 Atrial booster-pump function

Atrial booster-pump function is the active contribution of atrial contraction to ventricular filling. In the left atrium, contraction late in ventricular diastole helps drive blood through the open mitral valve. It supplements earlier filling associated with atrial conduit function, rather than accounting for all filling during the cardiac cycle.^[ref]

A volumetric descriptor compares the chamber volume just before contraction, $V_{\mathrm{preA}}$, with the subsequent minimum, $V_{\min }$. Their difference is the observed active-phase volume loss; the left atrial active emptying fraction usesFor constructed values 50 and 40 mL, the volume loss is 10 mL and this fraction is $20\%$. Choosing the denominator is part of defining the descriptor.

That loss is not automatically all of the blood flow through the mitral valve during the interval. Integrating the left atrium's balance giveswhere $V_{\mathrm{PV}}$ is signed net pulmonary vein inflow over the same interval. If $V_{\mathrm{PV}}=8$ mL in the constructed example, 18 mL leaves through the mitral valve despite a chamber-volume decrease of only 10 mL.

A primary atrial flow component analysis reconstructed flow from time-resolved computed tomography and computational fluid dynamics, distinguishing modeled passage and residence histories.^[ref] This helps separate a phase-associated volume measurement from the route taken by each parcel. Likewise, an observed contraction-associated volume loss is not itself a controlled measurement of how much less ventricular filling would have occurred without contraction; pressure, timing and continuing inflow can also differ.