Cardiac Resynchronization Therapy (CRT)

Heart Devices to Manage Arrhythmia

Cardiac Resynchronization Therapy (CRT)

What is a CRT Device?

A cardiac resynchronization therapy (CRT) device is a small, implantable device that helps bring your heartbeat back into sync. Understanding how it works is a little complicated, so let’s break it down.

The two lower chambers of your heart (also known as the ventricles) and the CRT device work as a team to keep your heart properly pumping. Think of those lower two chambers as two separate teammates who must squeeze together in sync. This synchronized squeezing is called ventricular synchrony.

Sometimes though these teammates struggle to communicate, and they start to work independently, so their once-synchronized squeezing becomes out of sync. This is called ventricular desynchrony.

They need a heart coach to bring them together. A CRT device is that coach. It gives the two chambers a tap via an electrical pulse. This action synchronizes the two chambers, allowing them to once again act as a team to effectively pump blood to your entire body so you can continue your normal activities.

When Does It Make Sense to Have a CRT Device?

The heart is powered by a complex, natural electrical system that helps it maintain a healthy rhythm while pumping blood throughout the body. A CRT device can help if you have one of these conditions:

  • Atrial fibrillation (AF)
  • Heart failure (HF)

Atrial fibrillation is an arrhythmia with an irregular and, often, rapid heartbeat that causes decreased blood flow to the body. During atrial fibrillation, your heart’s two upper chambers (the atria) beat out of sync with your heart’s two lower chambers (the ventricles).

If your heart’s “electrical” system isn’t working like it should, your doctor may recommend a CRT device.

Heart failure is when the lower chambers of the heart (the ventricles) are unable to effectively pump blood to the entire body. You might have shortness of breath or be extremely tired. If you have moderate-to-severe (or chronic) heart failure your doctor might recommend a CRT device.

There are the two types of CRT devices, depending on your heart condition:

  1. Cardiac Resynchronization Therapy Defibrillator (CRT-D) device
  2. Cardiac Resynchronization Therapy Pacemaker (CRT-P) device

What Are the Benefits of a CRT Device?

Improved Functioning

Heart failure is a chronic, progressive disease. Early use of a CRT device can actually help reverse some of the damage to your heart caused by heart failure. Studies show that CRT devices can improve one’s energy and quality of life.3

Earlier Detection and Treatment

The CRT device also stores information about your heart rhythm. Based on this information, your doctor may adjust the settings of your CRT device to best meet your needs.

Abbott’s CRT Solutions—Built to Sync With Your Beat

We want you to enjoy more of life’s moments each day, uninterrupted. That’s why our CRT solutions are designed with exclusive algorithms to seamlessly monitor and manage an irregular heartbeat.


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Guide to electromagnetic interference and your CRT device

Guide to electromagnetic interference and your CRT device

Your Beat, Monitored Remotely

There are more ways to allow you to live life to the fullest. Remote monitoring of your Abbott implanted CRT heart device may help you do just that, and it gives you and your doctor the feeling of safety and security of continuous monitoring of your heart from the time of implant to the time you are at home.

With remote monitoring, your CRT device is able to communicate to your doctor's office or clinic without you having to go in for an in-person visit. Your doctor may schedule your in-person visits less frequently, based on the data they receive from your device.

After your CRT device is implanted, you will use either a transmitter or downloadable mobile app to transmit information to your doctor.

myMerlinPulse Mobile App

The myMerlinPulse™ Mobile App works with Abbott’s next generation Gallant™ and Entrant™ CRT devices. The app can automatically or manually (as requested) collect relevant data from your implanted heart device and send it to your doctor.

 myMerlinPulse™ Mobile App

Merlin@home Transmitter

Certain Abbott CRTs work with the Merlin@home™ Transmitter. This transmitter syncs with your CRT device and collects data about your heart’s activity. Device and cardiac activity are monitored, and the data is shared with your doctor or clinic.

 Merlin@home Transmitter

Indications, Safety & Warnings

Rx Only

Brief Summary: Prior to using these devices, please review the User’s Manual for a complete listing of indications, contraindications, warnings, precautions, potential adverse events and directions for use.

