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Experimental production of atrial septal defects in dogs A review and new technique
Experimental production of atrial septal defects in dogs A review and new technique W. G. Friend, M.D.,* New York, N. Y., W. E. Andrews, M.D.,** Minneapolis, Minn., P. K. Donahoe, M.D.,*** Boston, Mass., and W. M. Rogers, Ph.D.,**** New York, N. Y.
/~V more complete understanding of any disease process may be achieved by simu lating that condition in an experimental an imal. This report reviews older techniques and proposes a new procedure for the cre ation of experimental atrial septal defects in dogs. Review of techniques Attempts to maintain a patent foramen ovale after gestation by either genetic or artificial means have been generally unre warding, save for a report by Schellong40 of 14 atrial septal defects produced by ex posing pregnant dogs to oxygen deficiency. The first experimental atrial septal defect Supported by grants from the New York Heart Associa tion ( W M R ) , the Lillia Babbitt Hyde Foundation ( W M R ) , and U. S. Public Health Service, No. l-GS-96 ( W G F ) . Recipient in part of the Borden Undergraduate Research Award in Medicine, Columbia University, 1964. Received for publication May 11, 1965. *Intern, Department of Surgery, Roosevelt Hospital, 428 West 59th Street, New York, N. Y. 10019. **Intern, Department of Surgery, University of Minnesota Medical Center, Minneapolis, Minn. ***Inlern, Department of Surgery, Tufts New England Center Hospital, Boston, Mass. ****Associate Professor of Anatomy, Columbia Univer sity, College of Physicians and Surgeons, New York, N. Y.
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(ASD) was created in Berlin in 1926 by Dmitrieff12 who digitally invaginated both atrial appendages to identify the septum and then thrust a small clamp through the sep tum and enlarged the defect with one finger from the opposite side. In 1947, Cohn9 created the defect by inserting a hemostat through the left atrial appendage and open ing it in the septum. This technique was soon repeated by others.6' 25· 32 Then Mar tin28 and Swan4" advanced a scalpel through the atrial appendage to the vicinity of the septum and incised blindly. In 1907, Haecker' 7 of Germany intro duced temporary venous inflow occlusion. This innovation provided a dry field and allowed the operator to approach the sep tum from either incised atrium. Thus with forceps and scissors, numerous investigators throughout the world independently created ASD'S 1 ' 14' 19' 21' 22> 27' 31' 34' 35 ' 44 ' 40,47 ' 51 In 1948, Blalock and Hanlon 3 published their now well-known procedure for cre ating a posterior septal defect by the use of a clamp which encompassed a portion of both atria and their common septum. Com plete interruption of blood flow was not necessary during this procedure. A variety of trocars have been used by
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a number of investigators. Blakemore- was probably the first to use a punch device on the atrial septum in the late 1930's. The technique was later attempted by Hufnagel10 and by Griffin15 who added a rotary punch and a rotating blade around a cardioscope. Griffin also created interventricular septal defects with a trocar which Donald11 later adopted for ASD's. Kay-0 used a sharpened cork borer and added suction with which to grasp the septum. Riberi36 attached a tro car to a drill with suction. A special guide wire and punch device were used by Margutti2'1 of Brazil and by Bukharin7 of Rus sia. In 1962, Torok50 of Hungary reported good results with a cork borer and Pacheco33 of Mexico repeated the use of suc tion on a metal cylinder. Boerema4 of Holland and Lewis24 of To ronto utilized hypothermia and made ASD's by direct vision in 1951. In 1953, Miller20 used extracorporeal bypass to create the defect. A number of techniques designed to gain access to the septum have been reported. Martin27 tried excising the septum blindly through an incision in the atrial wall, and later2S sutured the wall of the atrium to the septum to facilitate excision of the lat ter. Gross16 sutured a "rubber well" to the wall of the atrium and excised the septum blindly under a pool of blood. Dodrill10 used a large, double ring clamp to compress the atria against the septum which was then excised from within the ring; and Swan40 bent the blades of a large forceps for the same purpose. Sondergaard45 of Denmark used an elaborate clamping device in the atrial wall through which the septum could be grasped and excised without venous oc clusion. In 1963, Schuster42 reported a novel pro cedure of twice thrusting the sharp points of a scissors on either side of the interatrial grove posteriorly so as to cut a triangular wedge out of the septum, again without interruption of blood flow. The hemodynamic equivalent of an ASD has been attempted (a) by anastomosing the two atrial appendages,37 possibly done
in 1912, n (b) by the use of an extracardiac interatrial prosthesis," and (c) by a com plex but ingenious intra-atrial prosthesis developed by Senning13 for the treatment of transposition of the great vessels. The present authors had occasion to cre ate experimental ASD's for a phonocardiographic diagnostic study reported else where.39 In the course of this investigation a number of the above procedures were performed and, finally, the following tech nique was perfected. Methods and materials Mongrel dogs, weighing 11 to 18 kilo grams were anesthetized with Nembutal. Ventilation was provided by positive pres sure with room air. A right thoracotomy was performed in the fifth intercostal space or through the bed of the fifth rib. The azygos vein was permanently ligated at its termination in the superior vena cava and umbilical tapes were placed loosely about the superior and inferior venae cavae. The pericardium was incised anterior to the phrenic nerve and reflected. Two stay su tures of 4/0 silk were placed through the right atrial wall about 3 cm. apart and in the axis of the venae cavae. Traction on these sutures permitted the fold of right atrium lying between them to be grasped with a Beck angle clamp. The atrial wall was then incised between the jaws of the clamp, with the stay sutures defining the ends of the incision. The venae cavae were occluded by snugging down rubber sleeves over the umbilical tapes and securing them with bulldog clamps. As soon as inflow oc clusion was established, the Beck clamp was released and the right atrium opened widely. The chamber was evacuated with suction, which was then maintained intermittently over the coronary sinus to provide a dry field. The fossa ovalis was identified and a 3/0 silk suture was placed at its center; the suture was not tied and both ends were left long and led out through the incision. At this point the atrium was flooded by releasing the caval tapes and the atrium was closed by reapplying the Beck clamp.
