Passive standing tests for the office diagnosis of postural tachycardia syndrome: New methodological considerations

Figures & data

Figure 1. The derivation of the study sample.

Figure 2. The correlation of paired pre-test and post-test supine heart rates for the full sample of 93 participants (Figure 2(a)) and the medication-naïve subset of 58 (Figure 2(b)).

Table 1. Demographic and heart rate values during the standing test by HR group*.

	Group 1	Group 2	Group 3	ANOVA
a. Full sample
(N = 93)	(N = 10)	(N = 70)	(N = 13)
Demographic
Median age (years)	16.5	17	15
Female (%)	60%	70%	77%
Heart rate variables
Pre-test supine HR	62.8 (12.2)	67.3 (9.7)	73.0 (8.5)	F (2, 90) = 3.2; P = 0.045; Post-hoc tests: Group 3 vs 1: P = 0.046; 3 vs 2: P = 0.17; 2 vs 1: P = 0.54
Peak HR standing	103.5 (12.9)	114.5 (12.5)	107.6 (8.7)	F (2, 90) = 4.8; P = 0.01; Post-hoc tests: Groups 2 vs 1: P = 0.03; 3 vs 2: P = 0.19; 3 vs 1: P = 1.00
Mean HR increase‡	40.7 (3.7)	50.7 (7.8)	43.4 (7.6)	F (2, 90) = 11.5; P < 0.001; Post-hoc tests: Group 2 vs 1: P < 0.001; 2 vs 3: P = 0.005; 1 vs 3: P = 1.00
Post-test supine HR	71.6 (10.3)	65.1 (11.5)	64.2 (6.9)	F (2, 90) = 1.7; P = 0.19
b. Medication-naive sample
(N = 58)	(N = 8)	(N = 38)	(N = 12)
Demographic
Median age (years)	16.5	16	15
Female (%)	63%	68%	75%
Heart rate variables
Pre-test supine HR	61.3 (13.0)	66.1 (10.2)	72.3 (8.4)	F (2, 55) = 3.00; P = 0.06; Post-hoc tests: Group 3 vs 1: P = 0.06; 3 vs 2: P = 0.23; 2 vs 1: P = 0.65
Peak HR standing	101.3 (13.3)	113.6 (11.8)	106.6 (8.2)	F (2, 55) = 4.8; P = 0.01; Post-hoc tests: Group 2 vs 1: P = 0.02; 2 vs 3: P = 0.20; 1 vs 3: P = =0.93
Mean HR increase‡	40.1 (4.0)	51.4 (7.3)	43.0 (7.8)	F (2, 55) = 12.4; P < 0.001; Post-hoc tests: Group 2 vs 1: P < 0.001; 2 vs 3: P = 0.002; 1 vs 3: P = 1.00
Post-test supine HR	70.0 (10.7)	63.4 (12.1)	63.6 (6.8)	F (2, 55) = 1.2; P = 0.31

*Group 1: met HR criteria for POTS using the pre-test supine HR only; Group 2: met HR criteria for POTS using either the pre-test or the post-test supine HR data (the lowest of these two supine measures was used to calculate the HR increase); Group 3: met HR criteria for POTS using the post-test supine HR only.

‡Mean HR increase = peak HR standing minus lowest HR supine.

Table 2. Proportions reporting increased orthostatic symptoms during 10 min of passive standing.

	Full	Medication-naïve
	sample	sample
	(N = 93)	(N = 58)
Symptoms	%	%
Lightheadedness	72	69
Fatigue	57	50
Pain	41	43
Warmth	40	31
Dyspnea	33	31
Cognitive difficulties	28	24
Headache	27	29
Nausea	20	14
Paresthesias	18	19
Anxiety	13	9
Visual disturbances	12	7
Sweating	11	10
Heaviness in limbs	10	10
Limb pruritus	9	12
Muscle weakness	8	10
Chest discomfort	7	9

Figure 3. Survival curves illustrating the time during the standing test at which point the HR criteria for POTS could be confirmed for those in the full sample (Figure 3(a)) or the medication-naïve subset (Figure 3(b)).

Table 3. Proportion of POTS diagnoses that would be missed at each minute of an abbreviated standing test (full sample, N = 93).

Minutes upright	POTS diagnoses missed at each minute
%	(95% CI)
1	70 (60–78)
2	53 (43–63)
3	43 (33–53)
4	37 (27–47)
5	27 (19–37)
6	24 (16–33)
7	15 (9–24)
8	10 (5–17)
9	5 (2–12)
10	0