Thứ Hai, 19 tháng 1, 2015
HEPATIC HEMODYNAMICS DURING VALSALVA MANEUVER
The Valsalva maneuver is a widely used physiologic technique for the non-invasive evaluation of heart murmurs and ventricular function [1-3]. The Valsalva maneuver consists of forceful expiration against a closed glottis, resulting in an increase in both intra-thoracic and intra-abdominal pressure, and activation of autonomic nervous function [4-6]. Although the hemodynamic changes during Valsalva maneuver have been well documented, these have been focused on cardiac chambers, aorta and systemic large veins [4,7-10]. Anatomically, venous return consists of systemic and hepatic venous return, and systemic venous return decreased markedly during the Valsalva maneuver [8,11]. However, it was not well defined that hemodynamic changes focused on the liver during Valsalva maneuver.
Clinically, the Valsalva maneuver is considered as main cause of defecation syncope and surgery Hepatic hemodynamics during Valsalva maneuver performed in a patient with functional suprahepatic inferior vana cava (IVC) obstruction during the Valsalva maneuver . Collapsed IVC showed during the maneuver in normal healthy subjects using ultrasonography study, but IVC howed angular appearance and not collapsed during the maneuver in the venography study [10,11]. The change of IVC during the maneuver is ambiguous and hemodynamic contribution of hepatic vein and portal vein during the maneuver has not been studied in normal healthy subjects. Duplex Doppler ultrasonography of the liver provides important information about liver condition [11,13]. Hepatic vein flow depends on hepatic parenchymal compliance, thoracoabdominal pressure, and right atrial pressure. It is known that hepatic vein Doppler waveform is triphasic pattern which is composed of two anterograde flow peaks toward the heart and one retrograde flow peak toward the liver in healthy subjects . Recently, volume flow measurement has been used for quantification of blood flow and it showed good correlation with magnetic resonance in quantification of cerebral blood flow [15-17]. Therefore, analysis of flow pattern and quantification of liver flow can be helpful to understand liver
condition under the Valsalva maneuver. Even the liver hemodynamic changes during the Valsalva maneuver in healthy volunteers have been studied in previous reports, its contribution to venous return is not focused enough [18,19]. We hypothesized that the hepatic circulation might be an important role to maintain venous return to the heart during Valsalva maneuver.
The aim of our study was to assess the hemodynamic change of liver including hepatic vein and portal vein during the Valsalva maneuver.