Cardiac Resynchronization Therapy (CRT) — How It Works, Benefits & Recovery — Procedure Guide, Recovery & Risks | MyMedicPlus

Cardiac resynchronization therapy (CRT) is a specialised pacemaker implantation procedure designed to treat heart failure caused by dyssynchronous ventricular contraction. In a healthy heart, the left and right ventricles contract simultaneously. In patients with left bundle branch block (LBBB) or other intraventricular conduction delays — a common complication of heart failure — the left ventricle contracts later and less effectively than the right, reducing cardiac output. CRT uses a biventricular pacemaker with three leads (right atrium, right ventricle, and left ventricle via the coronary sinus) to coordinate contraction of both ventricles simultaneously, restoring normal mechanical synchrony. Devices may be CRT-P (pacemaker only) or CRT-D (with added defibrillator function for sudden cardiac death prevention). CRT is implanted by interventional electrophysiologists or cardiac device specialists in accredited cardiac centres. The landmark CARE-HF and COMPANION trials established that CRT reduces all-cause mortality by 36–40% and hospitalisation by 50% in appropriately selected patients. Cardiac resynchronization therapy (CRT) is a specialised pacemaker implantation procedure designed to treat heart failure caused by dyssynchronous ventricular contraction. In a healthy heart, the left and right ventricles contract simultaneously. In patients with left bundle branch block (LBBB) or other intraventricular conduction delays (QRS duration above 130–150 ms), the lateral left ventricular wall contracts later than the septum, reducing mechanical efficiency and worsening heart failure. CRT delivers precisely timed biventricular pacing via leads placed in the right ventricle and left ventricle (via the coronary sinus and its branches) to restore synchronous contraction. A CRT defibrillator (CRT-D) additionally provides automatic defibrillation for patients at risk of sudden cardiac death. CRT improves left ventricular ejection fraction, reduces hospitalisation, and extends survival in appropriately selected patients. Approximately 250,000 CRT devices are implanted annually worldwide, performed by electrophysiologists or cardiac electrophysiology (EP) specialists.

CRT is indicated for patients with symptomatic heart failure (NYHA class II–IV) despite optimal guideline-directed medical therapy (maximally tolerated doses of ACE inhibitor or ARB, beta-blocker, and mineralocorticoid receptor antagonist), with a reduced left ventricular ejection fraction (LVEF) of 35% or less, and an electrocardiographic QRS duration of 150 ms or more with left bundle branch block (LBBB) morphology. These criteria are endorsed by the European Society of Cardiology (ESC) 2021 guidelines as a Class I (Level A) recommendation. Patients with LBBB QRS duration 130–149 ms receive a Class I Level B recommendation. Non-LBBB QRS morphologies receive a weaker recommendation (Class IIa). The strongest predictors of CRT response are LBBB morphology, wider QRS duration, ischaemic cardiomyopathy versus non-ischaemic, and female sex. Patients with permanent atrial fibrillation may still benefit but with lower response rates. CRT is also indicated for patients requiring right ventricular pacing (pacemaker-induced cardiomyopathy) who develop worsening LV function — upgrade from conventional pacemaker to CRT is supported.