CRT-D Indications: The devices are intended to provide ventricular antitachycardia pacing and ventricular defibrillation for automated treatment of life-threatening ventricular arrhythmias. Cardiac Resynchronization Therapy Defibrillators (CRT-Ds) are also intended to resynchronize the right and left ventricles in patients with congestive heart failure. Contraindications: Contraindications for use of the pulse generator system include ventricular tachyarrhythmias resulting from transient or correctable factors such as drug toxicity, electrolyte imbalance or acute myocardial infarction. Adverse Events: Implantation of the pulse generator system, like that of any other device, involves risks, some possibly life-threatening. These include but are not limited to the following: acute hemorrhage/ bleeding, air emboli, allergic reaction, arrhythmia acceleration, cardiac or venous perforation, cardiac tamponade, cardiogenic shock, cyst formation, death, erosion, exacerbation of heart failure, extracardiac stimulation, extrusion, fibrotic tissue growth, fluid accumulation, hematoma formation, histotoxic reactions, inappropriate shocks, infection, keloid formation, myocardial irritability/damage, nerve damage, pneumothorax, thromboemboli, venous occlusion. Other possible adverse effects include mortality due to: component failure, device-programmer communication failure, lead abrasion, lead dislodgment or poor lead placement, lead fracture, inability to defibrillate, inhibited therapy for a ventricular tachycardia, interruption of function due to electrical or magnetic interference, shunting of energy from defibrillation paddles, system failure due to ionizing radiation. Other possible adverse effects include mortality due to inappropriate delivery of therapy caused by: multiple counting of cardiac events including T waves, P waves or supplemental pacemaker stimuli. Among the psychological effects of device implantation are imagined pulsing, dependency, depression, fear of inappropriate pulsing and fear of losing pulse capability.

CRT-P Indications: The devices are indicated in one or more of the following permanent conditions: syncope, presyncope, fatigue, disorientation due to arrhythmia/bradycardia, or any combination of those symptoms. Cardiac Resynchronization Therapy Pacemakers (CRT-Ps) are indicated for patients who would benefit from resynchronization of the right and left ventricles and have one or more conventional indications for the implantation of a pacemaker. Rate-Modulated Pacing is indicated for patients with chronotropic incompetence, and for those who would benefit from increased stimulation rates concurrent with physical activity. Dual Chamber Pacing is indicated for those patients exhibiting: sick sinus syndrome, chronic, symptomatic second- and third-degree AV block, recurrent Adams-Stokes syndrome, symptomatic bilateral bundle branch block when tachyarrhythmia and other causes have been ruled out. Atrial Pacing is indicated for patients with sinus node dysfunction and normal AV and intraventricular conduction systems. Ventricular Pacing is indicated for patients with significant bradycardia and normal sinus rhythm with only rare episodes of A-V block or sinus arrest, chronic atrial fibrillation, severe physical disability. AF Suppression™ pacing is indicated for suppression of paroxysmal or persistent atrial fibrillation episodes in patients with one or more of the above pacing indications. Contraindications: Devices are contraindicated in patients with an implanted cardioverter-defibrillator. Rate-Adaptive Pacing may be inappropriate for patients who experience angina or other symptoms of myocardial dysfunction at higher sensor-driven rates. An appropriate Maximum Sensor Rate should be selected based on assessment of the highest stimulation rate tolerated by the patient. AF Suppression stimulation is not recommended in patients who cannot tolerate high atrial-rate stimulation. Dual-Chamber Pacing, though not contraindicated for patients with chronic atrial flutter, chronic atrial fibrillation, or silent atria, may provide no benefit beyond that of single-chamber pacing in such patients. Single-Chamber Ventricular Demand Pacing is relatively contraindicated in patients who have demonstrated pacemaker syndrome, have retrograde VA conduction, or suffer a drop in arterial blood pressure with the onset of ventricular pacing. Single-Chamber Atrial Pacing is relatively contraindicated in patients who have demonstrated compromise of AV conduction. Atrial Fibrillation. Allure™ devices are contraindicated in patients having chronic atrial fibrillation or intermittent atrial fibrillation that does not terminate. For specific contraindications associated with individual modes, refer to the programmer’s on-screen help. Potential Adverse Events: The following are potential complications associated with the use of any pacing system: air embolism, allergic reaction, body rejection phenomena, cardiac tamponade or perforation, hematoma, bleeding hematoma, seroma, formation of fibrotic tissue, local tissue reaction, inability to interrogate or program due to programmer or device malfunction, infection/erosion, interruption of desired pulse generator function due to electrical interference, either electromyogenic or electromagnetic, lead malfunction due to conductor fracture or insulation degradation, loss of capture or sensing due to lead dislodgement or reaction at the electrode/tissue interface, loss of desired pacing and/or sensing due to lead displacement, body reaction at electrode interface, or lead malfunction (fracture or damage to insulation), loss of normal device function due to battery failure or component malfunction, pacemaker migration or pocket erosion, pectoral muscle or diaphragmatic stimulation, phrenic nerve stimulation, pneumothorax/ hemothorax, device migration and pocket erosion, endocarditis, excessive bleeding, induced atrial or ventricular arrhythmias, myocardial irritability, pericardial effusion, pericardial rub, pulmonary edema, rise in threshold and exit block, valve damage, cardiac/coronary sinus dissection, cardiac/coronary sinus perforation, coronary sinus or cardiac vein thrombosis, death.

Refer to the User’s Manual for detailed indications, contraindications, warnings, precautions and potential adverse events.

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