J . small Anim Pract. (1975) 16, 743-749.
Recanalized patent ductus arteriosus in the dog G E O R G E E . E Y S T E R , R O B E R T D. W H I P P L E , A . T H O M A S EVANS, J. D A V I D H O U G H AND L O R E L K. A N D E R S O N Department of Small Animal Surgery and Medicine, Michigan State University, East Lansing, Michigan 48824
ABSTRACT In 140 consecutive operations for patent ductus arteriosus at the Michigan State University Veterinary Clinic over a period of 10 years, three animals have had recanalized defects (2 %), and of these, one dog recanalized for the second time. Of the 140 surgeries, fifteen were suture divisions and the remaining 125 were ligations. All recanalized cases had been ligated in the original operation. We believe, due to the ease of surgery, ligation is the preferred method. However, if the ductus recanalizes, division and suture should be accomplished in the second operation.
Patent ductus arteriosus, the most common of the observed congenital anomalies in the dog, is fortunately the most easily corrected. Surgical correction has been accomplished routinely in veterinary medicine since the early 1960s. Although there has been some personal preference as to the method of surgery (Breznock et al., 1971 ; Buchanan, Soma & Patterson, 1967), in general, the accepted manner is double ligation. Division and suture of the ends of the ductus is difficult, demands excessive surgical time and instrumentation, and is often dangerous. At the Michigan State University Veterinary Clinic, over the past 10 years, 140 patent ductus arterious operations have been performed. In these procedures, surgical results have been comparable with human surgery (Hardyetal., 1966; Zachman et al., 1974). One hundred and twenty-two of these canine procedures have been accomplished by double ligation with 2-0 silk suture, two with umbilical tape ligation, and one with stainless steel clip ligation. Fifteen have been divided using patent ductus clamps and their ends sutured with a double row of 5-0 or 6-0 suture material. During this 10 year period, three animals have had recanalization of the patent ductus and one of them recurred twice. 743
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Cue 1 A 1-day-old female Poodle was first seen with its mother after whelping and was considered normal. The dog was seen again at 2 months for vaccination and, at that time, was noted to have a patent ductus arteriosus. The dog was otherwise normal. Surgery was advised. At 3 months, the dog was presented for patent ductus arteriosus surgery. At this time, the patient was still asymptomatic. Surgery was performed uneventfully and the dog was discharged. One month later, when the dog was being vaccinated against distemper and hepatitis, a continuous murmur was again ausculted a t the base of the heart on the left side. Two weeks later the animal was returned for surgery. On admission for the second operation, the patient was still normal. However, electrocardiogram now indicated left ventricular hypertrophy and there was radiographic enlargement of the left side of the heart. At surgery, the ductus had recanalized anterior to the still present ligatures. There were significant adhesions and the left anterior lung lobe was removed. T h e ductus was freed and again double ligated. The patient was discharged in good condition. Three months later, the dog had a new owner and was again referred to the Michigan State University Veterinary Clinic for patent ductus arteriosus. Reported symptoms were listlessness and a cough. A ‘machinery’ murmur, lung congestion, and radiographic evidence of cardiac enlargement were present. The animal was discharged to be returned for a third operation for patent ductus arterious. When readmitted for the third surgery, division and suture were recommended. At surgery, the ductus was found to have again recanalized anterior to the sutures. The shunt was dissected with difficulty due to adhesions, but patent ductus clamps were placed and the ductus was divided. Continuous double row suture was used to close the shunt. The pulmonary artery side was closed using5-Osilk and the aortic side with 6-0 silk. The animal recovered uneventfully, was discharged, and has remained healthy. Case 2
An 8-month-old German Shepherd female was referred to the Michigan State University Clinic for patent ductus arteriosus surgery. The dog had been quite healthy, but the referring veterinarian had been aware of a murmur for 4 months. O n examination, the dog was normal except for the ‘machinery’ murmur and slight lung congestion. Radiographs and electrocardiogram were consistent with a diagnoiis of patent ductus arteriosus and mitral insufficiency probably due to heart dilation. The animal was presented for surgery and, after ligation of the aortic side with 2-0 silk, a slight diastolic thrill persisted in the pulmonary artery. This was considered to be due to pulmonary artery deviation by the suture. T h e thrill disappeared after ligation of the pulmonary artery side. The mitral insufficiency murmur disappeared in 2 days and the dog was discharged. However, because of the abnormal palpable diastolic finding a t surgery, the owner was requested to have the dog re-examined in 6 weeks. When examined 6 weeks after surgery, it had a continuous murmur, no fever, but a white count of 24,000. The dog was
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hospitalized and treated with antibiotics. Although it never demonstrated fever, the white count ranged between 12 and 24,000. As the dog was in oestrus, it was assumed that this might be a contributory factor to the elevated white count. The patient was discharged on medication to be returned in 2 weeks for surgery. O n re-admission, the animal’s white count were still high. There were increased expiratory sounds, and a patent ductus arteriosus murmur. I n addition Proteus was cultured from a sterile urine sample. Antibiotic sensitivity was run and the patient was then treated with the indicated antibiotic, and surgery was arranged At surgery the anterior left lobes were adherent and removed, The ductus was partly obscured by the adhesions. After dissection in the adhesions, the ductus was clamped with patent ductus clumps and the murmur disappeared. The ductus was then transected. A small amount of bleeding commenced. Double row continuous 5-0 silk sutures were placed in the pulmonary artery, and a 6-0 suture line was started on the aortic side, but complete closure on the posterior ventral wall of the aorta could not be accomplished. Bleeding continued and after multiple attempts to control the haemorrhage, the patient died. Autopsy revealed that the ductus had recanalized to the right of the old sutures and to the main and right pulmonary artery. The haemorrhage at surgery had developed from a small persisting portion of the recanalized ductus in the right pulmonary artery and to a small degree from the right end of the shunt to the aortic side. These openings could not be seen at the time ofsurgery. Case 3
