to obtain an adequate image of the pulmonary outflow tract and valve. Spectral Doppler of pulmonary artery flow is also often difficult to obtain in these animals. Color-flow Doppler will delineate the boundaries of the outflow tract and may help position the Doppler cursor. Examine all four views for obtaining the pulmonary artery. If pulmonary flow cannot be obtained, check for tricuspid insufficiency as an alternative way to derive right ventricular pressures.
Severe right ventricular hypertrophy is always present as a consequence of the pressure overload generated by the pulmonic stenosis (34,133). The right ventricular cavity is usually small unless valvular regurgitations are present. Left ventricular chamber size is also small secondary to poor preload when Tetralogy of Fallot is present regardless of whether the shunt is right to left or left to right. The left ventricle will appear to be concentrically hypertrophied, and invasive studies of left ventricular pressures in dogs with Tetralogy of Fallot reveal left ventricular pressures as low as 36 in some (34,133). A left to right shunt would typically volume overload the left ventricle and sometimes the right ventricle, but when a moderate to severe pulmonic stenosis is present, there is decreased volume flowing through the pulmonary circulation and into the left side of the heart. Although logically a right to left shunt should volume overload the left ventricle, the overriding aorta causes the shunted blood to flow directly into the aorta, and the left ventricle never receives the volume. The severe pulmonic stenosis, which must be present with right to left shunts, additionally results in decreased preload within the left ventricular chamber.
Tetralogy of Fallot
LV concentric hypertrophy pattern
Pseudohypertrophy
Due to decreased preload
The ventricular septal defect is usually very obvious and large. The interventricular septum is aligned with the center of the aorta (Figure 10.56). Only when septal hypertrophy is very severe will the defect become less obvious. Manipulating the transducer and sound beam in slightly different directions can help define whether the septum is indeed intact and whether the aorta is overriding. Color-flow and spectral Doppler will show shunting of blood across the defect no matter how hard it is to elucidate on real-time images. The direction of shunting may be left to right and positive on spectral displays, bidirectional low velocity flow, or right to left negative flow on spectral tracings (Figure 10.57). Pressure gradients are derived just as they are for isolated ventricular septal defects.
Figure 10.56 The ventricular septal defect of tetralogy of Fallot is usually very obvious. (A) The walls of the aorta (arrows) will straddle or override the ventricular septum. Right ventricular hypertrophy is severe. (B) The ventricular septum is lined up with the center of the aortic valves (arrow) in this dog with tetralogy of Fallot. There is severe right and left ventricle hypertrophy. Septal hypertrophy is also creating obstruction to left ventricular outflow. Plane = right parasternal long-axis left ventricular outflow view, RV = right ventricle, LV = left ventricle, VS = ventricular septum, AO = aorta, LA = left atrium.
Figure 10.57 (A) Flow through the ventricle septal defect of a tetralogy of Fallot is typically reversed and a negative flow profile is recorded. (B) Flow may be bidirectional, however, when right and left ventricular pressures are fairly equal.
When a pressure gradient can be obtained from both the pulmonic stenosis and the ventricular septal defect, they should make sense in that the gradient across the septal defect should reflect right-sided pressures and the degree of pulmonic stenosis. A pulmonary stenosis gradient of 130 mm Hg for instance suggesting a right ventricular pressure of approximately 140 to 150 mm Hg should result in right to left shunting, and a pressure gradient across the septum should be approximately 20 to 30 if systemic systolic pressure is 120 mm Hg. A dog with a blood pressure of 120 mm Hg and a gradient of 60 mm Hg across a left to right flowing septal defect suggests that right ventricular pressures are about 60 mm Hg, and the pulmonic stenosis would therefore have a gradient of approximately 40 to 50 mm Hg if pulmonary pressures are assumed to be about 10 to 20 mm Hg. Pulmonary pressure will typically be lower than the 20 to 25 mm Hg present in healthy dogs because of the pulmonary stenosis however (133). When multiple defects are present, always cross-check the derived gradients. They should make sense, and if they do not, one of the gradients is in error.
