Wall Thickness and Diastolic Properties of the Left Ventricle

Abstract

Diastolic properties of the left ventricle (LV) are probably influenced by several factors, including completeness of ventricular relaxation, composition of the ventricular wall, and wall thickness. This study has utilized a combined ultrasonic and hemodynamic technique to examine the influence of LV posterior wall thickness at end diastole (h_p) on LV diastolic characteristics in 24 patients with various forms of heart disease. The slope of late diastolic LV pressure-diameter relations (ΔP/ΔD) was calculated and used as a measure of effective diastolic stiffness (S) late in diastole. S was normalized for average LV pressure during the interval of measurement (P) as S/P, called S_N. LV end diastolic pressure (LVEDP), volume index (LVEDVI), and mass index (LVMI) were measured in each patient during the same study at which h_p, S and S_N were determined. The range of h_p was 5.6 to 18.6 mm; it was highest in a patient with aortic stenosis, and lowest in those with mitral stenosis. Linear regression of h_p against S, S_N and LVEDP showed significant correlation, with r = 0.85, 0.75, and 0.74 respectively (P < 0.001 for each regression analysis). Poor correlation was noted with LVEDVI, ΔP, and ΔD. Of 12 patients with LV hypertrophy (LVH) by ECG, four had normal h_p (7.9 ± 1.0 mm) and eight had abnormal h_p (13 ± 0.6 mm). Those with normal h_p had nearly normal values for S (3.5 ± 0.5 mm Hg/mm) while those with abnormal h_p showed significant increases in S (7.7 ± 1.5 mm Hg/mm), indicating that LVH may alter S only insofar as there is an associated increase in h_p. Consistent with this was the observation that within the group of patients having increased LVMI, LVMI itself was a poor predictor of S (r = 0.50, NS) while h_p remained an excellent predictor of S (r = 0.86, P < 0.001). In summary, this study suggests that wall thickness is an important determinant of left ventricular diastolic stiffness and pressure, and that wall thickness appears to predict diastolic stiffness independent of the presence or absence of LVH or increased LV mass.