Page 20 - The role of advanced echocardiography in patients with ischemic heart disease - Rachid Abou
P. 20

Chapter one. General introduction and outline of the thesis
CLINICAL APPLICATIONS OF LV GLOBAL LONGITUDINAL STRAIN Early detection of LV systolic dysfunction and heart failure
LV GLS is a more sensitive marker of LV dysfunction than LVEF, and this is attributed to: 1) the longitudinal orientation of subendocardial LV fibres, which are susceptible to ischaemia, and 2) compensatory increase in circumferential fibre function in the presence of longitudinal dysfunction, whereby LVEF is maintained in the normal range.1 Impaired LV GLS has been reported in asymptomatic patients with type 2 diabetes mellitus and normal LVEF suggesting the presence of early structural changes of the myocardium (increased myocardial triglyceride content, accumulation of ceramides, reactive fibrosis), i.e. the hallmarks of diabetic cardiomyopathy.11, 12 In individuals with hypertension, LV GLS can be impaired despite having a normal LVEF.7 These findings could be explained by the increased afterload and the response of the myocardium with hypertrophy.13 In addition, obesity has been associated with a reduction in LV GLS independently of increased blood pressure, LV mass and circulating insulin.14 These cardiovascular risk factors: diabetes, hypertension and obesity, are highly prevalent and frequent co-exist. They have been associated with cardiovascular events such as myocardial infarction, heart failure and cardiovascular mortality in various population- based studies.8, 15-17 The Copenhagen City Heart Study included 1296 participants (mean age 57 years, 42% male) with a body mass index of 25 kg/m2 and a prevalence of diabetes of 9% and hypertension of 38%.8 The mean LV GLS was -18% and individuals within the lowest quartile of LV GLS (>-15.8%) were significantly older, had significantly higher values of blood pressure, heart rate and body mass index and the prevalence of hypertension was the highest (52%). After a median follow-up of 11 years, 12% of participants presented with heart failure, acute myocardial infarction, or cardiovascular death. Each 1% deterioration in LV GLS was independently associated with a 12% increased risk of the composite endpoint.8
Why is LV GLS an earlier marker of LV systolic dysfunction than LVEF in these populations? This was elegantly demonstrated by Stokke and coworkers in a mathematical model:1 each 1% reduction in myocardial shortening (GLS) should be compensated by 0.5% increase in circumferential shortening, 0.9 mm increase in wall thickness or a reduction in LV end-diastolic volume by 6 to 9 ml in order to maintain LVEF. This dependency of LVEF on wall thickness and end-diastolic volume support the use of LV GLS as an alternative measure of LV systolic function.
14






























































































   18   19   20   21   22