Bubble studies can document the presence of a right to left shunt across a ventricular septal defect. Inject a milliliter or 2 of saline that has been shaken vigorously into a peripheral vein. The
microbubbles will appear echodense on echocardiographic images, and they will be seen flowing into the left ventricular outflow tract when a reverse shunt is present. When a left to right shunt is present, the defect is harder to document with bubble studies unless an area of negative contrast is seen (33,131,133).
Significant septal hypertrophy may at times create a secondary obstruction in the left ventricular outflow tract. Look for the following M-mode signs of obstruction: systolic anterior mitral valve motion and early systolic aortic valve closure (Figure 10.58). Spectral and color-flow Doppler may show aliased and high velocity signals when left-sided obstruction is present. A left-sided obstruction, if present, is usually proximal to the ventricular septal defect, and analysis of pressure gradients should reflect this. In other words, systemic pressures are used in assessing the shunt and right ventricular pressures, not the left ventricular pressures as is done with isolated ventricular septal defects.
Figure 10.58 Significant septal hypertrophy may create a secondary obstruction in the left ventricular outflow tract. Look for systolic anterior mitral valve motion (arrow). RVW = right ventricular wall, RV = right ventricle, VS = ventricular septum, LV = left ventricle, MV = mitral valve.
References
1.Grossman W, Jones D, McLaurin L. Wall stress and patterns of hypertrophy. J Clin Invest 1975;56:56–64.
2.Oyama MA, Thomas WP. Two-dimensional and M-mode echocardiographic predictors of disease severity in dogs with congenital subaortic stenosis. J Am Anim Hosp Assoc 2002;38:209–215.
3.Oyama MA, Sisson DD. Evaluation of canine congenital heart disease using an echocardiographic algorithm. J Am Anim Hosp Assoc 2001;37:519–535.
4.Tidholm A. Retrospective study of congenital heart defects in 151 dogs. J Small Anim Pract
1997;38:94–98.
5.Chetboul V, Trollé JM, Nicolle A, et al. Congenital heart diseases in the boxer dog: A retrospective study of 105 cases (1998–2005). J Vet Med A Physiol Pathol Clin Med 2006;53:346–351.
6.Kienle RD, Thomas WP, Pion PD. The natural clinical history of canine congenital subaortic stenosis. J Vet Intern Med 1994;8:423–431.
7.Buoscio D, Sisson D, Zachary J, et al. Clinical and pathological characterization of an unusual form of subvalvular aortic stenosis in four golden retriever puppies. J Am Anim Hosp Assoc 1994;30:100–
8.Stepien R, JD B. Aortic stenosis: clinical findings in six cats. J Sm Anim Prac 1991;32:341–350.
9.O’Grady M, Holmberg D, Miller C, et al. Canine congenital aortic stenosis: a review of the literature and commentary. Can Vet J 1989;30:811–815.
10.Pyle RL, Patterson DF, Chacko S. The genetics and pathology of discrete subaortic stenosis in the Newfoundland dog. Am Heart J 1976;92:324–334.
11.Buchanan J. Causes and prevalence of cardiovascular disease. In: Kirk RW, Bonagura JD, eds, Current Vet Therapy XI, Philadelphia, PA, WB Saunders 1992: 647–655.
12.Watson TD, Marr CM, McCandlish IA. Aortic valvular dysplasia in a calf. Vet Rec 1991;129:380–
13.Bolton GR, Liu SK. Congenital heart diseases of the cat. Vet Clin North Am 1977;7:341–353.
14.Wingfield WE, Boon JA, Miller CW. Echocardiographic assessment of congenital aortic stenosis in dogs. J Am Vet Med Assoc 1983;183:673–676.
15.Bussadori C, Amberger C, Le Bobinnec G, et al. Guidelines for the echocardiographic studies of suspected subaortic and pulmonic stenosis. Journal of Veterinary Cardiology 2000;2:15–22.
16.Kaplan PM. Congenital heart disease. Prob Vet Med 1991;3:500–519.
17.Lehmkuhl LB, Bonagura JD. Comparison of transducer placement sites for Doppler echocardiography in dogs with subaortic stenosis. Am J Vet Res 1994;55:192– 198.
18.Quintavalla C, Pradelli D, Domenech O, et al. Transesophageal echocardiography of the left ventricular outflow tract, aortic valve and ascending aorta in Boxer dogs with heart murmurs. Vet Radiol Ultrasound 2006;47:307–312.
