Table 1.

Summary of Different Experimental In Vitro and Ex Vivo Studies Concerning the Presence of Beat-rate Variability (BRV) and Power-law Behavior of Isolated Cells and Denervated Hearts

Protocol	Authors	Methods	Findings
Spontaneously firing cells isolated from embryonic chick hearts	Clay and DeHaan [28]	Coefficient of variation (CV)	CV was inversely proportional to the square root of the number of interconnected cells
Neonatal rat atrial and ventricular cardiac cells	Jongsma, et al. [33]	Coefficient of variation (CV)	CVs diminished when cells were interconnected by gap junction channels
Monolayers with spontaneously beating neonatal rat ventricular myocytes	Kucera et al. [18]	Fast Fourier transformation (FFT) and power law β exponent	Power law behavior with a β exponent around -1.35
Isolated atrial and ventricular myocytes	Yokogawa and Harada [20]	Detrended fluctuation analysis (DFA) estimating fractal properties	Similarity between atrial and ventricular myocytes in terms of long-term correlations of beat rate fluctuations
Effects of afterload, preload, and temperature changes on IBI variability of intact isolated hearts of Sprague-Dawley rats	Langer and colleagues [21]	C 90 as a measure of CV and FFT	Isolated rabbit right atrium and rat hearts exhibited significantly smaller IBI fluctuations related with isolated SAN cells
Adult rabbit hearts	Frey et al. [43]	FFT (total power)	Presence of inherent HRV in isolated hearts