A 5-month-old Welsh Corgi female with a diagnosis of patent ductus arteriosus was donated to the Michigan State University Veterinary Clinic for teaching purposes. The animal was normal except for the murmur. Electrocardiogram and radiographs were consistent with the diagnosis. The animal was used in a teaching programme and eventually by the resident surgery laboratory. The patent ductus was ligated uneventfulk and the dog was given to a veterinary student. Two months after surgery, the student reported that the murmur had recurred. Examination confirmed the diagnosis and, because of the initial experience, the dog was catheterized to confirm the location of the recanalization. This confirmed the shunt to the main or left pulmonary artery. Surgery was accomplished 2 weeks later. The left anterior lung lobes were adherent and removed. The ductus had recanalized (anterior to the sutures) to the main pulmonary artery. The sutures were still in place. The shunt was isolated, clamped and divided. The pulmonary artery was closed with double row continuous 5-0 Tycron and the aortic side with 6-0 Tycron. The patient recovered uneventfully and is normal. DISCUSSION T h e ductus arteriosus, a major fetal shunt, closes at about the end of the first week after birth (Hause & Ederstrom, 1968). I n a small number of dogs, the ductus re-
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mains open and should be closed surgically. Various methods of closure have been used :(1)division andsuturingthe twoends, (2) catheter introducedplugs (Porstman, et al., 1974), (3) metal clips (Breznock et al., 1971), and (4) in veterinary medicine, the most popular is a simple double ligation. Each of these various procedures has advantages and, to some degree, disadvantages. Results have been generally good and, in veterinary medicine, the technique can be considered safe and effective in a disease that is otherwise fatal. Recanalization of the ductus is rare, but it does occur (Buchanan, 1967). It is likely that recurrence is most frequently associated with theligation technique, since the aorta and pulmonary artery are, in fact, pulled more closely together (Figs 1 and 2). The authors believe the ligation isthe preferred method ofrepair ofa patent ductus arteriosus in the dog, particularly in the small animal. Surgical procedure is then quick, carries the least risk, and requires the least specialized equipment. The dissection of the ductus is similar in all procedures, but in ligation, there is no need for a completely free shunt from end to end. The ligations can be easily placed and the procedure concluded. In some large dogs with very large shunts, the
FIG.1. Ductus prepared for placement of sutures. One suture has been passed around the shunt.
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FIG. 2. Double suture placed around the ductus and ligated. T h e ductus is pinched together and the aorta and pulmonary artery are in close contact.
ligation may add to the risk of tearing the ductus, while the ligature is tightened. Thirteen of the cases reviewed at Michigan State University were of this type. All were ligated with no complications'; however, one of three recurred in this group (Case 2). Stainless steel clamps are applied in the routine manner after dissection of the ductus but in the author's limited experience have no niajor advantage over ligation. Catheter-placed plugs have not yet been used clinically in veterinary medicine. Division and suture should be accomplished in all dogs that recanalize. It is not known whether a predisposition to recanalization exists, but certainly one must suspect it because in one of our three dogs it recurred twice. There has been no opportunity to explore further this possibility since all recanalized cases are now divided and sutured a t the second operation (Figs 3 and 4). After division and suture the aorta and pulmonary artery are no longer attached, or in contact at the ductus area, and it is very unlikely that recanalization can recur. Division-andsuture technique requires the use of two very thin, non-traumatic, non-slip vascu-
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FIG.3. Patent ductus clamps on the divided ductus. Suture of the end is being accomplished.
FIG.4. Sutures completed in the divided ductus. The aorta and pulmonary artery are now separated and fistula formation between them is exceedingly unlikely.
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lar clamps (patent ductus clamps). In addition, the division-and-suture technique usually takes twice as long as the simple ligation technique. In three of four recanalizations, the shunts recurred anterior to and around the ligations. The authors cannot explain the predilection for this area, nor the one patient that recanalized to the right, encompassing part of the right pulmonary artery. However, this particular case did have a wide and short ductus. One speculates that the friction between the aorta and pulmonary artery may have allowed the fistula to develop. Catheterization is recommended to determine the position of the recanalized ductus, since shunt to the right is \?irtually impossible to reach from the usual left lateral thoracotomy. ACKNOWLEDGMENT
The authors wish to thank Dr Ed. Foster of Charlotte, Michigan, Dr James Kingsley of Eaton Rapids, Michigan, Dr Joe Watkins of Southfield, Michigan, and Ms Sheila McMonagle for help in preparation of this manuscript. REFERENCES BREZNOCK, E.M., WISLOH, A., HELWIG, R.W. & HAMLIN, R.L. (1971).J . Am. Vet. Med. Ass. 158, 753. D.F. (1967).J. A m . Ve&.Med. Ass. 151,701. BUCHANAN, J.W., SOMA,L.R. & PATTERSON, BUCHANAN, J.W. (1967). Personal communication HARDY, J.D., WEBB,W.R., TIMMIS, H., WATSON, D.G. & BLAKE, T.M. (1966). Ann. SurE. 164,877. HAUSE, E.W. & EDERSTROM, H.E. (1968). Anat. Rec. 160,289. K., WIERNI, L. & WORNKE, H. (1974).Circ. 50,376. PORSTMANN, W., HIERONYMI, ZACHMAN, R.D., STEINMETZ, G.P., BATHAN, R .J., GRAVEN, S.M. & LEDBETTER, M.K. ( 1974). Xm. HeartJ. 87,697.