Echocardiographic Understanding of Left Ventricular Hypertrophy in the Era of Metabolic Diseases

Abstract

Classic concept of hypertrophy of a muscle fiber is a compensatory response against increased workload on it. Regarding the hypertrophy of cardiac muscle fiber, left ventricular hypertrophy(LVH) is one of the most important prognostic marker for cardiovascular disease. The measurement of LVH using two-dimensional echocardiography is feasible and of acceptable accuracy. The workload on the cardiac muscle fiber can be also assessed by blood pressure and stroke volume in clinical practice. But now it is very well known that non-hemodynamic factors such as genetic traits, humoral factors and local tissue factors other than body size and gender may be involved in the hypertrophy of left ventricle. It was hypothesized that trophic effects of growth factors can be a cause of the LVH. Adipose tissue may be one of the sources of the humoral factors related to left ventricular hypertrophy. Increased body mass index and insulin resistance were reported to be associated with the left ventricular hypertrophy. As more potent antihypertensive drugs are available, it is easier to get the blood pressure down to the target level. But with the same extent of blood pressure lowering, the magnitude of LVH regression is known to be different among the classes of antihypertensive drugs. For better understanding of these discordant phenomena and for better surveillance of the non-hemodynamic influence on the LVH, it may be useful to differentiate the non-hemodynamic influence from hemodynamic impact on the LVH. With the hypothesized definition of LVH referred by hemodynamic factor, the other part, i.e. non-hemodynamic factors may be measurable. The limitations concerning the definition of "hemodynamic LVH", of course, have to be overcome. The pitfalls related to the echocardiographic measurement of LV mass still need to be addressed. At the same time, the structural and function implications of "non-hemodynamic LVH deserve clinical attention and surveillance. This approach might be a way to understand the conflicting data regarding the functional aspect of LVH in addition to the compositional difference among hypertrophied left ventricles to the same extent. Hypothetical differences of LVH according to the metabolic characteristics of the subjects may be interesting in terms of diagnosis, prognosis, and the response to various antihypertensive therapies. The concept of inappropriateness of LV mass from the viewpoint of hemodynamic workload may be a practical tool for above-mentioned issues.