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Congenital coronary-pulmonary arterial shunt in a German shepherd dog: Diagnosis and surgical correction
Journal of Veterinary Cardiology (2011) 13, 153e158
www.elsevier.com/locate/jvc
Congenital coronary-pulmonary arterial shunt in a German shepherd dog: Diagnosis and surgical correction* ˆte ´, DVM b, George E. Eyster, DVM, MS a Augusta Pelosi, DVM a,*, Etienne Co a
College of Veterinary Medicine, Michigan State University, East Lansing, MI, USA Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island, Canada and Centre Ve´te´rinaire DMV, Montre´al, Que´bec, Canada
b
Received 9 September 2010; received in revised form 7 March 2011; accepted 18 March 2011
KEYWORDS Surgery-cardiac; Heart; Cardiac; Aorticopulmonary; Veterinary
Abstract Background: A 10 week-old intact female German shepherd dog was examined because of a heart murmur. Methods: An echocardiogram revealed an extracardiac left-to-right shunt. An angiogram identified shunting between the aorta and the pulmonary artery in an unusual location. Results: Thoracotomy was performed to better identify and correct the lesion; a tubular shunt between the left coronary artery and the pulmonary artery was found and ligated in a closed-heart procedure. The murmur resolved immediately upon ligation and the dog’s heart size normalized over a period of several months after surgery. Conclusion: In the dog, surgical correction of a coronary artery-pulmonary artery shunt can be performed without complications and can be associated with reversal of cardiac remodeling. ª 2011 Elsevier B.V. All rights reserved.
*
A unique aspect of the Journal of Veterinary Cardiology is the emphasis of additional web-based images permitting the detailing of procedures and diagnostics. These images can be viewed (by those readers with subscription access) by going to http://www. sciencedirect.com/science/journal/17602734. The issue to be viewed is clicked and the available PDF and image downloading is available via the Summary Plus link. The supplementary material for a given article appears at the end of the page. Downloading the videos may take several minutes. Readers will require at least Quicktime 7 (available free at http://www.apple.com/quicktime/ download/) to enjoy the content. Another means to view the material is to go to http://www.doi.org and enter the doi number unique to this paper which is indicated at the end of the manuscript. * Corresponding author. E-mail address: [email protected] (A. Pelosi). 1760-2734/$ - see front matter ª 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.jvc.2011.03.001
154 A 10 week-old intact female German shepherd dog was referred for evaluation of a heart murmur. The dog’s owner had not noted any overt manifestations of illness and, when questioned, reported no known instances of exercise intolerance, dyspnea, cough, or syncope. The dog was bright, alert, responsive, and in good body condition (body weight: 8 kg). The ausculted heart rate (100 beats/min) and rhythm (regularly irregular, consistent with respiratory sinus arrhythmia) were considered normal. A grade III/VI continuous heart murmur was heard immediately dorsal to the region of the heart base at the level of the left 3rd intercostal space. The point of maximal intensity (PMI) of this murmur was identified as conspicuously more dorsal than that of a typical patent ductus arteriosus (PDA). A hyperkinetic pulse and a normal respiratory rate and effort were present. An electrocardiogram showed sinus arrhythmia with a non-specific intraventricular conduction delay. Thoracic radiographs revealed moderate cardiomegaly (vertebral heart score ¼ 12.8; normal ¼ 9.7 0.51) and evidence of pulmonary overcirculation (Fig. 1a,b). Transthoracic echocar-
A. Pelosi et al. diography (TTE) showed continuous flow through a shunt identified in the region of the left coronary artery (Fig. 2; Video 1) between the aorta and the pulmonary artery immediately cranial to the pulmonic valve (Video 2), but the full extent of the shunt could not be visualized. Values for the left ventricular internal diameter at end-diastole (LVIDd; 45.6 mm [normal ¼ 28.4 1.8 mm]) and systole (LVIDs; 33.7 mm [normal ¼ 18.6 1.7 mm]) were markedly higher than normal.2 Values for the ratio of left atrial to aortic diameters (LA:Ao; 1.6:1 [normal ¼ 0.9 0.08 :1]) and for aortic velocity (3.3 m/s [normal ¼ 0.99e2.3 m/s]) were mildly increased, and moderate aortic insufficiency was noted; the two-dimensional appearance of the aortic valve was unremarkable. The echocardiogram was suggestive of an aorticopulmonary (AP) shunt, and further investigation was recommended. Supplementary data associated with this article can be found, in the online version, at doi:10. 1016/j.jvc.2011.03.001. The dog was referred to Michigan State University, where results of the physical exam and initial imaging
Figure 1 Lateral and dorsoventral radiographs taken before (a, b) and 5 months after (c, d) surgery. A reduction in cardiac size, and decrease in the diameters of pulmonary arteries and veins, are apparent after surgery.
