Cardiac Resynchronization Therapy (CRT) is used for restoring the left ventricle synchrony in patients with widened QRS and dilated cardiomyopathy. This is a clinically proven option for treatment for individuals with heart failure or abnormal heartbeats. In heart failure, the heart muscle of the patient gets weak and is unable to pump sufficient amount of blood to properly support the overall function of the body. This can further deteriorate the condition of the patient, especially if the chambers of the heart are not in sync to one another.
CRT is used in such scenarios to send electric signals to the heart which enables it to beat in such a manner that enhances the blood amount which his being pumped from the heart. This therapy might also reduce the other heart failure symptoms and risk of complications.
How Does CRT Work?
A small electronic device called a pacemaker is implanted under the skin of the patient. This device monitors the rhythms of the heart and sends electric pulses to the heart in case the heart beats are irregular or abnormal. Using a minor surgery, this device in inserted in the chest of the patient.
In the surgery, the insulated wires called electrodes or leads are implanted in a major vein which is underneath the collarbone and is then guided towards the heart through the assistance of x-ray images. One end of every wire is attached securely to a specific position on the heart and the other end is connected to the pulse generator which sends electric pulses to the heart, in case of abnormal heartbeats.
There are two major types CRT devices which are used in therapy:
- Pacemaker (CRT-P) – a pacemaker has three wires or leads which connects this CRT device to the heart’s upper right chamber and the two lower chambers.
- ICD (CRT-D) and Pacemaker – the patients with heart failure and who are at increased risk of experiencing cardiac arrest can be treated with CRT using both pacemaker and ICDs. This helps detect the life threatening abnormal heart beats by sending strong shock energy pulses which are higher than the pacemaker alone.
This surgery for implantation of these CRT devices can take a few hours. The patient might be required to stay overnight after CRT. Moreover, these devices need regular checkups from the physicians to ensure they are properly functioning.
The latest development in CRT includes expansion in CRT indications of patients with mild heart failure to the patients suffering from mild ejection fraction which needs regular pacing of right ventricle. Additionally, even thought the guidelines of CRT includes atrial fibrillation indications, with newer advancements is it clearer that the most effective indication is when pacing is 100% utilized at all times. It typically needs atrioventricular (AV) junction ablation.
Moreover, improved strategies are being developed to maximize the response of CRT by identifying electric delay or delayed mechanical contraction for LV lead placement. Lastly, latest research on multicentre trials has concluded that the usual practice of AV delay optimization is not recommended.