Congestive Heart Failure (cont.)
Medications
Until recently, the selection of medications available for the treatment of
congestive heart failure was frustratingly limited and focused mainly on controlling the symptoms.
Medications have now been developed that both improve symptoms, and, importantly, prolong survival.
Angiotensin Converting Enzyme (ACE) Inhibitors
ACE inhibitors have been used for the treatment of hypertension for more than 20 years. This class of drugs has also been extensively studied in the treatment of
congestive heart failure. These medications block the formation of angiotensin II, a hormone with many potentially adverse effects on the heart and circulation in patients with heart failure. In multiple studies of thousands of patients, these drugs have demonstrated a remarkable improvement of symptoms in patients, prevention of clinical deterioration, and prolongation of survival. In addition, they have been recently been shown to prevent the development of heart failure and heart attacks. The wealth of the evidence supporting the use of these agents in heart failure is so strong that ACE inhibitors should be considered in all patients with heart failure, especially those with heart muscle weakness.
Possible side effects of these drugs include a:
When used carefully with proper monitoring, however, the majority of
congestive heart failure patients tolerate these medications without significant problems. Examples of ACE inhibitors include:
For those patients who are unable to tolerate the ACE inhibitors, an alternative group of drugs,
called the angiotensin receptor blockers (ARBs), may be used. These drugs act on the same hormonal
pathway as the ACE inhibitors, but instead block the action of angiotensin II at its receptor site
directly. A small, early study of one of these agents suggested a greater survival benefit in elderly
congestive heart failure patients as compared to an ACE inhibitor. However, a larger, follow-up study failed to demonstrate
the superiority of the ARBs over the ACE inhibitors. Further studies are underway to explore the use of
these agents in congestive heart failure both alone and in combination with the ACE inhibitors.
Possible side effects of
these drugs are similar to those associated with the ACE inhibitors, although the dry cough is much
less common. Examples of this class of medications include:
Beta-blockers
Certain hormones, such as epinephrine (adrenaline), norepinephrine, and other similar hormones, act on the beta receptor's of various body tissues and produce a stimulative effect. The effect of these hormones on the beta receptors of the heart is a more forceful contraction of the heart muscle. Beta-blockers are agents that block the action of these stimulating hormones on the beta receptors of the body's tissues. Since it was assumed that blocking the beta receptors further depressed the function of the heart, beta-blockers have traditionally not been used in patients with
congestive heart failure. In congestive heart failure, however, the stimulating effect of these hormones, while initially useful in maintaining heart function, appears to have detrimental effects on the heart muscle over time.
However, studies have demonstrated an impressive clinical benefit of beta-blockers in improving heart function and survival in
congestive heart failure patients who are already taking ACE inhibitors.
It appears that the key to success in using beta-blockers in congestive
heart failure is to start with a low dose and increase the dose very slowly. At first, patients may even feel a little worse and other medications may need to be adjusted.
Possible side effects include:
Beta-blockers should generally not be used in people with certain significant diseases of the airways (for
example, asthma, emphysema) or very low resting heart rates. While carvedilol (Coreg) has been the most thoroughly studied drug in the setting of
congestive heart failure, studies of other beta-blockers have also been promising. Research comparing carvedilol directly with other beta-blockers in the treatment of
congestive heart failure is ongoing. Long acting metoprolol (Toprol XL) is also very effective in patients with
congestive heart failure.
Digoxin
Digoxin (Lanoxin) has been used in the treatment of
congestive heart failure for hundreds of years. It is naturally produced by the
foxglove flowering plant. Digoxin stimulates the heart muscle to contract more forcefully. It also has other actions, which are incompletely understood, that improve
congestive heart failure symptoms and can prevent further heart failure. However, a large-scale randomized study failed to demonstrate any effect of digoxin on mortality.
Digoxin is useful for many patients with significant
congestive heart failure symptoms, even though long-term survival may not be affected. Potential side effects include:
These side effects, however, are generally a result of toxic levels in the blood and can be monitored by blood tests. The dose of digoxin may also need to be adjusted in patients with significant kidney impairment.
Diuretics
Diuretics are often an important component of the treatment of congestive
heart failure to prevent or alleviate the symptoms of fluid retention. These drugs help keep fluid from building up in the lungs and other tissues by promoting the flow of fluid through the kidneys. Although they are effective in relieving symptoms such as shortness of breath and
leg swelling, they have not been demonstrated to positively impact long term survival.
Nevertheless, diuretics remain key in preventing deterioration of the patient's condition thereby requiring hospitalization. When hospitalization is required, diuretics are often administered intravenously because the ability to absorb oral diuretics may be impaired,
when congestive heart failure is severe. Potential side effects of diuretics include:
It is important to prevent low potassium levels by taking supplements, when appropriate. Such electrolyte disturbances may make patients susceptible to serious heart rhythm disturbances. Examples of various classes of diuretics include:
One particular diuretic has been demonstrated to have surprisingly favorable effects on survival in
congestive heart failure patients with relatively advanced symptoms. Spironolactone (Aldactone) has been
used for many years as a relatively weak diuretic in the treatment of various
diseases. Among other things, this drug blocks the action of the hormone
aldosterone.
Aldosterone has many theoretical detrimental effects on the heart
and circulation in congestive heart failure. Its release is stimulated in part by angiotensin II (see
ACE inhibitors, above). In patients taking ACE inhibitors, however, there is an
"escape" phenomenon in which aldosterone levels can increase despite low levels
of angiotensin II. Medical researchers have found that spironolactone
can improve the survival rate of patients with congestive heart failure. In that the doses used in
the study were relatively small, it has been theorized that the benefit of the
drug was in its ability to block the effects of aldosterone rather than its
relatively weak action as a diuretic (water pill). Possible side effects of this
drug include elevated potassium levels and, in males, breast tissue growth (gynecomastia). Another aldosterone inhibitor is eplerenone (Inspra).
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