Overview
Cardiac resynchronization therapy (CRT) is a treatment designed to help the lower chambers of your heart beat together again when heart failure or electrical delays cause them to fall out of sync. In a healthy heart, the right and left ventricles contract at the same time, allowing your heart to pump blood efficiently. When this coordination breaks down, the heart has to work harder, and symptoms like shortness of breath, swelling, and fatigue become more noticeable.
A CRT device, sometimes called a biventricular pacemaker, sends small electrical impulses to both ventricles so they contract in unison. This restored synchronization helps the heart pump more effectively. Many patients experience improved activity levels, fewer hospitalizations, and a better quality of life. Some CRT systems also include a defibrillator (CRT-D), which protects against dangerous heart rhythms in addition to providing synchronized pacing.
The device looks similar to a standard pacemaker but uses three leads instead of one or two. One lead sits in the right atrium, another in the right ventricle, and a third reaches the left ventricle through a vein on the outside of the heart. This extra lead is what makes resynchronization possible. CRT doesn’t cure heart failure, but it helps the heart make better use of its remaining strength. Most devices last seven to ten years and require regular follow-up to ensure the therapy remains effective.
Why You Might Need One
CRT is recommended only for certain heart failure patients who show both weakened pumping function and electrical conduction delays. It is most beneficial when the ejection fraction—the percentage of blood the left ventricle pumps with each heartbeat—is 35 percent or lower. This level indicates that the heart is struggling to move enough blood.
The other key factor is a widened QRS complex on an electrocardiogram, usually 150 milliseconds or more. This widening means the electrical signal is moving too slowly through the ventricles, causing them to contract at different times. Left bundle branch block is the most common pattern associated with CRT and often responds particularly well to resynchronization.
CRT is usually considered for patients who continue to have moderate to severe symptoms despite taking optimal heart failure medications. If everyday activities such as climbing stairs, walking short distances, or lying flat to sleep are difficult, CRT may help. Patients classified as NYHA class II, III, or IV are typical candidates.
Some patients show exceptional improvement, known as “super-responders.” Those with left bundle branch block, very wide QRS complexes, and women often respond especially well. CRT is less helpful when the QRS complex is narrow, since the heart is already contracting in a coordinated fashion.
Before the Procedure
Before implanting a CRT device, your doctor performs several tests to confirm that you’re a good candidate. These include an electrocardiogram to review your conduction pattern, an echocardiogram to evaluate heart structure and pumping strength, and blood tests to assess kidney function and electrolytes. Some patients undergo cardiac catheterization to check for coronary artery blockages that may need treatment before CRT.
Your doctor also evaluates the veins along the outside of your heart to plan placement of the left ventricular lead. Medication review is important, especially if you take blood thinners or diabetes medicines. You’ll be asked to stop eating and drinking after midnight before the procedure.
Plan for a hospital stay of one to three days. Bring comfortable clothing and a complete list of your medications. Because CRT implantation is more complex than a standard pacemaker procedure—mainly due to the additional left ventricular lead—choosing an experienced team helps ensure a smoother and more successful procedure.
The Procedure
CRT implantation typically takes three to five hours and is performed under sedation with local anesthesia. A small incision is made under your collarbone, and a pocket is created to hold the device. Using imaging guidance, your doctor threads the right atrial and right ventricular leads through the veins and into position.
Placing the left ventricular lead requires navigating through the coronary sinus, a vein on the heart’s surface, and then into one of its branches. Because these veins vary in size and shape, this part of the procedure can be challenging. Once an appropriate branch is found, the lead is secured, and all three leads are tested to ensure they sense and pace properly.
Your doctor adjusts pacing configurations to find the settings that provide the best synchronization for your ventricles. After testing is complete, the leads are connected to the device, the device is placed in the pocket, and the incision is closed. In rare cases, the left ventricular lead cannot be positioned, and alternative approaches may be considered.
