Assesment of LV diastolic filling using color M-mode Doppler echocardiography: validation in new hydoraulic model

The effect of LV properties on v(p) and the E/v(p) ratio remains a matter of debate. Therefore,the objective of this study is to explore - in a new hydraulic model - the individual contributions of LV relaxation, filling pressure and compliance in changes of E, v(p) and E/v(p) for different stages of diastolic function. A new hydraulic model, consisting of an open cylindrical LA connected to an ellipsoidal LV, is designed. E and v(p) are measured for varying values of tau (45-60-90 ms), LV compliance (0.45-1.35 ml/mmHg) and filling pressure (3-10-30 mmHg). The results are used for predicting the evolution of E, v(p) and E/v(p) during different stages of diastolic function. An increase in compliance decreases E, whereas it augments v(p). v(p) is less load-dependent than E. E decreases with delayed relaxation, increases for the case of pseudonormalisation, and becomes higher than the reference values during restrictive filling. The v(p) value is lower for the case of delayed relaxation than for the reference situation. During pseudonormalisation, the value of v(p) remains lower than the reference value but higher than the value for delayed relaxation. v(p) further decreases during restrictive filling. In conclusion, the effect of simultaneous changes in compliance and loading counterbalance changes in v(p). Therefore, under normal physiologic conditions where load and compliance are coupled, v(p) is apparently load-intensive and E/v(p) increases as filling pressure increases. Moreover, in the different stages of diastolic dysfunction, due to the interference of the co-varying relaxation, the increase in E/v(p) is more pronounced.