Cyanotic Heart Disease

Question 1

What is cyanosis?

Answer 1

• Cyanosis is the bluish discoloration of the skin and mucous membranes.
• Occurs due to an increased amount of reduced haemoglobin within the RBCs

Question 2

What is central cyanosis?

Answer 2

desaturation of arterial blood or the presence of a Hb derivative.

Question 3

What is peripheral cyanosis?

Answer 3

desaturation of blood due to a regional reduction in blood flow.

Question 4

Why is cyanosis an insensitive indicator of oxygenation?

Answer 4

• Insensitive indicator of the state of oxygenation because it is difficult to recognise until oxygen saturation of Hb in arterial blood reaches 80% or less.
• Therefore it is an emergency condition requiring early recognition and treatment

Question 5

What is Arterial hypoxaemia?

Answer 5

PAO2 below normal (85-100 mmHg)

Question 6

What factors may influence cyanosis being detected?

Answer 6

• Lighting conditions
• Presence of anaemia
• Pigmentation

Question 7

What is the appropriate emergency management and ongoing management of cyanosis?

Answer 7

• Emergency management: Oxygenate, Hands off!
• Going forwards treat the cause

Question 8

Clinical signs of Cyanotic Congenital Heart Disease?

Answer 8

• Some of these dogs will show significant stunted growth
• OFTEN STABLE AT REST
• Exercise intolerance is a frequent clinical sign
• Collapse / syncope is also common especially on hindlimbs a very common sign in dogs with rPDA
• The owner may notice cyanosis

Question 9

What is Reverse Patent Ductus Arteriosus and why does it occur?

Answer 9

• The fetal ductus connecting the pulmonary artery and aorta (allows blood to bypass the lungs in utero) does not close after birth.
• Due to the presence of pulmonary hypertension in the new born.
• Blood continues to shunt from the pulmonary artery into the aorta.

Question 10

Clinical signs of Reverse Patent Ductus Arteriosus?

Answer 10

• These dogs may not have a murmur or a low grade murmur of tricuspid regurgitation
• May have a split S2
• Differential cyanosis is usually present
• Later on these dogs will be polycythaemic with associated clinical signs of hyperviscocity

Question 11

What is differential cyanosis?

Answer 11

• Vulval or penile mucous membranes are cyanosed whilst the gingival mucous membranes are pink.
• With exercise the oral mucous membranes can also become cyanotic

Question 12

What is Tetralogy of Fallot?

Answer 12

• Complex congenital heart disease composed of four specific features:
  
  • Pulmonic stenosis
  • Ventricular septal defect
  • Over-riding aorta
  • Right ventricular hypertrophy and dilation

Question 13

What diagnostics would you use for cyanotic heart disease?

Answer 13

• Routine haematology
• Routine biochemistry
• Arterial blood gases
• Echocardiography
• Thoracic radiographs (extreme care sedating these patients)
• ECG

Question 14

What non-therapeutic management factors may be used for cyanotic heart disease?

Answer 14

• Exercise restriction
• Cold weather can make these animals significantly worse due to pulmonary hypertension
• Weight control

Question 15

How is cyanotic heart disease medically treated?

Answer 15

• Management of their clinical signs.
• Control of the polycythaemia is important, this can be done by various methods:
  
  • Regular blood letting
  • Chemotherapy

Question 16

What methdos of blood letting are carried out in cyanotic heart disease?

Answer 16

• Phlebotomy is the most common, although there are successful reports of the use of leeches in cats
• Phlebotomy 10-20ml/kg of blood is removed in order to reduce the haematacrit to a target level of 55%
• Need to monitor protein levels carefully

Question 17

Which chemotherapy drug may be used in cyanotic heart disease?

Answer 17

Hydroxycarbamide (myelosuppressant drug which reduces RBC production in the bone marrow)