Diagnosing postural tachycardia syndrome: comparison of tilt testing compared with standing haemodynamics

Abstract

Postural tachycardia syndrome (POTS) is characterized by increased heart rate (ΔHR) of ≥30 bpm with symptoms related to upright posture. Active stand (STAND) and passive head-up tilt (TILT) produce different physiological responses. We hypothesized these different responses would affect the ability of individuals to achieve the POTS HR increase criterion. Patients with POTS (n=15) and healthy controls (n=15) underwent 30 min of TILT and STAND testing. ΔHR values were analyzed at 5 min intervals. Receiver Operating Characteristics analysis was performed to determine optimal cut point values of ΔHR for both TILT and STAND. TILT produced larger ΔHR than STAND for all 5 min intervals from 5 min (38±3 bpm vs. 33±3 bpm; P=0.03) to 30 min (51±3 bpm vs. 38±3 bpm; P<0.001). Sensitivity (Sn) of the 30 bpm criterion was similar for all tests (TILT-10=93%, STAND-10=87%, TILT30=100%, and STAND30=93%). Specificity (Sp) of the 30 bpm criterion was less at both 10 and 30 min for TILT (TILT10=40%, TILT30=20%) than STAND (STAND10=67%, STAND30=53%). The optimal ΔHR to discriminate POTS at 10 min were 38 bpm (TILT) and 29 bpm (STAND), and at 30 min were 47 bpm (TILT) and 34 bpm (STAND). Orthostatic tachycardia was greater for TILT (with lower specificity for POTS diagnosis) than STAND at 10 and 30 min. The 30 bpm ΔHR criterion is not suitable for 30 min TILT. Diagnosis of POTS should consider orthostatic intolerance criteria and not be based solely on orthostatic tachycardia regardless of test used.

Fludrocortisone for the Prevention of Vasovagal Syncope

“…Patients were excluded if they had other causes of syncope; could not provide informed consent; had significant comorbidities, a permanent pacemaker, glaucoma, diabetes mellitus, hepatic disease, blood pressure (BP) $130/85 mm Hg, or had a clinical need for or contraindication to fludrocortisone; or had previously used fludrocortisone for the treatment of vasovagal syncope. Patients were excluded if, during a 5-min stand test, they had postural tachycardia (15) (heart rate increase $30 beats/min) or orthostatic hypotension (BP decrease $20/10 mm Hg). Patients were randomized in syncope and arrhythmia clinics, and each center completed a screening log of eligible, nonrandomized patients.…”

Autonomic function testing: an important diagnostic test for patients with syncope

“…When actively standing, there is compression on the lower extremity veins that results in increasing venous return to the heart: the so-called ‘skeletal muscle pump’ 15. Unlike the tilt table test, which is a passive transition from supine to upright, the active stand involves these physical compensatory manoeuvres of muscle contraction and more realistically simulates a patient's daily movements.…”

Autonomic Dysfunction in Dizziness Clinic

“…The timing of heart rate increment is either not mentioned [7] or defined within 5 minutes [8] or within 10 minutes or longer [9] of the upright posture. Early description of POTS also required the absolute heart rate 120 BPM or more, while the heart rate below 120 during the tilt test was termed as mild orthostatic intolerance [8].…”