Left Ventricular Relative Wall Thickness in Patients with Aortic Valve Disease

Abstract

Left ventricular (LV) “relative wall thickness,” expressed as the end-diastolic volume/mass (V/M) or radius/wall thickness (R/Th) ratio, has been shown to provide important diagnostic and prognostic information in patients with heart disease. Measurement of the LV relative wall thickness also provides insight into some of the differences between the various forms of myocardial hypertrophy. The basis for these observations rests in the La Place relation which states that LV wall stress (S) is directly proportional to intracavitary pressure (P) and chamber radius (R), and inversely proportional to wall thickness (Th): S = PxR/Th. Because normal myocardial growth proceeds in a fashion so as to maintain normal systolic wall stress, a constant relation between systolic pressure and the ratio of chamber radius to wall thickness (R/Th) is maintained in the normal growing child [1]. This constant relation between pressure and the R/Th ratio is also maintained in trained athletes, in normal pregnant subjects (both of which may have increased LV chamber size), and in many patients with compensated valvular heart disease. When sufficient hypertrophy does not develop in response to a hemodynamic load, and normal systolic wall stress is not maintained, the R/Th ratio is generally increased. As will be seen, measurement of the end-diastolic R/Th ratio provides information which can be extremely useful in the analysis of a broad variety of cardiac disorders. The purpose of this paper is to discuss the diagnostic and prognostic importance of the LV relative wall thickness with emphasis on patients with aortic valve disease.