Speckle-Tracking and Volume Expansion

Overview

Volume expansion is the cornerstone of hemodynamic management of patients suffering from circulatory failure. The main objective of volume expansion is to increase stroke volume. This increase in stroke volume is due to myocardial contractility improvement. Nowadays, this improvement cannot be assessed using classical monitoring used at the bedside. The main objective of this study is to evaluate left ventricular contractility using Speckle-Tracking before and after volume expansion in intensive care unit patients, to determine if this technology is more sensitive than previous for left ventricular contractility assessment.

The main objective of volume expansion is to increase stroke volume. Frank-Starling curve is schematically divided into two portions: a vertical portion which mean that an increase in preload secondary to volume expansion will induce an increase in stroke volume; and a flat portion which mean that a same increase in preload will not induce an increase in stroke volume. Stroke volume increase is due to a myocardial contractility improvement. Nowadays this improvement cannot be assessed using classical monitoring used at the bedside (left ventricular ejection fraction, fractional area changes, etc …). A new method is available to assess left ventricular contractility at the bedside. Two-dimensional speckle tracking images with echocardiography allows one to track a natural myocardial marker within the myocardium by standard transthoracic echocardiography. It provides unique insights into myocardial function such as tissue deformations and strain rate, which is the rate of deformation. This method is more sensitive than classical echographic left ventricular ejection fraction evaluation. Few data are available about the potential interest of speckle tracking to track an improvement of left ventricular contractility following a volume expansion in intensive care unit patients. This study is observational, prospective in one center. Patients needing a volume expansion will benefit from an echocardiography (stroke volume and longitudinal strain assessment) before and after fluid challenge (500mL of crystalloids). The follow up will be restricted to the duration of volume expansion. The last data will be collected just after the end of volume expansion.