Effective Arterial Elastance of Irregular Beats during Atrial Fibrillation in Canine Left Ventricle.

Abstract

) was originally defined as the end-systolic pressure (ESP)/stroke volume (SV) ratio of the left ventricle (LV) [1][2][3]. E a is approximately equal to heart rate (HR) times total peripheral resistance (TPR) under stable hemodynamics [1][2][3]. E a has the same dimensions as an index of ventricular contractility (E max ) defined as the ESP/endsystolic volume (ESV) ratio [1][2][3][4][5][6]. E a proved to be powerful in evaluating the ventriculo-arterial coupling from the viewpoint of cardiac mechanoenergetics in regular beats [1][2][3][4][5][6]. The mechanical energy efficiency from LV total mechanical energy (PVA) to SV is maximal when E a equals E max [1][2][3][4][5][6][7][8][9][10][11]. The mechanical work efficiency from LV oxygen consumption to SV is maximal when E a is appropriately (around 50%) smaller than E max [3][4][5][6][7][8][9][10][11]. Both efficiencies are re- Abbreviations: AF, atrial fibrillation; CO, cardiac output; E a (ϭESP/SV), either effective arterial elastance conventionally, or effective afterload elastance in this study; E max , an index of ventricular contractility defined as the maximum or end-systolic elastance of the ventricle, or end-systolic pressure-volume ratio; EDP, end-diastolic pressure; EDV, end-diastolic volume; ESP, end-systolic pressure; ESV, end-systolic volume; G i (t), electrical conductance of intraventricular blood; G p , parallel conductance; HR, heart rate; LV, left ventricle; LVP, left ventricular pressure; LVV, left ventricular volume; PVA, total mechanical energy of contraction, or systolic pressure-volume area; RR, cardiac beat interval measured as the interval between two R waves of ECG; RR1 through RR6, first through sixth preceding RRs; SV, stroke volume; TPR, total peripheral resistance; V c , ventricular correction volume equivalent to parallel conductance Gp; V 0 , ventricular unstressed volume.

Frequency Distribution, Variance, and Moving Average of Left Ventricular Rhythm and Contractility during Atrial Fibrillation in Dog.

“…We have found that not only RR, but also E max , E a , and ventriculo-arterial coupling (E a /E max ) distributed nonnormally with considerable skewness (lack of symmetry of a frequency distribution) and kurtosis (peakedness or flatness of a frequency distribution) [14]. Their meanϮSD values could not uniquely characterize their nonnormal frequency distributions [14], unlike a normal frequency distribution [15,16].We recognized in the present study the necessity of isovolumic contractions to scrutinize the frequency distributions of E max during AF for the following reason. Although E a and E a /E max require ejecting contractions whether in situ or ex vivo [13,14,17] Key words: arrhythmia, statistics, histogram, normality, variance.…”

“…However, the minimal number of beats from which the mean RR has been reliably obtained varied widely between only 4 beats to as many as the number of beats for 2 min among investigators and their purposes [9][10][11]. In some of these studies, mean RR was obtained to characterize the average RR even either in case of the nonnormal distribution or without testing its normality [1,5,6,[8][9][10][11].We have recently studied the frequency distributions not only of RR, but also of ventricular contractility (E max ) [12] and effective arterial elastance (E a ) [13] in in situ ejecting left ventricles during AF [14]. We have found that not only RR, but also E max , E a , and ventriculo-arterial coupling (E a /E max ) distributed nonnormally with considerable skewness (lack of symmetry of a frequency distribution) and kurtosis (peakedness or flatness of a frequency distribution) [14].…”

“…Their meanϮSD values could not uniquely characterize their nonnormal frequency distributions [14], unlike a normal frequency distribution [15,16].…”

“…We have recently studied the frequency distributions not only of RR, but also of ventricular contractility (E max ) [12] and effective arterial elastance (E a ) [13] in in situ ejecting left ventricles during AF [14]. We have found that not only RR, but also E max , E a , and ventriculo-arterial coupling (E a /E max ) distributed nonnormally with considerable skewness (lack of symmetry of a frequency distribution) and kurtosis (peakedness or flatness of a frequency distribution) [14].…”

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.…”