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Fig. 1. A, Trephine assembled for use in ophthalmology. B, Trephine with depth guard re versed for use in this experiment. A 3 to 5 minute "recovery period" was allowed, during which time a corneal tre phine* was threaded over both ends of the septal suture. Both 6.5 and 9.0 mm. trephines were used in these experiments. The trephines were assembled as shown in Fig. 1. The atrium was then opened as be fore and the trephine was advanced to en gage the septum around the septal suture. Gentle countertraction was maintained on the septal suture while the cutting edge of the trephine was rotated in the fossa ovalis. The last bridge of tissue which remained to complete the excision was carefully parted with scissors to avoid undue trauma to the septum. The thus-excised circular portion of the septum was removed at the end of the suture, and the resultant defect inspected as to size, contour, and position. The atrium was flooded and closed as be fore, and the atrial incision sutured with a single continuous row of 4/0 silk. The pericardium was reapproximated and the chest closed in layers. The estimated blood loss, mainly incurred while flooding the atrium, was 20 to 60 c.c. Each animal re ceived an intravenous infusion of 100 to 300 c.c. of 5 per cent dextrose/water during the procedure, and all were given penicillin and streptomycin intramuscularly postoperatively. The duration of each period of inflow occlusion was usually under 60 and *Castroviejo corneal transplant trephine. Storz Instrument Co., 4570 Audubon Avenue, St. Louis 10, Mo. Eye Instrument Catalogue Nr. E-3110. Available in sizes 4 through 12 mm. at 0.5 mm. increments. Additional sizes on special order.
Fig. 2. Drawing depicts a nearly completed ex cision of the fossa ovalis during venous occlusion. never in excess of 90 seconds. On a few occasions as many as four such periods were required to precisely position the sep tal suture before creating the defect. This procedure is depicted graphically in Fig. 2. Results Atrial septal defects were created by the trephine procedure in a final series of 19 successive animals. Three of these were sacrificed in acute experiments for the pur pose of filming the procedure.38* Phonocardiographic data obtained from studies *A movie demonstrating this procedure was shown in September 1963 at the Rome meeting of the Joint Forum of the International Cardiovascular Society and the International Surgical Society.
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Table I. A trial septal defects created in 19 successive dogs by the trephine technique
Dog
Trephine size (mm.)
Defect size at operation (mm.)
1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19.
6.5 6.5 6.5 6.5 6.5 9.0 9.0 6.5 6.5 6.5 9.0 6.5 6.5 6.5 6.5 6.5 6.5 6.5 6.5
6.5 6.5 6.5 6.5 6.5 9.0 9.0 6.5 6.5 6.5 9.0 6.5 6.5 4.0 6.5 5.0 6.5 6.5 6.5
Disposition
* * * ** ** ** ** *** *** *** *** *** *** #-1: *
***
*** ##*
*** ***
Defect size at autopsy (mm.) 6.5 6.5 6.5 6.5 6.5 9.0 9.0 6.5 6.5 6.5 9.0 6.5 6.5 4.0 6.5 Closed No autopsy 6.5 Closed
Days
followed 0 0 0 0 2 0 0 12 20 24 25 31 36 41 42 43 43 46 47
* Sacrificed at operation. ** Operative death. *** Chronic preparation.
of these animals have been presented in a previous communication.39 There occurred four operative deaths in this series. In none of these could the cause of death be defi nitely established; all occurred following technically adequate and successful proce dures. The 12 dogs which survived the op eration were kept for periods of 12 to 47 days and then sacrificed to determine the status of the defect (Table I ) . Morbidity related to the procedure was observed in only 1 dog, who emerged from anesthesia with persistent signs of localized cerebral damage. All of the dogs intentionally sacrificed at operation or classified as operative deaths were found to have atrial septal defects corresponding to the size of the trephine employed (Figs. 3 and 4 ) . The defects were circular or only slightly irregular and all were positioned within the fossa ovalis with one intentional exception. Nine of the dogs used in chronic experiments had patent de fects. In all but one of these, the size of the defect was the same as that which had been created. The defects were circular with
smooth, completely endothelized margins, and all were positioned as intended. The defects were completely closed in 2 of the animals and partially closed in another. No autopsy was performed on the remaining animal. Discussion This technique for the creation of atrial septal defects was developed for the pur pose of preparing experimental animals for hemodynamic and other studies. The au thors have found it well suited in this re spect and believe it to have the following advantages. 1. A defect anatomically corresponding to and functioning as a septum secundum defect can be made. The septal suture pre cisely defines the area of potential defect and may be withdrawn and repositioned as necessary under direct vision for accuracy in placement. All defects in this series were placed centrally in the fossa ovalis with one exception, as noted below. Other sites might also have been chosen, since the en tire septum is accessible by this approach.
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Fig. 3. Heart of Dog No. 18 demonstrates a 6.5 mm. atrial septal defect 46 days after operation.
Fig. 4. Dog No. 18—6.5 mm. trephine with excised specimen of fossa ovalis containing septal suture.
2. The use of the corneal trephine per mits standardization of both size and shape of the defects, all of which were uniformly circular and smooth-edged. The corneal trephine was selected in preference to other similar instruments because it is the sharp est, circular cutting device available, and the need for a finely honed edge was a prere quisite for the success of this technique. This trephine is available in a wide variety of sizes well suited for this work. It is com mercially obtainable, relatively inexpensive, and may be returned to the factory for shar pening as necessary. No modifications other than reassembly are required. 3. The technique of inflow occlusion, while permitting exposure of the entire sep tum otherwise obtainable only with cardiopulmonary bypass, retains much of the sim plicity and speed of the "blind" or "closed"
procedures. One operative hazard elimi nated by direct vision is that of inadvertent injury to other structures (conduction fibers, tricuspid valve, posterior atrial wall, aorta, etc.). The periods of caval occlusion em ployed were within the safest limits of ca nine tolerance to anoxia as defined by Cohen8 and Templeton.49 Not all animals are as well suited for inflow occlusion.13 Systemic air embolization, a theoretical risk in this procedure, was the probable source of the single morbidity observed. We made no effort to evacuate air from the left heart through the defect, having found that com plete flooding of the right atrium prior to closure was adequate to avoid this prob lem. Others who have created ASD's under direct vision have recognized the potential danger of air embolism and have evacuated air from the left atrium via saline per-
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„..„.JV-
Fig. 5. Dog No. 11—9.0 mm. trephine with excised circular fossa ovalis lying on edge to demonstrate "membranous" and "muscular" portions of the septum.
