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
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Hypertrophic
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Restrictive
|
|
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Biventricular dilatation
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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
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↓
|
Normal or ↑
|
Normal or ↓
|
|
Ventricular filling pressure
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↑
|
Normal or ↑
|
↑
|
|
Chamber size
|
↑
|
Normal or ↓
|
Normal or ↑
|
|
Ejection fraction
|
↓
|
↑
|
Normal to ↓
|
|
Diastolic compliance
|
Normal
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↓
|
↓
|
|
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
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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
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Increase Obstruction
|
Decrease Obstruction
|
||
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Mechanism
|
Physiologic
or Pharmacologic Factors
|
Mechanism
|
Physiologic
or Pharmacologic Factors
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|
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