1524 HANDBOOK OF PHYSIOLOGY -^ CIRCULATION II 



Atretic HV. 



fig. 3. Anomalous coronary artery commu- 

 nications: A: retrograde flow from right ven- 

 tricular cavity to epicardial coronary arteries 

 via myocardial sinusoids in presence of pul- 

 monic (or aortic) atresia with intact ventricular 

 septum and competent auriculoventricular 

 valves. B: composite illustration of aortic 

 communication with the cardiac chambers via 

 the coronary arteries. C: communication of the 

 aorta with the pulmonary artery via aber- 

 rantly coursing coronary arteries. D: anoma- 

 lous origin of the left coronary artery from the 

 pulmonary artery. [From Edwards (101).] 



ronary a 



Congenital coronary arteriovenous fistulae have 

 been demonstrated in humans at thoracotomy, or 

 preoperatively utilizing angiocardiography and coro- 

 nary arteriography (104, 356). While gasometric 

 analyses may suggest a left-to-right shunt similar to 

 septal defects or a patent ductus arteriosus, ausculta- 

 tory findings have more often suggested the latter. 

 Clinical symptoms and signs, present in half the 

 cases, reflect a high output congestive failure, the 

 shunts averaging 40 per cent of the cardiac output 

 (356). The embryologic defect is probably a per- 

 sistence of myocardial sinusoids although the large, 

 sometimes aneurysmal, dilatation and veinlike thin- 

 ning of the arterial wall is a "common feature to all 

 arteries proximal to an arteriovenous shunt," and 

 may, therefore, be a secondary rather than a primary 

 alteration (101). A recent review now totals 71 cases 

 (104). 



The anomalous left coronary artery has recently 

 become a subject of increasing clinical and physio- 



logic interest, not only because it is the most common 

 of the congenital coronary artery aberrations and 

 readily diagnosed with modern clinical techniques, 

 but also because of the controversy concerning the 

 direction of blood flow in the aberrant vessel. There 

 have been over 60 cases reported in various reviews on 

 this anomaly, approximately one-fourth occurring in 

 adults in whom an apparent attenuation of the patho- 

 physiologic process is manifested. As the truncus is 

 dividing into aorta and pulmonary artery (5th week of 

 gestation), the primordial coronary ostial buds have 

 already been established and the growth of solid 

 arterial cords has commenced (8, 6g) (fig. 4). The 

 predominant finding of normal and equal-sized 

 aortae and pulmonary arteries strongly implicates a 

 malposition anteriorly of the left coronary artery as 

 the primary developmental defect, but the occurrence 

 of hypoplastic aortae, in rare cases, does not negate 

 the possibility of an abnormal division of the truncus 

 arteriosus. 