Fig. 6. Photomicrograph of specimen in Fig. 5.
fusion40·49 or by the use of special vents.30 Permanent arrhythmias were not encoun tered in our series, although transient ar rhythmias8 were regularly observed during and following inflow occlusion. Spontaneous closure has been known to occur with disturbing regularity in the vast majority of previous studies. It has been suggested that spontaneous closure was pri marily related to placement of the defect in highly muscular portions of the septum,37 to the size of the defect,1 and to the inflic tion of undue trauma to the defect mar gins.1' -'- We created smooth-margined cir cular defects in the predominantly mem branous fossa ovalis. The defects remained constant in size and shape for periods up
to 41 days in 7 animals, and all had com pletely endothelized margins. In 1 animal the defect was intentionally placed so as to include a portion of the heavy muscular ridge overlying the fossa (Figs. 5 and 6 ) . After 25 days, this defect was found to be eccentric, the muscular part having closed over (Fig. 7). The defects were completely closed in 2 dogs and partially closed (4 mm.) in another. In 2 of these it was known that the initial defect was less than 6.5 mm. These observations suggest that the ten dency toward spontaneous closure is en hanced by creating the defect in more mus cular portions of the septum and can be minimized by placing it wholly within the fossa ovalis. We found it unnecessary, as
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Fig. 7. Heart of D o g N o . 11, 25 days after creation of atrial septal defect, shows partial closure of the defect in the area of the "muscular" portion of the septum.
well as undesirable, to excise beyond the boundaries of the fossa, as previously re ported.5· 22 Spontaneous closures, including partial closure, occurred in 3 dogs and were related to incomplete excision of the fossa. The remaining defects showed absolutely no tendency toward closure and remained exactly as they were created with respect to size, shape, and position. The trephine technique has been applied thus far only within the experimental field. It may be that some of the advantages de scribed will lend it to clinical application, for instance, in the palliative treatment of transposition of the great vessels. Summary 1. A review of the world literature on the methods of creating experimental atrial septal defects is presented. 2. A new technique for producing a sep tum secundum defect with the use of a corneal trephine and temporary venous inflow occlusion is described. 3. Factors governing spontaneous closure and its prevention are discussed. REFERENCES 1 Arroyave, R., Murga, F., MacDonald, R., Alvarez, B., and Marcucci, M.: Produccion de
2 3
4
5
comunicacciones interauriculares bajo vision directa en perros, Rev. Col. Med. Guatemala 11: 88-91, 1960. Blakemore, A . H.: In discussion of Murray, 1948. 32 Blalock, A., and Hanlon, C : Interatrial Septal Defect: Its Experimental Production Under Direct Vision Without Interruption of the Circulation, Surg., Gynec. & Obst. 87: 183187, 1948. Boerema, I., Wildschut, A., Schmidt, W., and Broekhuysen, L.: Experimental Researches Into Hypothermia as an Aid in the Surgery of the Heart, Arch. chir. need. 3: 25-34, 1951. Bowes, D . E., Kirklin, J., and Swan, H.: The Hemodynamic Effects of Large Atrial Septal Defects, J. THORACIC SURG. 33: 350-360, 1957.
6 Brecher, G. A., and Opdyke, D.: The Relief of Acute Right Ventricular Strain by the Production of an Interatrial Septal Defect, Circulation 4: 496-502, 1951. 7 Bukharin, V. A.: Sozdanie defekta mezhpredsednoi peregorodki v esperimente, Eksp. Khir. 2: 6-12, 1957. 8 Cohen, M., Hammerstrom, R., Spellman, M., Varco, R., and Lillehei, C : The Tolerance of the Canine Heart to Temporary Complete Vena Caval Occlusion, S. Forum 3: 172-177, 1952. 9 Cohn, R.: An Experimental Method for the Closure of Interauricular Septal Defects in Dogs, A m . Heart J. 33: 453-457, 1947. 10 Dodrill, F . D.: A Method for Exposure of the
Cardiac
Septa,
J.
THORACIC
SURG.
18:
652-660, 1949. 11 Donald, D . E., Kirklin, J., Ellis, F., and
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Grindlay, J.: Methods of Closure of Experi mentally Produced Atrial Septal Defects, S. Forum 4: 41-46, 1953. 12 Dmitrieff, I. P.: Experimentelle Beitrage zur Frage über den Operativen Zugang zu den Herklappen und der Vorhofsscheidewand, Zentrarb]. Chir. S3: 715-718, 1926. 13 Eiseman, B., and Spencer, F.: Surgical Treat ment to Produce Chronic Cyanosis in the Newborn Calf, Med. Thoracal. 19: 573-575, 1962 (Suppl.). 14 Fufin, V. I.: Obrazovanie i zakrytie defekta v mezhpredserdnoi peregorodke, Eksp. Khir. 1: 17-24, 1956. 15 Griffin, G. D., and Essex, H . : Experimental Production of Interventricular Septal Defects, Surg., Gynec. & Obst. 92: 325-332, 1951. 16 Gross, R. E., Watkins, E., Pomeranz, A., Gold smith, E.: A Method for Surgical Closure of Interauricular Septal Defects, Surg., Gynec. & Obst. 96: 1-23, 1953. 17 Haecker, R.: Experimentalle Studien zur Path ologie und Chirurgie des Herzens, Arch. Klin. Chir. 84: 1035-1098, 1907. 18 Hawthorne, E. W., Brownlee, G., and Spellman, M.: Prophylaxis Against Acute Pulmo nary Edema and Death in Dogs With Aortic Insufficiency Following Renal Artery Constric tion Afforded by Prior Construction of an Atrial Septal Defect, A m . J. Physiol. 