Trilogy of Fallot in a Dog

J Vet Clin 29(5) : 404-407 (2012)

Ran Choi, Hyo-Jin Ahn and Changbaig Hyun1 Section of Small Animal Internal Medicine, College of Veterinary Medicine, Kangwon National University, Chuncheon 201-100, Korea

(Accepted: October 05, 2012)

Abstract : A 3 years-old female mixed dog (weighing 5.3 kg) was referred to veterinary teaching hospital of Kangwon National University with primary complaints of syncope, severe exercise intolerance, depression and lethargy. Diagnostic studies revealed polycythemia, right sided cardiac enlargement on thoracic radiography and right-to left atrial septal defect, severe pulmonary stenosis (~5 m/s of peak velocity) and right ventricular hypertrophy. Based on diagnostic findings, the dog was diagnosed as trilogy of Fallot. To improve clinical condition of this dog, diltiazem and enalapril were prescribed with weekly phlebotomy. To author’s best knowledge, this is the first case of trilogy of Fallot in Korea. Key words : trilogy of Fallot, atrial septal defects, pulmonic stenosis, right ventricular hypertrophy, CHD.

Introduction ring veterinarian, the dog had history of cardiac murmur after birth and occasional syncopal episodes (increasing frequency Trilogy of Fallot is a compound congenital heart defects recently). On the physical examination, the dog had grade 2/6 (CHD) comprised of pulmonary stenosis, atrial septal dys- mild systolic murmur at right apex and left base of heart. The morphogenesis (e.g. atrial septal defect and patent foramen systolic blood pressure measured by Doppler method was ovale) and right ventricular hypertrophy (1). The CHD are 100-110 mmHg. broadly classified into cyanotic CHD and non-cyanotic CHD. Laboratory tests revealed mild leukocytosis (21.8 K/uL, ref- Common cyanotic CHDs included Ebstein's anomaly, hypo- erence range 6-17 K/uL) with lymphocytosis (13.9 K/uL, ref- plastic left heart, pulmonary atresia, tetralogy of Fallot, total erence range 1-5 K/uL), polycythemia (11.75 M/uL, reference anomalous pulmonary venous return, transposition of the range 5.5-7.5 M/uL) with marked increased hematocrit (72.8%, great vessels, tricuspid atresia, truncus arteriosus and so on reference range 37-55) and mild azotemia (blood urea 29 mg/ (6). In addition, any heart defects complicated with pulmo- dL, reference range 7-25 mg/dL). nary hypertension or right ventricular pressure overload can Electrocardiogram showed marked sinus arrhythmia with also cause cyanotic CHD in dogs. intermittent sinus exit block and right ventricular enlargement Any heart defect having right-to-left (R-L) shunt can cause pattern (i.e. S-wave in lead I, II and QRS right axis deviation; cyanosis and polycythemia secondary to tissue hypoxia, Fig 1). In addition, there was Osborne wave in lead III, indi- whereas any heart defect having left-to-right (L-R) shunt can cating hypoxic injuries in the myocardium (Fig 1). cause ventricular dilation resulted from recirculation circuit Dorsoventral view of thoracic radiography showed reversed and volume overload from the shunt flow. Recirculation cir- D shaped cardiac shadow with enlargement of right ventricle cuit refers the blood flow re-entering the pulmonary circula- and main pulmonary artery (Fig 2A) and lateral view showed tion through the L-R shunt. The case described here is a increased sternal contact of cardiac shadow, elevation of tra- compound CHD having R-L shunt resulted from right ven- chea, right atrial enlargement, increased soft tissue density at tricular pressure overload by pulmonary stenosis compli- cardiac base (Fig 2B). The caudal vena cava was also enlarged cated with atrial septal defect. in both views of thoracic radiography. Those findings strongly suggested right-sided heart failure. Case On echocardiography, the right ventricle was remarkably thickened (Fig 3A). Due to right ventricular hypertrophy, there A 3 years-old female mixed dog (weighing 5.3 kg) was were relative narrowing of left ventricular inner dimension and referred to veterinary teaching hospital of Kangwon National septal flattening (Fig 3B). Therefore, the % fractional shorten- University with primary complaints of syncope, severe exer- ing (FS) and %left ventricular ejection fraction (LVEF) were cise intolerance, depression and lethargy. According to refer- remarkably increased (%FS: 93%, %LVEF: 100%; Fig 3B). The left atrial-aortic diameter ratio (LA:Ao) was 1.08:1, indi- 1Corresponding author. cating there was no left atrial dilation. Color Doppler imag- E-mail : [email protected] ing at the interatrial septum revealed shunt flow indicating 404 Trilogy of Fallot in a Dog 405

Fig 1. The electrocardiogram of this dog. Electrocardiogram showed marked sinus arrhythmia with intermittent sinus exit block and right ventricular enlargement pattern (i.e. S-wave in lead I, II and QRS right axis deviation). In addition, there was Osborne wave in lead III (arrow), indicating hypoxic injuries in the myocardium.

