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Postural orthostatic tachycardia syndrome (POTS) is a form of autonomic imbalance characterized by abnormally increased heart rate (HR) and various symptoms of orthostatic intolerance (OI). This study aimed to determine POTS in adolescents using NASA 10-minute Lean Test. This crosssectional study was conducted at Government Medical College, Srinagar, J&K, India, between October 2017 and November 2019. Adolescents with symptoms of OI were enrolled for this study and NASA 10-minute Lean Test was performed. Characteristics of POTS group were the compared with non-POTS group. There was a significant difference in BMI (P< 0.0001) between POTS and non-POTS group. However, the number of females with features of POTS was greater than males. There was a significant difference in resting HR between the two groups (P<0.0001). During upright posture there was a significant difference in maximum upright HR between the two groups (P<0.0001), highest increment in upright HR also differed significantly (P<0.0001).POTS group had significantly higher HR than non-POTS group. It may be inferred from this preliminary study that NASA 10-minute Lean Test can be used to diagnose POTS. Introduction Postural orthostatic tachycardia syndrome [POTS] is a form of cardiovascular autonomic imbalance defined by an increased resting heart rate with features of chronic orthostatic intolerance [OI] (1,2). In adolescents, POTS is characterized by an increase in heart rate [HR] ≥ 40 beats/minute [bpm] from the resting HR values in the first 10 minutes upon assuming an upright posture or if the HR remains ≥ 120 bpm in a supine position (3). It is accompanied by symptoms of OI such as lightheadedness, nausea, shortness of breath, diaphoresis, headache, fatigue, cognitive dysfunction usually described as” brain fog” and other features of autonomic imbalance which sometimes may be severe enough to decrease the quality of life (2,4). Typically orthostatic hypotension [OH] is not seen in POTS (3). POTS is seen in all age groups although it is more common in young population especially in premenopausal females with an overall prevalence of 0.21% (5). In adolescents Ac ce pt ed p ap er POTS has been seen to occur at a rate of 6.8% which affects their quality of life (6). POTS has a multifactorial etiology such catecholamine excess, autoimmune disorders, hypovolemia, vaccination, infection and pregnancy (1). In clinical settings tilt-table test remains the gold standard for the diagnosis of POTS (7). To the best of our knowledge this is the first study to use NASA 10-minute Lean Test which is regarded as an equivalent to tilt-table test (8) for the diagnosis of POTS in adolescents Therefore this study was aimed to see whether NASA 10 minute Lean Test can be used to diagnose POTS in adolescents Materials and Methods This observational cross-sectional study was conducted in the Department of Physiology at GMC & SMHS hospital, Srinagar, J&K, India, between October 2017 and November 2019 after obtaining the approval from Institutional Ethical Committee. In this study 200 adolescent subjects, aged 12 to 19 years, were enrolled. A questionnaire was filled by them to report the symptoms of OI. Out of 200 subjects150 reported symptoms of OI. Eventually 150 subjects with symptoms of OI were selected for this study. Participants who had history of smoking, chronic diseases, infectious diseases, head trauma, diabetes mellitus, anemia, psychiatric disorders and intake of drugs affecting autonomic functions were excluded from this study by taking a thorough history. OI was assessed with the help of orthostatic intolerance questionnaire [OIQ] (9) which was filled by all the subjects. They were asked to report to the autonomic function testing laboratory in the Department of Physiology, GMC & SMHS hospital where they were explained the protocol of NASA 10 Minute Lean Testing in detail such as limiting fluid and sodium intake at least 24 hours before testing, not to wear compression socks and withhold medicine that might influence autonomic functions such as β blockers, Midodrine, fludrocortisones, antidepressants and caffeine.. The test was performed in between 9 to 11 am and standardized conditions were maintained throughout the procedure. Anthropometric measurements such as height, weight and BMI were calculated. After that all the Ac ce pt ed p ap er participants were rested in a supine position for at least 10-15 minutes to achieve hemodynamic equilibrium. After 15 minutes of rest in supine position, systolic blood pressure (SBP mmHg), diastolic blood pressure (DBP mmHg) and HR were recorded with the help of a digital sphygmomanometer (OMRON-HEM-7120, Kyoto, Japan). Vitals were again measured 1 minute later. Readings were taken again incase vitals were not similar until two consecutive readings were almost same. This was done to determine true resting vitals. This was followed by asking the participants to stand up and walk to a specified wall and lean against the wall in such a way that only their