Congenital Heart Disease in Companion Animals

Nancy and Rosie - 6 30 15Nancy Laste, DVM, DACVIM (Cardiology)

This is the first of a multi-part series of articles discussing the more common congenital heart diseases seen in companion animals and in-depth review of pulmonic stenosis in the dogs.

When spending time at Boston Children’s hospital, one runs across a myriad of very complex congenital heart diseases that we never see in clinical veterinary practice (even a busy cardiology practice). Because our animal friends do not have intensive prenatal diagnostic tests and attended births, the vast majority of veterinary patients with complex congenital heart disease perish prior to birth or die in the early neonatal period. For this reason, most of the congenital heart diseases that we diagnose in dogs and cats are less complex. Table 1 shows the approximate incidence of canine congenital heart disease. Feline congenital heart diseases are listed in Table 2. A recent large retrospective study of all patients presenting to a single shelter (76,301 patients), screened for murmurs by the shelter staff and having echocardiograms by a single veterinary cardiologist showed a relatively low incidence of congenital heart disease (11). The incidence in the mixed breed dogs and cats (57,025 screened patients) was 0.13% in dogs and 0.14 % to 0.2 % in cats. This is much lower than the described incidence of heart disease in most typical studies done through cardiology services at larger referral hospitals. The purpose of the study was an attempt to identify the true incidence of congenital heart disease in the companion animal population at large as opposed to in purebred dogs, which are overrepresented in the population of patients presenting to referral hospitals for cardiac evaluation. Previous published reports on the incidence of congenital heart disease were obtained from those populations (9).

Table 1: Canine Congenital Heart disease in approximate order of incidence.  More common diseases noted in bold font.

Cardiac Defect Typical Affected Breeds
Pulmonic Stenosis Pit bull terrier, Airedale Terrier, Bulldog, Terriers, Beagle, Chihuahua, Schnauzer, Newfoundland, Bull Mastiffs
Patent ductus arteriosis Poodles, Maltese, Newfoundland, Pembroke Welsh Corgi, Cavalier King Charles Spaniel, Pomeranian, Chihuahua, Shetland sheepdog, Springer Spaniel, German Shepherd dog, Cocker spaniel
Subaortic stenosis Newfoundland, German Shepherd dog, Rottweiler, Golden retriever, Pug, German Shorthaired Pointer
Ventricular septal defect Lakeland terrier. West Highland White Terrier, Basset Hound, Keeshond, Akita, Shih Tzu, English Bulldog
Tricuspid dysplasia Labrador retriever, Golden Retrievers, Boxers
Tetralogy of Fallot Keeshond, English bulldog
Atrial septal defect Poodles
Common AV canal Collie
Cor triatriatum dexter
Mitral stenosis English Bull Terrier
Mitral dysplasia English Bull Terrier
Truncus arteriosus

Table 2: Feline Congenital Heart disease in approximate order of incidence. More common diseases noted in bold font.

Cardiac Defect
Ventricular septal defect
Hypertrophic obstructive cardiomyopathy (mitral dysplasia?)
Aortic, Subaortic stenosis
Pulmonic stenosis
Patent ductus arteriosus
Tetralogy of Fallot
Atrial septal defect
Common AV canal
Tricuspid dysplasia
Cor triatriatum sinustrum
Mitral stenosis


Canine Pulmonic Stenosis

Pulmonic stenosis is a commonly diagnosed congenital heart disease with terrier breeds, beagles and pitbulls most commonly affected. Affected patients present with a typical harsh, holosystolic ejection type murmur loudest over the left heart base with minimal referral up the carotid arteries (typical of AS/SAS). The femoral pulses are palpably synchronous. Patients are often asymptomatic with the murmur as the presenting complaint. The most common symptoms associated with PS are syncope, (generally exertional) or exercise intolerance. With severe pulmonary stenosis, right sided congestive heart failure (ascites) can develop although this is relatively rare and is a poor prognostic indicator.