19.Patterson D. Two hereditary forms of ventricular obstruction in the dog: pulmonary valve dysplasia and discrete subaortic stenosis. In: Nora J, Takao A, eds. Congenital Heart Disease: Causes and Processes. Mt Kisco: Futura Publishing, 1984;43–63.
20.Sisson D, Thomas W, Bonagura J. Congenital heart disease. In: Ettinger S, ed. Textbook of veterinary internal medicine. 5th ed. Philadelphia: WB Saunders Co, 2000;737–787.
21.Fuentes V. Aortic stenosis in Boxers. Vet Annu 1993;33:220–229.
22.Patterson DF. Congenital defects of the cardiovascular system of dogs: studies in comparative cardiology. Adv Vet Sci Comp Med 1976;20:1–37.
23.Bonagura J, Lehmkuhl L. Congenital heart disease. In: Fox P, Sisson D, Moise N, eds. Textbook of canine and feline cardiology: principles and clinical practice. Philadelphia: WB Saunders, 1999;471–
24.Monnet E, Orton EC, Gaynor JS, et al. Open resection for subvalvular aortic stenosis in dogs. J Am Vet Med Assoc 1996;209:1255–1261.
25.Margiocco ML, Zini E. Fixed subaortic stenosis in a cat. Vet Rec 2005;156:712–714.
26.Bonagura JD. Problems in the canine left ventricular outflow tract. Journal of Veterinary Internal Medicine 2001;15:427–429.
27.Bonagura J. Contemporary issues in small animal practice: cardiology. New York: Churchill Livingston, 1987.
28.Darke P. Congenital heart disease in dogs and cats. J Sm Anim Prac 1989;30:599–607.
29.Bélanger MC, Di Fruscia R, Dumesnil JG, et al. Usefulness of the indexed effective orifice area in the assessment of subaortic stenosis in the dog. Journal of Veterinary Internal Medicine 2001;15:430–
30.Brown D, Knight D, King R. Use of pulse-wave Doppler echocardiography to determine aortic and pulmonary velocity and flow variables in clinically normal dogs. Am J Vet Res 1991;52:543–550.
31.Bélanger MC, Di Fruscia R, Dumesnil JG, et al. Usefulness of the indexed effective orifice area in the assessment of subaortic stenosis in the dog. J Vet Intern Med 2001;15:430–437.
32.Devereaux R, De Simone G, Ganau A, et al. Left ventricular hypertrophy and hypertension. Clin Exper Hyperten 1993;15:1025–1032.
33.Bonagura JD, Herring DS. Echocardiography. Congenital heart disease. Vet Clin North Am Small Anim Pract 1985;15:1195–1208.
34.Wingfield WE, Boon JA. Echocardiography for the diagnosis of congenital heart defects in the dog. Vet Clin North Am Small Anim Pract 1987;17:735–753.
35.Schober KE, Fuentes VL. Doppler echocardiographic assessment of left ventricular diastolic function in 74 boxer dogs with aortic stenosis. Journal of Veterinary Cardiology 2002;4:7–16.
36.Boon J, Wingfield W, Miller C. Echocardiographic indices in the normal dog. Vet Rad Ultra 1983;24: 214–221.
37.Carabello BA. The relationship of left ventricular geometry and hypertrophy to left ventricular function in valvular heart disease. J Heart Valve Dis 1995;4 Suppl 2:S132–138; discussion S138–139.
38.Donner R, Carabello BA, Black I, et al. Left ventricular wall stress in compensated aortic stenosis in children. Am J Cardiol 1983;51:946–951.
39.Reichek N, Devereux RB. Reliable estimation of peak left ventricular systolic pressure by M-mode echographic-determined end-diastolic relative wall thickness: Identification of severe valvular aortic stenosis in adult patients. American Heart Journal 1982; 103:202–209.
40.Motro M, Schneeweiss A, Shem-Tov A, et al. Two-dimensional echocardiography in discrete subaortic stenosis. Am J Cardiol 1984;53:896–898.
41.Schober KE, Fuentes VL. Mitral annulus motion as determined by m-mode echocardiography in normal dogs and dogs with cardiac disease. Veterinary Radiology & Ultrasound 2001;42:52–61.
