The Significance of Cardiac Remodeling

Cardiac remodeling is a term that refers to changes in the heart’s size and shape that occur in response to cardiac disease or cardiac damage.

When doctors talk about “remodeling,” they are usually talking about the left ventricle, though occasionally this term is applied to other cardiac chambers.

When you remodel your house, that is often considered a good thing. The opposite is true with remodeling of the heart. In general, the greater the degree of ventricular remodeling, the worse the patient’s outcome is likely to be.

Causes

When the left ventricle is damaged—for instance, by a myocardial infarction (heart attack) or by cardiomyopathy—changes often occur in the size and shape of the ventricle. The ventricle tends to become enlarged, its general shape becomes more globular and less elliptical, and the muscular wall of the ventricle often becomes thinner. This remodeling occurs due to mechanical stress on the heart muscle produced by the underlying disease process.

In the early stages of a heart attack, some degree of remodeling can help the ventricle compensate for the damage that has occurred. But if this initial remodeling process continues, and the changes in the size and shape of the ventricle become more exaggerated, cardiac function deteriorates and heart failure ensues.

How It's Measured

Doctors can assess whether cardiac remodeling is present, and can follow the extent of remodeling over time, with imaging studies that allow them to assess the size, shape, and function of the left ventricle. The most common studies used to measure remodeling are echocardiography and MRI. These tests are noninvasive and do not expose the patient to radiation, so they can be repeated as often as necessary.

A useful surrogate measure of remodeling is the left ventricular ejection fraction (LVEF). Typically, as the size of the ventricle increases, as it becomes more globular in shape, and as the function of the cardiac muscle deteriorates, the LVEF worsens. If remodeling improves, the LVEF also improves.

Importance

While it has been known for many decades that cardiac enlargement and a reduced LVEF are bad, the concept of “cardiac remodeling” has been in common usage among cardiologists only since the 1990s.

This has proven to be a useful concept because it helps to explain why some therapies for heart failure typically improve cardiac survival, and why other therapies do not.

For instance, at one time the use of inotropic drugs was widespread in treating heart failure. These drugs improve the ability of weakened heart muscle to contract more forcefully. While these drugs did improve overall cardiac function, as well as the symptoms of heart failure, they did not improve cardiac survival, and in fact, hastened death. Notably, inotropic drugs usually do not improve cardiac remodeling.

In contrast, other kinds of heart failure therapy—for instance, ACE inhibitors and beta-blockers—do significantly improve not only the symptoms but also the survival of patients with heart failure. These therapies also limit remodeling, and where remodeling has already occurred they can improve the size and shape of the damaged left ventricle. 

This ability to improve cardiac remodeling (a trait that cardiologists often refer to as “reverse remodeling”) is now thought to be extremely important in the therapy of heart failure.

Beta-blockers perhaps offer the most striking example of this newer thinking. Beta-blockers tend to reduce the force of contraction of cardiac muscle, and for this reason, for a long time, it was thought these drugs ought to be absolutely avoided in anyone with heart failure. But beta-blockers also improve the geometry of the left ventricle, and in patients with heart failure it turns out that these drugs reliably reduce the LVEF, improve symptoms, and prolong survival. 

The experience with beta-blockers now points to the new paradigm that has arisen in the treatment of heart failure—the best treatments for heart failure appear to be those that reduce or reverse ventricular remodeling. 

Treatment

Finding treatments that prevent or reverse remodeling is now a major theme in the treatment of heart failure. Here is a list of therapies for heart failure that improve cardiac remodeling:

• Beta-blockers
• ACE inhibitors and angiotensin II receptor blockers
• Hydralazine plus nitrates
• Aldosterone inhibition with spironolactone
• SGLT 2 inhibitors
• Bypass surgery or stenting in patients with hibernating myocardium
• Cardiac resynchronization therapy