Heart Failure

Congestive heart failure (CHF), or heart failure, occurs when a damaged heart is not able to pump enough blood to the body’s other organs for them to function properly.

The Canadian Cardiovascular Society estimates that there are 400,000 Canadians currently living with congestive heart failure. That number will likely grow as we become more and more successful at treating the underlying causes of heart failure, such as heart attack and high blood pressure. As people with damaged hearts live longer, they become more susceptible to heart failure.

The Society also estimates that, of people diagnosed with heart failure, an average of ten per cent die each year; 40 to 50 per cent die within five years of diagnosis.

Cardiovascular disease as a whole – which includes both heart disease and stroke – accounts for the death of more Canadians than any other disease. In 2004, it accounted for 32 per cent of all deaths in Canada, or more than 72,000. It costs the Canadian economy more than $18 billion every year in physician services, hospital costs, lost wages and decreased productivity.

 

Causes

Congestive heart failure is the end result of at least one other cardiovascular problem in the body, such as coronary artery disease (which accounts for 60 to 70 per cent of all cases of heart failure), where the arteries that supply blood to the heart muscle become narrowed or blocked, leading to heart attacks, which weaken the heart muscle. As well, scar tissue from past heart attacks can interfere with the heart muscle’s normal work. Other causes include:

  • long-standing high blood pressurea faulty heart valve (often caused by rheumatic fever)
  • an infection of the heart valves (endocarditis) and/or heart muscle (myocarditis)
  • congenital heart defects (abnormalities in the heart present at birth)
  • inflammation of the heart (often caused by viruses)

Diabetes and excessive alcohol and drug use can also lead to heart failure.

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Effects

The causes of heart failure may be different, but they all have the same effect: they damage the heart muscle in some way, which reduces its ability to pump blood.

The “failing” heart keeps working, but not as efficiently as it should, and blood returning to the heart through the veins backs up. This causes congestion in the tissues and in the kidneys, which may lead to swelling (edema) throughout the body, most often the legs and ankles.

At time goes on, the heart tries to compensate by increasing in size and the heart muscle thickens (like any other muscle under strain), which causes the heart to grow even larger. But instead of strengthening the heart, this enlargement continues to weaken it by further reducing how efficiently it can pump blood. Eventually, the heart is unable to keep blood circulating properly throughout the body. Blood pressure begins to drop and fluid may build up in the lungs, causing shortness of breath, especially when lying down.

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Symptoms

The most common signs of heart failure are swollen legs or ankles or difficulty breathing. Someone with heart failure may also experience tiredness and a constant cough (from fluid in the lungs), as well as weight gain if fluid builds up in the abdomen.

These symptoms may worsen if the person eats a high-salt diet, drinks an excessive amount of fluids, takes medications that cause water- or salt-retention, or comes down with a cold or the flu.

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Treatment

There is no cure for heart failure, but it can be controlled by treating the underlying conditions that cause it. The goals for treatment are to:

  • improve symptoms
  • stop the heart failure from getting worse, and
  • prolong life span

Treatment for people with mild or moderate heart failure usually includes lifestyle changes – such as more rest, a low-salt diet and modified daily activities – and medications. These medications might include ACE inhibitors and vasodilators to expand blood vessels and allow blood to flow more easily; beta blockers to improve how well the heart pumps blood; digitalis to increase the pumping of the heart; or diuretics to help the body eliminate excess salt and water.

Other treatment will depend upon the root cause of the heart failure and might include:

Surgery to repair or replace a faulty heart valve.

During the surgery, the patient’s heart is stopped and a machine takes over the work of the heart and lungs while the surgeons operate. Replacement valves are either mechanical (made from durable metals, carbon, ceramics or plastics), or biological (made from animal or human tissue).

Doctors are also now using non-surgical techniques to repair or replace faulty heart valves in some patients. Instead of opening the chest to operate on the heart, doctors insert a long, flexible tube called a catheter into an artery (usually in the groin or arm) and thread it through the blood vessels into the heart. This procedure does not require stopping the heart or the use of a heart-lung machine.

Patients must take blood thinners after a heart valve replacement to prevent blood clots.

Coronary artery bypass surgery.

In this surgery – performed on people with severe atherosclerosis to improve blood flow to the heart muscle, especially those who experience marked exercise limitations due to chest pain (angina) – doctors take a healthy piece of blood vessel (artery or vein) from the patient’s leg, arm, or chest to create a detour or bypass around a blocked portion of the coronary artery.

As with heart valve surgery, the patient’s heart is stopped and a machine takes over the work of the heart and lungs while the surgeons operate.

An implantable pacemaker.

In this procedure, surgeons implant a device called a pacemaker to regulate the heart rate and rhythm in patients with arrhythmia (abnormal heart rates or rhythms). Electrodes inside the pacemaker transmit electrical signals to the heart muscle from a pulse generator. These electrical signals then cause the heart muscle to contract (pump).

Most pacemakers are implanted under local anesthesia; they do not require open-heart surgery.

A mechanical heart pump.

In this procedure, surgeons place a mechanical heart pump inside the patient’s body to take over the heart’s pumping action and help maintain blood circulation. Some pumps require open-heart surgery; others – known as balloon pumps – can be inserted non-surgically, using a catheter.

Heart pumps may be left in permanently, but are also often used to temporarily support patients who are awaiting a heart transplant.

For cases where the heart is so damaged it cannot be repaired, a heart transplant may be the only option.

A heart transplant is an open-heart surgery in which a severely diseased or damaged heart is replaced with a healthy heart from someone who recently died.