Echocardiogram is helpful in confirming the diagnosis of pulmonic stenosis, the level of the stenosis (valvular, subvalvular or supravalvular); and allowing the severity of obstruction to be estimated by measuring the maximal velocity of flow across the stenotic lesion. Use of the modified Bernoulli equation (Pressure = 4 x mean velocity2) allows the severity of obstruction to be estimated as mild (0-50 mmHg), moderate (50-80 mmHg) or severe (>80 mmHg). Patients with very high pressure gradients (200 mmHg+} may be identified as having “critical” pulmonic stenosis. Careful inspection of the pulmonary annulus and the valve leaflets allows determination of whether the obstruction is an uncomplicated (type A PS) valvular obstruction (doming of the leaflets but a normal pulmonary annulus and valve leaflets that are not excessively thickened or whether pulmonary artery hypoplasia and/or pulmonic valve dysplasia are present (type B PS). It is important to confirm that two distinct coronary arteries arise from the aortic root, particularly in breeds at risk for a single coronary artery associated with pulmonic stenosis (English Bulldogs, Boxer dogs, French Bulldogs, English Springer Spaniels).(1) Pets that have the R2A coronary artery defect have a single right coronary sinus which gives rise to the left coronary artery which encircles the pulmonary artery at the level of the pulmonary stenosis, adding a component of subvalvular pulmonic stenosis.  Pets with this defect are at higher risk for complications with balloon valvuloplasty (BV).  Patients with type A PS are considered very good candidates for BV.  Measurement of the pulmonary annulus allows for balloon selection for BV.  Pressure gradients tend to increase as the patients grow, with relative plateau of the severity of obstruction at six to nine months of age. Incremental increases in pressure may occur due to secondary right ventricular hypertrophy that occurs over time. Patients with pressure gradients over 80 mmHg are generally started on a beta blocker (typically atenolol at 1 mg/lb po bid — start with lower doses on larger dogs titrating upward as tolerated). Case selection for balloon valvuloplasty is generally aimed at dogs with pure valvular stenosis with severe obstruction. Patients with moderate obstruction who are symptomatic will be evaluated for surgery, after careful inspection for concurrent cardiac defects. The presence of a patent foramen ovale (one of the more common concurrent conditions) is not a contraindication for balloon valvuloplasty (6). Patients with significant pulmonary dysplasia and/or pulmonary artery hypoplasia (type B) generally do not respond well to BV. Patients with a R2A coronary defect who are experiencing clinical signs may respond to BV using a small balloon in patients who are experiencing clinical signs (4).


There are many reports of the overall prognosis associated with PS (2,5,8). In general, the prognosis for mild to moderate PS is favorable. Patients with severe PS have a more variable prognosis but may respond well to BV. The presence of right sided congestive heart failure is an unfavorable prognostic indication and a clear indication for intervention.

Balloon Valvuloplasty

Balloon valvuloplasty is done in the cardiac catheterization lab. Patients are anesthetized and the venous access site (the jugular vein or the femoral vein) aseptically prepared for surgery. The procedure may be done percutaneously (no incision) or a surgical approach may be made to isolate the selected vein. A catheter introducer is put in place to facilitate bloodless entrance and removal of the multiple catheters that will be passed during the procedure. The first step is to try to pass a flow- directed balloon catheter or a “general purpose catheter” (one with a gentle bend) out into the pulmonary artery. This allows the measurement of intracardiac pressures and to evaluate the pressure gradient across the stenotic valve. The pressure gradient under anesthesia is usually approximately 50% of that measured when the patients are awake. A pulmonic pressure tracing is depicted on figure 1. Once the pressure tracing is obtained, right ventricular angiography is performed (figure 2).


Figure 1: Pressure tracing schematic for patient with valvular pulmonic stenosis

Fig 2

Figure 2: Right ventricular angiogram on a patient with valvular pulmonic stenosis showing stenotic pulmonic valve, post-stenotic dilation of the main pulmonary artery and right ventricular hypertrophy.

The injection of radiopaque contrast allows full definition of the right ventricle, the pulmonary annulus, the pulmonic valve leaflets, the post stenotic dilation and pulmonary artery anatomy. The level of the stenosis is confirmed and the pulmonary artery annulus measured at the hinge points of the valve leaflets. The contrast injection is ideally made through a catheter with no end hole and at least two side holds (this catheter replaces the flow-directed balloon catheter temporarily). The fluoroscopy evaluation is continued through the “levophase,” the recirculation of the raidoopaque dye from the right to the left side of the heart which allows general evaluation of the coronary anatomy. If the coronary anatomy is in question, a selective aortic root injection can be made but requires catheterization of the left side of the heart. Once the measurements are made, a balloon dilation catheter diameter is selected that is 1.2-1.5 times the size of the pulmonary annulus starting on the lower end of the range, increasing to the upper end of the range as needed. The balloon directed flow catheter (or multi-purpose purpose catheter) is subsequently positioned as far out in the pulmonary arterial tree as is possible. A long, stiff “exchange wire guide” is then placed through the catheter, and remains as distal as possible.  The catheter is then removed, leaving the wire in place and the balloon subsequently introduced over the wire.  The balloon catheters are stiff and relatively non- steerable: passing the balloon catheter through the hypertrophied right ventricle (taking a more than 180 degree turn) can be very challenging and often associated with severe arrhythmias.  Patients showing irritability with catheter manipulation are pretreated with a lidocaine bolus (2 mg/kg slow iv) in addition to the lidocaine CRI typically administered to these patients by the anesthesiologist. A very large catheter introducer is needed to accommodate the larger balloon sizes.  Sometimes, the balloon catheters must be passed directly into the femoral or jugular vein if the vein will not accommodate the larger introducer. Once the balloon catheter is positioned, it is inflated rapidly with radiopaque contrast. The ideal scenario is visible waisting of the balloon (figure 3) followed by a “bursting” open of the hour glass appearance leaving a fully inflated balloon.  Subsequent inflations (done after adequate cardiac recovery) should not result in any significant indentation of the balloon. Repeat measurements of the pressure gradient should show significant (greater than 50%) reduction of the gradient. Right bundle branch block typically develops after balloon dilation (occasionally temporary, often permanent) with a resulting atypical appearance to the ECG (see figure 4). Once the procedure has been completed, the catheters are removed, the catheter introducer removed and the vein either repaired or ligated. Wound closure is standard. Recovery from the procedure is generally smooth.  Dogs should be monitored for arrhythmias the night of the procedure, with some patients requiring antiarrhythmic treatment. Patients are generally discharged the following day on NSAID therapy. Surgical discomfort tends to be minimal. Suture removal standardly occurs at 10-14 days.

