Category:Cardiovascular System - Developmental Pathology

Chamber Development

Atrial Septal Defect

Ventricular Septal Defect

Patent Ductus Arteriosus

Great Vessels

Vascular Ring Anomaly

Most commonly found in dogs and cats. Acyanotic; clinical signs due to constriction of the oesophagus:

• Regurgiation of food, usually noticed at weaning.
• Aspiration pneumonia.

Persistent Right Aortic Arch

Most common vascular ring anomaly, increased incidence in GSDs, and Irish setters. vascular ring forms between the ductus arteriosus/ligamentum arteriosum and the persistent right aorta. Megaoesophagus is seen cranial to the constriction.

Other causes include:

Double aortic arch

Anomalous subclavian arteries

Arise form the aortic arch rather than the brachiocephalic artery.

Diagnosis:

• Ventral deviation of the trachea and dilation of the oesophagus on radiology.
• Barium swallow definitive.

Treatment:

• Surgical resection possible.
• Dietary management usually sufficient to control regurgitation.

Tetralogy of Fallot

• Pulmonic stenosis
• Right ventricular hypertrophy
• High VSD
• Overriding aorta

Commonly reported in certain breeds, E.g Keeshond, Schnauzer, Poodles and terriers.

Clinical Signs:

• Cyanotic; see severe exercise intolerance.
• Systolic murmur due to pulmonic stenosis +/- precordial thrill.
• Polycythemia due to chronic hypoxia.

Diagnosis:

• Right ventricular enlargement on radiology and ECG.
• Post stenotic dilatation of pulmonary artery on radiology and pulmonary undercirculation due to right to left shunting.
• Echocardiography may show right ventricular hypertrophy, paradoxical motion of interventricular septum (pressure RV>LV), visulaisation of VSD and overriding aorta.
• Doppler useful to image pulmonic stenosis and VSD.

Valve Development

Aortic Stenosis

Obstructs blood flow from the left ventricle to the aorta. Stenosis may be:

• Subvalvular (most common in dog and cat).
• Valvular.
• Supravalvular.

Subvalvular stenosis results in a jet of blood hitting the aortic valve, leading to damage and increased risk of developing endocarditis.

Incidence:

• Increased prevalence in Boxers and Golden retrievers.
• Autosomal dominant in Newfoundlands.

Clinical Signs:

• Vary from asymptomatic to degrees of exercise intolerance, syncope and even sudden death.
• Harsh systolic murmur at left heart base.

Grade correlates with grade of murmur. High grade murmurs also have a precordial thrill.

• Murmur may have a diastolic component due to aortic valve damage and insufficiency.
• Weak femoral pulse.

Diagnosis:

• Left ventricular enlargement on radiology and ECG.
• Post-stenotic dilatation of the aorta may be visible on radiographs.
• Echogenic fibrous ring may be seen on echocardiography. Again, Doppler is useful to detect flow rates.

Treatment:

• Balloon valvuloplasty; often unsuccessful.
• Mild cases need no management.
• Medical management; Beta-blockers to decrease myocardial oxygen consumption.
• Prognosis guarded, death due to arrythmias in abnormal myocardium.

Pulmonic Stenosis

Obstructs blood flowing form the right ventricle to the pulmonary artery. As with aortic stenosis may be subvalvular, valvular or supravalvular. Valvular stenosis is the most common form in the dog.

Incidence:

• Increased incidence in English bulldogs, Cocker spaniels, Chihuahuas.
• Autosomal dominant in Beagles.

Clinical Signs:

• Asymptomatic if mild or moderate.
• If severe; exercise intolerance, stunting, syncope, right sided heart failure E.g. ascites.
• Harsh systolic murmur at left heart base.
• May hear splitting of the second heart sound due to delayed closure of the pulmonic valve.
• Femoral pulse quality good but jugulars distended.

Diagnosis:

• Right ventricular enlargement on radiology, along with post-stenotic dilatation of the pulmonary artery and pulmonary undercirculation.
• Abnormal valve can be imaged using echocardiography.
• Severity of stenosis can be assessed using Doppler to calculate flow rates.

Treatment:

• Balloon valvuloplasty is treatment of choice.

Mitral Dysplasia

Often associated with mitral regurgitation and left atrial volume overload. Usually progresses to left sided heart failure.

Incidence:

• Most common congenital defect in cats.
• Also reported in pure breed dogs E.g GSD, Great Danes.

Clinical Signs:

• Often murmur is the only clinical sign; pansystolic with increased intensity over the mitral valve area.
• May also see exercise intolerance, dyspnoea and coughing.

Diagnosis:

• Left atrial enlargement on radiology and ECG.
• Doppler echocardiography can dtect abnormal flow.

Treatment:

• Prognosis poor, medically manage left heart failure with ACE-inhibitors etc.

Tricuspid Dysplasia

Tricuspid regurgitation results in volume overload of the right atrium and may progress to right heart failure.
Ebstein's Anomaly: Atrioventricular ring is displaced ventrally into the right ventricle so that part of the wall of the right atrium is made up of ventricular wall.

Incidence:

• Second most common congenital anomaly seen in cats.
• Also reported in large breeds of dog including Weimeraner.

Clinical Signs:

• Often the murmur is the only clinical sign; low grade and pansystolic with increased intensity over the tricuspid area.
• May also see right sided failure, signs include; ascites, hepatomegaly and splenomegaly.

Diagnosis:

• Right ventricular enlargement on radiology and ECG.

Miscellaneous

Peritoneo-pericardial Diaphragmatic Hernia

Represents an embryological malformation of the ventral midline with communication to varying degress of the pericardial sac and the peritoneal cavity. Often associated with other malformations for example sternal deformities and ventricular septal defects. Usually results in gastrointestinal or respiratory signs. Visible radiologically as a round cardiac silhouette which merges with the diaphragm. The trachea will be displaced dorsally. Intestines may be visible on radiographs. Repaired surgically.

Ectopia Cordis

The heart is normal in anatomy but situated in an abnormal location within the body. Cattle and pigs show the highest incidence. The heart may be found in the cervical region or the abdomen.

Endocardial fibro-elastosis

Seen in Burmese kittens. Collagen and elastin are deposited in the endocardium, limiting its function. Animals are often found dead at 2-3 months of age.