(Also Called 'Cardiac Resynchronization Therapy')
What is cardiac resynchronization therapy?
- Cardiac resynchronization therapy (CRT) is used to treat the delay in heart ventricle contractions that occur in some people with advanced heart failure
- Heart failure means the heart’s pumping power is weaker than normal. With heart failure, blood moves through the heart and body at a slower rate, and pressure in the heart increases. A delay between the contraction of the right and left ventricles often occurs with heart failure, so the walls of the left ventricle are unable to contract at the same time.
- The CRT pacing device (also called a biventricular pacemaker) is an electronic, battery-powered device that is surgically implanted under the skin.
- The device has 2 or 3 leads (wires) that are positioned in the heart to help the heart beat in a more balanced way. The leads are implanted through a vein in the right atrium and right ventricle and into the coronary sinus vein to pace the left ventricle.
How it works:
When your heart rate drops below the set rate (programmed by your doctor), the device generates (fires) small electrical impulses that pass through the leads to the heart muscle. These impulses make the lower chambers (ventricles) of the heart muscle contract, causing the right and left ventricles to pump together. The end result is improved cardiac function.
The CRT device (biventricular pacemaker) has 2 or 3 leads that are positioned in the:
- Right atrium
- Right ventricle
- Left ventricle (via the coronary sinus vein)
Electrical system of the heart
The atria and ventricles work together, alternately contracting and relaxing to pump blood through the heart. The electrical system of the heart is the power source that makes this possible.
Normally, the electrical impulse begins at the sinoatrial (SA) node, located in the right atrium. The electrical activity spreads through the walls of the atria, causing them to contract.
Next, the electrical impulse travels through the AV node, located between the atria and ventricles. The AV node acts like a gate that slows the electrical signal before it enters the ventricles. This delay gives the atria time to contract before the ventricles do. From the AV node, the electrical impulse travels through the His-Purkinje network, a pathway of specialized electricity- conducting fibers. Then the impulse travels into the muscular walls of the ventricles, causing them to contract. This sequence occurs with every heartbeat (usually 60-100 times per minute).
Benefits of CRT
CRT improves symptoms of heart failure in about 50% of patients who have been treated maximally with medications but still have severe or moderately severe heart failure symptoms. CRT improves survival, quality of life, heart function, the ability to exercise, and helps decrease hospitalizations in select patients with severe or moderately severe heart failure.
CRT and ICD therapy
Some patients with heart failure may benefit from a combination of CRT and an implantable cardiac defibrillator (ICD). These devices combine biventricular pacing with anti-tachycardia pacing and internal defibrillators to deliver treatment as needed.
Of the patients who receive a biventricular device at Cleveland Clinic, about 90 percent receive a device that also provides defibrillator therapy. However, only about 40 percent of the patients who receive defibrillators are also candidates for a device that includes biventricular stimulation (CRT/ICD combination device).
The CRT/ICD combination devices:
- Resynchronize the heartbeat
- Slow down an abnormal fast heart rhythm
- Prevent abnormally slow heart rhythms
- Record a history of the patient’s heart rate and rhythm
Some CRT and ICD combination therapies have an internal monitoring device inside so your doctor or nurse can track your heart rhythm and heart function, such as the pressure in areas of your heart.
You may be asked to use a telephone to transmit data electronically from your device to a computer server so your doctor or nurse can monitor your condition.
Is the device implant procedure safe?
A device implant is generally a very safe procedure. However, as with any invasive procedure, there are risks. Special precautions are taken to decrease your risks. Please discuss your specific concerns about the risks and benefits of the procedure with your doctor.
Will CRT improve my ejection fraction?
Yes, CRT can help improve your ejection fraction. Ejection fraction (EF) is the measurement of how much blood is being pumped out of the left ventricle of the heart. A normal EF ranges from 50% to 70%. People with heart failure who have a poor ejection fraction (EF less than 35%) are at risk for fast, irregular and sometimes life-threatening heart rhythms. The CRT/ICD combination device can help protect you against these dangerous, fast heart rhythms.
Success of CRT
Cleveland Clinic experience has shown that CRT improves patients’ ejection fraction by 5% to 10%. In some cases, patients with a CRT device develop normal ventricular function. Based on our experience, it is not rare for a patient to increase his or her ejection fraction over 40%.
Who is eligible to receive a CRT device?
People with heart failure who have a poor ejection fraction (<35%) are at risk for fast, irregular and sometimes life- threatening heart rhythms. Ejection fraction is the measurement of how much blood is being pumped out of the left ventricle of the heart. CRT may be appropriate for people who:
- have severe or moderately severe heart failure symptoms
- are taking medications to treat heart failure
- have delayed electrical activation of the heart (such as intraventricular conduction delay or bundle branch block)
- Have a history of cardiac arrest or are at risk for cardiac arrest
Together, you and your doctor will determine if this treatment is right for you.
