12 I 6 



HANDBOOK OF PHYSIOLOGY " CIRCULATION II 



\ VSCULAR MALFUNCTION IN GENERAL 



Vascular malfunction might be denned as that 

 temporar\ or permanent condition which exists 

 when the circulation fails to meet its intended func- 

 tions of a) temperature regulation, b) tissue nutrition, 

 and c I repair. 



Malfunction might arise through active vasomotor 

 or passive structural (anatomic) mechanisms. Vaso- 

 motor (not limited only to neuromuscular) mecha- 

 nisms include a) increase in vessel tone ("vasotighten- 

 ing"), decrease in luminal cross-sectional area, or a 

 combination of these (vasoconstriction), or b) decrease 

 in vessel tone ("vasoloosening"), increase in luminal 

 cross-sectional area, or a combination ol these 

 (vasodilatation). Vasomotor changes might be 

 induced through neural mechanisms, humoral 

 mechanisms, primary muscular action, physical 

 factors affecting any of the vessel wall coats, other 

 unknown factors, or any combination of these. These 

 reactions imply a degree of reversibility. 



Structural or anatomic mechanisms by which 

 vascular malfunction might occur are a) structural 

 obstruction (occlusive), b) structural dilatation 

 (aneurysm or varix), or c) abnormal vascular com- 

 munications. These changes imply a degree of 

 irreversibility. 



Somewhat difficult to define as either active vaso- 

 motor or passive structural changes are vascular 

 distention and vascular collapse (the latter not refer- 

 ring to the "shock syndrome"). Vascular distention 

 or congestion implies a relative increase in vessel 

 tone (as opposed to vasodilatation) but with an 

 increase in luminal cross-sectional area. Vascular 

 collapse implies a relative decrease in vessel tone (as 

 opposed to vasoconstriction) but with a decrease in 

 luminal cross-sectional area. These are, of course, 

 potentially reversible states. 



Structural diseases have been termed "organic," 

 whereas the vasomotor diseases have been called 

 "functional."' Division of peripheral vascular diseases 

 into organic and functional categories, although 

 convenient, is purely arbitrary. Certainly, altered 

 phvsiology has its structural counterpart. Means to 

 resolve this artificial dichotomy then are dependent 

 simply on the sensitiveness of methods for morpho- 

 logic observations. In the past, the division of diseases 

 from the anatomic standpoint has been dependent 

 largely on light microscopy. Under existing classi- 

 fications, for example, early and mild Raynaud's 

 disease is a functional disorder. However, with the 

 use of more sensitive methods such as electron 



microscopy the same stage of the disease might be 

 shown to be associated with structural defects whether 

 it be in the vasculature itself or in the nervous system 

 or in both. Thus, by present "policy" the disease is 

 now considered both organic and functional. 



Regardless of the above criticisms, it is still con- 

 venient for clinical purposes to classify vascular 

 disease within organic or functional categories. This 

 focuses attention on the more observable underlying 

 mechanisms in the characteristic manifestations of 

 the disease. With this in mind, more emphasis shall 

 be placed here on the disorders in which altered phy- 

 siology is the most readily detectable underlying 

 mechanism; these diseases include predominately, 

 but certainly not exclusively, the functional disorders. 

 It should be remembered that none are purely 

 organic or purely functional and that all vascular 

 diseases have elements of each. 



Changes which influence the circulation and its 

 functions, although not directly arising from the 

 vessel wall itself, pertain to such factors as blood 

 volume, cardiac output, pulse rate, blood viscosity, 

 sludging, blood gases, neurogenic and psychogenic 

 disorders, endocrine and humoral factors, and many- 

 others. Many of these factors operate simultaneously 

 to various degrees and with temporal variations. These 

 topics are covered in ether chapters of this volume. 



APPROACH OF THE CLINICIAN AND CLINICAL 

 PHYSIOLOGIST TO THE STUDY OF PATIENTS WITH 

 DISEASES OF THE PERIPHERAL CIRCULATION 



The clinical peripheral vascular physiologist has 

 a difficult and complex task. He must observe the 

 symptoms and clinical and laboratory signs in his 

 subject which suggest the possibility cf pathological 

 alteration in the peripheral circulation. He must 

 attempt to discover the underlying pathologic anat- 

 omy of the clinical manifestation. Most difficult of 

 all, he must attempt to explain the observed changes 

 in terms of pathophysiologic mechanisms, establish 

 a diagnosis and then introduce corrective therapeutic 

 measures based upon established pharmacodynamic 

 and physiologic principles. This is done with an aim 

 to modify the altered pathophysiology in order to 

 establish as near normal vascular function as possible 

 for as long a period of time as possible. This objective 

 requires a satisfactory understanding of the normal 

 and abnormal functions of the interrelated organ 

 systems which may influence the diseased state. The 

 clinician must attempt to estimate properly the 



