Cardiac Resynchronization Therapy (CRT) | Doctors & Treatment Information

Cardiac resynchronization therapy—abbreviated as CRT—is a treatment method that can be used for severe heart failure (cardiac insufficiency).

“Cardiac” is the medical term for the heart, and “synchronous” means simultaneous. Normally, the right and left sides of the heart beat simultaneously; this is the only way to ensure proper blood flow. If the two ventricles are activated out of sync or irregularly, heart failure occurs, which can cause severe symptoms and, in extreme cases, lead to cardiac arrest.

The most common cause of irregular excitation of the heart chambers is an acute heart attack or its aftermath. A heart attack causes damage not only to the heart muscle but also to the cardiac conduction system. The latter is primarily responsible for the heart’s regular and coordinated activity, which is always closely correlated with the current level of physical exertion. For example, during physical exertion, the heart must beat faster and more forcefully; during sleep, it slows down and the volume of blood it pumps out is significantly lower. All of this is controlled and regulated by the cardiac conduction system.

Cardiac resynchronization aims to make both ventricles beat in unison again through targeted electrical stimuli. This is achieved by supporting the heart’s contractions with a pacemaker. The pacemaker can measure the right atrium’s own electrical activity and simultaneously stimulate both the right and left ventricles. Through this simultaneous stimulation and pulse delivery, both ventricles then beat in unison again, and heart function improves noticeably.

The leads of this type of pacemaker are located in three places: 

1. the right atrium, which acts as the pacemaker (=sinus node)
2. the right and 
3. the left ventricle

Since the leads are located in both ventricles as well as the right atrium, this type of pacemaker is also called a “three-chamber pacemaker.” Another term that is also frequently used is “biventricular pacemaker,” since both ventricles are stimulated (bi = two; ventricular = relating to the ventricle). This should be distinguished from a two-chamber pacemaker, in which one lead is placed in the right atrium and the second in the right ventricle. However, this type of pacemaker cannot perform resynchronization.

Anatomy of the Heart © designua / Fotolia

In heart failure, the two ventricles no longer contract in unison. This is particularly the case when a condition known as left bundle branch block is present. This is a specific type of conduction disorder in the heart. The greater the discrepancy in the rhythm of the ventricles, the poorer the heart’s pumping efficiency. The result for patients is that they experience shortness of breath even with mild exertion. In addition, the unnatural strain further weakens the already compromised heart, which can become life-threatening. If symptoms of severe heart failure do not improve significantly even with optimal medication, cardiac resynchronization therapy (CRT) may be considered.

In addition to these factors, there are other criteria for the use of CRT:

• the patient has dilated cardiomyopathy, meaning a significant enlargement of the heart chambers
• the left ventricle has reduced pumping capacity
• certain changes in the ECG indicate a left bundle branch block, meaning a disturbance in the electrical conduction in the left ventricle

Whether CRT is an option for you must be determined on a case-by-case basis by your treating physicians.

Implanting a three-chamber pacemaker requires surgery, which should ideally take place at a specialized cardiology clinic. This type of pacemaker ensures that the individual parts of the heart work in unison again. General anesthesia is sometimes necessary, but in most cases the procedure can and should be performed under local anesthesia. The patient is given a sedative during the procedure.

As with other pacemakers, one electrode is placed in the right ventricle and another in the right atrium of the heart. To do this, fine wires are advanced through a vein and then secured in the correct position. With CRT, a third electrode is then attached to the left ventricle. It is also possible to combine this with an implantable defibrillator. This can be life-saving, especially if the heart develops dangerous arrhythmias, such as ventricular fibrillation.

The pacemaker itself is placed near and slightly below the collarbone; it is inserted under the skin, which is then sutured closed after a functional test. The procedure often takes about 30 to 60 minutes. In rare exceptional cases—for example, if the leads are difficult to place—the procedure may take longer. Depending on the hospital, the procedure is scheduled as an outpatient procedure or a short inpatient stay. Most patients can leave the hospital after three days at the latest.

At the hospital, you will receive detailed instructions on how to care for your CRT device. During the first few days, you should monitor the surgical wound and have it checked if you notice any abnormalities (such as fever, redness, or chest pain). Redness and swelling may be caused by a harmless allergic reaction to the suture material, but they could also indicate a wound healing disorder or even a deep infection extending into the pacemaker pocket. In the latter case, it may even be necessary to surgically open the wound.

Fortunately, however, this complication is very rare. Nevertheless, a wound check is generally necessary after about 10 to 14 days; if the wound appears normal, the sutures will be removed. In some cases, the wound is also sutured with intradermal absorbable sutures, which means that the sutures lie beneath the skin, are not visible from the outside, and dissolve on their own. Once the wound has healed, you can gradually resume your normal activities. Only the arm on the side of the surgery should be rested for about 4 to 6 weeks.

Be careful not to overexert yourself at first; instead, gradually resume physical activity. To program the CRT device precisely to your needs, another inpatient hospital stay is usually necessary. Your heart rate and heart rhythm will be closely monitored, and then the pacemaker will receive its final programming. Now the pacemaker can begin functioning and correct the irregularities through targeted electrical impulses.

During regular follow-up appointments, the doctor checks whether there is still enough power in the pacemaker’s battery. This check can be performed externally by placing a programming head against the skin. How long the battery lasts depends on the individual settings, which are also adjusted using the programming head. If the battery’s charge drops too low, it must be replaced. This is done through a minor surgical procedure. The skin pocket containing the CRT device is opened, and the device is replaced with a new one. The electrodes attached to the heart can usually remain in place during this procedure, so the surgery is completed quickly.

Once cardiac resynchronization therapy begins, you will receive a pacemaker ID card. This card contains all the information about your pacemaker that may be important for other medical treatments. Always carry your pacemaker ID card with you and inform other healthcare providers about your CRT device before starting any treatment.

The first follow-up appointment, during which the device is precisely programmed, takes place immediately after implantation. After about three months, the settings should be checked again and adjusted if necessary. If everything is in order, follow-up appointments every six months are sufficient; under certain circumstances, even every twelve months. The intervals between follow-up appointments must be shortened if

• the device is expected to be replaced soon
• certain special functions need to be adjusted, or
• the readings are unstable

Most patients tolerate cardiac resynchronization therapy well, and the surgery proceeds without complications. In a small number of patients, however, complications may occur, such as infections in the surgical wound area or injuries to blood vessels or even the heart wall. Some patients find the CRT device under their skin uncomfortable even after the recovery period. Often, reassuring words from the treating physicians—confirming that the device is unobtrusive and has healed well—are sufficient. In the past, pacemaker devices were much larger than today’s modern devices. They are very flat and, in some cases, only about the size of a 2-euro coin. If you do develop any symptoms, however, a medical checkup is strongly recommended, preferably by the surgeons who performed your surgery. 

The CRT device enhances blood flow and the heart’s performance. As a result, symptoms of heart failure improve significantly in most patients. Physical endurance increases, while shortness of breath, dizziness, and excessive fatigue decrease. This allows many patients to regain a whole new quality of life. At the same time, the risk of hospitalizations and life-threatening emergencies decreases significantly. As a result, CRT improves both the life expectancy and quality of life for patients in many cases.