Under local anaesthesia with conscious sedation (or general anaesthesia for complex cases), the procedure is performed in a cardiac catheterisation laboratory with fluoroscopic imaging. A subclavian, axillary, or cephalic vein is accessed through a small infraclavicular incision. Three pacing leads are advanced under fluoroscopy: the right atrial lead to the right atrial appendage, the right ventricular lead to the right ventricular apex or septum, and the left ventricular lead transvenously through the coronary sinus into a posterolateral cardiac vein on the lateral wall of the left ventricle. LV lead positioning is guided to maximise mechanical resynchronisation — the posterolateral or lateral vein position is optimal. If coronary sinus LV lead placement fails (in approximately 5–10% of cases due to unfavourable venous anatomy), epicardial LV lead placement via a small thoracotomy is performed. The pulse generator (device) is placed in a subcutaneous pocket below the left clavicle. Device programming sets AV and VV intervals to optimise resynchronisation. Operative time is 2–4 hours. Under local anaesthesia with conscious sedation, the procedure is performed in a cardiac catheterisation laboratory under fluoroscopic imaging. A subclavian, axillary, or cephalic vein is accessed through a small infraclavicular incision. Three pacing leads are advanced under fluoroscopic guidance — the right atrial lead to the right atrial appendage, the right ventricular lead to the right ventricular apex or interventricular septum, and the left ventricular lead threaded through the coronary sinus and positioned in a posterolateral or lateral coronary vein branch to pace the latest-activated left ventricular segment. Lead positions are tested for sensing, pacing thresholds, and absence of phrenic nerve stimulation before final fixation. A subcutaneous pocket is created infraclavicularly and the generator secured. The wound is closed in layers. The procedure takes 2–4 hours; complex cases with anatomical coronary sinus variants may require longer, and epicardial lead placement via thoracotomy is occasionally needed when transvenous access fails.

CRT produces measurable clinical and echocardiographic benefit in approximately 70–80% of appropriately selected patients (non-responders, 20–30%, are being studied to improve selection). LVEF improves by an average of 10–15 percentage points — termed 'reverse remodelling' — with corresponding reduction in left ventricular end-diastolic diameter. The CARE-HF trial demonstrated a 36% reduction in all-cause mortality and a 52% reduction in hospitalisation for heart failure in CRT versus optimal medical therapy alone. Quality of life scores (NYHA class) improve by one to two classes in responders, with significant improvements in six-minute walk distance (50–80 m increase). CRT-D provides simultaneous protection against sudden cardiac death from ventricular arrhythmias, which is common in this patient population. The procedure avoids open-heart surgery. From a medical tourism perspective, CRT implantation in India costs approximately INR 3,00,000–6,00,000 (USD 3,600–7,200) including the device, compared to USD 40,000–80,000 in the USA.

CRT implantation is a technically demanding procedure with a complication rate of approximately 5–10% related to the LV lead — the most challenging component. Coronary sinus dissection or perforation during LV lead placement occurs in under 1%. Phrenic nerve stimulation (diaphragm pacing) affects 10–15% and may require lead repositioning. Pneumothorax from subclavian venous access occurs in 1–3%. Pocket haematoma (3–5%) usually resolves without intervention. Device infection occurs in 0.5–2% and requires antibiotic therapy or complete system extraction (a complex and higher-risk redo procedure). Lead dislodgement — more common with the LV lead — occurs in 3–7% and may require reoperation. Cardiac tamponade from lead perforation is rare (under 0.5%). Non-response to CRT — defined as no clinical or echocardiographic improvement — occurs in 20–30% and may be due to suboptimal LV lead position, inadequate device programming, severe co-morbidities, or incorrect patient selection. Contrast nephropathy risk requires pre-procedure hydration and renal function monitoring.

Patients are admitted to a cardiac ward for 1–3 days following CRT implantation. Chest X-ray and 12-lead ECG confirm lead positions post-procedure. The device is programmed before discharge with optimal AV and VV delays set by the implanting team. Wound care involves a sterile dressing for 7–10 days; showering is permitted after 48 hours once the wound is dry. The ipsilateral arm is restricted from raising above the shoulder for 4–6 weeks to prevent lead dislodgement — this is the most important early restriction. Driving is prohibited for 4 weeks in most countries following device implantation. Cardiology device clinic follow-up at 4–6 weeks programmes the device further and assesses for phrenic nerve stimulation. Echocardiogram at 3 months evaluates LVEF improvement and response to resynchronisation. Annual device check appointments thereafter monitor battery life (typically 5–8 years for CRT-D, 8–12 years for CRT-P before elective generator replacement). Patients must inform airport security of their device and carry a device identification card at all times.