MYOCARDIAL DISEASE

MYOCARDIAL DISEASE

Cardiomyopathy

Definition. A disease involving the heart muscle itself.

Classification.Cardiomyopathies can be classified according to morphologic and hemody- namic characteristics

Table 5-11. Morphologic and Hemodynamic Characteristics of   Cardiomyopathies

	Dilated	Hypertrophic	Restrictive
	Biventricular dilatation	Marked hypertrophy of left ventricle and occasionally of right ventricle; can have disproportionate hypertrophy of septum	Reduced ventricular compliance; usually caused by infiltration of myocardium (e.g., by amyloid, hemosiderin, or glycogen deposits)
Cardiac output	↓	Normal or ↓	Normal to ↓
Stroke volume	↓	Normal or ↑	Normal or ↓
Ventricular filling pressure	↑	Normal or ↑	↑
Chamber size	↑	Normal or ↓	Normal or ↑
Ejection fraction	↓	↑	Normal to ↓
Diastolic compliance	Normal	↓	↓
Other findings	May have associated functional mitral or tricuspid regurgitation.	Obstruction may develop between interventricular septum and septal leaflet of mitral valve.	Characteristic ventricular pressure tracing that resembles those recorded in constrictive pericarditis, with early diastolic dip-and-plateau configuration

Dilated (congestive) cardiomyopathy

Characterized by diminished myocardial contractility, usually involving both ventricles; most common cause for heart  transplants.

Etiologies of Dilated (Congestive) Cardiomyopathy

•            Idiopathic: most common

•            Alcoholic

•            Peripartum

•            Postmyocarditis due to infectious agents (viral, parasitic, mycobacterial, Rickettsiae)

•            Toxins (cobalt, lead, arsenic)

•            Doxorubicin hydrochloride, cyclophosphamide, vincristine

•            Metabolic: chronic hypophosphatemia, hypokalemia, hypocalcemia, uremia

Clinical Manifestations. Symptoms and signs of left and right ventricular failure. Typical symptoms of systolic dysfunction.

Diagnosis

•            X-ray: cardiomegaly with pulmonary congestion

•            EKG: sinus tachycardia, arrhythmias, conduction disturbances

•            Echo (key diagnostic study): dilated left ventricle, generalized decreased wall motion, mitral valve regurgitation

•            Catheterization: dilated hypocontractile ventricle, mitral regurgitation

Differential diagnosis

•            Valvular heart disease (e.g., regurgitant valve lesions)

•            Coronary artery disease (ischemic cardiomyopathy)

•            Hypertensive heart disease

Treatment. Patients are treated as those with systolic heart failure. ACE, beta blockers, and spironolactones lower mortality. Diuretics and digoxin decrease symptoms. Implantable defi- brillator may decrease risk of sudden death when the ejection fraction is <35%.

Hypertrophic  Obstructive Cardiomyopathy

Etiology. Although hypertrophic cardiomyopathy can apparently develop sporadically, it is hereditary in more than 60% of cases and is transmitted as an autosomal dominant trait.

•            An abnormality on chromosome 14 has been identified in the familial form of the disease.

•            The distinctive hallmark of the disease is unexplained myocardial hypertrophy, usu- ally with thickening of the interventricular septum.

Pathophysiology

•            As a result of the hypertrophy, left ventricular compliance is reduced, but systolic performance is not depressed.

•            Diastolic dysfunction is characteristic, resulting in decreased compliance and/or inability for the heart to relax.

•            The heart is hypercontractile, and systole occurs with striking rapidity.

•            Ejection fractions are often 80–90% (normal is 60%, ±5%), and the left ventricle may be virtually obliterated in systole.

The ability to provoke obstruction or to increase or decrease already existing obstruction is influenced by the factors found in Table

Table 5-12. Factors That Modify Obstruction in Hypertrophic Obstructive Cardiomyopathy

Increase Obstruction		Decrease Obstruction
Mechanism	Physiologic or Pharmacologic  Factors	Mechanism	Physiologic or Pharmacologic  Factors
Increase in contractility	•            Tachycardia •            Digitalis glycosides •            b-adrenergic stimulation (e.g., epinephrine, exercise) •            Premature beats	Decrease in contractility	•            b-adrenergic blockade •            Heavy sedation and general anesthesia •            Calcium channel blockers, disopyramide, and other drugs that depress myocardial function
Reduction in preload	•            Valsalva maneuver •            Decrease in intravascular volume •            Standing •            Nitroglycerin •            Vasodilator drugs •            Tachycardia	Increase in preload	•            Intravascular volume expansion •            Squatting •            Bradycardia •            b-adrenergic blockade
Reduction in afterload	•            Hypovolemia •            Nitroglycerin and related drugs •            Vasodilator drugs	Increase in afterload	•            Intravascular volume expansion •            Squatting •            a-adrenergic stimulation (e.g., phenylephrine) •            Handgrip

Clinical Manifestations

•            Dyspnea, angina, presyncope, syncope, and palpitations

•            Large jugular A wave, bifid carotid pulse, palpable S4 gallop, systolic murmur and thrill, mitral regurgitation murmur

•            Sudden death can sometimes be the first manifestation.

Diagnosis

•            EKG: left ventricular hypertrophy, pseudo Q waves (often seen V1–V3), ventricular arrhythmias

•            Echo: mainstay of diagnosis; hypertrophy, systolic anterior motion of mitral valve, and midsystolic closure of aortic valve

Treatment

•            Beta-blockers

•            Calcium channel blockers

•            Disopyramide, occasionally

•            Use implantable defribillator if there is syncope

•            Surgery in severe cases—septoplasty

Restrictive cardiomyopathy

Least common of the causes of cardiomyopathy. Myocardial disorder characterized by rigid noncompliant ventricular walls.

Etiologies

•            Infiltrative

–           Sarcoidosis; amyloidosis

–           Hemochromatosis

–           Neoplasia

•            Scleroderma

•            Radiation

Pathophysiology. The myocardium is rigid and noncompliant, impeding ventricular filling and raising cardiac filling pressures from abnormal diastolic function. Systolic performance is often reduced, but the overriding problem is impaired diastolic filling, which produces a clinical and hemodynamic picture that mimics constrictive pericarditis.

Clinical Manifestations

•            Dyspnea, exercise, intolerance, weakness

•            Elevated jugular venous pressure, edema, hepatomegaly, ascites, S4 and S3 gallop, Kussmaul sign

Diagnosis

•            X-ray: mild cardiomegaly, pulmonary congestion

•            EKG: low voltage, conduction disturbances, Q waves

•            Echo: characteristic myocardial texture in amyloidosis with thickening of all cardiac structures

•            Catheterization: square root sign; elevated left- and right-sided filling pressures

Treatment. There is no good therapy; ultimately results in death from congestive heart failure or arrhythmias; consider heart transplantation