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HANDBOOK OF PHYSIOLOGY 



CIRCULATION II 



fig. 13. Effects of coronary 

 arterial injection of Pitressin, 

 nitroglycerin, and acetylcholine 

 in the anesthetized dog. Catheter 

 in the first part of the anterior 

 descendens branch (left lateral 

 view). Radiopaque material in- 

 jected in all cases 5 cc. A : control 

 angiogram (BP 150/115; HR 90) 

 before Pitressin. B: (BP 145/115; 

 HR 85) 1 min after Pitressin in- 

 jection (0.008 units/kg). C: con- 

 trol angiogram (BP 175/125; 

 HR 75). D: (BP 165/115 HR 

 78) after nitroglycerin injection 

 (5 MgAg). E: control (BP 177/ 

 115; HR 84). F: (BP 170/117; 

 HR 84) immediately after acetyl- 

 choline injection (0.04 MgAg). 

 [Modified after West & Guzman 

 (393)0 



increasing the oxygen available to the myocardium 

 but at the expense of an increased oxygen usage and 

 cardiac work (91). It would probably be preferable 

 to increase the oxygen availability without stimulation 

 of myocardial oxygen metabolism, as has been shown 

 for nitroglycerin and papaverine in animal studies 



(75, 117, 214). Hydralazine, which may precipitate 

 anginal attacks in hypertensive patients, possesses 

 what are usually considered the desired properties 

 for a coronary vasodilator: it increases coronary 

 blood flow, increases oxygen availability, and does 

 not alter the oxygen uptake of the myocardium (316). 



