DISEASE SUMMARIES
Figure 18a
Lateral thoracic radiograph of a ten-year- old female Domestic Short Hair cat with idiopathic dilated cardiomyopathy.
Figure 18b
Dorsoventral thoracic radiograph of a ten-year- old female Domestic Short Hair cat with idiopathic dilated cardiomyopathy.
associated with scapulohumeral wasting in English Springers.
Persistent left cranial vena cava
The left cranial vena cava is normally present in the foetus, but may persist abnormally after birth. This abnormality is relatively common, but is of no significance to the animal unless it is undergoing thoracic surgery.
Persistent right aortic arch
This is a malformation in the foetal develop- ment of the vascular system, which leads to the oesophagus being partially occluded. This leads to regurgitation once the animal starts weaning. See also Vascular ring anomaly under Gastro- intestinal conditions.
Pulmonic stenosis
This is a common congenital condition, affecting 20% of dogs diagnosed with congenital heart disease. The condition may be asymptomatic, or may cause signs of syncope and right-sided con- gestive heart failure.
Sick sinus syndrome
This dysrhythmia often involves periods of bradycardia and tachycardia, leading to syncope.
Tetralogy of Fallot
This condition accounts for approximately 4% of congenital heart disease. Pulmonic stenosis, ventricular septal defect, a dextrapositioned or overriding aorta and a secondary right ventricu- lar hypertrophy comprise the four parts of this abnormality.
Tricuspid dysplasia
This is a malformation of the tricuspid valve, the consequence of which is to allow blood to flow back from the right ventricle into the right atrium. Affected dogs may have other congen- ital heart lesions. In some cases the animals are asymptomatic for many years, while others show progressive heart failure leading to death.
Ventricular ectopy
Ventricular ectopic beats are abnormal beats of the heart arising within the ventricles instead of the normal pacemaker in the atria. They can breeds of dog, although this is not yet proven.
The lesion consists of a malformation of the mitral valve, the normal function of which is to prevent blood flowing back from the left vent- ricle to the left atrium. Many animals with this condition do not show symptoms, and those that do usually demonstrate exercise intolerance and congestive heart failure.
Patent ductus arteriosus
The ductus arteriosus carries blood from the pulmonary artery to the aorta in the foetus to bypass the lung, which is not in use. It normally closes within the first week after birth. It is prob- ably the commonest congenital heart condition of dogs, but is less common in cats. Females are at a higher risk of developing the condition than males. Symptoms range from none, to congest- ive heart failure and poor body condition, to weakness, collapse and seizures.
Pericardial effusion
This condition involves a build up of fluid between the heart wall and the pericardium. It can be caused by tumours of the heart, but often has no apparent cause (‘benign’ or ‘idiopathic’ pericardial effusion). The idiopathic form is poorly understood, and it is not known whether it is inherited. However, it does tend to affect large-breed and giant dogs. Symptoms are precipated by the inability of the heart to fill properly because of restriction caused by the fluid-filled pericardial sac. Chronic cases exhibit weight loss, ascites and dyspnoea resulting from pleural effusion. Acute cases may show rapidly progressing weakness, collapse and death.
Peritoneopericardial hernia
This uncommon congenital disease is seen in only about 0.5% of cases of congenital heart disease. It involves a continuation of the pericardium with the peritoneum, and often abdominal viscera are found within the peri- cadial sac. It may be asymptomatic, or may cause signs of respiratory distress, vomiting and colic.
Persistent atrial standstill
This is a rare condition caused by an enlarge- ment and thinning of the atria. It is often
respiratory and gastrointestinal signs, and the prognosis is poor. A defect in zinc metabolism may be involved in the pathogenesis.
Aguirre syndrome
Unilateral periocular depigmentation. It may be associated with Horner’s syndrome, ocular and respiratory problems.
Alopecia areata
This condition is uncommon, leading to an asymptomatic, non-inflammatory alopecia.
Anal sac disease
Infections and impactions of the anal sacs are common, causing self-trauma to the perineal area and other parts of the body.
Atopy (see plate 14)
This is a common condition involving hyper- sensitivity reactions to environmental allergens. It is thought to be inherited but the exact mode of inheritance has not yet been determined. Symptoms consist of pruritus, erythema and self-trauma with secondary bacterial infection.
Black hair follicular dysplasia
A rare disorder causing alopecia in areas of black hair.
Blastomycosis
See under Infectious conditions.
Bullous pemphigoid
A rare autoimmune condition leading to ulcera- tion of the mucocutaneous junctions, skin and oral cavity.
Calcinosis circumscripta
An uncommon condition, usually of unknown cause, although it may be associated with hyper- adrenocorticism. Most affected dogs are of large breeds, and pressure points are commonly involved.
Callus dermatitis/pyoderma
Calluses form in response to trauma. Secondary infection occurs in chronic cases, leading to ulceration.
Dermatological Conditions
183have a number of causes, such as heart disease, kidney disease and sepsis. They are also in- herited in German Shepherd Dogs. If they occur frequently they can cause symptoms of collapse, and the rhythm can degenerate into fatal ventricular fibrillation.
Ventricular septal defect
This condition accounts for approximately 7% of canine congenital heart disease. Defects vary in size but can be very large. Small defects may be asymptomatic, but larger defects can cause congestive heart failure, pulmonary vascular disease and pulmonary hypertension.