42.Hess O, Villari B, Krayenbuehl H. Diastolic dysfunction in aortic stenosis. Circ 1993;87(Suppl): IV:73–76.
43.Eichhorn P, Grimm J, Koch R, et al. Left ventricular relaxation in patients with left ventricular hypertrophy secondary to aortic valve disease. Circ 1982;65:1395–1404.
44.Pollick C, Morgan C, Gilbert B, et al. Muscular subaortic stenosis: the temporal relationship between systolic anterior motion of the anterior mitral leaflet and the pressure gradient. Circ 1982;66:1087–1094.
45.Kaplan P. Instrumentation, principles, and pitfalls of ultrasonography. Pron Vet Med 1991;3:457–
46.O’Grady M. The incidence of aortic valve insufficiency in congenital canine aortic stenosis: a Doppler echocardiographic study. J Vet Int Med 1990;4:129.
47.Winsberg F, Gabor G, Hernberg J, et al. Fluttering of the aortic valve in aortic insufficiency. Circ 1970;41:225–229.
48.Lehmkuhl LB, Bonagura JD, Jones DE, et al. Comparison of catheterization and Doppler-derived pressure gradients in a canine model of subaortic stenosis. J Am Soc Echocardiogr 1995;8(5) Pt 1:611–620.
49.Weyman AE. Aortic stenosis: Physics and physiology—what do the numbers really mean?
Reviews in Cardiovascular Medicine 2005;6:23–32.
50.Weyman A. Left Ventricular outflow tract: the aorta and subvalvular outflow tract In: Weyman A, ed. Principles of Flow. 2 ed. Philadelphia: Lea and Febiger, 1994;498–574.
51.Abbott JA, MacLean HN. Comparison of Doppler-derived peak aortic velocities obtained from subcostal and apical transducer sites in healthy dogs. Vet Radiol Ultrasound 2003;44:695–698.
52.Riesen SC, Doherr MG, Lombard CW. Comparison of Doppler-derived aortic velocities obtained from various transducer sites in healthy dogs and cats. Vet Radiol Ultrasound 2007;48:570–573.
53.Moise NS. Doppler echocardiographic evaluation of congenital cardiac disease. An introduction. J Vet Intern Med 1989;3:195–207.
54.Thomas W. Doppler echocardiographic estimation of pressure gradients in dogs with congenital pulmonic and subaortic stenosis. Proc 8th ACVIM 1990:867–869.
55.Richards KL. Assessment of aortic and pulmonic stenosis by echocardiography. Circulation 1991;84(3) Suppl: I182–187.
56.Yuill C, O’Grady M. Doppler-derived velocity of blood flow across the cardiac valves in the normal dog. Can J Vet Res 1991;55:185–192.
57.Gaber C. Normal pulsed wave Doppler flow velocities in adult dogs. Proc 5th ACVIM 1987:923.
58.Brown D, Knight D, King R. Use of pulsed-wave Doppler echocardiography to determine aortic and pulmonary velocity and flow variables in clinically normal dogs. Am J Vet Res 1991;52:543–550.
59.Kirberger R, Bland-van den Berg P, Grimbeek R. Doppler echocardiography in the normal dog: Part II, Factors influencing blood flow velocities and a comparison between left and right heart blood flow. Vet Rad Ultra 1992;33:380–386.
60.Bonagura JD, Miller MW, Darke PG. Doppler echocardiography. I. Pulsed-wave and continuouswave examinations. Vet Clin North Am Small Anim Pract 1998; 28:1325–1359, vii.
61.Darke P. An evaluation of transducer sites for measurement of aortic and pulmonary flows by Doppler echocardiography. Proc 9th ACVIM 1991:703–705.
62.Sisson D, Brown W. Pulsed wave Doppler blood flow velocities and transvalvular flow estimates in adult male hounds. J Vet Int Med 1996;10:164.
63.Eyster G. Pulmonic stenosis. In: Bojrab M, ed. Current Techniques in Small Animal Surgery 2nd ed. Philadelphia: WB Saunders, 1983;462–469.
64.Malik R, Church D, Hunt G. Valvular pulmonic stenosis in bullmastiffs. J Sm Anim Prac 1993;34:288–292.
