Heart Failure & Cardiac Resynchronization Therapy (CRT)
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Heart Failure (HF)
HF is a chronic condition that affects over 5 million Americans and accounts
for more hospitalization among elderly people than any other condition,
according to the American Heart Association. HF is not a condition in which the
heart abruptly stops beating. Instead, it refers to a dysfunction in the
pumping action of the heart due to the heart's inability to contract or relax
properly. It is generally experienced by patients who have suffered a heart
attack or whose hearts have been damaged by other conditions which have
disrupted the heart's natural electrical conduction system.
Patients with heart failure generally experience breathlessness, fatigue and
fluid build-up in the arms and legs. This is caused by the heart's inability to
pump enough blood to meet the body's demands. The heart can become enlarged as
it attempts to compensate for the lack of pumping ability, which only worsens
the condition. Typically, it is the lower chambers of the heart (ventricles)
that do not beat efficiently or in synchrony (together)—as they do in a healthy
heart—resulting in an increasingly ineffective heart.
Cardiac Resynchronization Therapy (CRT)
CRT provides an electrical solution to the symptoms and other difficulties
brought on by HF. Electrical impulses are delivered to the tissue in the
heart's two lower chambers (and one upper chamber). This is called
biventricular pacing, and it causes both ventricles to beat at the same time.
Biventricular pacing improves the efficiency of each contraction of the heart
and the amount of blood pumped to the body. This helps to lessen the symptoms
of heart failure and, in many cases, helps to stop the progression of the
disease.
Watch CRT System movie
CRT Delivery
CRT is administered via a pacemaker, called a CRT-P, or an ICD that has a
built-in pacemaker, called a CRT-D. A CRT-D has the added ability to
defibrillate the heart if a patient is at risk for life-threatening
arrhythmias. A traditional ICD or pacemaker has either one lead placed in the
heart's right upper chamber (right atrium, or RA) or the heart's RV, or two
leads, placed in the heart's RA and RV. CRT devices have three leads—one in the
RA, one in the RV and one in the left ventricle (LV). It is this addition of
the third lead that enables the device to deliver CRT, thereby helping to
alleviate the effects of heart failure.
Left-Ventricular Leads
Only in recent years has cardiac arrhythmia management successfully ventured
into the heart's left lower chamber. This is because the LV has a tortuous
system of vessels and veins that make maneuvering a lead more challenging.
Manufacturers have developed products that aid in navigation and positioning of
a lead. Left-ventricular leads are shaped differently than traditional pacing
leads, and they require a delivery system to help position them.
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