Hemodynamic effects of volume expansion on left ventricular-arterial interactions in circulatory shock-a prospective...

Left ventricular-arterial interaction, also termed ventricular-arterial coupling (VAC), determines cardiovascular efficiency by matching cardiac performance and arterial functions, and comprehensively assesses cardiac contractility and arterial load in a common framework. Volume expansion is a commonly used hemodynamic measure in the management of circulatory shock. However, its hemodynamic effects on each component of the cardiovascular system are not fully understood. This study aimed to evaluate the effects of volume expansion on the left VAC and determine whether the left VAC is associated with fluid responsiveness in circulatory shock.

This prospective observational study enrolled mechanically ventilated patients with circulatory shock, for whom the attending physician decided to perform a fluid challenge. Hemodynamics and left VAC were measured immediately before and after the fluid challenge. Fluid responsiveness was defined as a 15% or greater increase in cardiac index following the fluid challenge. Left VAC was quantified by the ratio of arterial elastance (Ea) to left ventricular end-systolic elastance (Ees), measured by echocardiography. Multivariable logistic regression analyses were used to identify hemodynamic variables associated with fluid responsiveness.

Of 58 enrolled patients, 26 (44.8%) were fluid responders. Fluid responders exhibited a higher baseline Ea/Ees ratio compared to non-responders (1.22 ± 0.28 vs. 1.02 ± 0.30, P = 0.011), while the Ea and Ees were comparable between them. Volume expansion caused significant reductions in the Ea and the Ea/Ees ratio in fluid responders, and led to remarkable increases in the Ea and the Ea/Ees ratio in non-responders, while the Ees remained unchanged in both groups. The baseline Ea/Ees ratio was significantly correlated with the fluid-induced changes in cardiac index (r = 0.373, P = 0.004). Multivariable regression analysis suggested that the baseline Ea/Ees ratio was independently associated with fluid responsiveness after adjusting for confounders (odds ratio 1.339, 95% confidence interval: 1.075-1.668, P = 0.009).

In mechanically ventilated patients with circulatory shock, volume expansion optimized the left VAC in preload-dependent patients, primarily by reducing arterial load, and the baseline left VAC was associated with fluid responsiveness.