Left Ventricular Long Axis Dynamics in Pathological and Physiological Left Ventricular Hypertrophy
Sub-endocardial fibres line the inner surface of both ventricles and are responsible for longitudinal oscillations of the mitral annulus, such oscillations may be measured using tissue Doppler echocardiography (TDE). During systole the annulus descends and during early diastole (ETDE) and atrial systole (ATDE) it ascends. This thesis examined whether changes in the velocity of the annulus in each of these phases of oscillation, measured using tissue Doppler echocardiography (TDE), could determine the nature of increases in left ventricular size (pathological or physiological). Study one examined differences at rest in longitudinal velocities between individuals with hypertrophic cardiomyopathy (HCM), hypertension (HT), weightlifters, runners and controls, (n = 15 all groups) and all groups were aged between 20 - 36 years. The results demonstrated that both pathological groups had systolic and ETDE velocities significantly lower than groups with physiological hypertrophy (weightlifters or runners) or controls p < 0.05. ATDE however was not significantly different between groups. Additionally runners also demonstrated a significantly higher ETDE than either weightlifters or controls (p < 0.05). Binomial logistic regression identified longitudinal systolic velocity < 9 cm s-1 and ETDE velocity < 11 cm s-1 as the best combination of variables to predict pathological increases in heart size. Study two examined older subjects in order to determine whether the criteria set out in study one were applicable to senior athletes. The subject groups were the same as in study one however all subjects were aged between 36-55. In this case systolic annular velocity was significantly lower in groups with pathological LVH but ETDE < 9 cm s-1 was a better differentiator. Binomial logistic regression identified ETDE < 9 cm s-1 and a mitral E / A ratio < 1 as the best combination of variables to predict pathological LVH. Study three examined the age related changes in long axis function using the pooled data from studies one and two. This demonstrated that in the pathological LVH groups only ETDE / ATDE ratio was significantly correlated with age (r = - 0.5 p < 0.05) suggesting that there appears to be no summation of the effects of pathology and age on mitral annular velocities. The control groups demonstrated a significant age related reduction in all long axis variables (systolic velocity r = - 0.7 p < 0.05; ETDE r = - 0.6 p < 0.01; ATDE r = 0.5 p < 0.05; ETDE / ATDE r = - 0.5 p < 0.01). Weightlifters however did not demonstrate an age related decline in either systolic or diastolic annular velocities. Runners had no age related decline in systolic annular velocities, and whilst they had an age dependent fall in ETDE ( r = - 0.62 p < 0.05) the older runners ETDE were still significantly faster (p < 0.05) than that seen in control subjects. Study four investigated relationship between mitral annular velocity and V̇O2PEAK in runners, weightlifters and controls. These results demonstrated peak exercise ETDE strongly correlated to V̇O2PEAK (r = 0.8 p < 0.01). Conclusions. Taken together these data suggest that longitudinal velocities of the mitral annulus may be useful in determining the nature of increases in heart size, in addition the increased performance of endurance - trained athletes is due in part to functional changes of the long axis.
Left ventricular hypertrophy, changes in the velocity of the annulus, Tissue Doppler Echocardiography (TDE)
Networked Digital Library of Theses and Dissertations