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

• Published in: Arquivos brasileiros de cardiologia Vol. 107; no. 4; pp. 354 - 364
• Main Authors: 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
• Format: Journal Article
• Language: English; Portuguese
• Published: Brazil Sociedade Brasileira de Cardiologia - SBC 01-10-2016; Sociedade Brasileira de Cardiologia (SBC)
• Subjects: Adolescent; Adult; Aged; Aged, 80 and over; Anthropometry; Blood Pressure - physiology; CARDIAC & CARDIOVASCULAR SYSTEMS; Case-Control Studies; Hemodynamics - physiology; Humans; Middle Aged; Original; Orthostatic Intolerance - physiopathology; Postural Orthostatic Tachycardia Syndrome/physiopathology; Reference Values; Retrospective Studies; Stroke Volume; Supine Position - physiology; Syncope - physiopathology; Systole - physiology; Tilt-Table Test - methods; Time Factors; Vascular Resistance; Young Adult; Stroke Volume; Volume Sistólico; Postural Orthostatic Tachycardia Syndrome/physiopathology; Vascular Resistance; Intolerância Ortostática/fisiopatologia; Síndrome da Taquicardia Postural Ortostática/fisiopatologia; Orthostatic Intolerance/physiopathology; Resistência Vascular
• ISSN: 0066-782X; 1678-4170; 1678-4170
• DOI: 10.5935/abc.20160135

Orthostatic intolerance patients' pathophysiological mechanism is still obscure, contributing to the difficulty in their clinical management.
To investigate hemodynamic changes during tilt test in individuals with orthostatic intolerance symptoms, including syncope or near syncope.
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.
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.
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.