The Contractile Function of the Left Ventricle Assessed by Speckle Tracking in Healthy Subjects is Not Affected by the Initiation of Mechanical Ventilation. Comparison with Conventional Echocardiographic Methods

Background Assessment of left ventricular function via ultrasound has become essential in the haemodynamic evaluation of critical care patients. This method has several limitations, including operator dependency, influence by loading conditions, and inability to detect early regional abnormalities. Speckle-tracking echocardiography offers a more sensitive and reproducible method to evaluate cardiac mechanics by measuring myocardial deformation. Global longitudinal strain has emerged as a sensitive marker for systolic dysfunction with greater prognostic value than the left ventricular ejection fraction. Although extracardiac factors such as mechanical ventilation can influence cardiac mechanics, the specific impact of mechanical ventilation initiation on left ventricular function requires further evidence. This study aimed to investigate the changes in speckle-tracking echocardiography-derived left ventricular function and in conventional echocardiographic parameters with the initiation of mechanical ventilation. Materials and Methods A prospective observational study was designed to assess the left ventricular response to mechanical ventilation via conventional echocardiography and speckle-tracking echocardiography. Twenty healthy subjects who underwent scheduled surgery under general anaesthesia were included. Echocardiographic evaluations were performed before and after the initiation of mechanical ventilation. Parameters, including the left ventricular ejection fraction, left ventricular outflow tract velocity-time integral, mitral annular plane systolic excursion, mitral S' wave velocity, and E/e' ratio, were measured. Global longitudinal strain from the apical four-chamber view and its segmental values were analysed offline. Results No significant differences were found in global longitudinal strain, left ventricular ejection fraction, left ventricular outflow tract velocity‒time integral, or the E/e' ratio after the initiation of mechanical ventilation. The six individual segments comprising the global longitudinal strain from the apical four-chamber view showed no significant changes. However, significant differences were observed in mitral annular plane systolic excursion and lateral S' wave velocity. All values after mechanical ventilation initiation remained within the normal range. Conclusion This study revealed that the initiation of mechanical ventilation in healthy subjects does not significantly alter global left ventricular contractile function, as assessed by speckle tracking. While subtle changes were noted in specific longitudinal parameters (mitral annular plane systolic excursion and S' lateral), the overall global left ventricular function remained stable. These findings are crucial for guiding noninvasive hemodynamic monitoring in patients undergoing mechanical ventilation.