and severe pulmonary stenosis (peak velocity 4.5-5 m/s, pressure gradient 90-100 mmHg; Fig 4B). Furthermore, transmi- tral flow profiling revealed delayed filling of left ventricle (E-peak 0.37 m/s, A-peak 0.39 m/s). However, aortic flow was within normal range (0.86 m/s). Microbubble study using agitated saline found R-L shunt at systole. Based on diagnostic imaging study, the dog was diagnosed as trilogy of Fallot (i.e. severe pulmonary stenosis, R-L shunted atrial septal defect and severe right ventricular hypertrophy) with International small animal cardiac health council Fig 2. Thoracic radiography of this dog. A: Dorsoventral view of (ISACHC) IIIb graded heart failure. thoracic radiography showed reversed D shaped cardiac shadow Since marked cyanosis and exercise intolerance were main with enlargement of right ventricle and main pulmonary artery. complaints of this patient and the dog has never been treated, B: Lateral view of thoracic radiography showed increased sternal the initial therapeutic goals were 1) to improve tissue oxygen- contact of cardiac shadow, elevation of trachea, right atrial en- ation using oxygen therapy (hospitalized at the oxygen cage largement, increased soft tissue density at cardiac base. The cau- with 5 L/min oxygen supply), 2) to increase the ventricular dal vena cava was also enlarged in both views of thoracic radi- relaxation (diastolic filling) using calcium channel blocker ography. (diltiazem SR, 1 mg/kg, q12h, PO, Handok, Korea), and 3) to prevent neurohormonal activation (enalapril, 0.5 mg/kg, q12h, atrial septal defect (Fig 4A). Further continuous wave Dop- PO; Merial, USA). Balloon dilation for pulmonary stenosis pler study revealed R-L shunt flow at systole (peak velocity and septal occlusion for atrial septal defect was planned to ~0.8 m/s) and L-R shunt at diastole (peak velocity ~0.8 m/s; correct anatomical cardiac defects in this dog. However, the Fig 4A). In addition, there were moderate tricuspid regurgita- condition of dog was not stabilized, the interventional thera- tion (peak velocity 2.71 m/s, pressure gradient 29.4 mmHg) pies were postponed. After 3 days of intensive care, the dog

Fig 3. Echocardiography of this dog. A: The 2D-echocardioraphy showed the right ventricle was remarkably thickened. B: The M- mode echocardiography showed relative narrowing of left ventricular inner dimension and septal flattening. The % fractional short- ening (FS) and %left ventricular ejection fraction (LVEF) were remarkably increased (%FS: 93%, %LVEF: 100%). 406 Ran Choi, Hyo-Jin Ahn and Changbaig Hyun

Fig 4. Echocardiography of this dog. A: Color Doppler imaging at the interatrial septum revealed shunt flow indicating atrial septal defect. B: Continuous wave spectral Doppler study revealed R-L shunt flow at systole (peak velocity ~0.8 m/s) and L-R shunt at diastole (peak velocity ~0.8 m/s).

Fig 5. Echocardiography of this dog. A: Continuous wave spectral Doppler study at tricuspid valve revealed moderate tricuspid regur- gitation (peak velocity 2.71 m/s, pressure gradient 29.4 mmHg). A: Continuous wave spectral Doppler study at pulmonic valve revealed severe pulmonary stenosis (peak velocity 4.5-5 m/s, pressure gradient 90-100 mmHg;). was stabilized and released with prescription of diltiazem SR tricular pressure overload causing the right ventricular hyper- (1 mg/kg, q12h, PO) and enalapril (0.5 mg/kg, q12h, PO). To trophy. Due to right ventricular hypertrophy, the right ven- stabilize hematocrit of this patient, weekly phlebotomy was tricular filling pressure was gradually increased and resulted performed to maintain hematocrit less than 65%, One month in the increased right atrial pressure and tricuspid regurgita- later, the clinical condition of dog was improved. The dog tion. The increased right atrial pressure could the cause of was alert and could take a walk with the owner. Due to risk of shunt reversal at the interatrial septum (R-L shunt). The R-L table death, the owner refused the interventional therapies. shunt caused the clinical signs of this patient, such as cyano- The dog is currently treated with diltiazem and enalapril with sis and exercise intolerance. The poor oxygenation from the regular phlebotomy. R-L shunt was the reason for absolute polycythemia and systemic hypotension. The major causes of shunt reversal were Discussion right ventricular hypertrophy and pulmonary hypertension in dogs (4). Therefore theoretically any compound cardiac sep- Pulmonic stenosis (PS) is a common congenital heart defect tal defects having right ventricular hypertrophy and pulmo- in dogs. According to human literature, various degree of atrial nary hypertension will have shunt reversal (R-L shunt) as dysmorphogenesis (e.g. patent foramen ovale; PFO, atrial sep- noticed in this case. tal defect; ASD) are often accompanied with PS (1). Since this In human, R-L shunted atrial dysmorphogenesis is often condition often cause R-L shunt by pressure overload in the accompanied in patients with severe PS (1). According to right ventricle (right ventricular hypertrophy), this condition recent studies in dogs with PS, 7.9-39% of dogs with PS have refers as trilogy of Fallot (1.5). Furthermore, paradoxical various degree of R-L shunt through either PFO or ASD (2,3). embolism or systemic arterial oxygen desaturation is common Although all patient with severe PS did not have R-L shunted sequela of R-L shunt in human (2), although it has never been PFO or ASD, the presence of atrial dysmorphogenesis is a reported in domestic animals. key bad prognostic indictor of this patient. Furthermore, the In this case, severe PS was resulted in marked right ven- clinical signs can be rapidly worsening with the presence of Trilogy of Fallot in a Dog 407