Heart transplants have been successfully performed since 1967. Today, more than 85 per cent of heart recipients will live at least an additional year and more than 70 per cent will live five more years.

However, donor hearts are in short supply and patients face a lengthy waiting list to receive a donor heart. In addition, to prevent the body from rejecting the transplanted heart, recipients must receive immunosuppressant therapy – powerful drugs to suppress their immune systems – for the rest of their lives, which leaves them susceptible to a range of other diseases.


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Recent research

Scientists continue to look for new ways to prevent and treat heart failure. For example, recent studies conducted or supported by the National Heart, Lung, and Blood Institute revealed that both implantable defibrillators, which detect and treat fast or slow heart rates, and statin drugs, which can reduce cholesterol levels, can prolong the lives of some heart failure patients.

Researchers are also looking at genetics in relation to heart failure treatments (for example, one study is investigating whether patients who have certain genetic markers may respond better to beta blockers than those who do not) and at new surgical approaches to treatment. These new approaches include surgically removing scar tissue caused by a heart attack to restore some of a damaged heart's pumping capacity, and implanting a mesh-like device (developed at the University of Chicago) that limits the progressive enlargement of the heart and supports the heart’s swollen pumping chambers.

Researchers are also working to develop equipment that will improve the health and comfort of patients waiting for a donor heart, and to develop a mechanical heart that could permanently replace a damaged heart, inside the body with no external tubes or cables, and permanently solve the shortage problem. Known as “total artificial hearts,” several have been successfully implanted in humans, but the procedure is still experimental and only available in a few research centres.

Stem cell research

Stem cells are a new and very promising area for heart failure research.

Scientists believe that – because stem cells have the potential to grow into any one of the body’s more than 200 cell types – they may be able to use them to promote the growth of healthy heart tissue and blood vessels, and restore at least some of the lost heart function.

In one 2004 study of 20 patients with severe heart failure at the University of Pittsburgh School of Medicine, 10 patients had adult stem cells taken from the bone marrow in their hip bones. Researchers then isolated the particular stem cells that influence blood vessel and heart growth (CD34+ and CD45-), and – in a process that took about 10 minutes – injected the cells into the damaged areas of their hearts during heart bypass surgery. After six months, all the patients who had the stem cell procedure were able to pump more blood than the 10 patients who had bypass surgery alone. None of the patients experienced any serious side effects or complications.

Another study in Brazil found that bone marrow stem cells injected directly into the heart using a catheter – without bypass surgery or anesthesia – could also help patients with severe or inoperable heart failure. In this trial, 14 patients received an average of 15 injections containing about two million stem cells each. After two months, they had significantly less angina (heart pain), and their hearts were better able to pump blood than patients who had not received the treatment. They also performed better on treadmill tests.

Scientists at the University of California San Diego tried a similar procedure in 2007, but this time with stem cells from the thigh muscles of 23 patients with heart failure instead of the bone marrow. After six months, all the patients showed improvements in health and quality of life.

Studies using bone marrow stem cells from donors (rather than the patients themselves) have also shown some promise for people who have recently had a heart attack. After six months, some of the treated patients showed improved heart and lung function – which means they may be able to avoid heart failure in the future. Because the stem cells came from unrelated donors, it also means that the cells can be produced in large quantities and administered immediately as heart attack patients arrive at the hospital to prevent heart muscle damage.

Further, larger trials are underway for all of these adult stem cell procedures.

In addition, a Canadian study sponsored by the Stem Cell Network and led by  Dr Duncan Stewart in Ottawa is examining the use of gene-enhanced endothelial progenitor cells (cells derived from the adult bone marrow stem cells that circulate in the blood) to repair both damage to blood vessels caused by pulmonary hypertension (increased blood pressure in the pulmonary arteries, which carry blood from the heart to the lungs) and damage to the heart muscle caused by heart attack. In this kind of gene therapy, researchers take cells from a patient’s own blood, treat them to differentiate into cells that line the inside of blood vessels or form heart muscle, load them with therapeutic or “good” genes, and return them to the patient.

Human trials are also underway using embryonic stem cells. Because researchers currently believe that embryonic stem cells may be naturally less likely to be rejected, or could be more easily engineered to avoid immune rejection, they hold perhaps the most potential, especially for heart attack victims.

To date, studies on animals have shown that embryonic stem cells injected into heart muscle following a heart attack decreased the death of muscle cells and increased pumping strength. A study at the University of Rochester Medical Center is testing whether they will work as well (1) in humans, and (2) using a standard injection into the arm, rather than directly into the heart.

Looking to the future

The results of the trials using stem cells are encouraging, and many researchers now believe that cellular therapy will likely revolutionize approaches to heart failure: instead of being palliative and simply trying to alleviate symptoms, scientists may be able to regenerate healthy heart muscle and repair damaged hearts.

First, however, researchers have to determine exactly how the stem cells work. The theory is that stem cells introduced into a heart damaged by heart attack or chronic illness could feasibly differentiate into heart muscle cells and cells that promote new vessel growth, thereby improving the heart’s ability to contract effectively and restoring blood supply to the heart itself. However, researchers are not sure yet whether the improvements experienced by the patients in the trials who received stem cells have come from the growth of new heart muscle cells, or whether the stem cells triggered existing cells to come out of hibernation.

Researchers studying the use of embryonic stem cells are also trying to determine why, in animals, most implanted stem cells re-enter the circulation or die rather than engraft to the heart muscle wall to form new muscle cells. They are also looking at ways to use gene therapy to increase the number of embryonic stem cells that live on as new muscle cells.

General information

Heart and Stroke Foundation of Canada

American Heart Association

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