Case Report  Rapport de cas Acyanotic tetralogy of Fallot in a Persian cat Won-Jin Choi, Sang-Il Suh, Ran Choi, Changbaig Hyun Abstract — An 8-year-old, intact male Persian cat was presented with a prominent heart murmur, exercise intolerance, anorexia, and periodontitis. There was no cyanosis and no laboratory evidence for systemic hypoxemia. Echocardiography showed a dextropositioned aorta, moderate pulmonic stenosis (maximal velocity 4.06 m/s), ventricular septal defect, and right ventricular hypertrophy. The shunt direction was predominantly left-to-right in systole and minimally right-to-left in diastole. The cat was diagnosed with acyanotic (pink) tetralogy of Fallot and was managed medically with atenolol. Résumé — Tétralogie de Fallot acyanotique chez un chat Persan. Un chat Persan mâle intact âgé de 8 ans a été présenté avec un souffle cardiaque évident, une intolérance à l’effort, de l’anorexie et une parodontite. Il n’y avait pas de cyanose ni de résultats de laboratoire indiquant l’hypoxémie systémique. L’échocardiographie a montré une aorte en dextroposition, une sténose pulmonaire modérée (vélocité maximale de 4,06 m/s), une malformation septale ventriculaire et une hypertrophie ventriculaire droite. La direction du shunt était principalement de gauche à droite en systole et minimalement de droite à gauche en diastole. Un diagnostic de tétralogie de Fallot acyanotique (rose) a été posé et a été géré médicalement à l’aide d’aténolol. (Traduit par Isabelle Vallières) Can Vet J 2016;57:596–600

T

etralogy of Fallot (TOF) is a congenital malformation comprised of pulmonary stenosis (PS), overriding aorta (dextraposition of aorta), ventricular septal defect (VSD), and right ventricular (RV) hypertrophy. This malformation is more common in dogs than in cats (1–6), and can be divided into 5 types based on severity of PS and VSD, which play a key role in shunt direction (7). Classically, TOF is a cyanotic heart defect but type II TOF, or acyanotic (pink) TOF is characterized by mild to moderate PS and small to moderate VSD leading to left-to-right (L-R) shunt (7). Most patients with this type are acyanotic with minimal clinical signs related to heart failure, despite a loud heart murmur and generalized cardiomegaly. This report describes a rare case of acyanotic TOF in a mature cat without obvious clinical signs related to heart disease.

Section of Small Animal Internal Medicine, College of Veterinary Medicine, Kangwon National University, Chuncheon 201-100, South Korea. Address all correspondence to Dr. Changbaig Hyun; e-mail: [email protected] Drs. W-J Choi and S-I Suh contributed equally to this work. This study was supported through research funds from Kangwon National University. Use of this article is limited to a single copy for personal study. Anyone interested in obtaining reprints should contact the CVMA office ([email protected]) for additional copies or permission to use this material elsewhere. 596

Case description An 8-year-old, intact male, Persian cat, weighing 4.4 kg, was presented with clinical signs of exercise intolerance, anorexia, and periodontitis. On thoracic auscultation, we heard a grade IV/VI systolic murmur at the right sternum and III/VI systolic murmur at the left basal area. Systolic blood pressure and pulse rate were 140 mmHg (measured by Doppler method) and 170 beats/min, respectively. On the day of presentation, electrocardiographic (ECG) study showed sinus tachycardia (170 to 190 beats/min) and presence of S waves in leads I, II, III, suggesting RV enlargement (Figure 1). Laboratory tests including blood cell counts, blood chemistry, and blood gas analysis found no significant abnormalities except mild leukocytosis [19 3 109/L, reference range (RR): 4 to 15 3 109/L]. The patient was not cyanotic. Packed cell volume was 37.3% (RR: 25% to 41%). PaO2 and PaCO2 were 91.2 (RR: 80 to 104 mmHg) and 33.8 mmHg (RR: 33 to 40 mmHg), respectively. Heartworm antigen and antibody tests were negative. Thoracic radiographic studies revealed generalized cardiomegaly (vertebral heart scale 10.6; Figure 2). The convexity in the region of the RV with dorsal deviation of the cardiac apex suggested RV enlargement, while the rounding in the region of the left ventricle (LV) suggested LV enlargement (Figure 2). Abdominal radiographs showed no abnormalities except rounding of the hepatic margin suggesting hepatomegaly. Two-dimensional echocardiography taken at the right parasternal long-axis view of the LV and aorta revealed a region of discontinuity between the upper portion of the interventricular CVJ / VOL 57 / JUNE 2016

CA S E R E P O R T

Figure 1.  Electrocardiogram taken on the day of presentation showed sinus tachycardia (170 to 190 beats/min) and presence of S waves in leads I, II, III, suggesting right ventricular enlargement.

