Abnormal Cardiac Electrical Remodelling in POTS: Mechanistic Insights on Potential Autonomic Dysregulation

Abstract

Background: Postural Orthostatic Tachycardia Syndrome (POTS) is a syndrome characterised by dysautonomia. It remains unknown if POTS individuals have abnormal cardiac electrical changes. Here we assessed electrocardiographic markers of interatrial and ventricular conduction delay in POTS compared to patients with vasovagal syncope (VVS). Methods: Patients who met diagnostic criteria for POTS by tilt table test and free of other autonomic or structural heart disease were compared to VVS patients. 12 lead ECGs taken pre-treatment were digitised (minimum 8 good-quality signals) and analysed by a cardiologist blinded to treatment. P wave and RT dispersion (PWD, RTD) were calculated (maximum – minimum P wave/RT interval duration). Peak of T to end of T wave (TpTe), a marker of transmural dispersion of ventricular repolarisation, also sensitive to sympathetic stimulation, was measured in lead II. Results: 11 POTS patients were compared to 9 age and sex - matched VVS patients. Mean age was similar. Atrial volumes and left ventricular ejection fraction (LVEF) were normal in all patients. There was no difference in LVEF. POTS was associated with abnormal PWD (48 ± 5, normal <38 ms) and higher RTD (66 ± 7 ms); compared to VVS (31 ± 4; P = 0.02 and 46 ± 6 ms; P = 0.04), despite lower left atrial volume. Baseline TpTe did not differ. Conclusion: Compared to VVS, POTS is associated with both longer PWD (above normal limits) and increased RTD, whilst TpTe did not differ, despite systemic sympathetic predominance. Further clinical studies are warranted to assess the relative role of subclinical cardiac structural remodeling and impaired cardiac autonomic nervous system function.