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

Abstract

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 O(2) consumption per beat. In the present study, we analyzed the frequency distribution of PVA during AF by its chi(2), 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 (V(0)) 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 chi(2), 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.

Mode of frequency distribution of external work efficiency of arrhythmic beats during atrial fibrillation remains normal in canine heart

“…EW), EDV, and ESP also fluctuated simultaneously. As for these fluctuations under AF, we have already analyzed them in detail [4,5,8,[12][13][14][15]. Figure 2 plots LV EW (open circles) and its efficiency (solid circles) against the predicted LV VO 2 of arrhythmic beats for 30 s in one canine heart.…”

High Mechanical Efficiency of Left Ventricular Arrhythmic Contractions during Atrial Fibrillation

“…Suprathreshold electrical stimulation at 20 Hz via these electrodes induced and maintained AF [1,[3][4][5][6], which started on and stopped off the stimulation. We produced AF for 2 min and recorded LVP and LVV during the latter 1 min at sampling intervals of 3 ms with a computer.…”

“…In these studies, we have found the positive correlation between E max and the preceding beat interval [5]; the apparently nonnormal or non-Gaussian frequency distributions of the beat interval, heart rate, and effective arterial elastance (E a ) [1,2]; and the normal or Gaussian distributions of the end-systolic pressure-volume (P-V) ratio or maximal elastance (E max ) as a load-independent contractility index and the systolic P-V area (PVA) as a measure of the LV total mechanical energy [3,7]. As for the E max , E a , and PVA [7][8][9][10][11][12], see the LV P-V diagram schematically shown in Fig.…”

“…We found them to skew enough to account for the rightward skewed frequency distribution of the EW/PVA during AF with the unexpectedly high mean EW/PVA. These results indicate that the LV arrhythmia during AF per se does not directly suppress the mean level of LV mechanical efficiency in normal canine hearts.Key words: heart, arrhythmia, external work, pressure-volume area.We have been investigating the statistical characteristics of major mechanoenergetic variables of the left ventricle (LV) beating arrhythmically during atrial fibrillation (AF) in normal canine in situ hearts [1][2][3][4][5][6]. In these studies, we have found the positive correlation between E max and the preceding beat interval [5]; the apparently nonnormal or non-Gaussian frequency distributions of the beat interval, heart rate, and effective arterial elastance (E a ) [1,2]; and the normal or Gaussian distributions of the end-systolic pressure-volume (P-V) ratio or maximal elastance (E max ) as a load-independent contractility index and the systolic P-V area (PVA) as a measure of the LV total mechanical energy [3,7].…”

“…The anesthesia was maintained by fentanyl (100 µg/h per dog, i.v.) as usual in our laboratory [1][2][3][4]7].The chest of the dog was opened midsternally. A 3F catheter-tip micromanometer was inserted into the LV from the apex to measure the LV pressure (P).…”