Cardiomyopathy

Cardiomyopathy – disease of the heart muscle

Primary: heart muscle diseases of unknown cause – idiopathic
Secondary: where the myocardial abnormality is secondary to a systemic or infiltrative disease such as amyloidosis, hemochromatosis or sarcoidosis; may also be due to toxic agents such as alcohol, therapeutic agents or cobalt

Functional Classification of Primary Cardiomyopathies

(1) Congestive (Dilated) Cardiomyopathy (DCM)

Etiology: Unknown; most likely related to viral infections (Coxsackie B) possibly causing autoimmune disease

other possible etiologies include alcohol, HTN, and pregnancy (pregnancy may Ý the susceptibility to viral infection)

Pathology: failure of systolic or pump function; LV dilation with poor contractility; ß EF (can drop to as low as 20%); Ý LVEDP and LVEDV; Ý LV systolic volume

Histopathology: replacement of myocytes with fibrous tissue; ß mitochondrial function; coronary arteries are normal

Presentation: fatigue and shortness of breath from fluid backup into the lungs

Complications:

CHF

Arrhythmias Þ atrial and ventricular very common due to tissue damage, (50% of patients die from ventricular tachycardia or fibrillation)

Valvular disease Þ mitral regurgitation is common due to annular ring dilation

Thrombosis Þ due to blood stasis and may require anticoagulation therapy

Indications for Anticoagulation Therapy:

Previous strokes
Thrombus on echocardiogram
A-fib

Treatment: Ace inhibitors, b -blockers, diuretics, heart transplant

poor prognosis Þ 50% die in 5 years

(2) Hypertrophic Cardiomyopathy (HCM)

Etiology: unknown; often has genetic component Þ autosomal dominant inheritance; many cases are sporadic

Pathology: asymmetric septal hypertrophy; LV outflow tract obstruction may be present; small LV cavity due to hypertrophy; ß EDV; Ý EF; Ý pressure in LA Þ Ý pressure in lungs Þ pulmonary edema Þ shortness of breath

Histopathology: disorganized hypertrophy

LV Outflow Tract Obstruction: anterior leaflet of the mitral valve and the hypertrophied ventricular septum may obstruct outflow tract to the aorta; the thickened septum can pull the mitral valve into the outflow tract during contraction causing an obstruction

causes very loud systolic murmurs (3/6) heard best over the left sternal border

Mechanisms which ß Obstruction: Ý preload of the LV causes dilation of the ventricle and widens the outflow tract relieving the obstruction; Ý afterload relieves the obstruction by causing an increased resistance to contraction which slows the ejection of blood which in turn holds the outflow tract open

Mechanisms which Ý Obstruction: Ý contractility of the heart Ý the outflow tract obstruction because the contracted heart constricts the outflow path

Maneuver or Drug	Effect on Obstruction	Reasoning
Valsalva	Ý	ß preload (see above)
Leg Elevation	ß	Ý preload – murmur will decrease
Standing	Ý	ß preload
b -Blockers	ß	ß contractility
Verapamil	ß	ß contractility
Digoxin	Ý	Ý contractility
Catecholamines (Dopamine + Isoproterenol)	Ý	Ý contractility
Amylnitrite	Ý	ß preload due to vasodilation and Ý contractility

Premature Ventricular Contraction (PVC): Blood pressure (BP) ß with a PVC due to the ß preload and poor contractility

BP normally Ý during the next beat because of the Ý contractility of the ventricle due to the Ý calcium levels.

In a person with hypertrophic cardiomyopathy the BP does not Ý after a PVC because the Ý contractility of the ventricle closes the outflow tract Þ this observation can be useful in diagnosis

Treatment: b -blockers and Verapamil both ß contractility of the ventricle and ß obstruction of the outflow tract

surgery to remove the portion of the septum blocking the outflow tract Þ high mortality and risk of disrupting the conduction tissue

(3) Restrictive Cardiomyopathy (RCM) – very rare and difficult to treat

Pathology: unlike other cardiomyopathies, RCM involves impairment of diastolic function (systolic function is normal); Ý LVEDP and RVEDP; normal or small LV cavity; normal EF; stiffening of ventricle; Ý LVEDP leads to fluid in lungs and SOB

can mimic amyloidosis and constrictive pericarditis

Treatment: diuretics reduce fluid in lungs, but not helpful for heart itself