FRACTALS DESCRIBE BLOOD-FLOW HETEROGENEITY WITHIN SKELETAL-MUSCLE AND WITHIN MYOCARDIUM

A marked perfusion heterogeneity exists within single skeletal muscles and within the left ventricular (LV) myocardium. The relative dispersion (RD) of blood flows to regions <1 g amounts to similar to 0.35 in both organs in rabbits. RD is changed with refinement of spatial resolution because the observed variance in regional flows increases. It has been shown with fractal analyses that the fractal dimension (D) can describe the relationship between the measured RD and size of the region studied within both the myocardium and the lung. A similar study has not been done with skeletal muscle. Barbital-anesthetized rabbits, cats, and sheep were used. Regional blood flow distribution was assessed with the microsphere method. Microsphere deposition in organ regions was determined after successive regrouping of either the LV or one skeletal muscle into various sized regions. We found that the perfusion patterns could be described with fractals for both organs, with the corresponding D values of 1.22-1.37 for the myocardium and 1.30-1.46 for muscle. It appears that fractals also yield a good description of blood flow distribution within skeletal muscle. In rabbits, D for myocardium was strongly correlated to the D for muscle (correlation coefficient = 0.98). This surprising finding of the strong correlation in D sampled from two organs originating from the same rabbit has hitherto not been reported.