Congenital

cardiac anomalies

In the following you will find a brief overview of the most common congenital cardiac abnormalities, their effects on the heart, the changes that are to be expected with each disease as well as the resulting potential radiographic changes.

Stenoses

(Sub-)aortic stenosis

Most common canine cardiac malformation in Germany; the stenosis is mostly subvalvular. It is less common in cats; mostly valvular and subvalvular occur together.

Result: concentric hypertrophy of the left ventricle (LV)

Radiographs are often unremarkable; visible changes occur in chronic cases and include

  • Enlargement of LV
  • Possible enlargement of the left atrium (LA) – only with coexisting mitral insufficiency
  • Possible prominence of the ascending aorta – due to post-stenotic dilatation caused by turbulences

Pulmonic stenosis

2nd most common canine cardiac malformation in Germany; usually valvular stenosis in combination with stenosis of the right ventricular outflow tract due to secondary hypertrophy.

Sub-valvular stenosis due to aberrant coronary artery especially in breeds such as: English bulldog and Boxer, other breeds are rarely affected.

Result: concentric hypertrophy of the right ventricle (RV)

  • Enlargement of the main pulmonary artery (MPA) – due to post stenotic dilatation caused by turbulences
  • Possible hypoperfusion of the lung – depends on the degree of stenosis
  • Enlargement of the RV – only becomes apparent during the transition from concentric to eccentric hypertrophy
  • Possible enlargement of the right atrium (RA) – only with coexisting tricuspid insufficiency.

Mitral valve stenosis

Very rare in dogs and cats

Result: backlog of blood in the LA

  • Possible LA enlargement – depends on the degree of the stenosis
  • Possible pulmonary venous congestion
  • Possible pulmonary oedema
  • Should pulmonary hypertension due to Eisenmenger reaction occur
    → RV and subsequently RA enlargement

Tricuspid valve stenosis

Extremely rare. Only a few cases have been described in the literature.

Result: backlog of blood in RA

  • Possible enlargement RA – depends on the degree of stenosis
  • Possible congestion of caudal vena cava (CVC)
  • Possible hepatomegaly due to hepatic congestion with ensuing ascites

Shunts

Patent ductus arteriosus (PDA)

3rd most common canine cardia malformation in Germany.

Failure of the ductus arteriosus Botalli to close, thus the foetal connection between Aorta and pulmonary artery remains open.

Result: Left to right shunt

  • Enlargement of LV
  • Enlargement of LA
  • Aortic knuckle = enlargement of the descending aorta with abrupt narrowing distal to the PDA
  • Pulmonary hyperperfusion (artery and vein enlarged)
  • Possible enlargement of the left auricle (LAu) – in approx. 50% of the patients
  • Possible enlargement of the MPA – in approx. 50% of the patients
  • Possible enlargement of the aortic arch – in approx. 50% of the patients

Reversed PDA

Rare in dogs and cats

2nd most common cause of cyanotic cardiac diseases (most common cause of cyanotic cardiac diseases: Tetralogy of Fallot)

Clinical presentation: known as “differential cyanosis” = cranial half of the body is pink, caudal half of the body is cyanotic (blue)

Causes:

  • Persistent antenatal pulmonary hypertension
  • Idiopathic pulmonary hypertension
  • Reverse shunting due to Eisenmenger reaction (in approx. 5% of dogs with PDA)

Result: Right to Left shunting

  • Enlargement of the RV
  • MPA enlargement
  • In case of reversed shunting additional changes due to the PDA (ductus bump, LV and LA enlargement)

Atrial septal defect (ASD)

Types:
Type II: Ostium secundum defect is the most common type; localisation: Foramen ovale
Type I: Ostium primum defect; localisation: close to the AV-valve
Sinus venosus: localisation high
See www.embryology.ch for the different types

Result: Left to right shunt
Flow through the defect is during diastole.
Cause: when the valves are closed the pressure between both atria is approx. equal, thus no blood flow occurs. When the valves open during diastole the pressure in the RV is lower than in the L so that the blood follows the path of least resistance from LA via RA into the RV. During systole the blood is pumped from the RV into the pulmonary arteries resulting in hyperperfusion of the lungs. The pulmonary parenchyma initially reacts with a reversible vascular constriction but the final result is an irreversible vascular alteration (Eisenmenger reaction) causing pulmonary hypertension.

Radiographs are often unremarkable; visible changes occur in chronic cases and include

  • Enlargement of the RV
  • Possible enlargement of the RA
  • Possible MPA enlargement
  • Possible pulmonary hyperperfusion

Ventricular septal defect (VSD)

Radiographs are often unremarkable.

Location of defect is generally well proximal in the interventricular septum.

Bypassing the RV, the blood enters the right ventricular outflow tract directly from the LV to reach the lungs. From there it enters the LA where it can result in a volume overload.

→ Normo- to hyperperfusion of the lungs
→ possible concentric hypertrophy of the RV due to increased pulmonary artery pressure

Most likely LV and secondary to this LA enlargement because the L heart receives an increased blood volume from the lungs which has to be transported into the corporal circulation.

Persistent atrio-ventricular (AV) canal

Most common cause for cyanotic cardiac disease in cats
Partial: ASD + mitral dysplasia (on rare occasions associated tricuspid dysplasia)

  • Enlargement RA
  • Enlargement RV
  • Enlargement MPA
  • Enlargement LA

Complex: all 4 chambers are interconnected.

Dysplasia

Dysplasia usually results in insufficiency of the affected valve.

Aortic valve dysplasia

  • Insufficiency mostly in combination with stenosis
  • Radiographs are often unremarkable

Pulmonary valve dysplasia

  • Radiographs are often unremarkable

Atrio-ventricular (mitral- or tricuspid) valve dysplasia

Mitral valve –insufficiency or insufficiency combined with stenosis

  • Enlargement LA
  • Enlargement pulmonary veins
  • Possible pulmonary oedema

Tricuspid valve – mostly insufficiency alone

  • Enlargement RA
  • Wide CVC
  • Possible ascites

Complex anomalies

Tetralogy of Fallot

Most common cause of cyanotic cardiac diseases.

Pulmonic stenosis, VSD, concentric hypertrophy RV, overriding aorta (dextroposition)

  • Generally normal cardiac size
  • Possible enlargement RV
  • Pulmonary hypoperfusion
  • NO pulmonary artery enlargement

Cor atrium sinister or dexter

  • Enlargement of the affected atrium (L or R)
  • Possible pulmonary oedema or widening of CVC (only in case of an obstructing membrane)