Fig 3

Figure 3: Balloon catheter, partially inflated, across the stenotic valve.

Fig 4

Figure 4: ECG showing deep, wide S waves characteristic of right bundle branch block.

The Results of Balloon Valvuloplasty

Successful balloon valvuloplasty will generally move a patient with severe pulmonic stenosis and into the mild to moderate category where they have an excellent chance of living a normal, symptom free life span. Restenosis of the torn valve tissue can occur, but thankfully seems to be an infrequent occurrence. Repeat balloon dilation has been described but is rarely required.


Complications that can occur with cardiac catheterization and the procedure include arrhythmic death, cardiac perforation, cardiac arrest or breakage/embolization of the surgical materials. Patients with pulmonic stenosis generally tolerate general anesthesia well and these complications are relatively rare. Because patients tolerate mild and moderate pulmonic stenosis so well, in the absence of clinical signs surgical intervention is only on patients with a gradient higher than 80 mmHg.

Other Surgical Options

Patients who have type B pulmonic stenosis will be more successfully treated by open heart surgery or patch grafting. The readers are referred to the reference list for a description of these uncommonly performed procedures (12). Morbidity and mortality is high with these procedures. Patients with the R2A coronary artery anomaly (usually English Bulldogs) may be treated with the creation of a RV to PA conduit, bypassing the obstruction.  Keeping these shunts patent is very challenging in the canine patient. Symptomatic patients may have palliation with conservative balloon dilation (using a balloon smaller than the measured annulus) (4).

Next in the series:  Aortic and Subaortic stenosis in the dog.

For more information, please contact Dr. Nancy Laste at, or call the Cardiology Service at 617-541-5038

 References and recommended reading: 

  1. Buchanan JW. Pulmonic stenosis caused by single coronary artery in dogs:   Four cases (1965-1984).  JAVMA 1990; 197(1):115-120.
  2. Bussadori C, DeMadron E, Santilli R, Borgarelli M. Balloon Valvuloplasty in 30 Dogs with Pulmonic Stenosis: Effect of Valve morphology and Annular Size on Initial and 1-Year Outcome.  J Vet Intern Med 2001; 15(6): 553-8.
  3. Feigenbaum H. Role of M-mode in today’s echocardiography. J Am Soc Echocardiogr. 2010 Mar;23(3):240-57; 335-7
  4. Fonfara, S, Martinez Pereira Y, et al. Balloon Valvuloplasty for Treatment of Pulmonic Stenosis in English Bulldogs with an Aberrant Coronary Artery. J Vet Intern Med 2010. 24 (2): 354-9.
  5. Francis AJ; Johnson MJS et al. Outcome in 55 dogs with pulmonic stenosis that did not undergo balloon valvuloplasty or surgery. J Small Anim Pract. June 2011;52(6):282-8.
  6. Fujii Y, Nishimoto Y, et al. Prevalence of patent foramen ovale with right-to-left shunting in dogs with pulmonic stenosis. J Vet Intern Med. 2012 Jan-Feb ;26(1):183-5.
  7. Fujiwara M, Harada K, et al. Surgical treatment of severe pulmonic stenosis under cardiopulmonary bypass in small dogs. J Small Anim Pract. February 2012;53(2):89-94.
  8. Locatelli, C, Spall I, et al. Pulmonic stenosis in dogs: survival and risk factors in a retrospective cohort of patients. J Small Anim Pract. September 2013;54(9):445-52.
  9. Oliviera P, Domenech O, et al. Retrospective Review of Congenital Heart Disease in 976 Dogs. J Vet Intern Med.  25 (3): 477–83.



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