In this post, I link to and excerpt from Passive standing tests for the office diagnosis of postural tachycardia syndrome: New methodological considerations [Abstract] [Full-Text HTML] [Full-Text PDF]. Published online: 25 Aug 2018
All that follows is from the above resource.
Background: Passive standing tests are a first-line, practical means of assessing individuals with chronic orthostatic symptoms.
Purpose: To identify the proportion reaching heart rate (HR) criteria for postural tachycardia syndrome (POTS) during a 10-minute passive standing test (PST) if measurement of the lowest supine HR incorporated a 2-minute period of post-test monitoring, rather than being restricted to the 5-minute pre-test values only, and to determine the proportion whose POTS would be missed by shorter periods upright.
Methods: Consecutive individuals ≥ 12 years from 2008 to 2017 who presented with chronic fatigue or lightheadedness and whose PST met criteria for POTS.
Results: Of the 93 enrolled (70% female, median age 17 years), the mean (SD) HR was higher in the 5 min supine before the 10 min upright than in the 2 min supine afterwards (67.6 [10.0] vs. 65.7 [10.9]; P = 0.01). Thirteen (14%; 95% CI, 7–21%) satisfied HR criteria for POTS using the supine HR from only the post-test period. The median time to reaching the HR criteria for POTS was 3 min. Of those reaching HR criteria, 53% (95% CI, 43–63%) would be missed by a 2-minute and 27% (95% CI, 19–37%) by a 5-minute test.
Interpretation: More adolescents and young adults are diagnosed with POTS during a 10-minute PST when the definition of their lowest supine HR includes a 2-minute post-test measurement along with the conventional pre-test measure. A full 10 min of standing is required to avoid underdiagnosing POTS in both clinical and epidemiologic studies.
- Postural tachycardia syndrome
- orthostatic intolerance
- myalgic encephalomyelitis
- chronic fatigue syndrome
Postural tachycardia syndrome (POTS) is a relatively common circulatory condition, estimated to affect 0.1–1% of the population , disproportionately affecting women in the adolescent and young adult age range [1–3]. POTS can be associated with a variety of clinical syndromes including myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS)  and Ehlers-Danlos syndrome [5,6]. The diagnosis of POTS requires an exaggerated increase in heart rate (HR) from supine to standing of at least 30 beats per minute for adults (20 years of age or older), or at least 40 bpm for adolescents over the course of 10 min upright, in the absence of orthostatic hypotension during the first 3 min . The diagnosis also requires the presence of chronic orthostatic symptoms such as fatigue, lightheadedness, blurry vision, weakness, cognitive difficulties, and nausea [1–3,8–10].
Eligible participants: We included consecutive patients age 12 years and older who were referred to the Johns Hopkins Chronic Fatigue Clinic for evaluation of chronic fatigue or orthostatic intolerance from 10/28/2008 to 11/17/2017, provided the passive standing test on their initial clinic visit was consistent with a diagnosis of POTS. We excluded individuals who (a) had undergone a head-up tilt table test or a standing test elsewhere under different conditions, (b) were already being treated for orthostatic intolerance, and (c) developed neurally mediated hypotension (NMH) during the standing test.
Exclusions a and b were intended in part to explore the hypothesis that the pre-test HR was higher due to apprehension about a new maneuver. Individuals whose other co-morbid conditions were being treated with selective serotonin-reuptake inhibitors (SSRI) or serotonin–norepinephrine re-uptake inhibitors (SNRI) for anxiety, mood, or pain, with oral or transdermal contraceptives or medroxyprogesterone for menstrual disorders or birth control, and stimulants for attention deficit disorder were included in the study. Exclusion c was based on the tendency for those with NMH to develop a cardio-inhibitory response at the time of hypotension, which would have caused an excessive reduction in the post-test supine HR that was not representative of the individual’s usual supine HR.
Definitions: We used the 2011 consensus definition of POTS, which requires an increase in HR during a maximum of 10 min of standing of at least 30 beats per minute (bpm) in those greater than 19 years and at least 40 bpm in adolescents 12–19 years, compared to the lowest value recorded during the supine period . We diagnosed POTS only if there was no orthostatic hypotension within the first 3 min of upright posture, and only if there was a history of chronic orthostatic symptoms such as fatigue, lightheadedness, exercise intolerance, or cognitive dysfunction. Florid POTS was defined as a peak HR ≥ 120 bpm. For the purposes of this study, the lowest supine HR used in the calculation of the HR increment from supine to peak standing could be recorded during either the 5 min supine before standing or the 2 min supine after the completion of 10 min standing.
The main comparison of interest for each subject for study objective 1 was the difference between the peak HR during 10 min of standing and either the lowest HR in the 5 min of supine posture before the test or the lowest HR in the 2 min supine after the completion of the standing test.
At the time of the standing test, no participant was being treated with any of the following for orthostatic intolerance: fludrocortisone, clonidine, midodrine, droxidopa, beta adrenergic antagonists, pyridostigmine bromide, disopyramide, angiotensin converting enzyme inhibitors, angiotensin receptor antagonists, desmopressin acetate, octreotide, ivabradine, or intravenous volume expansion. Thirty-five participants were being treated with a combination of (a) SSRI or SNRI medications for anxiety, depression, or pain (N = 21), (b) oral contraceptives or medroxyprogesterone for menstrual disorders or contraceptive purposes (N = 14), and (c) stimulants for attention deficit disorder (N = 7). The remaining 58 participants were not receiving any of the medications mentioned above.
Measuring the supine HR for 2 min after a PST improves detection of POTS
Our data show that the supine HR before a 10-minute standing test was significantly higher than the post-test supine HR. In the full sample, an additional 14% more adolescents and young adults were categorized as having POTS when the definition of their lowest supine HR included a brief 2-minute post-test measurement along with the conventional pre-test measure. The 95% confidence interval around that estimate suggests that between 9 and 21% more individuals would be classified as having POTS by incorporating the post-test supine HRs in the calculation of the increment between the supine and standing HR. For the medication-naïve group, an additional 21% (95% CI, 10–31%) would meet criteria for POTS.
Several comments about the study methods are germane. We elected to exclude individuals who developed a neurally mediated drop in blood pressure during the PST because the relative bradycardia after a vaso-vagal event would not be representative of the true baseline supine HR. Including patients who developed a cardio-inhibitory response would have had the potential to over-diagnose and mis-categorize individuals as having POTS.
…, it is unclear whether the participants in this study are representative of all adolescents and young adults with POTS, as they were being evaluated in a tertiary care chronic fatigue clinic. In pediatric and adult studies, individuals with ME/CFS and POTS have a greater symptom burden than those with POTS alone [21,22]. Confirmation of the same pattern of response in cardiology or neurology clinics would help define whether the phenomena we report are generally present in everyone with POTS or are more common in those with a prominent degree of fatigue.