Cardiac Resynchronization Therapy

Cardiac Resynchronization Therapy

Cardiac resynchronization therapy device is an advanced form of pacemaker. Heart is stimulated from both sides so as to improve pumping function and have better synchronization between both lower chambers of the heart. CRT therapy is advised for patients with cardiac muscle weakness and evidence of conduction abnormalities seen on electrocardiogram (ECG).

A CRT device can be a pacemaker called as cardiac resynchronization therapy pacemaker (CRTP) or a defibrillator called as cardiac resynchronization therapy defibrillator (CRTD). A CRTP device can pace (send a small amount of electric current to stimulate the heart muscle) the both lower chambers of the heart and help improve synchronicity between them and also improve pumping function of the heart in majority of patients. A CRTD device performs all the functions of a CRTP but in addition can also treat fast heart rhythms by shocking the heart back in to normal rhythm in the event of a cardiac arrest.Both CRTP and CRTD devices have been shown to have symptomatic and survival benefit in patients with heart failure.

CRT implantation procedure is very similar to pacemaker or a defibrillator implantation. However an additional lead is implanted on the left side of the heart and hence the procedure tends to last up to two hours. Procedure is performed under local anaesthesia which means patient undergoing CRT implantation would be conscious during the procedure. A cut (approximately equal to the length of an index finger) is made in the upper chest and a pocket (usually size equivalent to four finger breadths) under the skin and subcutaneous fat but above the muscle is created to lodge the CRT device and the leads. Leads are then introduced on to a blood vessel (vein which traverses from the left arm to the heart) under the collar bone. A small amount of contrast (dye used to opacify blood vessel under fluoroscopy) is sometimes injected in to a vessel in the arm so as to visualize the vein under X-rays. Once introduced in to the blood vessel, leads are gently pushed in to the heart under X-ray guidance. One lead is positioned in the right top chamber of the heart called right atrium, second lead is placed in the right bottom chamber of the heart called right ventricle and the third lead also called left ventricular (LV) lead is positioned in to a vein that connects the right top chamber of the heart to the left outer part of the heart. This is achieved using special suitably shaped sheaths called catheters and also contrast material is used to opacify this blood vessel under fluoroscopy (X-rays) to help us guide the lead in to an optimal position. Once leads are in a secure place in the heart the other end is connected to the CRT device battery which in turn is placed under the skin and over the muscle in the previously created pocket. CRT device site is closed using a series of absorbable sutures. The whole of this procedure take around 90-120 minutes.

A chest X-ray would be performed four hours post procedure to look for any evidence of complication and to ensure appropriate position of the leads. You would be asked not to lift the arm on the side of the device implantation, above the shoulder for about four weeks. You would however, be able to walk immediately after CRT implantation. You would be discharged home the following day. You will be asked to take it easy for a few days and avoid any form of exertion. You would also be asked to look for any signs of infection including redness, soreness or discharge from the device site and report promptly to the implanting team. You will be advised to visit clinic one week after discharge to check on the wound and also to make fine adjustments to the CRT using a laptop like device called programmer that can wirelessly communicate with your CRT device.

Following defibrillator insertion you are advised to make regular visits to the clinic initially for 3 months and subsequently once every 6-12 months. Defibrillator is checked for various parameters including remaining battery life, during interrogation using programmer. Most new generation defibrillator batteries last for about 8 years on an average may be less or more in some instances.

When a CRT approaches its end of battery life, you would be scheduled for a generator change procedure. This procedure is similar to CRT implantation but much shorter in duration. This is also done under local anaesthesia which means you would be conscious during the procedure. A cut is made at the device site and dissection is carried out to the level of the CRT device. Old device would be released from the leads and a new generator would be connected to the leads. The new battery would now be placed in the pocket and wound closed with series of absorbable sutures. You may be allowed home the same day or the following day in some instances. You would be advised to look for any signs of bleeding or infection at the wound site. You would be followed up in the doctor’s clinic in a similar way after you had your original device.

After initial few days of rest following CRT implantation, you would be able to travel. Following CRT implantation you be provided with an identification card which you can provide to airport security staff at the time of walk through the metal detector. It is always essential to carry the medical case notes related to your defibrillator implantation at the time of travel as it would be handy should you need any medical intervention whilst you are away from your home city.

You would be advised to take it easy for a few days and avoid any pressure over defibrillator area. For the first four weeks you would be advised not to reach out for things with your arm on the side of the device implantation, above the level of your shoulder. You would be able to resume normal activities after initial period of rest for a week or two and same would apply for resumption of sexual activity.

Dr. Venkat D Nagarajan

Dr. Venkat D Nagarajan

FHRS, FRCP Edin, CCT UK (Cardiology), CEPS, ECDS


Cardiac Sciences/Cardiology


Electrophysiology (EP) studies and ablation therapy for atrial and ventricular arrhythmia’s including atrial fibrillation and ventricular tachycardia. Implantation of cardiac devices including pacemakers for treatment of slow heart rhythms and advanced cardiac device (defibrillators, cardiac resynchronization therapy devices (CRT) and His bundle pacing) for patients with advanced heart failure.