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BACKGROUNDER
Cardiac Resynchronization Therapy
Overview
Cardiac resynchronization therapy (CRT) is a treatment for heart failure that uses an
implantable device to improve the pumping efficiency of the heart.
In healthy people, the four chambers of the heart contract in synchrony to move blood through
the body (people experience this as their heartbeat). However, for many patients with heart
failure, the electrical impulses that coordinate the contractions of the heart’s chambers may be
impaired. As a result, in up to 30 percent of people who have advanced heart failure – or 10
percent of all people with heart failure – the two lower chambers (ventricles) no longer contract
at the same time. This may worsen the symptoms of the disease, which include shortness of
breath, fatigue, and swelling of the feet and ankles.
In cardiac resynchronization therapy, a stopwatch-sized device is implanted in the upper chest
in an attempt to resynchronize the contractions of the ventricles by sending tiny electrical
impulses to the heart muscle. Resynchronizing the contractions of the ventricles can help the
heart pump blood throughout the body more efficiently and reduce the symptoms. Cardiac
resynchronization therapy, also known as biventricular pacing, is intended to complement
standard drug treatment, and dietary and lifestyle modifications.
Exclusive Features and Technology
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Medtronic’s latest cardiac resynchronization therapy-defibrillator (CRT-D) devices are
part of the Protecta™ portfolio and offer SmartShock™ Technology, a Medtronic
exclusive feature that distinguishes between life threatening and non-life threatening
arrhythmias and electrical noise within the device system in order to reduce
inappropriate shocks. Findings from the Virtual ICD study, based on a statistical model,
shows that 98 percent of patients with SmartShock Technology will be free of
inappropriate shocks one year after implant and 92 percent will be free of inappropriate
shock five years after implant.1
Within the Protecta family of devices, Protecta XT devices feature OptiVol® 2.0 Fluid
Status Monitoring, a Medtronic-exclusive feature that measures changes in fluid buildup in heart failure patients to predict worsening heart failure.2
Featuring Medtronic’s proprietary Conexus® Wireless Telemetry, device information is
automatically and wirelessly transmitted through a patient’s home monitor to a secure
Web site in the physician’s office via the Medtronic CareLink® Network, the industry’s
largest remote monitoring network. If the system detects notable changes in the
patient’s condition or device status, a notification will be sent to the physician, allowing
the physician to make treatment decisions before the condition worsens.
CRT System Implantation
A specially trained electrophysiologists, cardiologist or cardiovascular surgeon implants the
CRT system. The devices are implanted under the skin in the chest area. Three very thin
insulated wires (leads), with tiny electrodes on their distal ends, are maneuvered through veins
from the device to the heart:
 One lead is placed to touch the inner wall of the right atrium;
 another to touch the inner wall of the right ventricle; and
 the third lead is threaded through the coronary sinus and placed to touch the outer wall
of the left ventricle.
The implantation procedure is typically done with local anesthesia, so the patient remains
conscious. Because of the need to implant the third lead to pace the left ventricle, the procedure
takes longer than a regular pacemaker implant. The typical procedure time is between two-tothree hours and patients usually stay in the hospital overnight.
Therapy Benefits
For patients with heart failure who have electrical conduction problems of the heart, CRT
improves the flow of blood from the heart and throughout the body, which may result in fewer
symptoms, reduced hospitalizations and reduced mortality.3
About Medtronic
Medtronic, Inc. (www.medtronic.com), headquartered in Minneapolis, is the global leader in
medical technology – alleviating pain, restoring health, and extending life for millions of
people around the world.
CONTACT:
Wendy Dougherty
(763) 526-2853
[email protected]
Brief Statement
Medtronic ICDs and CRT-ICDs
Medtronic Implantable Cardioverter Defibrillators (ICDs) are indicated for ventricular antitachycardia pacing and ventricular
defibrillation for automated treatment of life-threatening ventricular arrhythmias. Medtronic Cardiac Resynchronization Therapy
(CRT) ICDs are indicated for ventricular antitachycardia pacing and ventricular defibrillation for automated treatment of lifethreatening ventricular arrhythmias and for the reduction of the symptoms of moderate to severe heart failure (NYHA Functional
Class III or IV) in those patients who remain symptomatic despite stable, optimal medical therapy and have a left ventricular
ejection fraction less than or equal to 35% and a prolonged QRS duration.
Contraindications
Medtronic ICDs and CRT-ICDs are contraindicated in patients whose ventricular tachyarrhythmias may have transient or
reversible causes, patients with incessant VT or VF, or patients who have a unipolar pacemaker. Medtronic ICDs are also
contraindicated for patients whose primary disorder is bradyarrhythmia.
Warnings and Precautions
Changes in a patient’s disease and/or medications may alter the efficacy of the device’s programmed parameters. Patients should
avoid sources of magnetic and electromagnetic radiation to avoid possible underdetection, inappropriate sensing and/or therapy
delivery, tissue damage, induction of an arrhythmia, device electrical reset, or device damage. Do not place transthoracic
defibrillation paddles directly over the device. Additionally, for CRT-ICDs, certain programming and device operations may not
provide cardiac resynchronization.
Potential Complications
Potential complications include, but are not limited to, rejection phenomena, erosion through the skin, muscle or nerve stimulation,
oversensing, failure to detect and/or terminate tachyarrhythmia episodes, acceleration of ventricular tachycardia, and surgical
complications such as hematoma, infection, inflammation, and thrombosis.
See the device manuals for detailed information regarding the implant procedure, indications, contraindications, warnings, precautions, and
potential complications/adverse events. For further information, please call Medtronic at 1 (800) 328-2518 and/or consult Medtronic’s website
at www.medtronic.com.
Volosin et. al. “Virtual ICD: A Model to Evaluate Shock Reduction Strategies.” Heart Rhythm. Vol. 7, N. 5, May supplement 2010.
(PO3-125).
2 Abraham WT, Compton S, Haas G, Foreman B, Canby RC, Fishel R, McRae S, Toledo GB, Sarkar S, Superior Performance of
Intrathoracic Impedance-Derived fluid Index versus Daily Weight monitoring in Heart Failure Patients: Results of the Fluid
Accumulation Status Trial (FAST) J Card Fail. Nov. 2009 Vol. 15(9): 813.
3 Anand, I, Carson, P, et al. Cardiac Resynchronization Therapy Reduces the Risk of Hospitalizations in Patients With Advanced
Heart Failure. Results From the Comparison of Medical Therapy, Pacing and Defibrillation in Heart Failure (COMPANION) Trial.
Circulation. Feb. 9, 2009. Published online.
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