aged 65 years or over, but the difference was not statistically significant. Male vs female participants showed longer Tpeak-Tend intervals; this sex difference was not statistically signifi- cant at birth and during childhood, whereas it was in adolescents and in adults. Conclusions: Repolarisation parameters showed age- and sex-based variations, which are important to know to differentiate normal from pathological values. 1 | INTRODUCTION Human ventricular wall comprises three electrophysiologically and functionally distinct cell types: epicardial, mid-myocardial and endo- cardial cells, with M cells showing the longest action potential (AP) duration; the intrinsic differences in AP duration lead to a transmu- ral repolarisation heterogeneity among the layers. 1 In pathological conditions, transmural electrical differences in APs are amplified, with the consequent higher dispersion of repolarisation across the ventricular wall and the increased vulnerability to ventricular arrhythmias. 2 Dispersion of ventricular repolarisation (DVR) can be assessed non-invasively using a 12-lead surface electrocardiogram (ECG). It has, in fact, been demonstrated, by means of monophasic action poten- tials recordings, that some electrocardiographic variables involving the terminal part ofQT, such as theTpeak-Tend (Tpe) interval, reflect indirectly DVR. 3 Tpe interval in precordial leads, its dispersion and its ratio with QT in V5 have been suggested to provide an indirect and non-invasive assessment of repolarisation heterogeneity, and they have been eval- uated in many cardiac and systemic diseases such as Brugada syn- drome, long and short QT syndrome, hypertrophic cardiomyopathy,