Cardiomyopathies

Cardiomyopathy refers to a primary global disorder of the myocardial tissue.

Classically cardiomyopathy is divided into several types with the two most common being:

1. Dilated Cardiomyopathy (DCM), characterized by:

• Systolic dysfunction (decreased muscle strength/decreased contractility)
• Ventricular cavity dilation (eccentric hypertrophy)
• Mild thinning of the ventricular walls
• Total ventricular mass is increased
• Well recognized in the cat and dog
• Etiology is often unknown in dogs
  • Likely genetic (familial) in many cases
    • A mutation in the titin protein gene may be responsible for DCM in Doberman Pinschers
    • A number of genetic mutations have been identified in humans with familial DCM
  • Due to a deficiency of taurine in some Cocker Spaniels
  • In some cases a deficiency of carnitine has been reported to be responsible for dilated cardiomyopathy (a family of Boxers)
  • A morphologic picture of DCM can be induced by tachyarrhythmias, certain chemotherapeutics (e.g. doxorubicin), and myocarditis
• A deficiency of taurine was previously responsible for the vast majority of cases of dilated cardiomyopathy in cats. It is not likely involved in feline DCM in cats on commercial cat food.

2. Hypertrophic Cardiomyopathy (HCM), characterized by:

• Diastolic dysfunction (impaired relaxation)
• Ventricular cavity of diminished dimension
• Thickening of the ventricular walls (concentric hypertrophy)
• Increased ventricular mass
• Well recognized in the cat
• Rare in the dog
• Etiology unknown in most cats
  • In many cats it appears to be familial and inherited as autosomal dominant
  • In Maine Coon and Ragdoll cats, mutations of the cardiac myosin binding protein C gene are involved
• Hypertension and thyrotoxicosis can induce a morphological picture of concentric hypertrophy. Growth hormone excess may cause concentric hyptertrophy.
• HCM has been subcategorized into an obstructive form and a non-obstructive form