Heart rate and heart rate variability comparison between postural orthostatic tachycardia syndrome versus healthy participants; a systematic review and meta-analysis.

Abstract

Background A number of published literatures have reported that, physiologically, heart rate variability in patients with postural orthostatic tachycardia (POTS) to be greatly confounded by age, sex, race, physical fitness and circadian rhythm. The purpose of this study was to compare between postural orthostatic tachycardia syndrome (POTS) patients versus healthy patients, in terms of heart rate (HR) and heart rate variability (HRV) after Head-Up tilt test, by systematic review and meta-analysis of available published literature.Methods MEDLINE (using PubMed interphase), EMBASE and SCOPUS were systematically searched for observational studies comparing between POTS patients versus healthy patients, in terms of heart rate (HR) and heart rate variability (HRV). HRV was grouped into Time and frequency domain outcome measurements. Time domain was measured as mean RR- interval and mean square root of mean of squares of successive R-R waves (rMSSD) in milliseconds. Frequency domain was measured as mean values of Low frequency power (LF), High frequency power (HF), LF/HF-ratio, LF-normalized units (LF(n.u)) and HF-normalized units (HF(n.u)). Demographic data, comorbidities, and mean values of HR, RR- interval, rMSSD, LF, HF, LF/HF-ratio, LF-(n.u) and H.F-n.u were extracted from each group and compared, by their mean differences as overall outcome measure. Computer software, RevMan 5.3 was utilized, at 95% significance level.Results Twenty (20) eligible studies were found to report 717 POTS and 641 healthy participants. POTS group had higher mean heart rate (p<0.05), lower mean RR-Interval (p<0.05), lower rMSSD (p<0.05) than healthy participants. Furthermore, POTS group had lower mean HF(p>0.05), lower mean LF(p>0.05), and lower mean HF(n.u) (p>0.05), higher LF/HF-Ratio (p>0.05) and higher LF(n.u) (p>0.05) as compared to healthy participants.Conclusion Despite massively supported fact that POTS patients have higher heart rate than healthy patients after HUTT, POTS patients have lower heart rate variability in terms of time domain measure but not in terms of frequency domain measure.