Before the procedure
Where is the procedure performed?
In most cases, the implant procedure takes place in a special room in the Electrophysiology Lab. When the epicardial implant approach is used (see next page), the procedure takes place in a surgical suite.
Should I take my medications?
If you take Coumadin, the results of your INR test (a blood test to evaluate the blood clotting) must be within a suitable range before the implant procedure can be performed. Usually you will be instructed to stop taking anticoagulant medications, including aspirin or Coumadin (warfarin), a few days before the procedure.
Your doctor may also ask you to stop taking other medications, such as those that control your heart rate. Do not discontinue any of your medications without first talking to your health care provider. Ask your doctor which medications you should stop taking and when to stop taking them.
If you have diabetes, ask the nurse how to adjust your diabetes medications or insulin.
Can I eat?
Eat a normal meal the evening before your procedure. However, DO NOT eat, drink or chew anything after 12 midnight before your procedure. This includes gum, mints, water, etc. If you must take medications, only take them with small sips of water. When brushing your teeth, do not swallow any water.
What should I wear?
Remove all makeup and nail polish. Wear comfortable clothes when you come to the hospital. You will change into a hospital gown for the procedure. Please leave all jewelry (including wedding rings), watches and valuables at home. The clothing you are wearing that morning will be returned to the person who accompanies you.
What should I bring?
You will not need a robe or toiletries when you first arrive. You may pack these items - your family member will need to keep your bag until after the procedure. Bring a one-day supply of your prescription medications. Do not take these medications without first talking with the doctor or nurse. You may bring guided imagery tapes or music and the appropriate player.
What happens before the procedure?
Before the procedure begins, a nurse will help you get ready. You will lie on a bed and the nurse will start an IV (intravenous line) in a vein in your arm or hand. The IV is used to deliver medications and fluids during the procedure.
To prevent infection and to keep the pacemaker insertion site sterile:
- An antibiotic will be given through the IV at the beginning of the procedure
- For men: The left or right side of your chest will be shaved
- A special soap will be used to cleanse the area
- Sterile drapes are used to cover you from your neck to your feet
- A soft strap will be placed across your waist and arms to prevent your hands from touching the sterile area
During the Procedure
Will I be awake?
A medication will be given through your IV to relax you and make you feel drowsy, but you will not be asleep during the procedure (with the endocardial approach).
Will I be monitored?
The nurse will connect you to several monitors that allow the health care team to check your heart rhythm and blood pressure during the procedure. The nurse continually monitors you during the procedure.
Monitors During the Procedure
- Defibrillator/pacemaker/cardioverter: Attached to one sticky patch placed on the center of your back and one on your chest. This allows the doctor and nurse to pace your heart rate if it is too slow, or deliver energy to your heart if the rate is too fast.
- Electrocardiogram or EKG: Attached to several sticky electrode patches placed on your chest, as well as inside your heart. Provides a picture on the monitors of the electrical impulses traveling through the heart.
- Blood pressure monitor: Connected to a blood pressure cuff on your arm. Checks your blood pressure throughout the procedure.
- Oximeter monitor: Attached to a small clip placed on your finger. Checks the oxygen level of your blood.
- Fluoroscopy: A large X- ray machine will be positioned above you to help the doctors see the leads on an X-ray screen during the procedure.
How is the device implanted?
- The CRT device can be implanted using the endocardial or epicardial approach.
- With the endocardial (transvenous) approach, a local anesthetic (pain- relieving medication) is injected to numb the area, and you will be awake during the procedure.
- Small incisions are made in the chest where the leads and device are inserted. The leads are inserted through the incision and into a vein, then guided to the heart with the aid of the fluoroscopy machine. Two leads are guided to the right atrium and right ventricle, while the third lead is guided through the coronary sinus to the left ventricle. The lead tips are attached to the heart muscle, while the other ends of the leads are attached to the pulse generator. The generator is placed in a pocket created under the skin in the upper chest.
- When the endocardial approach is used, the hospital recovery time is generally 24 hours.
- The endocardial technique is technically challenging. In some cases, this technique may not be successful due to the size, shape or location of the vein(s). If the endocardial approach cannot be used or is unsuccessful, the epicardial approach will be used.
- The epicardial approach may also be used to place the CRT if you are already having surgery to treat another heart condition.
- With the epicardial (surgical) approach, general anesthesia is given to put you to sleep during the procedure. The leads are guided to the heart with the aid of the fluoroscopy machine. Two leads are guided to the right atrium and right ventricle, while the third lead is guided through the coronary sinus to the left ventricle. The lead tips are attached to the heart muscle, while the other ends of the leads are attached to the pulse generator. The generator is placed in a pocket created under the skin in the lower abdomen.