185: 479-482, 1956. 19 Hufnagel, C. A., and Gillespie, J.: Closure of Interauricular Septal Defects, Bull. George town Univ. Med. Center 4: 137-139, 1951. 20 Kay, J. H., Thomas, V. and Blalock, A.: The Experimental Production of High Interven tricular Septal Defects, Surg., Gynec. & Obst. 96: 529-535, 1953. 21 King, H., and Riberi, A.: I difetti del setto interatriale: la loro produzione e chiusura chirurgica: lavoro sperimentale, Minerva Cardioangiol. 2: 71-76, 1954. 22 Kiriluk, L. B., Hoag, E., and Meredino, K.: Experimental Interauricular Septal Defects: A Physiologic Study With an Evaluation of Methods of Closure, S. Forum (1951), pp. 199204, 1952. 23 Lang, E., Ruffo, A., Goffrini, P., and Castelli, D.: Studio sperimentale sulla genesi delle lesioni delle valvole cardiache da communicazioni interatriali e interventriculari, Minerva Chir. 7: 67-77, 1952. 24 Lewis, F . L, and Taufic, M.: Closure of Atrial Septal Defects With the Aid of Hypothermia, Surgery 33: 52-59, 1953. 25 Little, R. C , Opdyke, D., and Hawley, J.: Dynamics of Experimental Atrial Septal De fects, Am. J. Physiol. 128: 241-250, 1949. 26 Margutti, R., Saraiva, J., Gait, A, Pasqualucci, M., Borges, S., Steinberg, O., Magri, A.,
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Filho, C , Bataglia, O., and Amorim, G.: Nova tecnica para producao de defeito do septo in terauricular. Trabalho Experimental, Rev. Paul. Med. 50: 161-176, 1957. 27 Martin, W. B., and Essex, H.: Production and Closure of Atrial Septal Defects in the Dog, Am. J. Physiol. 155: 453, 1948. 28 Martin, W. B., and Essex, H.: Experimental Production and Closure of Atrial Septal D e fects, With Observations of Physiologic Ef fects, Surgery 30: 283-297, 1951. 29 Miller, B. L, Gibbon, J., Greco, V., Smith, B., Cohn, C , and Albritten, F.: The Produc tion and Repair of Interatrial Septal Defects Under Direct Vision With the Assistance of an Extracorporeal Pump-Oxygenator Cir cuit, J. THORACIC SURG. 26: 598-616, 1953.
30 Miller, B. J., Gibbon, J., Greco, V., Cohn, C , and Albritten, F . : The Use of a Vent for the Left Ventricle as a Means of Avoiding Air Embolism to the Systemic Circulation During Open Cardiotomy With the Mainte nance of the Cardiorespiratory Function of Animals by a Pump Oxygenator, S. F o r u m 6: 29-33, 1953. 31 Moore, T. C , and Schumacker, H.: Experi mental Creation of Atrial Septal Defects, With Some Notes on the Production of a Right to Left Atrial Shunt, Angiology 4: 244-252, 1953. 32 Murray, G.: Closure of Defects in Cardiac Septa, Ann. Surg. 128: 843-853, 1948. 33 Pacheco, C. R., Gelbar, C , and Arguero, R.: Production experimental y tratamiento de defectos septales intracardiacos, Gac. Med. Mex. 92: 755-771, 1962. 34 Parentela, A.: Further Experiences in the Sur gical Repair of Experimentally Produced Atrial Septal Defects, J. Internat. Coll. Sur geons 25: 30-34, 1956. 35 Pinto, V. A.: Experimental Interatrial Septal Defects, J. THORACIC SURG. 33: 585-608, 1957.
36 Riberi, A., and King, H.: I difetti del setto interventricolare, loro produzione e chiusura chirurgica; lavoro sperimentale, Minerva Cardioangiol. 2: 171-175, 1954. 37 Rogers, W. M.: Personal communication. 38 Rogers, W. M., Harrison, J., Friend, W., An drews, W., Donahoe, P., and Baker, D . : Atrial Septal Defects. A n Experimental Study (16 mm. sound movie available through W. M . Rogers). 39 Rogers, W. M., Harrison, J., Malm, J., Thom son, N., Simandl, E., Al-Naaman, Y., Demetz, A., Deterling, R., Friend, W., Andrews, W., and Donahoe, P.: Phonocardiographic Criteria in the Diagnosis of Atrial and Ventricular Septal Defects. In press. 40 Scheliong, G.: Herz- und gefassmissbildungen beim huhnchen durch kurzfristigen Sauerstoff mangel, Beitr. Path. Anat. 114: 212-242, 1954.
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41 Scheppelnian, E.: Versuche zur herzchirurgie, Arch. Klin. Chir. 97: 739, 1912. 42 Schuster, S. R., Kiernan, E., Rosencranz, J., and Bozer, A.: A New Technique for the Creation of an Atrial Septal Defect With Clinical Application, J. THORACIC & CARDIOVAS. SURG. 46: 510-521, 1963.
43 Senning, A.: Surgical Correction of Transpo sition of the Great Vessels, Surgery 45: 966980, 1959. 44 Sokolov, S. S.: Interauricular Septal Defect and Its Surgical Therapy in Experimental Conditions, Eksp. Khir. Anest. 7: 13-18, 1962. 45 Sondergaard, T., Sorensen, H., Poulsen, T., and Andersen, I.: Experimental Production of Atrial Septal Defects Under Direct Vision, Acta chir. scandinav. 107: 477-484, 1954. 46 Swan, H., Maresh, G., Johnsen, M., and War ner, G.: T h e Experimental Creation and Clo sure of Auricular Septal Defects, J. THORACIC SURG. 20: 541-551, 1950.
47 Teinesvari, A.: Experinientalle erzeugung eines vorhofseptumdefektes, zentralbl. Chir. 80: 1919-1921, 1955. 48 Temesvari, A.: Pitvari septum defectus keszitese kiserletben, Kiserl. Orvostud. 8: 242-244, 1956. 49 Templeton, J. Y., and Gibbon, J.: Experi mental Reconstruction of Cardiac Valves by Venous and Pericardial Grafts, Ann. Surg. 129: 161-176, 1949. 50 Torok, B., Szollossy, L., Kustos, G., Bartos, G., Toth, I., and Pap, J.: Septum-defectusok kiserlets eloidezese, Kiserl. Orvostud. 14: 532534, 1962. 51 Watkins, E., Jr., Pomeranz, A., Goldsmith, E., and Gross, R.: Experimental Production of Cyanosis in Dogs by a One-Stage Operation, S. Forum 4: 270-276, 1953.