Surgical correction of coronary-pulmonary shunt
Figure 2 Color-flow Doppler still frame image from a right parasternal long-axis view, showing the left ventricular outflow tract. Turbulence is evident between the aorta and a large shunt located at the level of the left coronary artery (arrow). The opening is not in the location of a ductus arteriosus and morphology and location are different from those of a traditional AP window. LV: left ventricle, RV: right ventricle.
were unchanged. For diagnostic cardiac catheterization, the dog was premedicated with butorphanol (0.2 mg/kg IM), and general anesthesia was induced with ketamine (5 mg/kg IV)/diazepam (0.3 mg/kg IV) to effect and maintained with an inhaled mixture of 2% isoflurane and oxygen. Aortic angiography revealed a shunt arising from the paraconal interventricular branch of the left coronary artery and inserting into the main pulmonary artery; the aortic catheter passed readily through this shunt and allowed injection directly into the main pulmonary artery (Fig. 3). The shunt coursed laterally and cranially from its aortic origin and entered the main pulmonary artery 2 cm distal to the pulmonic valve. The left coronary artery and the proximal part of its paraconal interventricular branch were markedly dilated, while the distal portion of the paraconal interventricular branch of the left coronary artery appeared normal in dimension. The rest of the angiographic findings were unremarkable, including subjectively adequate global systolic function and an absence of any visible segmental wall motion abnormalities. The right coronary artery was normal in appearance. Left- and right-sided intracardiac pressure measurements were within normal limits. The dog received hydromorphone (0.03 mg/kg IV) and acepromazine (0.02 mg/kg IV) upon completion of the procedure, and recovery was uneventful. Days later, the dog was premedicated with acepromazine (0.02 mg/kg IM) and hydromorphone (0.06 mg/kg IM). General anesthesia was induced with ketamine (5 mg/kg IV)/diazepam (0.2 mg/kg IV) given to effect, and maintained with fentanyl as
155
Figure 3 Angiogram obtained with the patient in left lateral recumbency; the venous catheter is in the right ventricle with the tip just below the right ventricular outflow tract, and the aortic catheter passes through the left coronary artery, through the shunt, and terminates in the pulmonary artery. The contrast injected from the aortic catheter highlights the main pulmonary artery, confirming a left-to-right shunt via the passage of the catheter through the shunt. Diagram to illustrate the angiogram: A: aortic catheter; B: contrast in pulmonary artery, injected via aortic catheter; C: aortic catheter through shunt; D: venous catheter.
a constant rate infusion (5 mcg/kg/min IV) and an inhaled mixture of sevoflurane and oxygen. Glycopyrrolate (0.02 mg/kg IM) was administered in anticipation of vagus nerve manipulation. An epidural injection of morphine PF (0.1 mg/kg) was given to reduce postoperative pain. A standard 4th left lateral thoracotomy and pericardial incision were performed, with stay sutures placed to create a pericardial basket. The left phrenic and vagus nerves were retracted dorsally. The ligamentum arteriosum was identified, ligated, and transected to allow better exposure of deeper structures and separation of the aorta and pulmonary artery. Blunt dissection around the pulmonary artery allowed identification of a large shunting vessel caudolateral to the aorta and craniomedial to the pulmonary artery. On closer inspection, the origin of the shunt was visible at the left coronary artery, 1 cm distal to the coronary artery’s origin from the aorta. The shunt measured approximately 1 cm in diameter and 4 cm in length, and a thrill was palpable on its surface. Although previously identified angiographically, the insertion of the shunt into the main pulmonary artery could not be confirmed grossly due to limited surgical exposure. Umbilical tape was passed around the shunt to temporarily occlude flow and assess whether any grossly visible changes
156 suggesting myocardial hypoperfusion occurred as a result, contraindicating definitive ligation. The thrill immediately disappeared. As no change was noted in the appearance of the myocardium upon temporary occlusion, 2-0 silk sutures were passed around the shunt and were tied to permanently ligate it. With ligation of the shunt, systemic arterial blood pressure immediately increased (systolic: from 80 to 110 mm Hg; diastolic: from 40 to 70 mm Hg), the thrill disappeared definitively, and the heart rate decreased (120e90 beats/min). The rest of the thoracic exploration, closure, and anesthetic recovery were unremarkable; a TTE, performed while the dog was still under anesthesia, showed equivocally depressed systolic function (shortening fraction ¼ 19.3%), mild tricuspid and mitral regurgitation, and absence of flow through the shunt. The dog was discharged three days after surgery, and the owner reported an uncomplicated and full postoperative recovery. Five months after surgery, the dog was bright, alert, responsive, and in normal body condition when reexamined locally. Body weight was 30.8 kg. Physical exam revealed respiratory sinus arrhythmia (70 beats/min), no murmur or gallop, a split second heart sound, and normal pulse strength and synchrony. Radiographically, reduction in the size of the cardiac silhouette was apparent, with no evidence of pulmonary overcirculation (Fig. 1c,d; vertebral heart score ¼ 11.4). An echocardiogram showed complete resolution of the abnormally large left ventricular diastolic diameter (LVIDd ¼ 36.1 [breed and gender normal: 49.3 4.4]), including a reduction in absolute LVIDd despite a greater than three-fold increase in body weight. When indexed to body weight, the change represented a near-halving of this corrected left ventricular dimension (preoperative wLVIDd: 2.87; postoperative wLVIDd: 1.45; normal for breed ¼ 1.68 0.20).3 The LVIDs measurement likewise decreased markedly, both absolutely and when indexed to body weight (31.5 mm [breed and gender normal: 34.3 3.2 mm]; preoperative wLVIDs: 2.12; postoperative wLVIDs: 1.26; normal for breed ¼ 1.25 0.21) indicating extensive cardiac remodeling during the postoperative period.3 Trivial pulmonic and mitral insufficiency were present and there was persistence of moderate aortic insufficiency. The peak aortic velocity (2.2 m/s), measured with spectral Doppler, was at the upper limit of the normal range. An 8-mm round hyperechoic structure was present adjacent to the aorta at the level of the left coronary cusp and was interpreted as suture and associated tissue. No residual shunt flow was identified on color-flow Doppler examination.
