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Heart failure

Description

An in-depth report on the causes, diagnosis, treatment, and prevention of heart failure.

Alternative Names

Cardiomyopathy; Congestive heart failure

Diagnosis

Doctors can often make a preliminary diagnosis of heart failure by medical history and careful physical examination.

The medical history risks for heart failure include:

• Hypertension
• Diabetes
• Poor cholesterol levels
• Heart or peripheral vascular disease
• Sleep apnea
• Thyroid problems
• Obesity
• Lifestyle factors (smoking, alcohol use)

The following physical signs, along with medical history, strongly suggest heart failure:

• Enlarged heart
• Irregular heart sounds
• Abnormal sounds in the lungs
• Swelling or tenderness of the liver
• Fluid retention in legs and abdomen
• Elevation of pressure in the veins of the neck

Laboratory Tests

Both blood and urine tests are used to check for problems with the liver and kidneys and to detect signs of diabetes. Lab tests can measure:

• Cholesterol and lipid levels
• Blood sugar (glucose)
• Red blood cell count (to rule out anemia)
• Blood sugar levels
• Thyroid function

Urine tests can be used to assess the presence of a protein called albumin. Albumin in the urine is usually a sign of kidney disease, but even tiny amounts (microalbumin) signal an increased risk for heart failure in people with and without diabetes.

Exercise Stress Test

The exercise stress test measures heart rate, blood pressure, and oxygen consumption while a patient is performing physically, usually walking on a treadmill. It is an important diagnostic component in determining heart failure symptoms. Doctors also use exercise tests to gauge long-term outlook and the effects of particular treatments.

Electrocardiogram

An electrocardiogram (ECG) cannot diagnose heart failure, but it can indicate underlying heart problems. It is sometimes called an EKG. The test is simple and painless to perform. It may be used to diagnose:

• Enlargement of the heart muscle, which may help to determine long-term outlook.
• The presence of coronary artery disease.
• Abnormal cardiac rhythms. A rhythm pattern called a prolonged QT interval, for example, might predict people with heart failure who are at risk for severe complications and would need more aggressive therapies.

The major benefit of an ECG is that it can help determine which patients do not need an echocardiogram, a more accurate (but more expensive) diagnostic test.

Echocardiography

The best diagnostic test for heart failure is echocardiography. Echocardiography is a noninvasive, entirely safe test that uses ultrasound to image the heart as it is beating. Cardiac ultrasounds provide the following information:

• Accurate indications of valve function
• The amount of blood flow through the heart's chambers
• The location of the failure and where it has occurred

Doctors use information from the echocardiogram for calculating the ejection fraction (how much blood is pumped out during each heartbeat), which is important for determining the severity of heart failure.

Imaging Tests

Radionuclide Ventriculography. Radionuclide ventriculography is an imaging technique that uses a tiny amount of radioactive material (called a trace element). The substance is injected into a patient. As it passes through the bloodstream it is picked up on x-rays. This is a very important imaging technique for patients with heart failure. It is very sensitive in revealing heart enlargement or evidence of fluid accumulation around the heart and lungs. It is typically used in concert with angiography.

Magnetic Resonance Imaging. Magnetic resonance imaging (MRI) scans that use contrast dyes to improve resolution are proving helpful for identifying patients with irreversible heart damage. Damage appears as very bright areas on the scan.

Angiography

Doctors may recommend angiography if they suspect that blockage of the arteries is contributing to heart failure. This procedure is invasive.

• A thin tube called a catheter is inserted into one of the large arteries in the arm or leg.
• It is gently guided through the artery until it reaches the heart.
• The catheter measures internal blood pressure at various locations, giving the doctor a comprehensive picture of the extent and nature of the heart failure.
• Dye is then injected through the tube into the heart.
• X-rays called angiograms are taken as the dye moves through the heart and arteries.
• These images help locate problems in the heart's pumping action or blockage in the arteries.

Major complications of angiography are rare (about 0.1%) but can occur. They include stroke, heart attacks, and kidney damage. The more experienced the medical center in this procedure, the lower the risk.

Tests for Markers

Researchers are looking for biologic factors (called biomarkers) that will confirm a diagnosis or suggest a better or worse prognosis. Many are under investigation.

Tumor Necrosis Factor. Elevated levels of tumor necrosis factor (TNF) may be a very strong and accurate predictor of a poor outlook. This immune substance is known to be a potent substance in the inflammatory process.

Natriuretic Peptides. Natriuretic peptides are substances that help regulate salt and water balance in the body. Levels of these peptides increase as heart failure symptoms worsen. Blood tests for brain natriuretic peptide (BNP) are now used to help diagnose heart failure. BNP testing is very helpful in correctly diagnosing heart failure in patients who come to the emergency room complaining of shortness of breath (dyspnea). A 2006 study indicated that this test can also help predict which patients with dyspnea are at greatest risk of dying within a year from heart failure.

Brain Metabolites. High levels of a compound called N-acetylaspartate, generated as a byproduct of chemical processes in the brain, may indicate a poor outlook.

• Review Date: 4/11/2006
• Reviewed By: Harvey Simon, M.D., Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital

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