Introduction

Cardiac Resynchronization Therapy (CRT) is a specialized treatment for certain patients with heart failure, particularly those whose heart’s electrical system is not working in sync. This desynchrony usually between the left and right ventricles, causes the heart to pump inefficiently, worsening symptoms such as fatigue, shortness of breath, and exercise intolerance. CRT improves the heart’s function by using a device (a special type of pacemaker, or sometimes a pacemaker with defibrillator capabilities) to send electrical signals to both ventricles so that they beat together in a coordinated manner.

The procedure in cardiac resynchronization therapy is not for everyone with heart failure. It is primarily recommended for individuals with reduced ejection fraction (≤35%), moderate-to-severe symptoms, and a wide QRS complex on ECG, especially with left bundle branch block (LBBB). When selected appropriately, CRT can lead to significant improvement in quality of life, reduction in hospital admissions, and in some cases, increased survival.

Procedure in Cardiac Resynchronization Therapy

Preoperative Evaluation and Patient Selection
The procedure begins with a comprehensive evaluation to determine whether the patient is an appropriate candidate for CRT. A thorough cardiac history is taken, focusing on symptoms like fatigue, reduced exercise tolerance, dyspnea, and previous hospitalizations for heart failure. Diagnostic tests include a 12-lead electrocardiogram (ECG) to assess QRS duration and morphology, an echocardiogram to measure ejection fraction and chamber sizes, and sometimes a cardiac MRI to assess scar tissue and viability of the myocardium.
Device Type Selection: CRT-P vs. CRT-D
Before surgery, the heart team decides whether the patient should receive a CRT-P (pacemaker) or a CRT-D (pacemaker with defibrillator). CRT-P is generally used for patients with advanced heart failure but no significant risk of sudden cardiac arrest. CRT-D is recommended for those who are at risk of life-threatening arrhythmias, such as those with ischemic cardiomyopathy, prior cardiac arrest, or episodes of ventricular tachycardia. The choice depends on factors including arrhythmia history, overall prognosis, age, co-morbidities, and patient preferences. Once decided, the correct device and lead system are prepared for implantation.
Preoperative Preparation
On the day of the procedure, the patient is admitted to the cardiac electrophysiology lab or operating room. Fasting is required for at least 6–8 hours prior. Blood tests, including coagulation profile, are reviewed, and any blood-thinning medications may be paused under medical supervision. An intravenous line is placed, and local anesthesia with mild sedation is administered. In rare cases or complex procedures, general anesthesia may be used.The skin around the chest area is sterilized and prepared for the incision, typically on the non-dominant side, just below the collarbone. Continuous ECG, oxygen, and blood pressure monitoring is performed throughout the procedure.
Venous Access and Lead Insertion
The procedure begins by accessing a central vein usually the subclavian or cephalic vein through which the leads are introduced. Three leads are used in a typical CRT system:
- A right atrial lead is inserted and positioned in the right atrium to assist in atrioventricular synchronization.
- A right ventricular lead is positioned at the apex or septum of the right ventricle to ensure consistent ventricular pacing.
- A left ventricular lead is inserted into the coronary sinus, a large vein on the posterior side of the heart and guided into one of its branches that runs along the left ventricle’s surface.
The placement of the left ventricular lead is the most technically demanding part. Fluoroscopy (real-time X-ray imaging) is used to visualize the coronary venous system and ensure correct lead positioning. If the coronary sinus anatomy is challenging or if transvenous access fails, an epicardial surgical approach may be considered.
Testing and Fixation of Leads
Once all three leads are positioned, each lead is tested to confirm proper sensing and pacing thresholds. Electrical measurements ensure that the leads can effectively stimulate the heart and detect intrinsic electrical activity. Adjustments are made if necessary to optimize lead position and function. After confirming that the leads are stable and functioning properly, they are connected to the CRT device, which is typically implanted in a subcutaneous pocket created under the skin and fat just beneath the collarbone. The device is programmed with initial settings tailored to the patient’s condition.
Wound Closure and Recovery
After successful implantation, the pocket is irrigated with an antibiotic solution to reduce the risk of infection. The incision is closed with absorbable sutures or staples and dressed with a sterile bandage. The entire procedure typically takes between 1.5 to 3 hours. The patient is moved to a recovery area for monitoring and observation. Vital signs, heart rhythm, and oxygen levels are checked regularly. Most patients remain in the hospital for 24–48 hours, depending on their clinical condition and response to the device. A chest X-ray is performed postoperatively to check for lead position and rule out complications like pneumothorax (collapsed lung).
Postoperative Care and Programming
Before discharge, the CRT device is reprogrammed as needed based on the patient’s intrinsic heart rhythm and pacing requirements. Device interrogation is performed using a specialized programmer to ensure the device is functioning optimally. Patients are instructed to avoid raising the arm on the device side above shoulder level for a few weeks to allow proper lead anchoring. Detailed instructions are given about wound care, activity restrictions, and follow-up schedules. Pain is usually mild and managed with over-the-counter analgesics.
Follow-Up and Optimization
Ongoing follow-up is a critical part of CRT therapy. The first follow-up is usually within 7–10 days after discharge to inspect the wound and perform basic device checks. More advanced testing, including echocardiography, may be scheduled after a few weeks or months to evaluate the effect of CRT on heart function. In some cases, CRT devices require reprogramming to achieve optimal synchrony. Advanced features such as adaptive pacing, rate responsiveness, and device-based diagnostic tools are used to personalize therapy. Remote monitoring may also be used to track device function and detect problems early.

Conclusion

Cardiac Resynchronization Therapy is a vital tool in managing advanced heart failure due to ventricular dyssynchrony. The procedure involves careful patient selection, precise placement of three pacing leads, and device programming to ensure the heart chambers beat in a coordinated and effective manner.

While the CRT procedure is relatively low-risk and minimally invasive, its impact can be transformative for patients suffering from debilitating heart failure symptoms. It improves cardiac output, reduces hospitalization, and significantly enhances quality of life.

The success of CRT depends not only on the procedure itself but also on post-implant follow-up, ongoing device optimization, and multidisciplinary heart failure management. With continued advancements in lead technology, imaging, and programming algorithms, CRT continues to evolve, offering better outcomes and renewed hope for heart failure patients worldwide.