CARDIOMYOPATHIES
Cardiomyopathy is a term utilized to describe diseased heart muscle. The term
"diseased heart muscle" generally makes one think of a weakened heart pump with
very poor contractility; however, although this is certainly the most common manifestation
of cardiomyopathy other forms of cardiomyopathy may in fact have a very well-contracting
heart pump but fail to relax properly. As a result, they do not allow adequate inflow of
blood into the main heart pumping chamber. This condition will also lead to a decrease in
the overall blood that is pumped to the rest of the body (a term referred to as
"cardiac output"). Cardiomyopathies are generally categorized into three forms:
A) hypertrophic cardiomyopathy, B) restrictive cardiomyopathies and C) dilated
cardiomyopathies.
Hypertrophic cardiomyopathy is a condition in which the
portion of the heart muscle that divides the two lower heart pumping chambers (the septum)
becomes quite thickened and usually is asymmetric with a thicker part of the septum
generally at the top near the aortic valve (though occasionally this may be elsewhere in
the septum). During contraction of the main heart pumping chamber (left ventricle), the
thickened portion of the septum makes contact with the opposite wall (or in many cases the
mitral valve apparatus) leading to a dynamic obstruction of blood flow from the left
ventricle. This may result in pressure buildup within the left ventricle, which may
produce not only chest discomfort but also fluid accumulation in the lungs (pulmonary
edema or congestive heart failure). It is frequently associated with heart rhythm
disturbances. In extreme forms, the decrease in blood flow to the rest of the body is so
marked that loss of consciousness may occur due to a lack of blood flow to the brain.
This particular cardiomyopathy is generally characterized by a very prominent heart
murmur that is made more prominent by postural changes. This is readily detected on
physical examination with a stethoscope. The echocardiogram
is absolutely diagnostic of this entity. This particular cardiomyopathy is the most common
cause of sudden death in young athletes.
Hypertrophic cardiomyopathy is generally treated with medications to reduce the
contractility of the heart (generally beta-blockers or a specific calcium channel-blocker
known as Verapamil). Surgical procedures are also available to resect the thickened
portion of the septum to reduce the outflow obstruction during heart contractility. Permanent pacing may also treat this condition by altering the
way in which the heart is activated electrically to change the dynamic outflow
obstruction.
The rarest of the cardiomyopathies is termed restrictive
cardiomyopathy. This generally is the result of a disease process infiltrating the heart
muscle and decreasing the relaxation of the muscle though the contractility of the heart
muscle is generally maintained until the disease is far advanced. The most common cause of
this particular cardiomyopathy is due to a side effect from cancer chemotherapy
particularly with the cancer chemotherapeutic agent adriamycin. Other causes are due to
infiltration of the heart with a protein substance known as amyloid, which generally
occurs secondary to tumors but may also be a primary condition. Deposition of iron in the
heart muscle may lead to this particular cardiomyopathy and is termed
hemochromatosis.
Sarcoidosis is a disease of unknown cause, which may lead to scarring of the lungs as well
as the heart and particularly the heart’s electrical system.
The echocardiogram is the diagnostic tool of choice
to discover this particular type of cardiomyopathy. Unfortunately, most therapies for
cardiomyopathy are ineffective or less effective in this particular cardiomyopathy
variant. Individuals with this particular type of cardiomyopathy frequently, though not
always, have a poor outcome.
The most common form of cardiomyopathy results in marked
enlargement and dilatation of the heart. This leads to a reduction in cardiac
contractility and thus cardiac output as well as poor relaxation characteristics. Termed
"dilated cardiomyopathy," this form has many causes. The most common cause in
the world is untreated and generally undiscovered long-standing high blood pressure. This
may also be seen due to multiple heart attacks from coronary artery disease. Viral
infections of the heart muscle lead to an inflammatory condition known as myocarditis and
may produce this type of cardiomyopathy as an end result. Toxins to the heart may produce
this with the most common being chronic alcohol consumption. This cardiomyopathy may occur
following childbirth and leads to a very severe cardiomyopathy in many cases known as
postpartum cardiomyopathy. This latter condition also does not respond well to most
medications. The most common form of dilated cardiomyopathy is known as
"idiopathic" which means that a precise cause cannot be established.
The echocardiogram is again the diagnostic tool of
choice and leads to very rapid diagnosis of this condition. The echocardiogram is also
used to follow individuals with this condition as medication adjustments are made.
The treatment of dilated cardiomyopathy is elimination of the
cause if one can be identified. Standard treatment generally includes the administration
of Digoxin (Lanoxin) which is a medication to help improve heart contractility as well as
to potentially control certain heart rhythm disturbances, which are prevalent in this
condition. Diuretics ("water pills") are frequently used to help clear the
excess fluid buildup, which occurs in a weakened heart muscle. Angiotensin-converting
enzyme (ACE) inhibitors are common place in the management of this condition (please see
related article by Denise Frankino, R.N. regarding
this under position papers).
The latest medication to be used in the management of dilated cardiomyopathy is a drug
known as Carvedilol. Carvedilol is a very unique medication which has characteristics of
beta-blockers, alpha-blockers (which block blood pressure elevations) and is a potent
anti-oxidant. This drug was released in the summer of 1997 and has had a huge impact on
patients with cardiomyopathy improving not only their overall heart performance but also
their sense of well being. In doing so, it has also allowed individuals with this
condition to become more active and to resume many activities that they thought they had
to give up permanently.
Unfortunately, cardiomyopathy is a very common problem in the United States. A major
new cardiomyopathy is diagnosed in the Helena Cardiology Clinic on average every 10 days
and this has been going on since the Clinic was established in 1983! The diagnosis of
cardiomyopathy certainly does not mean the end of the world; however, it generally does
mean potential alterations in lifestyle, new medications and follow-up visits to monitor
the progression of the cardiomyopathy with echocardiography and physical examination.
Adjustments in medicines are common place.
In 2002, a new
treatment began to be utilized in the United States for
management of cardiomyopathies known as
biventricular
pacing. Unlike standard pacemakers implanted into patients
for slow heart rates, these devices were designed for
people with normal heart rates and weak heart pumps. These
involve the placement of a special lead into a vein of the
heart to allow the stimulation of both lower heart pumping
chambers known as the ventricles. This therapy is growing
in popularity as the number of people on maximal medical
therapy for cardiomyopathy has increased who remain
symptomatic with shortness of breath and other symptoms.
This type of pacemaker is available in the
Helena
area.
In extreme cases, a cardiomyopathy may progress to the point where medication is not
going to result in further improvement. Depending upon the circumstances, an individual
potentially could be referred for a heart transplantation. The most common indication for
cardiac transplantation in the United States currently is a dilated cardiomyopathy.
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