Normal distribution of ventricular pressure-volume area of arrhythmic beats under atrial fibrillation in canine heart

We previously found the frequency distribution of the left ventricular (LV) effective afterload elastance (E_a) of arrhythmic beats to be nonnormal or non-Gaussian in contrast to the normal distribution of the LV end-systolic elastance (E_max) in canine in situ LVs during electrically induced atrial fibrillation (AF). These two mechanical variables determine the total mechanical energy [systolic pressure-volume area (PVA)] generated by LV contraction when the LV end-diastolic volume is given on a per-beat basis. PVA and E_max are the two key determinants of the LV O₂ consumption per beat. In the present study, we analyzed the frequency distribution of PVA during AF by its χ², significance level, skewness, and kurtosis and compared them with those of other major cardiodynamic variables including E_a and E_max. We assumed the volume intercept (V₀) of the end-systolic pressure-volume relation needed for E_max determination to be stable during arrhythmia. We found that PVA distributed much more normally than E_a and slightly more so than E_max during AF. We compared the χ², significance level, skewness, and kurtosis of all the complex terms of the PVA formula. We found that the complexity of the PVA formula attenuated the effect of the considerably nonnormal distribution of E _a on the distribution of PVA along the central limit theorem. We conclude that mean (SD) of PVA can reliably characterize the distribution of PVA of arrhythmic beats during AF, at least in canine hearts.