Preventing Heart Failure After Heart Attack
If you have had a myocardial infarction (MI, or heart attack), you’ve sustained a certain amount of damage to your heart muscle.
If enough damage has been done, you may be at risk of developing heart failure. So, taking measures to prevent heart failure is an
important aspect of therapy after an MI.
For people who have had a very large MI, the risk of heart failure can be quite high. In these patients the onset of heart failure can be acute,
often within the first few hours or days.
But even when an MI causes only a moderate amount of muscle damage, eventual heart failure is a possibility. Appropriate drug therapy and
lifestyle changes can be critical in delaying or preventing the onset of heart failure.
What Is Remodelling?
Whether or not heart failure occurs after an MI depends to a large extent on how the undamaged heart muscle responds. After an MI, the healthy
heart muscle "stretches" in an attempt to take over the workload of the damaged muscle. This stretching leads to the enlargement of the heart,
a process called cardiac "remodelling."
Stretching helps the undamaged heart muscle contract more forcefully, and allows it to do more work. The heart muscle behaves something like a
rubber band; the more you stretch it, the more "snap" it has. However, if you overstretch a rubber band, or keep stretching it over and over for
a long period of time, it eventually loses its "snap," and becomes flaccid.
Unfortunately, the heart muscle does the same thing. Chronic stretching of the heart muscle causes it to weaken, and heart failure may result.
So, while remodelling may help the heart work better in the short term, in the long-term remodelling is a bad thing. If remodelling can be prevented
or limited, the risk of developing heart failure diminishes.
How Is Remodelling Measured?
An important part of assessing your health after an MI is to estimate how much cardiac remodelling is taking place. This information can be obtained
by doing a MUGA scan or an echocardiogram, two methods of noninvasively visualising the left ventricle.
A good way to estimate the amount of heart muscle damage caused by an MI, and the amount of remodelling that is occurring, is to measure the
left ventricular ejection fraction (LVEF). The LVEF is the percentage of blood ejected by the left ventricle with each heartbeat. With heart enlargement
(that is, with remodelling), the ejection fraction falls. If the LVEF is less than 40 percent (normal being 55 percent or higher), then significant muscle
damage has occurred. The lower the LVEF, the greater the damage, the more remodelling—and the greater the risk of developing heart failure.
Preventing Cardiac Remodelling
Several clinical studies have shown that two classes of drugs can significantly reduce remodelling after an MI, and improve the survival of patients
who have signs of impending heart failure. These drugs are the beta blockers and the ACE inhibitors.
Beta blockers work by blocking the effect of adrenaline on the heart, and they have significant beneficial effects in several types of heart disease.
Beta blockers reduce the risk of angina in patients with coronary artery disease (CAD); improve the survival of patients with heart failure; reduce
the risk of sudden death in patients after heart attacks; and delay, prevent and even partially reverse cardiac remodelling after an MI.
So, unless there are strong reasons not to use them (some patients with severe asthma or other lung disease simply cannot take these drugs), virtually
every heart attack survivor should be placed on a beta blocker. The most commonly prescribed beta blockers after an MI are Tenormin (atenolol)
and Lopressor (metoprolol).
ACE inhibitors significantly improve long-term survival after an acute MI, and in addition, reduce the risk of developing heart failure
(apparently by preventing or delaying remodelling). They also reduce the risk of recurrent MIs, stroke, and sudden death.
ACE inhibitors, like the beta blockers, are considered a must if you have had a heart attack. Vasotec (enalapril) and Capoten (captopril) are
the drugs most commonly used after an MI.
Maintaining Cardiac Health
In addition to therapy aimed specifically at preventing heart failure after a heart attack, you will need other important therapies to maintain
your optimal cardiac health. Here is a post-heart attack checklist you should review with your doctor.
And while you can’t do anything about the fact that you already have CAD, there are very likely several things you can do to slow or stop
the worsening of your CAD, and thus to prevent further heart damage. These include measures to improve your diet, cholesterol levels, e
xercise capacity, and to optimise your weight and your blood pressure.