Abstract 18128: How Long Should We Tilt?: Challenging the 10-Minute Cutoff in the Diagnosis of Postural Tachycardia Syndrome (POTS)

Abstract

Background: Postural tachycardia syndrome (POTS) is defined by symptoms of orthostatic intolerance (OI) that correlate with an orthostatic tachycardia response. Current diagnostic criteria require a sustained increase in HR by ≥30 bpm [accentuated postural tachycardia (APT)], without a concurrent BP drop, within 10 minutes of standing or head-up tilt testing (HUTT). In many centers, the HUTT duration is predetermined to be 10 mins. However, many patients may exhibit APT after this cutoff. Research Question: How many patients with symptoms consistent with POTS demonstrate APT during HUTT after the 10-min cutoff, and what factors influence onset time? Methods: Using a cohort of 255 patients with OI, we characterized the temporal distribution of APT onset time during 45-minute HUTT at our referral center. We used multivariate linear regression to identify predictors influencing onset time, and plotted Kaplan-Meier failure function stratified by predictors. Results: The cohort's mean age was 33 years, 91% were female, 16% were obese, 13% had hypertension, 1.6% had diabetes, and 26% were smokers. Mean APT onset time was 17.5 mins (SD 10), and median onset time was 13 mins (IQR 11-22). About 15% had APT onset within 10 min, 60% in 15 mins, 75% in 20 mins, 90% in 30 mins, and 95% in 40 mins. Increasing age and BMI were associated with later APT onset time, whereas sex, diabetes, hypertension, and smoking were not influential Conclusion: The 10-min cutoff captured only 15% of patients with APT; extending the cutoff just 5 minutes longer captured an additional 60% patients. Our findings suggest that the current 10-min cutoff for POTS diagnosis is likely too restrictive, as a significant proportion of patients exhibit APT after this period but otherwise fit the clinical scenario of POTS. Increasing age particularly ≥40 yrs, and obesity were associated with a later APT response. Future definitions should consider extending the testing duration and cutoff time in the evaluation of POTS.