/~V more complete understanding of any disease process may be achieved by simu lating that condition in an experimental an imal. This report reviews older techniques and proposes a new procedure for the cre ation of experimental atrial septal defects in dogs. Review of techniques Attempts to maintain a patent foramen ovale after gestation by either genetic or artificial means have been generally unre warding, save for a report by Schellong40 of 14 atrial septal defects produced by ex posing pregnant dogs to oxygen deficiency. The first experimental atrial septal defect Supported by grants from the New York Heart Associa tion ( W M R ) , the Lillia Babbitt Hyde Foundation ( W M R ) , and U. S. Public Health Service, No. l-GS-96 ( W G F ) . Recipient in part of the Borden Undergraduate Research Award in Medicine, Columbia University, 1964. Received for publication May 11, 1965. *Intern, Department of Surgery, Roosevelt Hospital, 428 West 59th Street, New York, N. Y. 10019. **Intern, Department of Surgery, University of Minnesota Medical Center, Minneapolis, Minn. ***Inlern, Department of Surgery, Tufts New England Center Hospital, Boston, Mass. ****Associate Professor of Anatomy, Columbia Univer sity, College of Physicians and Surgeons, New York, N. Y.
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(ASD) was created in Berlin in 1926 by Dmitrieff12 who digitally invaginated both atrial appendages to identify the septum and then thrust a small clamp through the sep tum and enlarged the defect with one finger from the opposite side. In 1947, Cohn9 created the defect by inserting a hemostat through the left atrial appendage and open ing it in the septum. This technique was soon repeated by others.6' 25· 32 Then Mar tin28 and Swan4" advanced a scalpel through the atrial appendage to the vicinity of the septum and incised blindly. In 1907, Haecker' 7 of Germany intro duced temporary venous inflow occlusion. This innovation provided a dry field and allowed the operator to approach the sep tum from either incised atrium. Thus with forceps and scissors, numerous investigators throughout the world independently created ASD'S 1 ' 14' 19' 21' 22> 27' 31' 34' 35 ' 44 ' 40,47 ' 51 In 1948, Blalock and Hanlon 3 published their now well-known procedure for cre ating a posterior septal defect by the use of a clamp which encompassed a portion of both atria and their common septum. Com plete interruption of blood flow was not necessary during this procedure. A variety of trocars have been used by
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a number of investigators. Blakemore- was probably the first to use a punch device on the atrial septum in the late 1930's. The technique was later attempted by Hufnagel10 and by Griffin15 who added a rotary punch and a rotating blade around a cardioscope. Griffin also created interventricular septal defects with a trocar which Donald11 later adopted for ASD's. Kay-0 used a sharpened cork borer and added suction with which to grasp the septum. Riberi36 attached a tro car to a drill with suction. A special guide wire and punch device were used by Margutti2'1 of Brazil and by Bukharin7 of Rus sia. In 1962, Torok50 of Hungary reported good results with a cork borer and Pacheco33 of Mexico repeated the use of suc tion on a metal cylinder. Boerema4 of Holland and Lewis24 of To ronto utilized hypothermia and made ASD's by direct vision in 1951. In 1953, Miller20 used extracorporeal bypass to create the defect. A number of techniques designed to gain access to the septum have been reported. Martin27 tried excising the septum blindly through an incision in the atrial wall, and later2S sutured the wall of the atrium to the septum to facilitate excision of the lat ter. Gross16 sutured a "rubber well" to the wall of the atrium and excised the septum blindly under a pool of blood. Dodrill10 used a large, double ring clamp to compress the atria against the septum which was then excised from within the ring; and Swan40 bent the blades of a large forceps for the same purpose. Sondergaard45 of Denmark used an elaborate clamping device in the atrial wall through which the septum could be grasped and excised without venous oc clusion. In 1963, Schuster42 reported a novel pro cedure of twice thrusting the sharp points of a scissors on either side of the interatrial grove posteriorly so as to cut a triangular wedge out of the septum, again without interruption of blood flow. The hemodynamic equivalent of an ASD has been attempted (a) by anastomosing the two atrial appendages,37 possibly done
in 1912, n (b) by the use of an extracardiac interatrial prosthesis," and (c) by a com plex but ingenious intra-atrial prosthesis developed by Senning13 for the treatment of transposition of the great vessels. The present authors had occasion to cre ate experimental ASD's for a phonocardiographic diagnostic study reported else where.39 In the course of this investigation a number of the above procedures were performed and, finally, the following tech nique was perfected. Methods and materials Mongrel dogs, weighing 11 to 18 kilo grams were anesthetized with Nembutal. Ventilation was provided by positive pres sure with room air. A right thoracotomy was performed in the fifth intercostal space or through the bed of the fifth rib. The azygos vein was permanently ligated at its termination in the superior vena cava and umbilical tapes were placed loosely about the superior and inferior venae cavae. The pericardium was incised anterior to the phrenic nerve and reflected. Two stay su tures of 4/0 silk were placed through the right atrial wall about 3 cm. apart and in the axis of the venae cavae. Traction on these sutures permitted the fold of right atrium lying between them to be grasped with a Beck angle clamp. The atrial wall was then incised between the jaws of the clamp, with the stay sutures defining the ends of the incision. The venae cavae were occluded by snugging down rubber sleeves over the umbilical tapes and securing them with bulldog clamps. As soon as inflow oc clusion was established, the Beck clamp was released and the right atrium opened widely. The chamber was evacuated with suction, which was then maintained intermittently over the coronary sinus to provide a dry field. The fossa ovalis was identified and a 3/0 silk suture was placed at its center; the suture was not tied and both ends were left long and led out through the incision. At this point the atrium was flooded by releasing the caval tapes and the atrium was closed by reapplying the Beck clamp.
