Studies on Mechanical Dispersion by Strain Echocardiography in the General Population and among subjects with Stable Coronary Artery Disease

Abstract

Mechanical dispersion is a new echocardiography method to assess left ventricular (LV) dyssynchrony. Increased mechanical dispersion is associated with ventricular arrhythmias and sudden cardiac death in cardiomyopathies and after acute myocardial infarction. Knowledge on mechanical dispersion among the general population and patients with less severe cardiac disease, like stable coronary artery disease (CAD) is lacking. This thesis aimed to provide new information on mechanical dispersion in the general population and among subjects with stable CAD. Using data from a large Norwegian population study, the Akershus Cardiac Examination (ACE) 1950 Study, Erika Nerdrum Aagaard provides an upper reference value for mechanical dispersion of 61 ms for subjects in their mid-sixties. In the same age group, CAD and hypertension associated strongly with high mechanical dispersion, and mechanical dispersion associated independently with biomarkers of myocardial injury (high-sensitivity cardiac troponin T) and dysfunction (the natriuretic peptide NT-proBNP). Linking data from a cardiovascular screening survey conducted in the 1990s to the ACE 1950 Study, the author found that high body mass index and triglyceride concentration at age 40 years were independently associated with high mechanical dispersion more than 20 years later. Finally, in a population of stable CAD patients, mechanical dispersion associated with poor long-term prognosis, and provided incremental prognostic value to high-sensitivity cardiac troponin I and established echocardiography indices of LV function (ejection fraction and global longitudinal strain), but not to NT-proBNP. The findings of this thesis provide new and useful information on mechanical dispersion that warrants further investigation and may aid its implementation into clinical cardiology practice.