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Monday, December 28, 2015

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


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