A. Pelosi et al.
Discussion Coronary shunts are rare congenital or acquired coronary malformations, which can originate from one of the main coronary arteries and connect to a cardiac chamber (coronary-cameral shunt) or a great vessel (coronary arteriovenous shunt), bypassing the normal coronary capillary network. Most commonly, these conditions are described as coronary arterial-venous shunts (CAVS) and are considered central arteriovenous malformations, in contrast to peripheral arteriovenous shunts of the limbs or other extrathoracic structures. In humans, based on angiographic studies, the reported prevalence is approximately 0.26%.4e6 Occasionally, the acquired forms are seen following cardiac surgery,7 myocardial biopsy,8 pacemaker implantation,9 coronary intervention10 or trauma.5,11,12 In the present case, the patient’s signalment and history indicated that the defect was congenital. In humans, most CAVS (90%) drain into the right side of the heart. The right coronary artery or its branches are affected in 55% of cases, while the left coronary artery is involved in 35e42%.13,14 In asymptomatic patients, CAVS typically originate from the left coronary system and often drain into the pulmonary artery.12,15,16 The dog in this report showed no overt systemic signs arising from the disorder. The principal physical exam abnormalities were a continuous heart murmur and a hyperdynamic pulse. The location of the murmur’s PMI at the heart base, as noted in this dog, is expected with AP shunts; its presence in a location more dorsal than the expected PMI of a PDA may be explained at least in part by the orientation of the turbulent jet, which is typically directed ventrally with a PDA, but was directed craniolaterally in the present case (Video 2). The murmur of CAVS may present an unusual diastolic accentuation, producing a peak in mid-tolate diastole, while a systolic accentuation is noted in a patient with PDA17; these features were not noted in this dog, however. The murmur can be softer compared to the murmur of a PDA, and located in a lower (i.e., more caudal) position on the chest in humans.17 The echocardiographic findings in this case were consistent with volume overload of the left side of the heart but TTE did not allow full visualization of the abnormal coronary artery. This shortcoming is probably due to the limitations of imaging the complete course of coronary arteries in dogs with TTE. Other cases of AP shunts in dogs have similarly not been clearly visualized with TTE.18
Surgical correction of coronary-pulmonary shunt Preoperative left ventricular dilation and poor systolic function were attributed to chronic volume overload from the left-to-right shunt, aortic insufficiency, or a combination of both, but a primary cardiomyopathy could not be ruled out. However, the complete resolution of both diastolic and systolic left ventricular enlargement with surgery alone; the dramatic reduction of LVIDd that has been described in dogs undergoing occlusion of a hemodynamically similar lesion, PDAc; and the observation that growth from the age of 10 weeks to adulthood in dogs is associated with changes in left ventricular dimensions of typically less than 10% when indexed to body weight,3 indicate that the changes noted initially in this dog’s left ventricular dimensions were likely due solely to volume overload imposed by the shunt. Similarly, the reduction of aortic peak velocity from an abnormally high value to the upper limit of the normal range is expected with reduction in volume overload of the left ventricle, rather than aortic/ subaortic stenosis. In 23% of human cases, CAVS close spontaneously.15 For the remaining majority of cases, a decision to intervene is based on several factors including the presence of clinical signs, the magnitude of the CAVS, and possible complications.19 Although there is agreement among human surgeons to close CAVS in the symptomatic patient,14 the decision for intervention is sometimes controversial when patients are asymptomatic.15 Surgical intervention in asymptomatic cases is advised to prevent future problems (myocardial dysfunction, endocarditis) or in cases where large-volume, hemodynamically unstable shunting is noted with or without myocardial ischemia.14,18 In the present case, the extensive left ventricular changes noted at 10 weeks of age conferred a poor long-term prognosis for a normal life, and justified surgical intervention in the absence of overt physical signs. Corrective surgery usually is performed under cardiopulmonary bypass (80%), but it has been performed without cardiopulmonary bypass, in particular when the shunt connects the left coronary to the pulmonary artery,16 as was the case with our patient. Surgical closure via thoracotomy can be achieved with two different approaches: epicardial approach, (extracardiac without the use of bypass) and endocardial approach (intracardiac).20 Surgical techniques performed on human cardiology patients in referral centers carry a high success rate
c Stauthammer C, Nguyenba T, Tobias AH. Short- and longterm cardiac changes following complete occlusion of uncomplicated patent ductus arteriosus in dogs (abstract). J Vet Intern Med 2007; 21: 609.