R-L shunt in many cases, as noticed in this study. PS. To author’s best knowledge, this is the first case of tril- Although surgical corrections for trilogy of Fallot have been ogy of Fallot in Korea. reported in humans (1,5), it has never been attempted in veterinary fields, to date. One recent study in dogs with PS found Acknowledgement that the clinical signs could be improved by balloon dilation therapy. Therefore, in this study, we initially attempted to do This study was supported from the Institute of Veterinary balloon dilation for this dog. However, we could not perform Science, Kangwon National University. due to the owner’s refusal. Because either surgical correction or interventional pallia- References tive therapies were not attested for this dog, the medical therapy was the only option for this dog. Therapeutic goals for 1. Bross W, Bross T, Koltowski R, Kustrzycki A, Olejak B. this case were 1) to improve tissue oxygenation (i.e. oxygen Surgical treatment of trilogy and tetralogy of Fallot. Bull Soc cage), 2) to reduce the viscosity of blood (i.e. phlebotomy), Int Chir 1970; 29: 306-310. 3) to improve right ventricular filling (i.e. calcium channel 2. Fujii Y, Nishimoto Y, Sunahara H, Takano H, Aoki T. blocker), and 4) to block the rennin-angiotensin-aldosterone Prevalence of patent foramen ovale with right-to-left shunting in dogs with pulmonic stenosis. J Vet Intern Med 2012; 26: system (i.e. angiotensinogen converting enzyme blockers). 183-185. Because the dog did not show any signs of fluid retention, 3. Johnson MS, Martin M, Edwards D, et al. Pulmonic stenosis diuretic agents were not given to this dog. The target hemat- in dogs: Balloon dilation improves clinical outcome. J Vet ocrit for this dog was 65%, because too lower hematocrit Intern Med 2004; 18: 656-662. might cause poor oxygen carrying ability. However, those 4. Lombard CW, Ackerman N, Berry CR, King RR, Buergelt therapies were not curative but palliative and thus long-term CD. Pulmonic stenosis and right-to-left atrial shunt in three prognosis of this dog might be poor. dogs. J Am Vet Med Assoc 1989; 194: 71-75. Although there have been many human reports with long- 5. Saylam A, Ikizler C, Yurdakul Y, Aytaç A. Trilogy of Fallot: term survival and fair prognosis after surgical corrections, analysis of 10 cases undergone open heart surgery. Turk J there has no concrete study for survival rate and prognosis in Pediatr 1973; 15: 147-156. domestic animals, to date. Authors believed that the overall 6. Tidholm A. Retrospective study of congenital heart defects in 151 dogs. J Small Anim Pract 1997; 38: 94-98. prognosis might be poorer than that of dogs with an isolated

개에서 발생한 팔로삼징

최란·안효진·현창백1 강원대학교 수의학과 소동물 내과교실

요약:3년령 암컷 잡종개(체중 5.3 kg)가 실신, 운동불내성, 의기소침, 기면 등의 증상으로 강원대학교 동물병원에 내 원하였다. 진단검사상 적혈구증가증이 관찰되고, 흉부방사선 검사상 심한 우심종대 패턴이 관찰되었으며, 심초음파상 우-좌 단락의 심방중격 결손증, 심한 폐동맥 협착증(~5 m/s of peak velocity)과 우심실 비대소견이 관찰되었다. 환자는 진단영상학적 소견을 근거로 팔로삼징(trilogy of Fallot)으로 진단되었다. 환자의 임상증상을 안정화시키기 위해 diltiazem과 enalapril을 투여하였고 일주일에 한번씩 정맥사혈을 실시하고 있다. 본 증례는 국내에서 최초로 보고되는 팔로삼징의 증례이다. 주요어 : 팔로삼징, 심방중격 결손증, 폐동맥협착증, 우심실비대, 선천성 심장병