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Fig. 1. A, Trephine assembled for use in ophthalmology. B, Trephine with depth guard re versed for use in this experiment. A 3 to 5 minute "recovery period" was allowed, during which time a corneal tre phine* was threaded over both ends of the septal suture. Both 6.5 and 9.0 mm. trephines were used in these experiments. The trephines were assembled as shown in Fig. 1. The atrium was then opened as be fore and the trephine was advanced to en gage the septum around the septal suture. Gentle countertraction was maintained on the septal suture while the cutting edge of the trephine was rotated in the fossa ovalis. The last bridge of tissue which remained to complete the excision was carefully parted with scissors to avoid undue trauma to the septum. The thus-excised circular portion of the septum was removed at the end of the suture, and the resultant defect inspected as to size, contour, and position. The atrium was flooded and closed as be fore, and the atrial incision sutured with a single continuous row of 4/0 silk. The pericardium was reapproximated and the chest closed in layers. The estimated blood loss, mainly incurred while flooding the atrium, was 20 to 60 c.c. Each animal re ceived an intravenous infusion of 100 to 300 c.c. of 5 per cent dextrose/water during the procedure, and all were given penicillin and streptomycin intramuscularly postoperatively. The duration of each period of inflow occlusion was usually under 60 and *Castroviejo corneal transplant trephine. Storz Instrument Co., 4570 Audubon Avenue, St. Louis 10, Mo. Eye Instrument Catalogue Nr. E-3110. Available in sizes 4 through 12 mm. at 0.5 mm. increments. Additional sizes on special order.
Fig. 2. Drawing depicts a nearly completed ex cision of the fossa ovalis during venous occlusion. never in excess of 90 seconds. On a few occasions as many as four such periods were required to precisely position the sep tal suture before creating the defect. This procedure is depicted graphically in Fig. 2. Results Atrial septal defects were created by the trephine procedure in a final series of 19 successive animals. Three of these were sacrificed in acute experiments for the pur pose of filming the procedure.38* Phonocardiographic data obtained from studies *A movie demonstrating this procedure was shown in September 1963 at the Rome meeting of the Joint Forum of the International Cardiovascular Society and the International Surgical Society.
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Table I. A trial septal defects created in 19 successive dogs by the trephine technique
Dog
Trephine size (mm.)
Defect size at operation (mm.)
1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19.
6.5 6.5 6.5 6.5 6.5 9.0 9.0 6.5 6.5 6.5 9.0 6.5 6.5 6.5 6.5 6.5 6.5 6.5 6.5
6.5 6.5 6.5 6.5 6.5 9.0 9.0 6.5 6.5 6.5 9.0 6.5 6.5 4.0 6.5 5.0 6.5 6.5 6.5
Disposition
* * * ** ** ** ** *** *** *** *** *** *** #-1: *
***
*** ##*
*** ***
Defect size at autopsy (mm.) 6.5 6.5 6.5 6.5 6.5 9.0 9.0 6.5 6.5 6.5 9.0 6.5 6.5 4.0 6.5 Closed No autopsy 6.5 Closed
Days
followed 0 0 0 0 2 0 0 12 20 24 25 31 36 41 42 43 43 46 47
* Sacrificed at operation. ** Operative death. *** Chronic preparation.
of these animals have been presented in a previous communication.39 There occurred four operative deaths in this series. In none of these could the cause of death be defi nitely established; all occurred following technically adequate and successful proce dures. The 12 dogs which survived the op eration were kept for periods of 12 to 47 days and then sacrificed to determine the status of the defect (Table I ) . Morbidity related to the procedure was observed in only 1 dog, who emerged from anesthesia with persistent signs of localized cerebral damage. All of the dogs intentionally sacrificed at operation or classified as operative deaths were found to have atrial septal defects corresponding to the size of the trephine employed (Figs. 3 and 4 ) . The defects were circular or only slightly irregular and all were positioned within the fossa ovalis with one intentional exception. Nine of the dogs used in chronic experiments had patent de fects. In all but one of these, the size of the defect was the same as that which had been created. The defects were circular with
smooth, completely endothelized margins, and all were positioned as intended. The defects were completely closed in 2 of the animals and partially closed in another. No autopsy was performed on the remaining animal. Discussion This technique for the creation of atrial septal defects was developed for the pur pose of preparing experimental animals for hemodynamic and other studies. The au thors have found it well suited in this re spect and believe it to have the following advantages. 1. A defect anatomically corresponding to and functioning as a septum secundum defect can be made. The septal suture pre cisely defines the area of potential defect and may be withdrawn and repositioned as necessary under direct vision for accuracy in placement. All defects in this series were placed centrally in the fossa ovalis with one exception, as noted below. Other sites might also have been chosen, since the en tire septum is accessible by this approach.
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Fig. 3. Heart of Dog No. 18 demonstrates a 6.5 mm. atrial septal defect 46 days after operation.
Fig. 4. Dog No. 18—6.5 mm. trephine with excised specimen of fossa ovalis containing septal suture.
2. The use of the corneal trephine per mits standardization of both size and shape of the defects, all of which were uniformly circular and smooth-edged. The corneal trephine was selected in preference to other similar instruments because it is the sharp est, circular cutting device available, and the need for a finely honed edge was a prere quisite for the success of this technique. This trephine is available in a wide variety of sizes well suited for this work. It is com mercially obtainable, relatively inexpensive, and may be returned to the factory for shar pening as necessary. No modifications other than reassembly are required. 3. The technique of inflow occlusion, while permitting exposure of the entire sep tum otherwise obtainable only with cardiopulmonary bypass, retains much of the sim plicity and speed of the "blind" or "closed"
procedures. One operative hazard elimi nated by direct vision is that of inadvertent injury to other structures (conduction fibers, tricuspid valve, posterior atrial wall, aorta, etc.). The periods of caval occlusion em ployed were within the safest limits of ca nine tolerance to anoxia as defined by Cohen8 and Templeton.49 Not all animals are as well suited for inflow occlusion.13 Systemic air embolization, a theoretical risk in this procedure, was the probable source of the single morbidity observed. We made no effort to evacuate air from the left heart through the defect, having found that com plete flooding of the right atrium prior to closure was adequate to avoid this prob lem. Others who have created ASD's under direct vision have recognized the potential danger of air embolism and have evacuated air from the left atrium via saline per-
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„..„.JV-
Fig. 5. Dog No. 11—9.0 mm. trephine with excised circular fossa ovalis lying on edge to demonstrate "membranous" and "muscular" portions of the septum.