157 with few complications.21 Alternatively, the shunt can be approached via percutaneous catheterization using an occluding device.5,21e25 In recent years, coronary shunts have been occluded using coils,21,22 detachable balloons,5 Amplatz vascular plugs,24 or Bard PDA umbrella devices.25 Not all coronary shunts can be approached and occluded percutaneously, however. Important factors that determine whether percutaneous occlusion may be performed safely include the location of the shunt, its shape, the ability to catheterize the origin of the shunt and the presence of single or multiple vessels.5,20 In the present case, the structure of the shunt could not be fully elucidated during cardiac catheterization, and at least two critical complications were therefore possible: placement of an intravascular device could occlude part of the coronary circulation, causing myocardial ischemia/ infarction, and an intravascular device could not be placed with certainty in a position that would not interfere with normal pulmonary arterial flow. In response to such uncertainty, thoracotomy was pursued, allowing for temporary occlusion such that the surgeons could observe an absence of overt myocardial discoloration, and allowing for permanent, specific closure of the shunting vessel without interfering with pulmonary arterial flow. This patient’s outcome suggests that such an approach in dogs with suspected or confirmed CAVS is reasonable and effective.
Conflict of interest No conflict of interest declared.
Supplementary material Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.jvc.2011.03.001.
References 1. Buchanan JW, Bu ¨cheler J. Vertebral scale system to measure canine heart size in radiographs. J Am Vet Med Assoc 1995;206:194e199. 2. Cornell CC, Kittleson MD, Della Torre P, Ha ¨ggstro ¨m J, Lombard CW, Pedersen HD, Vollmar A, Wey A. Allometric scaling of M-mode cardiac measurements in normal adult dogs. J Vet Intern Med 2004;18:311e321. 3. Hall DJ, Cornell CC, Crawford S, Brown DJ. Meta-analysis of canine echocardiographic dimensional data using ratio indices. J Vet Cardiol 2008;10:11e23.
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4. Yamanaka O, Hobbs R. Coronary artery anomalies in 126,595 patients undergoing coronary angiography. Cathet Cardiovasc Diagn 1990;21:28e40. 5. Balanescu S, Sangiorgi G, Castelvecchio S, Medda M, Inglese L. Coronary artery fistulas: clinical consequences and methods of closure. A literature review. Ital Heart J 2001;2:669e676. 6. Baltaxe HA, Wixson D. The incidence of congenital anomalies of the coronary arteries in the adult population. Radiology 1977;122:47e52. 7. Reidy J, Anjos R, Qureshi SA, Baker EJ, Tynan MJ. Transcatheter embolization in the treatment of coronary artery fistulas. J Am Coll Cardiol 1991;18:187e192. 8. Henzlova M, Nath H, Bucy R, Bourge R, Kirklin J, Rogers W. Coronary artery to right ventricle fistula in heart transplant recipients: a complication of endomyocardial biopsy. J Am Coll Cardiol 1989;14:258e261. 9. Saeian K, Vellinga T, Troup P, Wetherbee J. Coronary artery fistula formation secondary to permanent pacemaker placement. Chest 1991;99:780e781. 10. Iannone LA, Iannone DP. Iatrogenic left coronary artery fistula to ventricle following PTCA: a previously unreported complication with non-surgical management. Am Heart J 1991;121:1848e1849. 11. Gowda RM, Balendu CV, Ijaz AK. Coronary artery fistulas: clinical and therapeutic considerations. Int J Cardiol 2006;107:7e10. 12. Sapin P, Frantz E, Jain A, Nichols TC, Dehmer GJ. Coronary artery fistula: an abnormality affecting all age groups. Medicine (Baltimore) 1990;69:101e113. 13. Lin FC, Chang HJ, Chern MS, Wen MS, Yeh SJ, Wu D. Multiplane transesophageal echocardiography in the diagnosis of congenital coronary artery fistula. Am Heart J 1995;130: 1236e1244. 14. Liberthson RR, Sagar K, Berkoben JP, Weintraub RM, Levine FH. Congenital coronary arteriovenous fistula: report of thirteen patients. Review of the literature and delineation of the management. Circulation 1979;59:849e854.
