Reduced Systolic Volume: Main Pathophysiological Mechanism in Patients with Orthostatic Intolerance?

Távora-Mehta, Maria Zildany P.; Mehta, Niraj; Magajevski, Adriano; Oliveira, Larissa de; Maluf, Débora Lee Smith; Concato, Letícia; Doubrawa, Eduardo; Ortiz, Márcio Rogério; Cunha, Cláudio L. Pereira da

doi:10.5935/abc.20160135

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Original Articles, Tilt Test • Arq. Bras. Cardiol. 107 (4) • Oct 2016 • https://doi.org/10.5935/abc.20160135 copy

Reduced Systolic Volume: Main Pathophysiological Mechanism in Patients with Orthostatic Intolerance?

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

Background:

Orthostatic intolerance patients' pathophysiological mechanism is still obscure, contributing to the difficulty in their clinical management.

Objective:

To investigate hemodynamic changes during tilt test in individuals with orthostatic intolerance symptoms, including syncope or near syncope.

Methods:

Sixty-one patients who underwent tilt test at - 70° in the phase without vasodilators were divided into two groups. For data analysis, only the first 20 minutes of tilting were considered. Group I was made up of 33 patients who had an increase of total peripheral vascular resistance (TPVR) during orthostatic position; and Group II was made up of 28 patients with a decrease in TPVR (characterizing insufficient peripheral vascular resistance). The control group consisted of 24 healthy asymptomatic individuals. Hemodynamic parameters were obtained by a non-invasive hemodynamic monitor in three different moments (supine position, tilt 10' and tilt 20') adjusted for age.

Results:

In the supine position, systolic volume (SV) was significantly reduced in both Group II and I in comparison to the control group, respectively (66.4 ±14.9 ml vs. 81.8±14.8 ml vs. 101.5±24.2 ml; p<0.05). TPVR, however, was higher in Group II in comparison to Group I and controls, respectively (1750.5± 442 dyne.s/cm⁵ vs.1424±404 dyne.s/cm⁵ vs. 974.4±230 dyne.s/cm⁵; p<0.05). In the orthostatic position, at 10', there was repetition of findings, with lower absolute values of SV compared to controls (64.1±14.0 ml vs 65.5±11.3 ml vs 82.8±15.6 ml; p<0.05). TPVR, on the other hand, showed a relative drop in Group II, in comparison to Group I.

Conclusion:

Reduced SV was consistently observed in the groups of patients with orthostatic intolerance in comparison to the control group. Two different responses to tilt test were observed: one group with elevated TPVR and another with a relative drop in TPVR, possibly suggesting a more severe failure of compensation mechanisms.

Keywords:
Orthostatic Intolerance/physiopathology; Stroke Volume; Vascular Resistance; Postural Orthostatic Tachycardia Syndrome/physiopathology

Variable	Group	Nº	Mean	Median	Minimum	Maximum	Standard Deviation	p value^* * ANOVA with p<0.05 factor
	I	33	56.2	58.0	18.7	90.2	16.9
	II	28	57.4	61.6	16.2	86.9	22.6
	Control	24	27.6	28.5	17.0	39.0	6.2	<0.001
Height (cm)	I	33	165.5	165.0	150.0	182.0	7.8
	II	28	168.4	168.5	151.0	190.0	8.9
	Control	24	170.2	169.0	152.0	192.0	10.9	0.161
Weight (kg)	I	33	70.6	71.0	47.0	110.0	12.6
	II	28	75.3	75.0	50.0	109.0	15.4
	Control	24	71.5	68.5	49.0	118.0	15.5	0.433
Body mass index	I	33	25.7	26.1	18.4	33.2	3.4
(kg/m²)	II	28	26.6	26.3	18.8	36.0	5.1
	Control	24	24.4	24.2	20.1	32.0	3.0	0.157
Body surface (cm²)	I	33	1778.0	1765.0	1462.0	2304.0	182.2
	II	28	1845.6	1853.0	1467.0	2283.0	196.5
	Control	24	1739.3	1757.0	642.0	2468.0	361.0	0.298

