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CRT-D and CRT-P

Getting a cardiac resynchronization therapy (CRT) is a procedure done in the Electrophysiology Lab. The procedure is performed under conscious sedation and local anesthesia. This procedure can take 2–4 hours depending on the anatomy of your heart.

Cardiac Resynchronization Therapy (CRT)

What is a CRT device?

Cardiac resynchronization therapy (CRT), also known as biventricular pacing, is an electrical method to coordinate and synchronize your heart's contraction in an attempt to improve your symptoms of heart failure. Not everyone with heart failure is a candidate for CRT. Your physician will screen you based on tests including your ejection fraction and your EKG.

The heart has its own pacemaker comprised of specialized conduction cells in the top right atrium, known as the sinus node. The sinus node typically sends electrical impulses at a rate of 60–90 times per minute. This electrical depolarization wave leads to the contraction of the upper atria with the signal traversing the AV node, located in the center of the heart, to the ventricles with synchronized ventricular contraction. In heart failure, this synchronized control can be disrupted, delaying either left or right ventricular contraction. A representative 12-lead EKG finding of this contraction delay is the presence of left bundle branch block (LBBB), which suggests left ventricular contraction delay. This asynchronous contraction can worsen or result from heart failure.

Biventricular pacing can be performed as either a biventricular pacemaker alone or a bundled device called a biventricular ICD. The key difference is that the biventricular ICD includes a generator capable of defibrillation via a specialized right ventricular shocking coil lead.

A CRT device has a left ventricular pacemaker lead, also known as a "coronary sinus" lead, implanted through the central chest veins. Under X-ray guidance, this lead is placed in the coronary sinus, a structure in the right atrium that drains the heart’s blood supply. It travels along the heart's backside to the left ventricular wall. This lead coordinates with the right ventricular pacing lead to reduce ventricular electrical delay and improve cardiac function and heart failure symptoms.

When is CRT the right choice?

What Is a CRT-D?

A CRT-D is an implantable cardiac resynchronization therapy (CRT) defibrillator for patients with heart failure. The device monitors the heart's rhythm, detects irregularities and corrects them with electrical impulses. Like an implantable defibrillator (ICD), a CRT-D is designed to stop life-threatening ventricular tachycardia and fibrillation with relatively weak and painless stimulation therapy or electrical shocks. CRT-Ds differ from ICDs in that they help your heart's lower chambers—the ventricles—work in tandem. To do this, CRT-Ds have three leads—wires that deliver energy to the heart—rather than one or two, as in an ICD. A CRT-P is a cardiac resynchronization therapy pacemaker that does not have the defibrillation capabilities of a CRT-D. CRT-Ds enhance diseased hearts' effectiveness and increase blood flow.