shoulder blades touched the wall without arching the lower back. In order to avoid the contact of buttocks and wall, subjects were asked to place the heels at a specified mark that was 6 inches away from the wall [Figure 1]. The test began once the subject leaned comfortably against the wall. After 1 minute of passive standing, SBP, DBP and HR were recorded. The whole procedure was repeated every minute for the next 9 minutes. At the end of every minute subjects were told to report symptoms of OI, if any. The whole procedure of NASA 10 minute Lean Test was demonstrated to each subject before the actual commencement of test. Written consent was obtained from all participants or their care-takers and the study was clarified beforehand. Participants had the choice to withdraw from the study at any time. Data was analyzed using GraphPad Prism Version 6 (GraphPad Software, San Diego, CA-92108, USA). Normality of various parameters was determined using D’Agostiono-Pearson omnibus test. Chisquare test with Yates correction was used for variables. Unpaired t-test was used to compare the two groups and for non-parametric data MannWhitney U test was used. Data was expressed in Mean ± Standard Deviation. P value of < 0.05 was considered statistically significant. Results A total of 200 subjects were enrolled out of which 150 reported symptoms of OI by means of a questionnaire that was filled by all the subjects enrolled in this study. Eventually 150 subjects were enrolled for this study. NASA 10-minute Lean Test was performed in all the subjects to assess OI Ac ce pt ed p ap er and POTS. During NASA 10-minute Lean Test the most common symptom reported was light headedness/dizziness (61.3%) which was followed by weakness (52.7%), tremulousness (46.7%), palpitations (46%), blurring of vision (41.3%), shortness of breath (38%), chest pain (30%), increased sweating (19.3%) and pre-syncope /syncope (13.3%) [Table 1]. It was observed that 40 participants fulfilled the criteria of POTS using this test. Characteristics of POTS group were compared with 110 nonPOTS group. There was no significant difference in age (16.29 ± 2.64 years Vs 17.23 ± 1.31 years; P= 0.381) and gender (χ2= 0.679; P= 0.410) of the two groups. BMI of the POTS group was significantly lower than non-POTS group (18.50 ± 0.53 kg/m2 Vs 21.38 ± 0.33 kg/m2; P< 0.0001) [Table 2].After a supine rest of about 10 -15 minutes systolic blood pressure (SBP) , diastolic blood pressure (DBP) and heart rate (HR) were recorded. There was no significant difference between resting SBP (117.7 ± 9.38 mmHg Vs 118 ± 10.47 mmHg; P=0.823) and resting DBP (72.71 ± 7.45 mmHg Vs 73.80 ± 7.91 mmHg; P= 0.657) between the two groups. However, the resting HR of the POTS group was significantly higher (93.94 ± 16.89 bpm Vs 75.66 ± 9.29 bpm; P<0.0001) [Table 2]. In supine position, there was no significant difference between the average SBP (116 ±10.11 mmHg Vs 115 ± 9.16 mmHg; P= 0.531) and average DBP (72.67 ± 8.21 mmHg Vs 72.91 ± 8.72 mmHg; P= 0.814) between the two groups. The average HR was significantly higher in POTS group (92.61 ± 15.32 bpm Vs 75.72 ± 9.01 bpm; P<0.0001) [Table 2]. During the lean test, vitals were recorded at the end of each minute for 10 minutes and average SBP and DBP were calculated. There was no significant difference in average SBP [112 ± 10.11 mmHg Vs 115 ± 9.16 mmHg; P= 0.531] and DBP [ 70.81 ± 11.21 mmHg Vs 71.10 ± 9.73; P=0. 645] of 10 minutes between the two groups. It was observed that highest rise in HR (133.6 ± 14.27 bpm Vs 91.67 ± 9.94 bpm; P< 0.0001) and the maximum increase in HR (40.91 ± 11.78 bpm Vs 16.34 ± 6.97 bpm; P< 0.0001) were significantly higher in POTS group [Table 2]. Discussion POTS is a form of dysautonomia characterized by an exaggerated HR and various symptoms of OI Ac ce pt ed p ap er in the absence of OH (10,11).POTS can occur in any age group however; it is more common in people aged 15-50 years predominantly in females as compared to males with a ratio of 4:1 which may be attributed to the dilation of vessels caused by female sex hormones (12,13). Symptoms of OI such as lightheadedness, chest pain, blurring of vision and palpitations are usually seen in POTS. These symptoms arise as a result of decreased venous return, reduced cardiac output and hypoperfusion (13). POTS has an abrupt onset with a multifactorial etiology and has negative impact on quality of life so its timely diagnosis is important especially in young population (13,14).In clinical settings, POTS is commonly diagnosed by a head-up tilt table test [HUTT] which is considered as gold standard for its diagnosis (1,5).In this study a simple, bedside and passive standing test called NASA 10-minute Lean Test was used to evaluate POTS. This test was basically used by NASA researchers to assess symptoms of OI in astronauts. Since it is a passive test, it reduces muscular impact on venous return. This test has been ratified as an equiv

Role of NASA 10-minute Lean Test in diagnosing postural orthostatic tachycardia syndrome: a preliminary study in young population