Canine cardiac stenosis can be age-related, but may also be congenital, hereditary and familial. Early detection and a strict therapeutic regimen that includes alternative therapies can help prevent progression of the disease. 

Cardiac stenosis is the second most common congenital cardiac anomaly in the dog, after the chronic valvular disease that creates mitral valve insufficiency. In this article, we look at the causes and types of cardiac stenosis in dogs, and how it may be managed using an integrative approach.   

Types of heart disease 

1. Congenital: Patent ductus arteriosus, valvular stenosis 
2. Acquired: Degenerative valve disease, infectious heart disease (heartworm, toxins, bacteria, etc.) and dilated cardiomyopathy (DCM). 

Congestive heart failure (CHF) 

Almost all forms of heart disease can and will lead eventually to congestive heart failure. 

Congestion is classified as the accumulation of blood or fluid as a cause of decreased cardiac function. Congestive heart failure is not curable but can be managed via careful monitoring and a comprehensive therapy plan. 

If a dog has congestive heart failure, avoid feeding foods high in sodium, as excess salt can lead to fluid retention and worsening heart strain. This includes processed treats, deli meats, cheese, canned foods with added salt, and table scraps like chips or fast food. 

Canine cardiac stenosis 

• Cardiac stenosis in dogs, specifically subaortic stenosis (SAS), is primarily caused by a congenital defect, where blood flow from the left ventricle to the aorta is obstructed. This is a progressive disorder and the narrowing vessel forces the heart to work harder, potentially leading to complications like heart failure or sudden death. 

• Aortic stenosis, typically caused by a ridge or ring of fibrotic tissue in the subaortic region (subaortic stenosis or SAS), is one of the most common congenital defects in large breed dogs. In most dogs, especially small and medium-sized breeds and mixed breeds, a cardiac murmur is detected, although most of those affected live normally if they avoid strenuous exercise. A heart murmur is typically an incidental finding except in more severely affected dogs, where it can be associated with a loud ejection murmur and weak peripheral pulses. 

Aortic stenosis is characterized by obstruction of the left ventricular outflow tract, resulting in pressure overload on the left ventricle. The cause of the obstruction is a fibromuscular nodule, ridge, or ring of tissue that increases aortic outflow tract velocity. The prevalence of this disease has been reported at 4.7%.  

In large breed dogs, this disease can result in fainting, a shortened life span, or even sudden death. Mildly affected dogs tend to have a normal lifespan, but severely affected dogs have an average lifespan of 19 months. Further, severely affected dogs have an increased risk of developing cardiac complications that include sudden death, congestive heart failure, syncope, and endocarditis.  

Currently, moderate and severely affected dogs given beta-blockers (atenolol) have experienced a 56-month survival time. Current clinical practice continues to prefer the use of pharmacological intervention over surgical intervention for SAS-affected dogs. Recurrence of the sub-valvular lesion can occur after post-surgical resection. 

In the Newfoundland, familial SAS is a dominant inherited trait with variable penetrance or expression in affected homozygous and heterozygous individuals.  It is one of the most common canine congenital heart defects and is inherited in both this breed and the Golden Retriever. A three-nucleotide exonic insertion in the phosphatidylinositol-binding clathrin assembly protein (PICALM) is associated with the development of SAS. Even equivocally affected individuals can pass on SAS to their progeny. 

• Pulmonic stenosis is most often due to commissural fusion or dysplasia of valve leaflets, producing a loud ejection murmur over the left base of the heart 

• Myocardial injury (MI) is not to be confused with myocardial infarction. A large European study included 102 dogs. Echocardiographic and electrocardiographic abnormalities were documented in 86 of 102 and 89 of 102 dogs, respectively.  

Among echocardiographic and electrocardiographic categories, the dilated cardiomyopathy phenotype (n = 52) and abnormalities of impulse formation (n = 67) were overrepresented, respectively. Among dogs in which a suspected etiological trigger was identified (68/102), the infective category was overrepresented (n = 20). Among dogs belonging to different echocardiographic, electrocardiographic, and etiological categories, cardiac troponin I(cTnI) did not differ significantly. The median survival time was 603 days; only eight of the 102 dogs died due to MI. 

There’s no single cause of heart disease in dogs. Aging, obesity, breed, and nutrition can all play a role. Heart valve problems are the most common issue and typically affect small breeds five years of age or older. No matter what heart condition the dog has, recognizing the signs early is important for management, treatment and prognosis.  Diagnosis requires a physical examination; electrocardiography EKG (usually normal); two-dimensional, Doppler and cardiac catheterization radiography; blood pressure reading; and routine blood diagnostics including adrenal and thyroid profiles. 

Treating canine cardiac stenosis 

Conventional therapy  

Treatment revolves around the type and severity of disease. Surgical excision of a sub-valvular lesion and replacement of the aortic valve is very costly and requires a heart-lung machine. Alternatively, one can incise, tear or stretch the sub-valvular fibrotic lesion using a balloon catheter (balloon valvuloplasty) or valve dilator. Regardless, the surgical outcome is not favorable and affected dogs are at high risk for bacterial endocarditis. Broad-spectrum antibiotics are needed perioperatively and afterwards. Some mild forms of heart disease will not need any pharmacological intervention. 

• Inotropes and chronotropes modulate heart rate and rhythm. 

• Inotropes such as pimobendin increase the strength of cardiac contractions by increasing calcium sensitization to troponin C and promoting vasodilation by inhibiting phosphodiesterase III, which increases cyclic AMP. 

• Chronotropes like dopamine, atropine, epinephrine and theophylline affect heart rate. 

• ACE inhibitors like enalapril, and beta-blockers like atenolol help reduce blood pressure.  

• Diuretics such as furosemide or spironolactone, an aldosterone antagonist, help prevent congestion.  

Medications should be tailored to each patient and will likely change as the condition progresses. 

Alternative therapies    

A range of alternative therapies can be used for canine patients with cardiac stenosis:  

• Acupuncture and acupressure 

• Essential oils 

• Botanicals and other nutrients – e.g. hawthorn berry as syrup or tea (see sidebar on page xx), L-taurine, L-carnitine, vitamin E, dimethyl glycine (DMG) liquid, manganese, potassium, selenium, Coleus forskolin root (diterpene used in Ayurveda for heart disease) 

• Coenzyme Q10 (CoQ10) — has antioxidant properties and can be beneficial to body tissues with high energy requirements. 

• Traditional Chinese Herbs (TCM) 

• Low sodium diet

Conclusion 

Heart disease is a very common condition affecting aging dogs. It also can be congenital, hereditary and familial. Though most forms are not curable, early detection with careful monitoring at home and in the clinic, as well as development of and adherence to a strict therapeutic regimen, can help prevent progression of the disease.  

References 

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