Diastolic function

In clinical cardiology the term 'diastolic function' is most commonly referred as how the heart fills. Parallel to 'diastolic function', the term 'systolic function' is usually referenced in terms of the left ventricular ejection fraction (LVEF), which is the ratio of stroke volume and end-diastolic volume. Due to the epidemic of heart failure, particularly the cases determined as diastolic heart failure, it is increasingly urgent and crucial to understand the meaning of “diastolic function”. Unlike 'systolic function' which can be simply evaluated by LVEF, there are no established dimensionless parameter for 'diastolic function' assessment. Hence to further study 'diastolic function' the complicated and speculative physiology must be taken into consideration. In clinical cardiology the term 'diastolic function' is most commonly referred as how the heart fills. Parallel to 'diastolic function', the term 'systolic function' is usually referenced in terms of the left ventricular ejection fraction (LVEF), which is the ratio of stroke volume and end-diastolic volume. Due to the epidemic of heart failure, particularly the cases determined as diastolic heart failure, it is increasingly urgent and crucial to understand the meaning of “diastolic function”. Unlike 'systolic function' which can be simply evaluated by LVEF, there are no established dimensionless parameter for 'diastolic function' assessment. Hence to further study 'diastolic function' the complicated and speculative physiology must be taken into consideration. How the heart works during its filling period still has many misconceptions remaining. To better understand diastolic function, it is crucial to realize that the left ventricle is a mechanical suction pump at, and for a little while after, the mitral valve opening. In other words, when mitral valve opens, the atrium does not push blood into the ventricle, instead, it is the ventricle that mechanically 'sucks' in blood from the atrium. The energy that drives the suction process is generated from phase of systole. During systole, to overcome the peripheral arterial load at ejection, ventricle contracts, which also compresses elastic tissues internal to and external to the myocardium. Then, when cardiac muscle relaxes, the energy captured by compressed elements releases, driving the recoil of ventricular wall until a new balanced equilibrium state is reached. During diastole, the ventricle of heart must remain elastic or compliant enough and have capacity to hold incoming blood to guarantee effectiveness of the filling phase. Hence stiffness and relaxation are ventricle's intrinsic feature parameters that are practical in evaluating and quantifying diastolic function. In addition, volumetric load serves as an extrinsic indicating parameter that modulates diastolic function.