FUNCTIONAL ANATOMY OF CARDIAC PUMPING 



7 6 3 



Most of these postulates were of speculative nature. 

 For example, Donders (39) stated that "the blood 

 which enters at the end of systole into the coronary 

 arteries seems to cause a slight active expansion of the 

 heart, especially of the ventricles. - ' This view was 

 originally formulated in 1855 by Briicke (26) and 

 also advocated by Luciani (102). Based on X-ray 

 kymograph studies, a modern modification of the 

 same hypothesis was presented by Cignolini (34) 

 without conclusive evidence. However, recent work by 

 Salisbury et al. (141) indicates that the filling of the 

 coronary bed affects the ventricular distensibility. 

 There are indeed significant differences in the 

 ventricular pressure volume relationship depending 

 upon whether the coronaries are perfused or not 

 [Brecher et al. (24)]. In figure 2 the S-shaped pressure 

 volume curve of the ventricle with an empty coronary 

 bed (solid line) is different from that obtained during 

 coronary perfusion (broken line). This shift of the 

 curve when the coronary bed is perfused indicates 

 that the perfused heart accommodates more fluid at 

 low intraventricular pressures and less fluid at high 

 intraventricular pressures. Around the elastic equilib- 

 rium state (zero transmural pressure) the perfused 

 heart is somewhat stiffer than the nonperfused heart. 

 The effect of varying degrees of engorgement of the 

 coronary bed upon the distensibility of the beating 

 ventricle during the different phases of the cardiac 

 cvcle is still unknown. 



The heart skeleton, the chordae tendineae, and 

 the cells of the Purkinje system are noncontractile, 

 yet are functional components of the myocardium. 

 The heart skeleton (fig. 3) is represented by four 

 interconnected fibrous rings of dense connective 

 tissue, which surround the orifices of the great 

 vessels. The musculature of the ventricles and atria, 

 the roots of the large vessels, and the heart valves are 

 attached to this skeleton, which also anchors the 

 tendinous endings of the ventricular muscle (see 

 below). An important function of the cardiac skeleton 

 is to provide a firm basis for the attachment of the 

 cardiac valves. Another function, though less fre- 

 quently mentioned, is to aid in keeping the orifices 

 open during the phases of blood inflow and outflow. 

 During ventricular activity, the orifices undergo 

 changes in form which probably involve also the 

 cardiac skeleton as indicated in the different outlines 

 of the orifices during systole and diastole in figures 4, 

 5, and 6. By inserting a finger through the atrial 

 appendage in the intact beating heart, one can 

 easily verify that the atrioventricular valve rings 

 become smaller during ventricular contraction and 

 larger during relaxation. This observation, which 

 has not been substantiated by precise measurements 

 as yet, indicates that the fibrous tissues of the heart 

 skeleton are passively deformed by myocardial con- 

 traction and thereby store energy which is released 



fig. 3. Anatomic components of the heart 

 depicting the relation of the fibrous skeleton 

 to the heart chambers and arterial roots. The 

 trunks of the aorta and pulmonary artery as 

 well as the atria are fastened to the cranial 

 aspect of the four annuli fibrosi, whereas the 

 ventricles are attached to the caudal aspect. 

 [From Rushmer (139).] 