- The hospital recovery time is generally 3 to 5 days. Although recovery with the epicardial approach is longer than that of the transvenous approach, minimally invasive techniques enable a shorter hospital stay and quicker recovery time. Your doctor will determine the best implant procedure approach for you, depending on your condition.
How are the leads tested?
After the leads are in place, they are tested to make sure lead placement is correct, the leads are functioning properly and the right and ventricle are synchronized. This lead function test is called “pacing.” Small amounts of energy are delivered through the leads into the heart muscle. This energy causes the heart to contract. You will be asleep for several minutes during the lead function test. Once the leads have been tested, the doctor will connect them to the device. The rate and settings of your CRT device are determined by your doctor. After the implant procedure, the doctor uses an external device (programmer) to program final device settings.
What will I feel?
With the endocardial approach: You will feel an initial burning or pinching sensation when the doctor injects the local numbing medication. Soon the area will become numb. You may feel a pulling sensation as the doctor makes a pocket in the tissue under your skin for the device. Please tell your doctor what symptoms you are feeling. You should not feel pain. If you do, tell your nurse right away.
With the epicardial (surgical) approach: You will be given anesthesia to put you asleep during the procedure, so you will not feel anything.
With both approaches, you may feel discomfort at the implant site during the first 48 hours after the procedure. The doctor will tell you what what medications you can take for pain relief. Please tell your doctor or nurse if your symptoms are prolonged or severe.
How long does the procedure last?
The device implant procedure may last from 2 to 5 hours.
After the procedure
Will I have to stay in the hospital?
Yes, you will be admitted to the hospital overnight. Usually you will be able to go home the day after your device was implanted, unless the epicardial approach was used during the procedure.
What should I expect during the recovery?
In your hospital room, a special monitor, called a telemetry monitor, will continually monitor your heart rhythm. The telemetry monitor consists of a small box connected by wires to your chest with sticky electrode patches. The box displays your heart rhythm on several monitors in the nursing unit. The nurses will be able to observe your heart rate and rhythm.
You will also have a holter monitor a small recorder attached to your chest with sticky electrode patches. The holter monitor records your heart rhythm for 12 hours to ensure that the pacemaker is functioning properly.
What tests will be done after the procedure?
A chest X-ray will be done after the device implant to check your lungs and the position of the device and leads. Before you are discharged, the holter monitor will be removed, and the results will be given to your doctor. You will then go to the Device Clinic.
What happens at the Device Clinic?
- You will sit in a reclining chair. Small sticky patches (electrodes) will be placed on your chest and connected via wires to a computer. A nurse will place a small device called a programmer directly over the CRT device. The programmer allows the nurse to change the device settings and to check the device and lead function. You may feel your heart beat faster or slower. Although this is normal, please tell the nurse what symptoms you are experiencing. The results of the device check are reported to your doctor, who then determines the appropriate settings for the device. The holter monitor results also are reviewed.
- Home-going instructions including incision care, activity guidelines and follow-up schedule also are reviewed.
- An echocardiogram may be performed as part of the Device Clinic evaluation or at your next follow-up appointment.
- If an echocardiogram (echo) is performed at your pacemaker check, the pacemaker nurse will be there during your echo and will change your pacemaker at least 3 times. The echo will be repeated with each change to evaluate heart function. The pacemaker will keep the settings that demonstrated your best heart function.
How will I feel?
You may feel discomfort at the pacemaker implant site during the first 48 hours after the procedure. The doctor will tell you what what medications you can take for pain relief. Please tell your doctor or nurse if your symptoms are prolonged or severe.
What instructions will I receive before I leave the hospital?
Your doctor will discuss the results of the procedure and answer any questions you have. You will receive specific instructions about how to care for yourself after the procedure including medication guidelines, wound care, activity guidelines, pacemaker care and maintenance, and a follow-up schedule.
You will also receive a temporary ID card that indicates what type of pacemaker and leads you have, the date of implant and the doctor who performed the implant. Carry this card with you at all times in case medical care is needed. Within three months you will receive a permanent card from the pacemaker company.
Ask your doctor if you can continue taking your previous medications.
Will I be able to drive myself home?
No. For your safety, a responsible adult must drive you home. Ask your doctor when you may resume driving.
If you have any questions, please ask.
Cardiac re-synchronization therapy is one part of a comprehensive heart failure management program. Medications, diet, lifestyle change, and close follow-up with a heart failure specialist, combined with device and/or surgical therapy, will help you decrease symptoms and live a more active life. Your doctor will help determine what treatment options are best for you.
For more information:
- Pavia SV, Wilkoff BL: Biventricular Pacing for Heart Failure, In Young, JB (ed): Cardiology Clinics, Vol. 19, No. 4, Philadelphia, WB Saunders Co, 2001, pp. 637-651.
- Heart Rhythm Society, Cardiac Resynchronization