Anatomy and physiology of ventricular function

NLY A FEW YEARS AGO, the theories of cardiac function and control were so widely accepted that they appeared to be settled for all time. The most important recent advance in this field has been growing awareness that much remains to be learned, particularly about muscular contraction in general, myocardial metabolism, functional anatomy of cardiac contraction, function of valves, and control of the cardiovascular system by neural and hormonal mecha-nisms. Many concepts of cardiac function and control are now being critically analyzed and revised. New and improved techniques are providing more precise and detailed information concerning adaptations of the heart to both experimentally controlled and spontaneous adjustments. Continuously recording flowmeters have been developed to monitor the flow of blood into and out of the heart and other organs. Roentgenographic techniques and gauges applied directly to the heart are being employed to probe changes in size, shape and volume of the heart and its component chambers in intact, unanesthetized animals and man. Coronary blood flow, myocardial oxygen consumption, total energy release and myocardial e5ciency can now be studied by catheterizing the coronary sinus. Thus, progress is being made toward the ultimate goal of describing cardiac function and control in terms of changes in heart rate, pressures, volumes, flow, useful work and myocardial ef-ficiency. Ultimately, changes in these parameters must be explored not only in con-trolled experiments but also under essentially normal conditions, with the neural and hormonal controlling systems fully operative. The complexity of neural reflex mechanisms in cardiovascular and respiratory control is becoming more apparent. For example, chemoreflexes and stretch receptors in the heart and lungs have been the subjects of two recent reviews in this journal (I, 2). The ramifications of cardiac function and control are so broad that a compre-hensive review of the anatomy and physiology of ventricular contraction could easily grow out of all reasonable proportion. For this reason, the following discussion is restricted to a few areas of personal interest, and the bibliographic citation is restricted to a few representative example