15. Sherwood MC, Rockenmacher S, Colan SD, Geva T. Prognostic significance of clinically silent coronary artery fistulas. Am J Cardiol 1999;83:407e411. 16. Kamiya H, Yasuda T, Nagamine H, Naoki Sakakibara N, Nishida S, Kawasuji M, Watanabe G. Surgical treatment of congenital coronary artery fistulas: 27 years’ experience and a review of the literature. J Cardiovasc Surg 2002;17: 173e177. 17. Qureshi SA. Coronary arterial fistulas. Orphanet J Rare Dis 2006;1:51e56. 18. Fujii Y, Aoki T, Takano H, Ishikawa R, Wakao Y. Arteriovenous shunts resembling patent ductus arteriosus in dogs: 3 cases. J Vet Cardiol 2009;11:147e151. 19. Cheung D, Au W, Cheung H, Chiu C, Lee W. Coronary artery fistulas: long-term results of surgical correction. Ann Thorac Surg 2001;71:190e195. 20. Lowe JE, Newland OH, Sabiston DC. Surgical management of congenital coronary artery fistulae. Ann Surg 1981;194: 373e380. 21. Mavroudis C, Backer CL, Rocchini AP, Muster AJ, Gevitz M. Coronary artery fistulas in infants and children: a surgical review and discussion of coil embolization. Ann Thorac Surg 1997;63:1235e1242. 22. Lee ML, Chaou WT. Successful transcatheter coil embolization of coronary artery fistula in an infant. J Thorac Imaging 2000;15:153e156. 23. Armsby LR, Keane JF, Sherwood MC, Forbess JM, Perry SB, Lock JE. Management of coronary artery fistulae. Patient selection and results of transcatheter closure. J Am Coll Cardiol 2002;39:1026e1032. 24. Wiegand G, Sieverding L, Kaulitz R, Hofbeck M. Transarterial and transvenous approach for transcatheter closure of a large coronary artery fistula with the Amplatzer vascular plug. Pediatr Cardiol 2009;30:172e175. 25. Perry S, Rome J, Keane J, Baim D, Lock J. Transcatheter closure of coronary artery fistulas. J Am Coll Cardiol 1992; 20:205e209.
Available online at www.sciencedirect.com
www.elsevier.com/locate/jvc
Congenital coronary-pulmonary arterial shunt in a German shepherd dog: Diagnosis and surgical correction* ˆte ´, DVM b, George E. Eyster, DVM, MS a Augusta Pelosi, DVM a,*, Etienne Co a
College of Veterinary Medicine, Michigan State University, East Lansing, MI, USA Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island, Canada and Centre Ve´te´rinaire DMV, Montre´al, Que´bec, Canada
b
Received 9 September 2010; received in revised form 7 March 2011; accepted 18 March 2011
KEYWORDS Surgery-cardiac; Heart; Cardiac; Aorticopulmonary; Veterinary
Abstract Background: A 10 week-old intact female German shepherd dog was examined because of a heart murmur. Methods: An echocardiogram revealed an extracardiac left-to-right shunt. An angiogram identified shunting between the aorta and the pulmonary artery in an unusual location. Results: Thoracotomy was performed to better identify and correct the lesion; a tubular shunt between the left coronary artery and the pulmonary artery was found and ligated in a closed-heart procedure. The murmur resolved immediately upon ligation and the dog’s heart size normalized over a period of several months after surgery. Conclusion: In the dog, surgical correction of a coronary artery-pulmonary artery shunt can be performed without complications and can be associated with reversal of cardiac remodeling. ª 2011 Elsevier B.V. All rights reserved.
