cardiac diseases

In the following you will find a brief overview of the most common acquired 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.

Acquired cardiac diseases

Degenerative atrio-ventricular (AV) valve diseases

Other names: endocardiosis, myxomatous AV-valve disease

Result: insufficiency of the affected valve

Radiographic changes depend on the severity of the disease. In mild cases the cardiac silhouette remains unchanged. Progression of the disease will result in

  • Enlargement of L or right atrium (RA)
  • Possible enlargement of L or right ventricle (RV)

Infectious AV valve diseases

Rare; mostly affects the mitral valve. Occurs secondary to an infection elsewhere in the body.

Result: insufficiency of affected valve

Radiographs are usually normal.

Primary myocardial diseases

Dilated cardiomyopathy (DCM)

Systolic as well as diastolic dysfunction of the heart is accompanied by eccentric hypertrophy (dilatation) of mostly the L but also the R ventricle.

Causes: not completely understood (genetic, toxic, infectious, nutritional)

Radiographic changes depend on the stage of the disease. Stage I (occult phase) and stage II (pre-clinical phase) are usually inconspicuous or associated with mild enlargement. Stage III (clinical phase) shows obvious radiographic changes.

Result: eccentric ventricular hypertrophy (L>R) followed by atrial enlargement

  • Enlargement LA
  • Enlargement LV
  • Late stage: all 4 chambers enlarged

N.B. Boxer and English bulldog: possible primary arrhythmia with primary enlargement of the RV.

Hypertrophic cardiomyopathy (HCM)

Cause: idiopathic or genetic mutation in the region of the myosin- or tropomyosin chains.

Result: severe concentric hypertrophy of interventricular septum and L ventricular free-wall.

On a DV or VD radiograph the cardiac silhouette shows a characteristic “Valentine” shape.

  • Enlargement LA
  • Possible enlargement LV
    (initial concentric hypertrophy (not radiographically detectable), later eccentric hypertrophy (visible radiographic enlargement))
  • Pulmonary hyperperfusion which finally results in pulmonary oedema

Restrictive cardiomyopathy (RCM)

Fibrotic induration and scarring of the myocardium.

Cause: unknown

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

  • Enlargement of LA
  • Pulmonary hyperperfusion which finally results in pulmonary oedema

Secondary myocardial diseases

Systemic hypertension

Cause, amongst others: hyperthyroidism, chronic renal disease, Cushing’s disease

Result: severe, concentric hypertrophy of interventricular septum and LV free wall.

Radiographic changes only when cardiac failure is present

  • Enlargement LA
  • Pulmonary hyperperfusion which finally results in pulmonary oedema

Cor pulmonale / pulmonary hypertension

Cor pulmonale describes R sided cardiac changes secondary to increased pressure of the pulmonary circulation (multitude of causes). Due to the increased pulmonary pressure first concentric and later eccentric hypertrophy of the RV ensues. Tricuspid insufficiency occurs once eccentric hypertrophy is present (at the latest). This results in enlargement of the RA.

Cause: e.g. Dirofilariasis infestation (heartworm), infection with angiostrongylus vasorum (lung worm), pulmonary fibrosis, R to L cardiac shunts, pulmonary thromboembolic disease.

In case of acute hypertension radiographs are unremarkable; in case of chronic hypertension and advanced disease

  • Enlargement of main pulmonary artery (MPA)
  • Enlargement of pulmonary arteries at the hilus
  • Enlargement of RV
  • Possible enlargement of RA

Pericardial diseases

Pericardial effusion

Causes: infectious, neoplastic, idiopathic, traumatic

Unremarkable radiographs in acute cases; in case of chronic effusions

  • Globular- or rectangular shape of the cardiac silhouette

Heart worm disease


Parasitic infection with Dirofilaria immitis

Result: pulmonary thrombo-embolic disease and pulmonary hypertension

Radiographs are initially unremarkable; with continuation of the disease process

  • RA enlargement
  • MPA enlargement
  • Central enlargement of the pulmonary arteries with tortuousity; possible abrupt change of luminal diameter (esp. in caudal lung lobes)
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