= Atrial delayed-ejection flow component
The \b[atrial delayed-ejection flow component] comprises <blood> leaving the <left atrium> during ventricular <diastole> after entering during the preceding <diastole> or earlier. The Bäck study calls this delayed outflow. In contrast, the <atrial reservoir flow component> enters during the intervening ventricular <systole>.<Comprehensive left atrial flow component analysis reveals abnormal flow patterns in paroxysmal atrial fibrillation by Sophia Bäck and others>[Methods, Flow Component Analysis; Figure 1]{ref}
This is a transport-history definition, not a statement that ventricular electrical activation was delayed. A constructed timeline illustrates it. Number successive one-second <cardiac cycles> so the current ventricular <systole> occupies $0\leq t<0.4$ s and its following <diastole> occupies $0.4\leq t<1$ s. Suppose a parcel entered in the previous <diastole> at $t=-0.2$ s and crosses the <mitral valve> at $t=0.6$ s. Its 0.8 s passage spans a ventricular <systole>. A second parcel entering at $t=0.5$ s and leaving at $t=0.8$ s instead belongs to the <atrial conduit flow component>.
For represented parcels with exit times $t_i^{\rm out}$, entry times $t_i^{\rm in}$ and volume weights $w_i$, a volume-weighted transit time within a selected exiting category is
$$
\overline{\tau}=\frac{\sum_iw_i(t_i^{\rm out}-t_i^{\rm in})}{\sum_iw_i}.
$$
Two hypothetical parcels representing 1 and 3 mL and taking 0.8 and 1.2 s give $\overline{\tau}=1.1$ s, rather than the unweighted mean of 1 s. If an entry occurred before the available record, the exact transit time is unknown: an observed exit can establish a category without recovering an exact entry date.
The <atrial delayed-ejection flow component> thus complements the <atrial retained-inflow component>: one identifies an observed exit of older atrial <blood>, while the other identifies entered <blood> still present at the specified endpoint.
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