title: The utility of right ventricular speckle tracking echocardiography strain analysis in the Intensive Care Unit and perioperative period
Creators: name: McErlane, James Patrick Gerrard
Publisher: name: University of Glasgow
Year: 2025

description: Right ventricular (RV) function is highly important, but underappreciated, in the intensive care unit (ICU) and the perioperative period. Right ventricular dysfunction (RVD) has been shown to be common in ICU and it is associated with poor outcomes in patients with sepsis and acute respiratory distress syndrome (ARDS). The prevalence and impact of RVD in patients in the perioperative period is less well understood. Global assessment of RV function is challenging, with conventional RV echocardiography parameters often only assessing localised function, and perform poorly compared with gold standard methods such as cardiovascular magnetic resonance imaging. RV speckle tracking echocardiography (STE) is a novel parameter thought to overcome some of these limitations. This thesis aims to assess the utility of RV-STE in ICU and the perioperative period. 

The fundamentals of RV anatomy and function are firstly described in Chapter 1. This includes a discussion about invasive and non-invasive methods for assessing RV function. The conventional echocardiography parameters are described, with which RV-STE is compared. 

The principles underlying RV-STE are described in Chapter 2. Consensus guidelines recommend the use of peak RV free wall longitudinal strain (RVFWLS), and this is the primary measure of RV-STE assessed in this work. Reference ranges and the effects of different strain software are described. 

A framework for utility is defined in Chapter 3, forming the basis for assessment of RVFWLS utility. Utility is assessed by three domains: feasibility, reproducibility, and validity. Feasibility is defined as the percentage of echocardiography studies of adequate image quality for RVFWLS analysis. Validity is explored via three subtypes; concurrent (comparing RVFWLS to a gold standard), predictive, and construct validity (hypothesis testing where expected relationships between variables and RV function are analysed using RVFWLS as a surrogate for RV function). 

To establish the current body of work investigating the utility of RVFWLS, a literature review is presented (Chapter 4). This review is divided into two parts, examining ICU and the perioperative period separately. Meta-analysis identified that RVFWLS feasibility in ICU is improved by prospective study design whereas increasing proportions of patients receiving mechanical ventilation reduces feasibility. In the perioperative group, preoperative echocardiography scans had better feasibility than postoperative. Reproducibility of RV-STE was high in both ICU and perioperative groups. In ICU patients, predictive validity was demonstrated with regards the association between RVFWLS and short-term mortality in patients with sepsis and coronavirus disease 2019 (COVID-19). Concurrent and construct validity was less well investigated in these groups. 

The COVID-RV study (Chapter 5) investigated the utility of RVFWLS in patients with COVID-19 requiring invasive mechanical ventilation. Patients underwent echocardiography post-intubation. High RVFWLS feasibility was identified, with excellent reproducibility. Abnormal RVFWLS was found in 28.7% of patients, and was independently associated with 30-day and one-year mortality. Abnormal RVFWLS was also associated with raised cardiac biomarkers and raised ventilatory driving pressures, implicating myocardial injury and injurious mechanical ventilation in the manifestation of RVD. These findings support the predictive and construct validity of RVFWLS in this setting.

The RV exercise study was undertaken (Chapter 6) to assess RVFWLS as a measure of dynamic RV function when undertaking exercise stress echocardiography (termed right ventricular contractile reserve: RVCR) in a perioperative group undergoing lung resection. Postoperative exertional symptoms are common in this group and this study aimed to investigate if impaired RVCR contributes to these symptoms. Results showed that exercise stress echocardiography was tolerable to patients, and RVFWLS feasibility and reproducibility were again high. There was no improvement in RVFWLS when patients underwent exercise pre- or postoperatively, however RVFWLS-rate was shown to increase pre-operatively when exercising and this relationship was lost postoperatively. This suggests that RVFWLS-rate may be the better measure for identifying RVCR, and that RVCR is impaired in patients following lung resection.

This thesis provides a comprehensive assessment supporting the utility of RV-STE in ICU and the perioperative period. The utility of RV-STE in the perioperative setting will be further investigated by the “IMPRoVE study”, set up by the author and his supervisors. This study aims, for the first time, to investigate the prevalence of perioperative RVD across a range of surgical specialties, and elucidate the mechanisms and impact of perioperative RVD on patient outcomes using RVFWLS as the primary measure of RV function.