congenital disease

• Murmur in a puppy or kitten

  • If loud (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 – re-assess at 3 and 6 months
• Below 3 = quieter than the heart sounds

  Grade 3 = heart sound

  Higher than 3 = higher than heart sound
• • Plateau murmurs - sound the same through
  • Ejection murmurs - sound sharp
  • Descesendo murmurs - musical and tend to be diastolic and can be heard in horses with aortic valve disease (due to aortic regurgitation)
• Most murmurs in SA are systolic, diastolic ones are rare. A patent ductus arteriosus can cause a constant murmur
• Left apex - first heart sound (AV valve) if this valve is leaky and then you'll hear the murmur hear loudest

  Base of the heart (push into the axilla) to heart is where the aortic / pulmonary valves are and this is where you are more likely to hear CHD murmurs
• fill in the blanks

  A) low grade

  B) left heart base

  C) mid-systolic

  D) minimal

  E) 6

  
• When you hear a murmur there are three main differentials for the cause…

  1. Innocent (a murmur for which there is no structural cause)
  2. Physiological/functional (blood becomes more turbulent because it is thin e.g. severely anaemia)
  3. Pathological (due to pathological change in the heart)

  • This can then be congenital or acquired.
  • Acquired examples are chronic degenerative valve disease, cardiomyopathy and endocarditis
• Some significant CHD may have no murmur (e.g. large VSD which is more severe despite being quiet) shunts while some small ventricular septal defects (VSD) may have very intense murmurs associated with only a moderate amount of shunting blood.
• There are other signs that can indicate a congenital heart disease such as

  • Arterial pulse quality
  • Hyperkinetic pulse (water hammer) –abnormal diastolic run off of aortic blood
  • Due to PDA /severe aortic regurgitation
  • Hypokinetic pulse –left ventricular / outflow tract obstruction
  • Due to aortic stenosis or poor left ventricular output.
  • mucous membrane colour (cyanosed with no respiratory difficulty)
  • Deoxygenated blood can be shunted into the systemic system causing the cyanosis
  • precordial impulse (where does the heart feel more vigorous as this can indicate where the problem is)
•  

  Which structures fail to develop properly?

  • atrial septum (fail to close)
  • Ventricular septum (fail to close)
  • The ductus arteriosus (a connection from the aorta to pulmonary artery which should close)
  • Malformation of the aortic valve
  • Malformation of the pulmonic valve
  • Malformation of the tricuspid valve
  • Malformation of the bicuspid valve
  • Tetralogy of fallot
• Aortic stenosis is the narrowing of the aorta and has 3 types

  • Sub-aortic stenosis(common)
  • Sub valvular narrowing caused by a fibrous or fibromuscular ring
  • Spectrum of severity and may have mitral dysplasia as well. it can increase in severity as dog matures reaching maximum severity at 1-2 years of age
  • Exercise / excitement can cause an increase in the intensity of the murmur
  • Boxers, Newfoundlands, Golden Retrievers
  • Valvular aortic stenosis (uncommon and is due to the valve cusps being stuck together)
  • Supra-valvular (rare)
• aortic stensosis findings vary from none to syncope depending on the age of the dog and the severity of the lesion, the most common findings are:

  • Lethargy, exertional weakness, syncope, sudden death occur in approximately 1/3 of dogs with sub-aortic stenosis. Often these dogs want to walk but get tired really quick
• Aortic stenosis causes a harsh systolic ejection murmur, loudest at the aortic valve and a precordial thrill at the left heart base which radiates to the right heart base

  • +/-diastolic murmur depending on the presence and severity of aortic insufficiency
• a patent ductus arteriosus (PDA) is where there is blood shunting from aorta into pulmonary artery and causes a continuous murmur which is best heard over left heart base but very cranial and dorsal (in axilla). It is very important to detect as potentially curable (with a balloon valvuloplasty to occlude)
• The functional closure of the ductus usually occurs within hours after birth and permanent closure occurs days to weeks post-birth.
• Animals with inherited PDA have histologically abnormal ductal walls that are unable to constrict. With fully patent ductus arteriosus blood shunts constantly from the descending aorta to the pulmonary artery during both systole and diastole causing a volume overload of the pulmonary circulation and left atrium and left ventricle. The volume overload leads to a large haemodynamic burden on the left ventricle which fails. After 12 months many dogs will progress into left-sided CHF and show typical clinical signs
• Pulmonic stenosis (PS) is the narrowing of the pulmonary artery and has 5 types

  • Infundibular
  • Sub-valvular pulmonic stenosis (uncommon)
  • Valvular pulmonic stenosis (common) this can be the leaflets themselves or the annulus of the valve
  • Supra-valvular (rare)
  • Some of these cases can have an anomalous coronary artery
• Pulmonic stenosis usually affects smaller breed dogs such as terriers, bulldogs. 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
  • They will have a prominent right apical beat and a murmur loudest at the left heart base that radiates cranially ventrally (High frequency systolic ejection murmur) and prominent jugular pulses
• Atrial septal defect are often found incidentally, there is very little shunting as the blood pressure isn't great in the atria
• Tricuspid dysplasia is common in labs and they go into RHS heart failure
• Ventricular septal defect (VSD) is common in cats. There are many different locations for VSD (7) occurring with different frequencies in different species. In dogs VSD are usually located high in the membranous part of the septum just below the aortic valve and under the tricuspid leaflet (Perimembranous)

  • VSD lead to volume overload of the pulmonary trunk, pulmonary circulation, so you get a dilated left ventricle
  • Small defects are usually clinically unimportant (restrictive). Moderate to large VSD lead to volume overload on the left side and potentially left sided congestive heart failure.
• Most dogs are asymptomatic but clinical signs depend on the size of the VSD

  • Exercise intolerance, left congestive heart failure
  • Systolic murmur loudest at the cranial right sternal border
  • +/-murmur of functional pulmonary stenosis
• PQRS is negative so the wave depolarisation is not going to lead 2 as the right ventricle is generating more electrical activity causing a right shift