442 



HANDBOOK OF PHYSIOLOGY >^ CIRCULATION I 



rzoo PREOPERATIVE 



no. 13. Intraradial and intra- 

 femoral arterial pulse contours in 

 a 34-year-old man with coarcta- 

 tion of aorta (left panel). Follow- 

 ing surgical repair of coarctation 

 (jight panel), pressure pulses are 

 nearly normal. (For discussion 

 see text.) 



POSTOPERATIVE 

 (</ 34 Years) 



In these patients a) systolic and, in most instances, 

 diastolic pressure in the radial artery is elevated above 

 the range of pressures encountered in normal subjects; 

 b) systolic pressure in the femoral artery is reduced or 

 is within the range of pressures encountered in 

 normal persons whereas diastolic pressure is, in most 

 instances, above the normal range; c) as a result of 

 these changes in radial and femoral pressure the 

 ratio of the femoral to the radial systolic pressure in 

 patients with coarctation of the aorta is below the 

 range of ratios obtained in normal subjects; d) the 

 onset of the femoral pulse wave is nearly always 

 delayed beyond the onset of the radial pulse wave in 

 patients with coarctation of the aorta; and e) the 

 value for the time elapsing between the onset and the 

 attainment of the peak in the femoral pulse wave is 

 nearly always beyond the range of values obtained in 

 normal subjects. 



The cause of arterial hypertension in coarctation of 

 the aorta has been studied by numerous investigators. 

 Three theories have been postulated, either singly or 

 in combination, to explain the blood pressure changes. 



Blumgart et al. (35) described the dynamics of the 

 circulation in two patients with coarctation. Since they 

 found the arteriolar resistance in the upper extremities 

 to be normal they concluded that the arterial hyper- 

 tension above the coarctation resulted from an 

 increased resistance to flow offered by the coarctcd 

 segment and the collaterals (mechanical theory). 



From studies of blood flow in the hand and upper 

 part of the arm, Prinzmetal & Wilson (194) and 

 Pickering (190) came independently to conclusions 

 that differed from the earlier notions of Blumgart 

 et al. They found that there was an increase in 

 resistance to blood flow in the upper extremities 

 which was of general distribution, but were unable to 

 agree upon the mechanism by which the increase was 

 brought about. Prinzmetal and Wilson believed that 

 the increase in arteriolar tone was due to hyperactivity 

 of the vasomotor nerves (nervous theory), for when 

 the vasoconstrictor activity was inhibited by applica- 

 tion of heat the increase in the flow of blood in the 

 hand was found to be much greater than in normal 

 individuals or in individuals .suffering from "essential" 

 hypertension. The results of Pickering's studies were 

 in accord with those of Prinzmetal and Wilson so far 

 as general distribution of increased resistance was 

 concerned. Pickering, however, was unable to show 

 any greater increase in the flow of blood than that 

 encountered in normal individuals either when heat 

 was applied to the arms or when the nerves of the 

 extremity had been injected with procaine (Novo- 

 caine). Evidence for the existence of nervous origin of 

 the arteriolar hypertonus was lacking in his experi- 

 ments, and he pointed out that there were no known 

 nervous pathways that could lead stimuli to affect 

 only the vasomotor system in the upper half of the 

 body and that the \iew that a substance circulating 