65.Patterson DF, Haskins ME, Schnarr WR. Hereditary dysplasia of the pulmonary valve in beagle dogs. Pathologic and genetic studies. Am J Cardiol 1981;47: 631–641.
66.Bonagura J. Congenital heart disease. In: Ettinger S, ed. Textbook of Veterinary Medicine. 3rd ed. Philadelphia: W.B. Saunders, 1989;1000–1005.
67.Fingland RB, Bonagura JD, Myer CW. Pulmonic stenosis in the dog: 29 cases (1975–1984). J Am Vet Med Assoc 1986;189:218–226.
68.Bussadori C, Quintavalla C, Capelli A. Prevalence of congenital heart disease in boxers in italy.
Journal of Veterinary Cardiology 2001;3:7–11.
69.Bussadori C, DeMadron E, Santilli RA, et al. Balloon valvuloplasty in 30 dogs with pulmonic stenosis: effect of valve morphology and annular size on initial and 1-year outcome. Journal of Veterinary Internal Medicine 2001;15:553–558.
70.Hawe R. Pulmonic stenosis in a cat. J Am Anim Hosp Assoc 1981;17:777–782.
71.Hopper BJ, Richardson JL, Irwin PJ. Pulmonic stenosis in two cats. Aust Vet J 2004;82:143–148.
72.Schrope DP, Kelch WJ. Clinical and echocardiographic findings of pulmonary artery stenosis in seven cats. Journal of Veterinary Cardiology 2007;9:83–89.
73.Emmanouilides G, Baylen B. Pulmonary Stenosis. In: Adam F, Emmanouilides G, eds. Moss’ Heart Disease in Infants, Children, and Adolescents. 3rd ed. Baltimore: Williams and Wilkins, 1993;308–323.
74.Hurst J, Schlant R. The pathology of normal physiology, clinical recognition and medical and surgical treatment of congenital heart disease. The Heart. New York: McGraw-Hill, 1990;726–730.
75.Martin M, Godman M, Fuentes L, et al. Assessment of balloon pulmonary valvuloplasty in six dogs. J Sm Anim Prac 1992;33:443–449.
76.Olivier N. Congenital heart disease in dogs. In: Fox P, ed. Canine and Feline Cardiology. New York: Churchill Livingston, 1988;357–389.
77.Serres F, Chetboul V, Gouni V, et al. Diagnostic value of echo-Doppler and tissue Doppler imaging in dogs with pulmonary arterial hypertension. J Vet Intern Med 2007;21:1280–1289.
78.Paige CF, Abbott JA, Pyle RL. Systolic anterior motion of the mitral valve associated with right ventricular systolic hypertension in 9 dogs. Journal of Veterinary Cardiology 2007;9:9–14.
79.Kittleson M, Thomas W, Loyer C, et al. Single coronary artery (type R2A). Letter to the editor. J Vet Intern Med 1992;6:250–251.
80.Buchanan J. Pulmonic stenosis caused by single coronary artery in dogs: four cases (1965–1984). JAVMA 1990;196:115–120.
81.Buchanan J. Pathogenesis of single right coronary artery and pulmonic stenosis in English Bulldogs. J Vet Int Med 2001;15:101–104.
82.Minami T, Wakao Y, Buchanan J, et al. A case of pulmonic stenosis with single coronary artery in a dog. Jap J Vet Sci 1989;51:453–456.
83.Kienle R. Congenital pulmonic stenosis. In: Kittleson M, ed. Small Animal Cardiovascular Medicine. St Louis: Mosby, 1998;248–260.
84.Schrope DP. Primary pulmonic infundibular stenosis in 12 cats: Natural history and the effects of balloon valvuloplasty. Journal of Veterinary Cardiology 2008;10: 33–43.
85.Houston AB, Simpson IA, Pollock JC, et al. Doppler ultrasound in the assessment of severity of
coarctation of the aorta and interruption of the aortic arch. Br Heart J 1987;57:38–43.
86.Carvalho JS, Redington AN, Shinebourne EA, et al. Continuous wave Doppler echocardiography and coarctation of the aorta: gradients and flow patterns in the assessment of severity. Br Heart J 1990;64:133– 137.
