Hydraulic forces contribute to left ventricular diastolic filling

Abstract

Myocardial active relaxation and restoring forces are known determinants of left ventricular (LV) diastolic function. We hypothesize the existence of an additional mechanism involved in LV filling, namely, a hydraulic force contributing to the longitudinal motion of the atrioventricular (AV) plane. A prerequisite for the presence of a net hydraulic force during diastole is that the atrial short-axis area (ASA) is smaller than the ventricular short-axis area (VSA). We aimed (a) to illustrate this mechanism in an analogous physical model, (b) to measure the ASA and VSA throughout the cardiac cycle in healthy volunteers using cardiovascular magnetic resonance imaging, and (c) to calculate the magnitude of the hydraulic force. The physical model illustrated that the anatomical difference between ASA and VSA provides the basis for generating a hydraulic force during diastole. In volunteers, VSA was greater than ASA during 75–100% of diastole. The hydraulic force was estimated to be 10–60% of the peak driving force of LV filling (1–3 N vs 5–10 N). Hydraulic forces are a consequence of left heart anatomy and aid LV diastolic filling. These findings suggest that the relationship between ASA and VSA, and the associated hydraulic force, should be considered when characterizing diastolic function and dysfunction.

Cardiac Helical Function

“…This mechanism is explained by the persistence of the ascending segment contraction during the isovolumic diastolic phase. (16)(17)(18)(19)(20)(21)(22) We have found that the endocardium is completely depolarized during the rst part of the QRS. If according to our studies the depolarization of the ascending segment starts 25.8 ms on average after that of the descending segment and its contraction persists for the same period of time, the condition of ventricular contraction will last approximately 400 ms. On the other hand, as ventricular systole lasts about 300 ms, the remaining 100 ms correspond to the diastolic isovolumic phase (erroneously called isovolumic relaxation, because as we see there is ventricular contraction).…”

Hydraulic force is a novel mechanism of diastolic function that may contribute to decreased diastolic filling in HFpEF and facilitate filling in HFrEF

“…Thereafter, the atrioventricular area difference, AVAD, was calculated both for end-diastole and end-systole. Calculations were performed to comply with the original method presented by Maksuti et al (9) as: AVAD = ventricular short-axis areaatrial short-axis area A positive AVAD indicates a net hydraulic force acting in the atrial direction, and consequently, a negative AVAD indicates a net hydraulic force acting in the opposite direction, toward the apex of the left ventricle (9). Atrioventricular plane displacement of the left ventricle (LV AVPD) was measured in long-axis images as the distance traveled by the valve plane from end-diastole to end-systole using an automatic tracking algorithm with manual adjustments when needed (18).…”

“…Maksuti et al (9) proposed a novel mechanism of importance for cardiac filling; a hydraulic force that acts upon the AV plane and contributes to the movement of the plane in the atrial direction. The authors show that the hydraulic force contributing to diastolic filling of the left ventricle in healthy hearts is a consequence of cardiac anatomy.…”

“…Due to the remodeling nature of several heart diseases, an understanding of how the geometry of the failing heart affects filling is of mechanistic interest, as it may either aid or impair diastolic filling. The short-axis atrioventricular area difference (AVAD) alone has been suggested as an indication of presence and direction of the hydraulic force and can be used despite not having access to measurements of the left atrial and left ventricular filling pressures (9). Diastolic dysfunction is present in several cardiac conditions such as heart failure (10), hypertrophic cardiomyopathy (HCM) (11), and cardiac amyloidosis (12).…”

Mitral Annular Dynamics and Left Ventricular Diastole

“…From a hydraulic perspective, based on the Pascal’s principle, MA displacement not only should assist in LV systolic function, but also MA apical to basal motion should aid in LV filling [ 6 ]. While maximal MA plane systolic excursion (MAPSE) and MA systolic velocity have been used as potential measures of LV systolic function [ 7 , 8 ] in certain clinical scenarios, both measures have limited diagnostic utility [ 4 ].…”