Fig. 6. Photomicrograph of specimen in Fig. 5.
fusion40·49 or by the use of special vents.30 Permanent arrhythmias were not encoun tered in our series, although transient ar rhythmias8 were regularly observed during and following inflow occlusion. Spontaneous closure has been known to occur with disturbing regularity in the vast majority of previous studies. It has been suggested that spontaneous closure was pri marily related to placement of the defect in highly muscular portions of the septum,37 to the size of the defect,1 and to the inflic tion of undue trauma to the defect mar gins.1' -'- We created smooth-margined cir cular defects in the predominantly mem branous fossa ovalis. The defects remained constant in size and shape for periods up
to 41 days in 7 animals, and all had com pletely endothelized margins. In 1 animal the defect was intentionally placed so as to include a portion of the heavy muscular ridge overlying the fossa (Figs. 5 and 6 ) . After 25 days, this defect was found to be eccentric, the muscular part having closed over (Fig. 7). The defects were completely closed in 2 dogs and partially closed (4 mm.) in another. In 2 of these it was known that the initial defect was less than 6.5 mm. These observations suggest that the ten dency toward spontaneous closure is en hanced by creating the defect in more mus cular portions of the septum and can be minimized by placing it wholly within the fossa ovalis. We found it unnecessary, as
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Fig. 7. Heart of D o g N o . 11, 25 days after creation of atrial septal defect, shows partial closure of the defect in the area of the "muscular" portion of the septum.
well as undesirable, to excise beyond the boundaries of the fossa, as previously re ported.5· 22 Spontaneous closures, including partial closure, occurred in 3 dogs and were related to incomplete excision of the fossa. The remaining defects showed absolutely no tendency toward closure and remained exactly as they were created with respect to size, shape, and position. The trephine technique has been applied thus far only within the experimental field. It may be that some of the advantages de scribed will lend it to clinical application, for instance, in the palliative treatment of transposition of the great vessels. Summary 1. A review of the world literature on the methods of creating experimental atrial septal defects is presented. 2. A new technique for producing a sep tum secundum defect with the use of a corneal trephine and temporary venous inflow occlusion is described. 3. Factors governing spontaneous closure and its prevention are discussed. REFERENCES 1 Arroyave, R., Murga, F., MacDonald, R., Alvarez, B., and Marcucci, M.: Produccion de
2 3
4
5
comunicacciones interauriculares bajo vision directa en perros, Rev. Col. Med. Guatemala 11: 88-91, 1960. Blakemore, A . H.: In discussion of Murray, 1948. 32 Blalock, A., and Hanlon, C : Interatrial Septal Defect: Its Experimental Production Under Direct Vision Without Interruption of the Circulation, Surg., Gynec. & Obst. 87: 183187, 1948. Boerema, I., Wildschut, A., Schmidt, W., and Broekhuysen, L.: Experimental Researches Into Hypothermia as an Aid in the Surgery of the Heart, Arch. chir. need. 3: 25-34, 1951. Bowes, D . E., Kirklin, J., and Swan, H.: The Hemodynamic Effects of Large Atrial Septal Defects, J. THORACIC SURG. 33: 350-360, 1957.
6 Brecher, G. A., and Opdyke, D.: The Relief of Acute Right Ventricular Strain by the Production of an Interatrial Septal Defect, Circulation 4: 496-502, 1951. 7 Bukharin, V. A.: Sozdanie defekta mezhpredsednoi peregorodki v esperimente, Eksp. Khir. 2: 6-12, 1957. 8 Cohen, M., Hammerstrom, R., Spellman, M., Varco, R., and Lillehei, C : The Tolerance of the Canine Heart to Temporary Complete Vena Caval Occlusion, S. Forum 3: 172-177, 1952. 9 Cohn, R.: An Experimental Method for the Closure of Interauricular Septal Defects in Dogs, A m . Heart J. 33: 453-457, 1947. 10 Dodrill, F . D.: A Method for Exposure of the
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652-660, 1949. 11 Donald, D . E., Kirklin, J., Ellis, F., and
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Grindlay, J.: Methods of Closure of Experi mentally Produced Atrial Septal Defects, S. Forum 4: 41-46, 1953. 12 Dmitrieff, I. P.: Experimentelle Beitrage zur Frage über den Operativen Zugang zu den Herklappen und der Vorhofsscheidewand, Zentrarb]. Chir. S3: 715-718, 1926. 13 Eiseman, B., and Spencer, F.: Surgical Treat ment to Produce Chronic Cyanosis in the Newborn Calf, Med. Thoracal. 19: 573-575, 1962 (Suppl.). 14 Fufin, V. I.: Obrazovanie i zakrytie defekta v mezhpredserdnoi peregorodke, Eksp. Khir. 1: 17-24, 1956. 15 Griffin, G. D., and Essex, H . : Experimental Production of Interventricular Septal Defects, Surg., Gynec. & Obst. 92: 325-332, 1951. 16 Gross, R. E., Watkins, E., Pomeranz, A., Gold smith, E.: A Method for Surgical Closure of Interauricular Septal Defects, Surg., Gynec. & Obst. 96: 1-23, 1953. 17 Haecker, R.: Experimentalle Studien zur Path ologie und Chirurgie des Herzens, Arch. Klin. Chir. 84: 1035-1098, 1907. 18 Hawthorne, E. W., Brownlee, G., and Spellman, M.: Prophylaxis Against Acute Pulmo nary Edema and Death in Dogs With Aortic Insufficiency Following Renal Artery Constric tion Afforded by Prior Construction of an Atrial Septal Defect, A m . J. Physiol. 