Small animal congenital heart disease

• What is congenital heart disease?

  Malformations of the heart and great vessels that are present at birth. CHD occurs due to altered or arrested embryonic development of the rudimentary heart leading to potentially gross anatomical alterations.
• What are innocent murmurs?

  No structural explanation of the murmur, no structural cardiac disease that you can see to explain the murmur
• What are physiological/ functional murmurs?

  OCcurs whe the blood is then as it becomes more turbulent when thin, occurs in anaemic patients.
• What are pathological murmurs?

  Can be congenital (e.g. aortic stenosis) or acquired (e.g. CDVD, cardiomyopathy, endocarditis).
• General murmur assessment:

  • Grade - how loud, graded 1-6
  • Systolic or diastolic (sounds like a decrescendo)
  • Point of max intensity (where is it loudest, e.g. over the base/apex, left or right side.) if loudest on the left side over the apex then is CDVD
  • Can assess shape
• characteristics of innocent murmurs:

  • Grade - low grade I-II/VI
  • PMI - left heart base
  • Timing - mid-systolic
  • Variability - varying intensity with the heart rate
  • Radiation - minimal
  • Resolution - usually resolve by 6 months old (exception in some large dog breeds).
• Characteristics of CHD murmurs:

  • Grade - II-VI
  • PMI - depends on the condition
  • Timing - depends on condition but tend to be longer in duration
  • Variability - Generally non-viable
  • Radiation - depends on pathology
  • Resolution - no resolution, tends to get worse.
• Is there a correlation between the grade of the murmur and the severity of the disease?

  A loud murmur doesnt necessarily mean severe disease. For example large ventricular septal defects tend to be quite quiet compared to small VSD’s as its not being forced through as small a hole.
• What is a hyperkinetic pulse?

  Sounds like a water hammer. Abnormal diastolic run off of aortic blood - PDA/ severe aortic regurgitation.
• What is a hypokinetic pulse?

  left ventricular/ outflow tract obstruction - tends to be due to aortic stenosis or poor left ventricular output.
• What to do in practice if you find a murmur in a puppy or kitten?

  If loud grade (grade 3+) more likely to be a congenital anomaly, but loud does not necessarily mean bad (think small VSD).

  If < grade 2 could be innocent - reassess at 3 and 6 months old.

  Can return to breeder and get money back but most clients have already bonded with the animal so will not o this.

  Ultimately can only assess nature and severity of lesion with a full Doppler echocardiogram.
• Which structures can fail to develop correctly?

  1. Atrial septum
  2. Ventricular septum
  3. Ductus arteriosis
  4. Aortic valve
  5. Pulmonic valve
  6. Mitral valve
  7. Tricuspid valve
  8. Tetralogy of fallot - aorta and pulmonary artery don’t develop correctly, animal is always cyanosed.
• Common types of CHD

  • Aortic stenosis
  • Patent ductus arteriosus
  • Pulmonic stenosis
  • Ventricular septal defect
• What are the 3 types of aortic stenosis

  Sub-aortic stenosis - sub valvular narrowing amused by a fibrous or fibromuscular ring (there is a spectrum of severity). +/- mitral dysplasia as well, can increase in severity as dog matures, with maximum severity at 1-2 years of age. Exercise/ excitement can cause an increase in the intensity of the murmur. Found in boxers, Newfoundlands and Golden Retreivers.

  Valvular aortic stenosis (uncommon) - valve cusps don't open correctly.

  Supra-valvular aortic stenosis - rare
• Common findings of aortic stenosis

  Lethargy, extertional weakness, syncope, sudden death occur in approximately 1/3 of dogs with sub-aortic stenosis. Findings can vary depending on the age of the dog and the severity of the lesion.
• What are the 5 types of Pulmonic stenosis?

  1. Infundibular
  2. Sub-valvular pulmonic stenosis (uncommon)
  3. Valvular pulmonic stenosis (common) - can be the leaflets themselves or the annulus of the valve.
  4. Supra-valvular pulmonic stenosis (rare)
  5. Anomalous coronary artery pulmonic stenosis
• Presentation and clinical signs of Pulmonic stenosis

  Many cases are asymptomatic on presentation, clinical signs depend on severity of lesion.

  Right sided heart failure, syncope, exercise intolerance.

  Sudden death does occur in some severe cases.

  Prominent right apical beat.

  PMI murmur left heart base.

  Radiation cranially ventrally.

  Prominent jugular pulses.
• Valvular pulmonic stenosis colour doppler echo.

  Right ventricular outflow tract highlighted, can see acceleration of the blood flow after it goes through the distorted valve (shown by the speckled colour).

  
• Echo of pulmonic stenosis, the thick distorted valve is circled in red

  
• Post-Stenotic dilation

  
• What is Patent Ductus Ateriosus (PDA)

  Functional closure of the ductus usually occurs with hours after birth. Permanent closure occurs days to weeks post birth.. Animals with inherited PDA have histologically abnormal ductal walls that are unable to constrict. With full PDA blood shuts constantly from the descending aorta to the pulmonary artery during both systole and diastole. Volume overload of the pulmonary circulation and LA and LV.
• Murmur of the patent ductus

  Blood shunting from aorta into Pulmonary artery. Continuous murmur. Best heard over left heart base but very cranial and dorsal (in axilla). Very important to detect as potentially curable. Have to listen right over the heart base to hear the murmur. Can be corrected surgically by physically tying it off or can be closed with catheters.
• Patent Ductus Arteriosus on clinical examination

  Continuos machinery murmur PMI left heart base.

  Hyperkinetic pulses (tapping pulses).

  Volume overload leads to a large haemodynamic burden on the left ventricle which fails.

  After 12 months many dogs will progress into left sided congestive heart failure and show typical clinical signs.
• What is VSD?

  Ventricular septal defects. Usually located high in the membranous part of the septum just below the aortic valve an under the tricuspid leaflet (perimembranous). VSD leads to volume overload of the pulmonary trunk, pulmonary circulation. Small defects are usually clinically unimportant (restrictive). Moderate to large VSD lead to volume overload and potentially LCHF.
• Clinical signs of VSD

  Most dogs are asymptomatic but clinical signs depends on the size of the defect.

  Exercise intolerance, LCHF.

  Systolic murmur PMI cranial right sternal border.

  +/- murmur of functional PS.