Figure 2.  Thoracic radiography (A — right lateral, B — ventrodorsal) taken on the day of presentation showed generalized cardiomegaly (vertebral heart scale 10.6). The convexity in the region of the right ventricle (RV) with dorsal deviation of the cardiac apex suggested RV enlargement, while the rounding in the region of the left ventricle (LV) suggested LV enlargement.

septum and the base of the aorta (Figure 3A). The VSD was 2 to 3 mm depending on echocardiographic views and was located at the perimembraneous region, directly under the aortic valve. The aorta was dextropositioned, overriding the ventricular septum just above the VSD (Figure 4B). The right ventricle was markedly hypertrophied (10.2 mm at diastole; RR 3.9 6 1.0 mm; Figures 3A, 4A). There was flattening of the interventricular septum in diastole (Figure 4A). The right atrium was mildly enlarged (15.5 mm; RR: 12.2 6 1.9 mm; Figure 3A). The right parasternal short-axis view of the pulmonary artery CVJ / VOL 57 / JUNE 2016

revealed narrowing of the RV outflow tract (Figure 4C). The left atrium and ventricle were not enlarged or hypertrophied. Color and continuous wave Doppler echocardiography revealed L-R flow across the VSD in systole (1.5 m/s, pressure gradient = 9 mmHg) and R-L flow in diastole (0.7 m/s, pressure gradient = 2 mmHg; Figures 3B, 3C). A contrast study was performed using agitated saline injected through the cephalic vein. Bubbles filled the right atrium then the right ventricle. They did not enter the left ventricle in systole and minimally entered the left ventricle in diastole (Figure 3D), suggesting mixed shunting. 597

R A P P O R T D E CA S

Figure 3.  Echocardiogram of the cat. A — Two-dimensional echocardiography taken at right parasternal long-axis view of the LV and aorta revealed a region of discontinuity between the upper portion of the interventricular septum and the base of the aorta. The ventricular septal defect was small. The RV was markedly hypertrophied. The RA was mildly enlarged. The LA and LV were not enlarged or hypertrophied. B — Color flow echocardiography taken at the same plane found blood entering from LV to RV in systole. C — Pulsed wave Doppler taken across the ventricular septal defect from the right parasternal long-axis view revealed right-to-left blood shunting across the VSD during diastole (D) and left-to-right blood shunting during systole (S). D — A contrast study was performed using agitated saline injected through the cephalic vein. Bubbles filled the RA then the RV. They did not enter the LV in systole and minimally entered the LV in diastole. RV-right ventricle, RA-right atrium, LV-left ventricle, LA-left atrium.

Continuous wave Doppler echocardiography taken at the left apical long axis view of RV outflow tract revealed maximal velocity of 4.06 m/s systolic jet (pressure gradient = 65.6 mmHg) at this region (Figure 4D), suggesting moderate/severe pulmonic stenosis. Further echocardiographic studies found there was no interatrial shunting. Based on these findings, the cat was diagnosed as having type III tetralogy of Fallot with dominantly L-R shunt at systole and minimally R-L at diastole (mixed shunt). Interestingly, the cat had no clinical signs of cyanosis, abdominal distension (ascites), or dyspnea (pleural effusion). His only symptom was mild exercise intolerance. A b-blocker was chosen to decelerate the heart rate for improvement of ventricular filling and prevention of dynamic RV obstruction by exertion or excitement. The cat was treated initially with atenolol (Atenol; Daewon Pharmaceuticals, Seoul, Korea), 6.25 mg, PO, q12h for heart disease and doxycycline (Vibravet; Pfizer, Seoul, Korea), 5 mg/kg, PO, q12h and prednisolone (Prednisolone; Daewoo, Seoul, Korea), 1 mg/kg, PO, q24h for periodontitis. 598

After a week the cat was re-checked. His clinical condition was remarkably improved after this treatment. The cat regained his appetite following treatment of periodontitis, suggesting that the clinical signs were caused primarily by dental disease. The cat is currently checked regularly and there have been no significant alterations in the echocardiographic findings.

