Figure 6.

Model study of the effect of atrial and ventricular factors on the mechanics of paroxysmal AF. (a) Average pressure-volume loops from 23 AF patients compared to loops from 6 patients with Wolff-Parkinson-White syndrome, in whom atrial function is relatively normal²⁸. AF loops are shifted to higher pressures with an increased reliance on active emptying. (b) Changes in model pressure-volume behavior due to higher pressure, larger size, and fibrosis compared to normal model (black); shape and conduction had little effect on atrial mechanics and are omitted for clarity. (c) The three-factor model (size, pressure, fibrosis) explained over 80% of the changes between healthy and AF hearts; note that volumes were validated against directly measured MRI volumes (Figure 7c), which were larger than conductance volumes used to plot loops in panel (a). (d) Simulated impaired LV relaxation increased reliance on active emptying, while simulated mitral valve stenosis or increased passive LV stiffness increased pressures and reduced active emptying.