 Left ventricular filling

Left ventricular filling is the inflow of blood into the left ventricle, primarily through the mitral valve during diastole. It depends on the pressure difference between the left atrium and ventricle, valve-flow resistance and the ventricle's changing mechanical state. A volume increase is an integrated transport observation, not simply another name for one measured pressure.

With an ideal open mitral pathway of hydraulic resistance $R$ and no simultaneous outflow, an original reduced model isThis expression applies while the pressure difference favors filling; an ideal one-way valve would otherwise set $Q=0$. To isolate a passive filling timescale, assume constant atrial pressure $p_A$ and a linear ventricular relation $p_V=(V-V_0)/C$, where $C$ represents ventricular compliance in a fixed mechanical state. ThenThe product $RC$ has units of time. A longer available filling interval and a different mechanical or hydraulic timescale have distinct effects on the final volume.

For stipulated $V_{\infty }=140$ mL, initial volume $V_i=60$ mL and $RC=1$ s, the modeled volumes at 0.5 and 1 s are approximately 91.5 and 110.6 mL. The added amounts are 31.5 and 50.6 mL. These are mathematical examples, not normal human reference values. Actual filling also involves active relaxation, atrial contraction, moving boundaries and changing flow conditions, all omitted from this constant-parameter model.

A primary experiment in six sheep reconstructed ventricular and mitral annulus markers using biplane fluoroscopy, then estimated how annular motion contributed to filling volume.^[ref] Its apparatus makes moving geometry observable, complementing a pressure-flow model rather than treating the chamber boundary as fixed.

A complete interpretation therefore identifies whether the observation is chamber volume, boundary motion, valve-flow speed or transported volume. Their relationship follows from the measurement geometry and conservation of mass, with any other inflow or outflow included in the balance.