Discussion Acyanotic (pink) TOF refers to a TOF in which the PS is moderate and a balanced shunt across the ventricular septum allows adequate oxygenation of hemoglobin (8,9). Therefore, cyanosis, a typical clinical feature of TOF, is either absent or delayed into adulthood. A VSD is an orifice in the inter-ventricular septum that allows blood to flow from one ventricle to the other (10). Because LV systolic pressure is higher than RV systolic pressure, blood typically shunts across the VSD from LV to RV (L-R shunt). A VSD can be observed as either an isolated defect or as a part of complex defects (e.g., TOF) as seen in this case. CVJ / VOL 57 / JUNE 2016

CA S E R E P O R T

Figure 4.  Echocardiogram of the cat. A — Two-dimensional echocardiography of left ventricular papillary level at the right parasternal short-axis view at diastole showing right ventricular (RV) hypertrophy and interventricular septal flattening, suggesting RV pressure overload. B — Two-dimensional echocardiography of the right parasternal 5 chamber of long axis view revealed the aorta was dextropositioned, overriding the ventricular septum just above the ventricular septal defect. C — Two-dimensional echocardiography of the right ventricular outflow tract from the right parasternal short-axis view showing hypoplasia of PA with thickening of pulmonic valve. D — Color flow with continuous wave Doppler of the right ventricular outflow tract from the right parasternal short-axis view. A right ventricular outflow tract-to-pulmonary artery peak velocity of 4.05 m/s is seen, corresponding to a pressure gradient of 65 mmHg, suggesting moderate/severe pulmonic stenosis. RV-right ventricle, LV-left ventricle, LA-left atrium, Ao-aorta, PA-pulmonary artery.

The shunt across the ventricular septum is determined by the pressure gradient across the defect, which is a function of the size of the VSD and the relative resistance of the systemic and pulmonary circulation. Generally, if the defect is small, it is unlikely to create volume overload of the pulmonary circulation and the left heart. However, if the defect is large, it causes chronic volume overload and left-sided congestive heart failure, if systemic vascular resistance (SVR) still exceeds pulmonary vascular resistance (PVR). However, if RV obstruction (e.g., PS or pulmonic atresia in TOF) is co-existent, the RV pressure overload may result in significant elevation of RV systolic pressure that may result in reversal of the shunt direction (R-L shunt) as commonly seen in typical TOF (10). Pulmonary stenosis is a narrowing of the pulmonary artery and is usually due to isolated valvular obstruction (10). When PS is present, resistance to blood flow across the stenotic valve increases RV systolic pressure. The RV pressure overload eventually causes RV concentric hypertrophy. Severe, chronic RV presCVJ / VOL 57 / JUNE 2016

sure overload can lead to right-sided heart failure. Pulmonary stenosis in cats may occur either as an isolated defect or part of complex congenital heart defects (e.g., TOF). Although the cat in this case had hypoplasia of PA with thickening of the pulmonic valve on the echocardiography, we could not clearly define the type of PS. The direction and magnitude of the shunt flow across the VSD is generally determined by the severity of the PS in TOF (7). Severe RV obstruction can result in a large R-L shunt with low pulmonary blood flow and severe cyanosis, while mild RV obstruction can result in L-R shunt without cyanosis. The mild RV obstruction can reduce the volume of flow across the VSD (reduced shunt fraction). This will reduce volume overload of the pulmonary vasculature and retard the development and progression of pulmonary artery hypertension. If pulmonary vasculature resistance increases over time, it may result in progressive RV pressure overload and hypertrophy, subsequently causing R-L shunting (Eisenmenger’s pathophysiology) (7). 599