*
A unique aspect of the Journal of Veterinary Cardiology is the emphasis of additional web-based images permitting the detailing of procedures and diagnostics. These images can be viewed (by those readers with subscription access) by going to http://www. sciencedirect.com/science/journal/17602734. The issue to be viewed is clicked and the available PDF and image downloading is available via the Summary Plus link. The supplementary material for a given article appears at the end of the page. Downloading the videos may take several minutes. Readers will require at least Quicktime 7 (available free at http://www.apple.com/quicktime/ download/) to enjoy the content. Another means to view the material is to go to http://www.doi.org and enter the doi number unique to this paper which is indicated at the end of the manuscript. * Corresponding author. E-mail address: [email protected] (A. Pelosi). 1760-2734/$ - see front matter ª 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.jvc.2011.03.001
154 A 10 week-old intact female German shepherd dog was referred for evaluation of a heart murmur. The dog’s owner had not noted any overt manifestations of illness and, when questioned, reported no known instances of exercise intolerance, dyspnea, cough, or syncope. The dog was bright, alert, responsive, and in good body condition (body weight: 8 kg). The ausculted heart rate (100 beats/min) and rhythm (regularly irregular, consistent with respiratory sinus arrhythmia) were considered normal. A grade III/VI continuous heart murmur was heard immediately dorsal to the region of the heart base at the level of the left 3rd intercostal space. The point of maximal intensity (PMI) of this murmur was identified as conspicuously more dorsal than that of a typical patent ductus arteriosus (PDA). A hyperkinetic pulse and a normal respiratory rate and effort were present. An electrocardiogram showed sinus arrhythmia with a non-specific intraventricular conduction delay. Thoracic radiographs revealed moderate cardiomegaly (vertebral heart score ¼ 12.8; normal ¼ 9.7 0.51) and evidence of pulmonary overcirculation (Fig. 1a,b). Transthoracic echocar-
A. Pelosi et al. diography (TTE) showed continuous flow through a shunt identified in the region of the left coronary artery (Fig. 2; Video 1) between the aorta and the pulmonary artery immediately cranial to the pulmonic valve (Video 2), but the full extent of the shunt could not be visualized. Values for the left ventricular internal diameter at end-diastole (LVIDd; 45.6 mm [normal ¼ 28.4 1.8 mm]) and systole (LVIDs; 33.7 mm [normal ¼ 18.6 1.7 mm]) were markedly higher than normal.2 Values for the ratio of left atrial to aortic diameters (LA:Ao; 1.6:1 [normal ¼ 0.9 0.08 :1]) and for aortic velocity (3.3 m/s [normal ¼ 0.99e2.3 m/s]) were mildly increased, and moderate aortic insufficiency was noted; the two-dimensional appearance of the aortic valve was unremarkable. The echocardiogram was suggestive of an aorticopulmonary (AP) shunt, and further investigation was recommended. Supplementary data associated with this article can be found, in the online version, at doi:10. 1016/j.jvc.2011.03.001. The dog was referred to Michigan State University, where results of the physical exam and initial imaging
Figure 1 Lateral and dorsoventral radiographs taken before (a, b) and 5 months after (c, d) surgery. A reduction in cardiac size, and decrease in the diameters of pulmonary arteries and veins, are apparent after surgery.
Surgical correction of coronary-pulmonary shunt
Figure 2 Color-flow Doppler still frame image from a right parasternal long-axis view, showing the left ventricular outflow tract. Turbulence is evident between the aorta and a large shunt located at the level of the left coronary artery (arrow). The opening is not in the location of a ductus arteriosus and morphology and location are different from those of a traditional AP window. LV: left ventricle, RV: right ventricle.
were unchanged. For diagnostic cardiac catheterization, the dog was premedicated with butorphanol (0.2 mg/kg IM), and general anesthesia was induced with ketamine (5 mg/kg IV)/diazepam (0.3 mg/kg IV) to effect and maintained with an inhaled mixture of 2% isoflurane and oxygen. Aortic angiography revealed a shunt arising from the paraconal interventricular branch of the left coronary artery and inserting into the main pulmonary artery; the aortic catheter passed readily through this shunt and allowed injection directly into the main pulmonary artery (Fig. 3). The shunt coursed laterally and cranially from its aortic origin and entered the main pulmonary artery 2 cm distal to the pulmonic valve. The left coronary artery and the proximal part of its paraconal interventricular branch were markedly dilated, while the distal portion of the paraconal interventricular branch of the left coronary artery appeared normal in dimension. The rest of the angiographic findings were unremarkable, including subjectively adequate global systolic function and an absence of any visible segmental wall motion abnormalities. The right coronary artery was normal in appearance. Left- and right-sided intracardiac pressure measurements were within normal limits. The dog received hydromorphone (0.03 mg/kg IV) and acepromazine (0.02 mg/kg IV) upon completion of the procedure, and recovery was uneventful. Days later, the dog was premedicated with acepromazine (0.02 mg/kg IM) and hydromorphone (0.06 mg/kg IM). General anesthesia was induced with ketamine (5 mg/kg IV)/diazepam (0.2 mg/kg IV) given to effect, and maintained with fentanyl as
155
Figure 3 Angiogram obtained with the patient in left lateral recumbency; the venous catheter is in the right ventricle with the tip just below the right ventricular outflow tract, and the aortic catheter passes through the left coronary artery, through the shunt, and terminates in the pulmonary artery. The contrast injected from the aortic catheter highlights the main pulmonary artery, confirming a left-to-right shunt via the passage of the catheter through the shunt. Diagram to illustrate the angiogram: A: aortic catheter; B: contrast in pulmonary artery, injected via aortic catheter; C: aortic catheter through shunt; D: venous catheter.