	Group I (I)	Group II (II)	Control (C)	p value (IxIIxC)	p value (IxII)	p value (I x C)	p value (II x C)
HR Supine^* * p value adjusted for age (ANCOVA) (bpm) HR (tilt 10')^* * p value adjusted for age (ANCOVA) (tilt 20')^* * p value adjusted for age (ANCOVA)	69.5±11 78.3±13.0 81.6±13.5	70.0±11.7 80.3±15.2 84.7±15.9	70.4±9.7 87.2±11.9 84.7±15.9	0.63 0.75 0.51	- - -	- - -	- - -
MBP Supine^* * p value adjusted for age (ANCOVA) (mmHg) MBP (tilt 10')^* * p value adjusted for age (ANCOVA) (tilt 20')^* * p value adjusted for age (ANCOVA)	96.6±11.4 105.6±10.6 103.4±12.2	97.7±15.7 99.4±15.3 94.7±12.5	84±8.7 102.1±10.0 98.9±9.1	0.13 0.13 0.01	- - 0,005	- - 0,15	- - 0,19
SV Supine^* * p value adjusted for age (ANCOVA) (ml) SV (tilt 10')^* * p value adjusted for age (ANCOVA) (tilt 20')^* * p value adjusted for age (ANCOVA)	81.8±14.8 65.5±11.3 61.4±8.6	66.4±14.9 64.1±14.0 62.4±14.4	101.5±24.2 82.8±15.6 79.6±16.6	<0.001 0.003 0.007	0.001 0.705 0.76	<0.001 <0.001 <0.001	<0.001 <0,001 <0.001
CD Supine^* * p value adjusted for age (ANCOVA) (l/min) CD (tilt 10')^* * p value adjusted for age (ANCOVA) (tilt 20') ^* * p value adjusted for age (ANCOVA)	5.71±1.57 5.06±1.0 5.03±1.0	4.53±0.81 5.02±0.84 5.11±0.92	6.95±1.56 7.13±1.3 7.33±1.43	<0.001 <0.001 <0.001	<0.001 0.86 0.75	<0.001 <0.001 <0.001	<0.001 <0.001 <0.001
TPVR Supine^* * p value adjusted for age (ANCOVA) ^┼ ┼ TPVR in dyne.seg/cm5 TPVR (tilt 10')^* * p value adjusted for age (ANCOVA) (tilt 20') ^* * p value adjusted for age (ANCOVA)	1424±404 1725±441 1704±466	1750±442 1576±324 1482±323	974.4±230 1155±222 1089±207	<0.001 0.003 0.001	<0.001 0.08 0.011	<0.001 <0.001 <0.001	<0.001 <0,001 <0.001

	Group I	Group II	Control (C)	(I x II) p	(I x C) p	(II x C) p
HR (bpm) (∆10'-S) (∆ 20'-S)^* * p value adjusted for age (ANCOVA).	8.8±7.2 12.1±7.6	10.3±7.8 14.7±9.4	16.8±6.6 22.8±8.3	NS 0.38	NS <0.001	NS 0.0001
SV (ml) (∆10'-S)^* * p value adjusted for age (ANCOVA). (∆ 20'-S)^* * p value adjusted for age (ANCOVA).	-16.3±12.1 -20.4±10.1	-2.2±11.2 -4.0±11.2	-18.8±18.4 -22.0±18.2	<0.001 <0.001	0.50 0.66	<0.001 <0.001
TPVR ^┼ ┼ TPVR in dyne.seg/cm5 (∆10'-S)^* * p value adjusted for age (ANCOVA). (∆ 20'-S)	301±218 280±176	-174±328 -268±266	180±260 115±190	<0.001 <0.001	0.09 0.005	<0.001 <0.001
MBP (mmHg) (∆10'-S)^* * p value adjusted for age (ANCOVA). (∆ 20'-S)^* * p value adjusted for age (ANCOVA).	9.1±8.6 6.8±10.6	1.7±15.4 -3.0±-39.9	18.1±9.4 14.9±4.9	0.010 0.001	0.003 0.008	<0.001 <0.001

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