87.Minors SL, O’Grady MR, Williams RM, et al. Clinical and echocardiographic features of primary infundibular stenosis with intact ventricular septum in dogs. J Vet Intern Med 2006;20:1344–1350.
88.Koie H, Kurotobi EN, Sakai T. Double-chambered right ventricle in a dog. J Vet Med Sci 2000;62:651–653.
89.Willard M, Eyster G. Double chambered right ventricle in 2 dogs. J AM Vet Med Assoc 1981;178:486–488.
90.MacLean H, Abbott J, Pyle R. Balloon dilation of double chambered right ventricle in a cat. J Vet Int Med 2002;16:478–484.
91.Martin JM, Orton EC, Boon JA, et al. Surgical correction of double-chambered right ventricle in dogs. Journal of the American Veterinary Medical Association 2002;220:770–774.
92.Singh M, Agarwala M, Grover A, et al. Clinical, echocardiographic, and angiographic profile of patients with double chambered right ventricle: experience with 48 cases. Angiology 1999;50:223–
93.Minors SL, O’Grady MR, Williams RM, et al. Clinical and echocardiographic features of primary infundibular stenosis with intact ventricular septum in dogs. Journal of Veterinary Internal Medicine 2006;20: 1344–1350.
94.Tidholm A, Nicolle AP, Carlos C, et al. Tissue doppler imaging and echo-doppler findings associated with a mitral valve stenosis with an immobile posterior valve leaflet in a bull terrier.
Journal of Veterinary Medicine Series A 2004;51:138–142.
95.Fox PR, Miller MW, Liu SK. Clinical, echocardiographic, and Doppler imaging characteristics of mitral valve stenosis in two dogs. J Am Vet Med Assoc 1992;201: 1575–1579.
96.Lehmkuhl LB, Ware WA, Bonagura JD. Mitral stenosis in 15 dogs. J Vet Intern Med 1994;8:2–17.
97.Kittleson M. Congenital abnormalities of the atrioventricular valves. In: Kittleson M, Kienle R, eds. Small animal Cardiovascular Medicine. St Louis: Mosby, 1998; 272–281.
98.Pipers FS, Bonagura JD, Hamlin RL, et al. Echocardiographic abnormalities of the mitral valve associated with left sided heart diseases in the dog. J AM Vet Med Assoc 1981;179:580–586.
99.Stamoulis M, Fox P. Mitral valve stenosis in three cats. J Sm Anim Prac 1993;34:452–456.
100.Shiu MF, Jenkins BS, Webb-Peploe MM. Echocardiographic analysis of posterior mitral leaflet movement in mitral stenosis. Br Heart J 1978;40: 372–376.
101.Feldman T. Rheumatic mitral stenosis. On the rise again. Postgrad Med 1993;93:93–94, 99–104.
102.O’Grady M, Bonagura J, Powers J, et al. Quantitative cross-sectional echocardiography in the normal dog. Vet Rad Ultra 1986;27:34–49.
103.Oyama MA, Weidman JA, Cole SG. Calculation of pressure half-time. Journal of Veterinary Cardiology 2008; 10:57–60.
104.Hatle L. Doppler echocardiographic evaluation of mitral stenosis. Cardiol Clin 1990;8:233–247.
105.Labovitz A, Williams G. Doppler echocardiography: the quantitative approach. Malvern, PA: Lea and Febiger, 1992.
106.Gorlin R, Gorlin S. Hydraulic formula for calculation of the area of stenotic mitral valve, other cardiac valves, and central circulation shunts. Am Heart J 1951; 41:1–19.
107.Messika-Zeitoun D, Yiu S, Cormier B, et al. Sequential assessment of mitral valve area during diastole using colour m-mode flow convergence analysis: new insight into mitral stenosis physiology. Eur Heart J 2003;24: 1244–1253.
108.Brown W, Thomas W. Balloon valvuloplasty of tricuspid stenosis in a labrador retriever. Journal of Veterinary Internal Medicine 1995;9:419–424.
109.Nicolle A, Chetboul V, Escoffier L, et al. What is your diagnosis? Tricuspid valve stenosis (TS). J Small Anim Pract 2005;46:157–158.
