The Impact of Noninvasive Positive Pressure Ventilation on Left Ventricular Strain in Acute HF

Wayne State University Department of Emergency Medicine

Acute heart failure (HF) is a leading cause of hospitalization worldwide, yet despite a significant commitment from the research community, post-discharge outcomes have remained largely unchanged over the past 20 years. Most notably rates of readmission and mortality after hospitalization are still unacceptably high, raising the question of whether the homogeneous approach to inpatient treatment of acute HF is completely effective. Non-invasive positive pressure ventilation (NIPPV) has been used for treatment of respiratory failure and impending respiratory failure in acute HF for approximately 20 years. Despite substantial evidence that the use of NIPPV reduces the rate of intubation as well as the length of stay in an intensive care unit (ICU), there is very little in the scientific literature regarding the effects of NIPPV on the failing left ventricle (LV). Perhaps we can achieve a more effective matching of therapy and patient through studying the direct impact of NIPPV on the LV?

Left ventricular (LV) strain, the amount of deformation between two points in the myocardium as measured using echocardiography, has been shown to be a more comprehensive way to describe the complicated cardiac mechanics than traditional measures such as left ventricular ejection fraction (LVEF). Strain can be accurately measured using semiautomated speckle-tracking software on standard 2D grayscale images. To our knowledge, our study team is the first to study LV strain in the setting of acute HF. Based on our own very promising preliminary data in this patient population (the first of its kind), we hypothesize that strain echocardiography will serve as a viable indicator of acute LV dysfunction that undergoes real-time changes with therapy including NIPPV.

For this proposal, we seek to describe the initial changes that occur in global longitudinal strain (GLS) and mechanical dispersion index (MDI), 2 indices of LV strain, with acute HF treatment (specifically NIPPV). We will enroll a cohort of moderate to severe acute HF patients in the emergency department and perform 3 point-of-care echocardiograms over the first 24 hours of treatment. We anticipate that approximately 1/3 of the study subjects will be treated with NIPPV with the rest undergoing conventional therapy. Using propensity score matching we will compare the changes in LV strain between these two groups of patients. Lastly, we will correlate the observed changes in GLS & MDI with post-discharge outcomes, namely 30-day readmission rates. This project will serve as the seminal work on strain echocardiography in the setting of moderate to severe acute HF, and will provide clinicians who are looking to treat patients with acute HF in a more individualized fashion with the answers on the impacts of NIPPV on the heart that they are seeking.

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