185: 479-482, 1956. 19 Hufnagel, C. A., and Gillespie, J.: Closure of Interauricular Septal Defects, Bull. George town Univ. Med. Center 4: 137-139, 1951. 20 Kay, J. H., Thomas, V. and Blalock, A.: The Experimental Production of High Interven tricular Septal Defects, Surg., Gynec. & Obst. 96: 529-535, 1953. 21 King, H., and Riberi, A.: I difetti del setto interatriale: la loro produzione e chiusura chirurgica: lavoro sperimentale, Minerva Cardioangiol. 2: 71-76, 1954. 22 Kiriluk, L. B., Hoag, E., and Meredino, K.: Experimental Interauricular Septal Defects: A Physiologic Study With an Evaluation of Methods of Closure, S. Forum (1951), pp. 199204, 1952. 23 Lang, E., Ruffo, A., Goffrini, P., and Castelli, D.: Studio sperimentale sulla genesi delle lesioni delle valvole cardiache da communicazioni interatriali e interventriculari, Minerva Chir. 7: 67-77, 1952. 24 Lewis, F . L, and Taufic, M.: Closure of Atrial Septal Defects With the Aid of Hypothermia, Surgery 33: 52-59, 1953. 25 Little, R. C , Opdyke, D., and Hawley, J.: Dynamics of Experimental Atrial Septal De fects, Am. J. Physiol. 128: 241-250, 1949. 26 Margutti, R., Saraiva, J., Gait, A, Pasqualucci, M., Borges, S., Steinberg, O., Magri, A.,
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Filho, C , Bataglia, O., and Amorim, G.: Nova tecnica para producao de defeito do septo in terauricular. Trabalho Experimental, Rev. Paul. Med. 50: 161-176, 1957. 27 Martin, W. B., and Essex, H.: Production and Closure of Atrial Septal Defects in the Dog, Am. J. Physiol. 155: 453, 1948. 28 Martin, W. B., and Essex, H.: Experimental Production and Closure of Atrial Septal D e fects, With Observations of Physiologic Ef fects, Surgery 30: 283-297, 1951. 29 Miller, B. L, Gibbon, J., Greco, V., Smith, B., Cohn, C , and Albritten, F.: The Produc tion and Repair of Interatrial Septal Defects Under Direct Vision With the Assistance of an Extracorporeal Pump-Oxygenator Cir cuit, J. THORACIC SURG. 26: 598-616, 1953.
30 Miller, B. J., Gibbon, J., Greco, V., Cohn, C , and Albritten, F . : The Use of a Vent for the Left Ventricle as a Means of Avoiding Air Embolism to the Systemic Circulation During Open Cardiotomy With the Mainte nance of the Cardiorespiratory Function of Animals by a Pump Oxygenator, S. F o r u m 6: 29-33, 1953. 31 Moore, T. C , and Schumacker, H.: Experi mental Creation of Atrial Septal Defects, With Some Notes on the Production of a Right to Left Atrial Shunt, Angiology 4: 244-252, 1953. 32 Murray, G.: Closure of Defects in Cardiac Septa, Ann. Surg. 128: 843-853, 1948. 33 Pacheco, C. R., Gelbar, C , and Arguero, R.: Production experimental y tratamiento de defectos septales intracardiacos, Gac. Med. Mex. 92: 755-771, 1962. 34 Parentela, A.: Further Experiences in the Sur gical Repair of Experimentally Produced Atrial Septal Defects, J. Internat. Coll. Sur geons 25: 30-34, 1956. 35 Pinto, V. A.: Experimental Interatrial Septal Defects, J. THORACIC SURG. 33: 585-608, 1957.
36 Riberi, A., and King, H.: I difetti del setto interventricolare, loro produzione e chiusura chirurgica; lavoro sperimentale, Minerva Cardioangiol. 2: 171-175, 1954. 37 Rogers, W. M.: Personal communication. 38 Rogers, W. M., Harrison, J., Friend, W., An drews, W., Donahoe, P., and Baker, D . : Atrial Septal Defects. A n Experimental Study (16 mm. sound movie available through W. M . Rogers). 39 Rogers, W. M., Harrison, J., Malm, J., Thom son, N., Simandl, E., Al-Naaman, Y., Demetz, A., Deterling, R., Friend, W., Andrews, W., and Donahoe, P.: Phonocardiographic Criteria in the Diagnosis of Atrial and Ventricular Septal Defects. In press. 40 Scheliong, G.: Herz- und gefassmissbildungen beim huhnchen durch kurzfristigen Sauerstoff mangel, Beitr. Path. Anat. 114: 212-242, 1954.
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41 Scheppelnian, E.: Versuche zur herzchirurgie, Arch. Klin. Chir. 97: 739, 1912. 42 Schuster, S. R., Kiernan, E., Rosencranz, J., and Bozer, A.: A New Technique for the Creation of an Atrial Septal Defect With Clinical Application, J. THORACIC & CARDIOVAS. SURG. 46: 510-521, 1963.
43 Senning, A.: Surgical Correction of Transpo sition of the Great Vessels, Surgery 45: 966980, 1959. 44 Sokolov, S. S.: Interauricular Septal Defect and Its Surgical Therapy in Experimental Conditions, Eksp. Khir. Anest. 7: 13-18, 1962. 45 Sondergaard, T., Sorensen, H., Poulsen, T., and Andersen, I.: Experimental Production of Atrial Septal Defects Under Direct Vision, Acta chir. scandinav. 107: 477-484, 1954. 46 Swan, H., Maresh, G., Johnsen, M., and War ner, G.: T h e Experimental Creation and Clo sure of Auricular Septal Defects, J. THORACIC SURG. 20: 541-551, 1950.
47 Teinesvari, A.: Experinientalle erzeugung eines vorhofseptumdefektes, zentralbl. Chir. 80: 1919-1921, 1955. 48 Temesvari, A.: Pitvari septum defectus keszitese kiserletben, Kiserl. Orvostud. 8: 242-244, 1956. 49 Templeton, J. Y., and Gibbon, J.: Experi mental Reconstruction of Cardiac Valves by Venous and Pericardial Grafts, Ann. Surg. 129: 161-176, 1949. 50 Torok, B., Szollossy, L., Kustos, G., Bartos, G., Toth, I., and Pap, J.: Septum-defectusok kiserlets eloidezese, Kiserl. Orvostud. 14: 532534, 1962. 51 Watkins, E., Jr., Pomeranz, A., Goldsmith, E., and Gross, R.: Experimental Production of Cyanosis in Dogs by a One-Stage Operation, S. Forum 4: 270-276, 1953.