110.Kunze CP, Abbott JA, Hamilton SM, et al. Balloon valvuloplasty for palliative treatment of tricuspid stenosis with right-to-left atrial-level shunting in a dog. Journal of the American Veterinary Medical Association 2002; 220:491–496.
111.Bayly WM, Reed SM, Leathers CW, et al. Multiple congenital heart anomalies in five Arabian foals. J Am Vet Med Assoc 1982;181:684–689.
112.Fawzy M, Mercer E, Dunn B, et al. Doppler echocardiography in the evaluation of tricuspid stenosis. Eur Heart J 1989;10:985–990.
113.Weyman A. Right ventricular inflow tract. In: Weyman A, ed. Principles and Practice of Echocardiography. 2 ed. Philadelphia: Lea and Febiger, 1994;498–574.
114.Pérez JE, Ludbrook PA, Ahumada GG. Usefulness of Doppler echocardiography in detecting tricuspid valve stenosis. Am J Cardiol 1985;55:601–603.
115.Adin D, Thomas W. Balloon dilation of cor triatriatum dexter in a dog. J Vet Intern Med 1999;13:617–619.
116.Brayley K, Lunney J, Ettinger S. Cor triatriatum dexter in a dog. J Am Anim Hosp Assoc 1994;30:153–156.
117.Tobias AH, Thomas WP, Kittleson MD, et al. Cor triatriatum dexter in two dogs. J Am Vet Med Assoc 1993;202:285–290.
118.Modi K, Senthilkumar A, Kiel E, et al. Diagnosis and surgical correction of cor triatriatum in an adult: combined use of transesophageal and contrast echocardiography, and a review of the literature.
Echocardiography 2006;23:506–509.
119.Hansing CE, Young WP, Rowe GG. Cor triatriatum dexter. Persistent right sinus venosus valve. Am J Cardiol 1972;30:559–564.
120.Mazzucco A, Bortolotti U, Stellin G, et al. Anomalies of the systemic venous return: a review. J Card Surg 1990;5:122–133.
121.Stafford Johnson M, Martin M, De Giovanni J, et al. Management of cor triatriatum dexter by balloon dilatation in three dogs. J Sm Anim Prac 2004;45:16–20.
122.Heaney A, Bulmer B. Cor triatriatum sinister and persistent left cranial vena cava in a kitten. J Vet Int Med 2004;18:895–898.
123.Mitten RW, Edwards GA, Rishniw M. Diagnosis and management of cor triatriatum dexter in a Pyrenean mountain dog and an Akita Inu. Aust Vet J 2001; 79:177–180.
124.Miller M, Bonagura J, DiBartoli S, et al. Budd-Chiari-like syndrome in two dogs. J Am Anim Hosp Assoc 1989;25:177–283.
125.Stern A, Fallon R, Aronson E, et al. Cor triatriatum dexter in a dog. Comp Cont Ed 1986;8:401–
126.Linde-Sipman J, Stokhof A. Triple atria in a pup. JAVMA 1974;165:539–541.
127.Patel V, Nanda N, Arellano I, et al. Cor triatriatum sinister: assessment by live/real time threedimensional transthoracic echocardiography. Echocardiography 2006;23:801–802.
128.Wander KW, Monnet E, Orton EC. Surgical correction of cor triatriatum sinister in a kitten. J Am Anim Hosp Assoc 1998;34:383–386.
129.Koie H, Sato H, Nakagawa H, et al. Cor triatriatum sinister in a cat. J of Sm Anim Prac 2000;41:128–131.
130.Patterson DF. Epidemiologic and genetic studies of congenital heart disease in the dog. Circ Res 1968;23: 171–202.
131.Reef V. Echocardiographic findings in horses with congenital cardiac disease. Comp Med 1991;13:109–117.
132.Reef VB. Cardiovascular disease in the equine neonate. Vet Clin North Am Equine Pract 1985;1:117–129.
133.Ringwald R, Bonagura J. Tetralogy of Fallot in the dog: clinical findings in 13 cases. J Am Anim Hosp Assoc 1988;24:33–43.
134.Patterson D, Pyle R, Van Mierop L, et al. Hereditary defects of the conotruncal septum in keeshond dogs: pathologic and genetic studies. Am J Cardiol 1979;34: 187–205.