Cardiac Procedures
Cardiac Resynchronization Therapy
The
normal heart beats in sequence from the upper chambers (atria or filling
chambers) to the lower chambers (ventricles or pumping chambers). Normally
the ventricles beat in synchrony, that is, at the same time. By doing
so, maximum force is generated to push blood from the right ventricle
to the lungs and from the left ventricle to the body. In some patients
with heart failure, electrical activity is delayed within the left ventricle.
This creates a loss of synchrony. The ventricles are not beating together
and their pumping efficiency is reduced.
Cardiac Resynchronization Therapy
uses a special pacemaker to restore cardiac synchrony. Electrical leads
are placed both within the right
ventricle (the usual site of a ventricular pacemaker lead) and the left
ventricle via one of the coronary veins. Electrical impulses are delivered
to both ventricles simultaneously thus restoring cardiac synchrony, improving
cardiac output and reducing symptoms of congestion and low cardiac output.
Cardiac
Resynchronization Therapy is not appropriate for all patients with heart
failure. Patients who benefit the most are those with moderate
to severe symptoms despite optimal medical therapy (NYHA Class III-IV),
reduced ejection fractions (LVEF < 35%), delayed electrical activation
of the left ventricle evidenced by a widened electrical QRS complex on
ECG (QRS duration 0.12-0.14 seconds or greater with a pattern of IVCD
or LBBB) or patients who already have a pacemaker implanted in the right
ventricle to guard against bradycardia (excessive slowing of the heart).
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