What to Expect During the Procedure
You remain comfortable throughout the procedure thanks to sedation and local anesthetic. You’ll feel pressure or tugging at the incision site but no sharp pain. Threading the leads inside your veins is painless, and any fluttering sensations you notice during testing are temporary.
Because the procedure is longer than a standard pacemaker implant, lying still on the table may become uncomfortable. The team provides support with pillows or small adjustments when possible. If contrast dye is used, you may briefly feel a warm sensation in your chest. Throughout the procedure, the staff will explain what’s happening and make sure you’re comfortable.
After the Procedure
After implantation, you’ll be monitored in a recovery area where your heart rhythm, incision site, and vital signs are checked closely. Some swelling, bruising, or tenderness around the device site is normal. A technician checks the device, confirms that all leads are functioning properly, and activates remote monitoring if available.
Most patients stay in the hospital for one to three nights. You’ll need someone to drive you home, and driving restrictions usually last at least a week, sometimes longer if you have a CRT-D device. Over the following weeks, your doctor may adjust the device settings based on how you respond to the therapy.
Recovery and Care at Home
Healing takes several weeks. The incision needs time to close, and the leads must settle into the heart tissue. Keeping the area clean and dry is important. You can shower after a few days but should avoid baths, pools, and hot tubs for at least two weeks.
Avoid raising your arm on the device side above shoulder level for four to six weeks to prevent lead displacement. Moderate walking is encouraged, while strenuous lifting or vigorous exercise should wait until your doctor approves. Many patients begin noticing improvements in breathing, energy levels, and sleep within weeks, though full benefits may take several months.
Living with CRT
Most people adjust quickly to living with a CRT device. You may feel the device under your skin, but it becomes less noticeable as swelling decreases. Household electronics are generally safe to use. Keep your cell phone at least six inches from your device and avoid placing it in a chest pocket.
Many CRT systems are MRI-conditional, meaning MRI scans can be performed under specific conditions. Always inform healthcare professionals about your device before any medical or dental procedure. If your device includes a defibrillator, you’ll receive instructions about what to do if it delivers a shock.
With improved heart function, many patients become more active. Walking, cycling, and cardiac rehabilitation programs help strengthen your heart and overall fitness. Monitoring your weight daily can help detect signs of fluid buildup early.
What Happens Without CRT
For patients who meet criteria for CRT, not receiving the therapy often leads to progressive heart failure. As the ventricles continue to contract out of sync, the heart works harder but pumps less efficiently. Symptoms like breathlessness, fatigue, and swelling gradually worsen, making daily tasks difficult or impossible.
Hospitalizations become more frequent, and each episode further weakens the heart. Over time, structural changes may progress to the point where other advanced treatments are no longer possible. The emotional burden of worsening heart failure—fear, anxiety, and loss of independence—adds to the physical decline.
Research clearly shows that appropriate candidates who receive CRT experience fewer hospitalizations, improved functional capacity, and in many cases, longer survival compared with medication alone.
When to Call Your Doctor
Contact your doctor if you notice increasing redness, swelling, warmth, drainage, or fever—these may be signs of infection. Sudden weight gain, worsening shortness of breath, or increased swelling in your legs or abdomen may indicate your heart failure is worsening.
If your device includes defibrillator function and delivers a shock, inform your doctor promptly. Multiple shocks or feeling unwell afterward requires emergency care. Report new fatigue, dizziness, or palpitations, as these may mean the device settings need adjustment.
Changes around the device pocket—such as new pain, skin thinning, or the device shifting position—also need evaluation. Before any medical or dental procedure, make sure the provider knows you have a CRT device.
Regular follow-up visits are essential to ensure your CRT system is functioning properly and providing maximum benefit. If you feel anxious or overwhelmed living with heart failure or your device, reach out—emotional support is an important part of your care.
You may also like to read these:
Implantable Cardioverter Defibrillators (ICDs)
Arrhythmias: Symptoms, Causes, and Treatment
Reference: Cardiac Resynchronization Therapy