a constant rate infusion (5 mcg/kg/min IV) and an inhaled mixture of sevoflurane and oxygen. Glycopyrrolate (0.02 mg/kg IM) was administered in anticipation of vagus nerve manipulation. An epidural injection of morphine PF (0.1 mg/kg) was given to reduce postoperative pain. A standard 4th left lateral thoracotomy and pericardial incision were performed, with stay sutures placed to create a pericardial basket. The left phrenic and vagus nerves were retracted dorsally. The ligamentum arteriosum was identified, ligated, and transected to allow better exposure of deeper structures and separation of the aorta and pulmonary artery. Blunt dissection around the pulmonary artery allowed identification of a large shunting vessel caudolateral to the aorta and craniomedial to the pulmonary artery. On closer inspection, the origin of the shunt was visible at the left coronary artery, 1 cm distal to the coronary artery’s origin from the aorta. The shunt measured approximately 1 cm in diameter and 4 cm in length, and a thrill was palpable on its surface. Although previously identified angiographically, the insertion of the shunt into the main pulmonary artery could not be confirmed grossly due to limited surgical exposure. Umbilical tape was passed around the shunt to temporarily occlude flow and assess whether any grossly visible changes
156 suggesting myocardial hypoperfusion occurred as a result, contraindicating definitive ligation. The thrill immediately disappeared. As no change was noted in the appearance of the myocardium upon temporary occlusion, 2-0 silk sutures were passed around the shunt and were tied to permanently ligate it. With ligation of the shunt, systemic arterial blood pressure immediately increased (systolic: from 80 to 110 mm Hg; diastolic: from 40 to 70 mm Hg), the thrill disappeared definitively, and the heart rate decreased (120e90 beats/min). The rest of the thoracic exploration, closure, and anesthetic recovery were unremarkable; a TTE, performed while the dog was still under anesthesia, showed equivocally depressed systolic function (shortening fraction ¼ 19.3%), mild tricuspid and mitral regurgitation, and absence of flow through the shunt. The dog was discharged three days after surgery, and the owner reported an uncomplicated and full postoperative recovery. Five months after surgery, the dog was bright, alert, responsive, and in normal body condition when reexamined locally. Body weight was 30.8 kg. Physical exam revealed respiratory sinus arrhythmia (70 beats/min), no murmur or gallop, a split second heart sound, and normal pulse strength and synchrony. Radiographically, reduction in the size of the cardiac silhouette was apparent, with no evidence of pulmonary overcirculation (Fig. 1c,d; vertebral heart score ¼ 11.4). An echocardiogram showed complete resolution of the abnormally large left ventricular diastolic diameter (LVIDd ¼ 36.1 [breed and gender normal: 49.3 4.4]), including a reduction in absolute LVIDd despite a greater than three-fold increase in body weight. When indexed to body weight, the change represented a near-halving of this corrected left ventricular dimension (preoperative wLVIDd: 2.87; postoperative wLVIDd: 1.45; normal for breed ¼ 1.68 0.20).3 The LVIDs measurement likewise decreased markedly, both absolutely and when indexed to body weight (31.5 mm [breed and gender normal: 34.3 3.2 mm]; preoperative wLVIDs: 2.12; postoperative wLVIDs: 1.26; normal for breed ¼ 1.25 0.21) indicating extensive cardiac remodeling during the postoperative period.3 Trivial pulmonic and mitral insufficiency were present and there was persistence of moderate aortic insufficiency. The peak aortic velocity (2.2 m/s), measured with spectral Doppler, was at the upper limit of the normal range. An 8-mm round hyperechoic structure was present adjacent to the aorta at the level of the left coronary cusp and was interpreted as suture and associated tissue. No residual shunt flow was identified on color-flow Doppler examination.