R A P P O R T D E CA S

In this case, the LV systolic pressure is still higher than RV systolic pressure. However, RV diastolic pressure exceeded LV diastolic pressure because of decreased RV compliance created by RV hypertrophy. This resulted in mild R-L shunt in diastole, so called “mixed shunting;” however, the mixed shunting in this case was clinically insignificant, since there was no evidence for cyanosis, no polycythemia or hypoxemia. In this cat, there was no evidence of LV hypertrophy and the presence of other extracardiac shunts on the echocardiogram. Worsening of the PS with time might prevent pulmonary overcirculation from chronic L-R shunt across the VSD. We assumed that the dominant defect responsible for cardiac remodeling in this cat might be the PS with marked RV hypertrophy. Probably the VSD in this cat might help to reduce chronic RV pressure overload through a small R-L shunt at diastole. Therefore this cat reached adulthood without obvious clinical signs, including cyanosis, related to heart disease. This cat was categorized as having a type III tetralogy (pink TOF). Pink TOF is reported in 5% of humans with TOF and generally has a better prognosis than the other types (11), although the prognosis of typical TOF in humans and animals is considered poor and survival to adulthood is extremely rare without medical or surgical treatment (12,13). However, in this cat, surgical treatment including balloon valvuloplasty was not considered, because it might have increased the L-R shunt, causing volume overload in the pulmonary circulation and left cardiac chambers. This would have caused left-sided heart failure with pulmonary edema or right-sided heart failure with cyanosis later in life (7). In conclusion, this report describes a rare case of acyanotic TOF in a mature cat without clinical signs related to heart disease. Balance of pressures between right and left cardiac

600

chambers resulting from moderate PS and L-R shunting VSD in this cat might be associated with prolonged survival. CVJ

References 1. Patterson DF, Pexieder T, Schnarr WR, Navratil T, Alaili R. A single major-gene defect underlying cardiac conotruncal malformations interferes with myocardial growth during embryonic development: Studies in the CTD line of keeshond dogs. Am J Hum Genet 1993;52:388–397. 2. Fruganti A, Cerquetella M, Beribè F, Spaterna A, Tesei B. Clinic and ultrasonographic findings in a cat with Tetralogy of Fallot. Vet Res Commun 2004;28 Suppl 1:343–346. 3. Eyster GE, Weber W, McQuillan W. Tetralogy of Fallot in a cat. J Am Vet Med Assoc 1977;171:280–282. 4. Kirby D, Gillick A. Polycythemia and tetralogy of Fallot in a cat. Can Vet J 1974;15:114–119. 5. Bush M, Pieroni DR, Goodman DG, White RI, Thomas V, James AE, Jr. Tetralogy of Fallot in a cat. J Am Vet Med Assoc 1972; 161:1679–1686. 6. Bolton GR, Ettinger SJ, Liu SK. Tetralogy of Fallot in three cats. J Am Vet Med Assoc 1972;160:1622–1631. 7. McCord MC, Van Elk J, Blount SG, Jr. Tetralogy of Fallot: Clinical and hemodynamic spectrum of combined pulmonary stenosis and ventricular septal defect. Circulation 1957;16:736–749. 8. Laniesse D, Hébert J, Larrat S, Hélie P, Pouleur-Larrat B, Belanger MC. Tetralogy of Fallot in a 6-year-old albino ferret (Mustela putorius furo). Can Vet J 2014;55:456–461. 9. Auslender J, Jahjah L, Morissens M. Uncorrected acyanotic tetralogy of fallot decompensated in adulthood after an acute onset of malaria. Acta Cardiol 2012;67:347–350. 10. Oyama MA, Sisson DD, Thomas WP. Congenital heart disease. In: Ettinger SJ, Feldman EC, eds. Textbook of Veterinary Internal Medicine. VII. St. Louis, Missouri: WB Saunders, 2010:1257–1271. 11. Abraham KA, Cherian G, Rao VD, Sukumar IP, Krishnaswami S, John S. Tetralogy of Fallot in adults: A report on 147 patients. Am J Med 1979;66:811–816. 12. Bertranou EG, Blackstone EH, Hazelrig JB, Turner ME, Kirklin JW. Life expectancy without surgery in tetralogy of Fallot. American J Cardiol 1978;42:458–466. 13. Park IC, Lee HS, Kim JT, Lee JS, Lee SG, Hyun C. Pentalogy of Fallot in a Korean Sapsaree dog. J Vet Med Sci 2007;69:73–76.

CVJ / VOL 57 / JUNE 2016

Acyanotic tetralogy of Fallot in a Persian cat.

Tétralogie de Fallot acyanotique chez un chat Persan. Un chat Persan mâle intact âgé de 8 ans a été présenté avec un souffle cardiaque évident, une in...
5MB Sizes 0 Downloads 14 Views