A. Pelosi et al.
Discussion Coronary shunts are rare congenital or acquired coronary malformations, which can originate from one of the main coronary arteries and connect to a cardiac chamber (coronary-cameral shunt) or a great vessel (coronary arteriovenous shunt), bypassing the normal coronary capillary network. Most commonly, these conditions are described as coronary arterial-venous shunts (CAVS) and are considered central arteriovenous malformations, in contrast to peripheral arteriovenous shunts of the limbs or other extrathoracic structures. In humans, based on angiographic studies, the reported prevalence is approximately 0.26%.4e6 Occasionally, the acquired forms are seen following cardiac surgery,7 myocardial biopsy,8 pacemaker implantation,9 coronary intervention10 or trauma.5,11,12 In the present case, the patient’s signalment and history indicated that the defect was congenital. In humans, most CAVS (90%) drain into the right side of the heart. The right coronary artery or its branches are affected in 55% of cases, while the left coronary artery is involved in 35e42%.13,14 In asymptomatic patients, CAVS typically originate from the left coronary system and often drain into the pulmonary artery.12,15,16 The dog in this report showed no overt systemic signs arising from the disorder. The principal physical exam abnormalities were a continuous heart murmur and a hyperdynamic pulse. The location of the murmur’s PMI at the heart base, as noted in this dog, is expected with AP shunts; its presence in a location more dorsal than the expected PMI of a PDA may be explained at least in part by the orientation of the turbulent jet, which is typically directed ventrally with a PDA, but was directed craniolaterally in the present case (Video 2). The murmur of CAVS may present an unusual diastolic accentuation, producing a peak in mid-tolate diastole, while a systolic accentuation is noted in a patient with PDA17; these features were not noted in this dog, however. The murmur can be softer compared to the murmur of a PDA, and located in a lower (i.e., more caudal) position on the chest in humans.17 The echocardiographic findings in this case were consistent with volume overload of the left side of the heart but TTE did not allow full visualization of the abnormal coronary artery. This shortcoming is probably due to the limitations of imaging the complete course of coronary arteries in dogs with TTE. Other cases of AP shunts in dogs have similarly not been clearly visualized with TTE.18
Surgical correction of coronary-pulmonary shunt Preoperative left ventricular dilation and poor systolic function were attributed to chronic volume overload from the left-to-right shunt, aortic insufficiency, or a combination of both, but a primary cardiomyopathy could not be ruled out. However, the complete resolution of both diastolic and systolic left ventricular enlargement with surgery alone; the dramatic reduction of LVIDd that has been described in dogs undergoing occlusion of a hemodynamically similar lesion, PDAc; and the observation that growth from the age of 10 weeks to adulthood in dogs is associated with changes in left ventricular dimensions of typically less than 10% when indexed to body weight,3 indicate that the changes noted initially in this dog’s left ventricular dimensions were likely due solely to volume overload imposed by the shunt. Similarly, the reduction of aortic peak velocity from an abnormally high value to the upper limit of the normal range is expected with reduction in volume overload of the left ventricle, rather than aortic/ subaortic stenosis. In 23% of human cases, CAVS close spontaneously.15 For the remaining majority of cases, a decision to intervene is based on several factors including the presence of clinical signs, the magnitude of the CAVS, and possible complications.19 Although there is agreement among human surgeons to close CAVS in the symptomatic patient,14 the decision for intervention is sometimes controversial when patients are asymptomatic.15 Surgical intervention in asymptomatic cases is advised to prevent future problems (myocardial dysfunction, endocarditis) or in cases where large-volume, hemodynamically unstable shunting is noted with or without myocardial ischemia.14,18 In the present case, the extensive left ventricular changes noted at 10 weeks of age conferred a poor long-term prognosis for a normal life, and justified surgical intervention in the absence of overt physical signs. Corrective surgery usually is performed under cardiopulmonary bypass (80%), but it has been performed without cardiopulmonary bypass, in particular when the shunt connects the left coronary to the pulmonary artery,16 as was the case with our patient. Surgical closure via thoracotomy can be achieved with two different approaches: epicardial approach, (extracardiac without the use of bypass) and endocardial approach (intracardiac).20 Surgical techniques performed on human cardiology patients in referral centers carry a high success rate
c Stauthammer C, Nguyenba T, Tobias AH. Short- and longterm cardiac changes following complete occlusion of uncomplicated patent ductus arteriosus in dogs (abstract). J Vet Intern Med 2007; 21: 609.
157 with few complications.21 Alternatively, the shunt can be approached via percutaneous catheterization using an occluding device.5,21e25 In recent years, coronary shunts have been occluded using coils,21,22 detachable balloons,5 Amplatz vascular plugs,24 or Bard PDA umbrella devices.25 Not all coronary shunts can be approached and occluded percutaneously, however. Important factors that determine whether percutaneous occlusion may be performed safely include the location of the shunt, its shape, the ability to catheterize the origin of the shunt and the presence of single or multiple vessels.5,20 In the present case, the structure of the shunt could not be fully elucidated during cardiac catheterization, and at least two critical complications were therefore possible: placement of an intravascular device could occlude part of the coronary circulation, causing myocardial ischemia/ infarction, and an intravascular device could not be placed with certainty in a position that would not interfere with normal pulmonary arterial flow. In response to such uncertainty, thoracotomy was pursued, allowing for temporary occlusion such that the surgeons could observe an absence of overt myocardial discoloration, and allowing for permanent, specific closure of the shunting vessel without interfering with pulmonary arterial flow. This patient’s outcome suggests that such an approach in dogs with suspected or confirmed CAVS is reasonable and effective.
Conflict of interest No conflict of interest declared.
Supplementary material Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.jvc.2011.03.001.
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