Devices for Heart Failure:
There are 2 devices which can be used in HF treatments (1) Cardiac Resynchronization Therapy and (2) Implantable Cardiac Defibrillator
(I) Cardiac Resynchronization Therapy:
The heart is made of 2 upper chambers called atria and 2 lower chambers called ventricles. An electrical system controls the synchronized pumping action of these chambers. The atria contract first followed by the 2 ventricles. The 2 ventricles contracts simultaneously to as to ensure optimal pumping of blood to the body and lungs. However this synchronized contraction (Synchrony) is lost between the atria and the ventricles and also between the 2 ventricles. This dys-synchrony leads to further less effective contraction of the heart thereby reducing thereby aggravating the heart failure. This Dys-synchrony can be easily diagnosed by the Physician with the help of the electrocardiogram and the echocardiogram.
CRT is designed to correct this dys-synchrony between the upper and lower chambers of the heart and also between the 2 lower chambers. This ensures simultaneous contraction of the 2 lower chambers thereby improving the contractions. In this procedure, a pacemaker (the size of a pager) is implanted just below the skin in the upper chest region and 3 wires (leads) are inserted into the heart to deliver electrical therapy. The 3 leads are positioned in the right upper, right lower chambers and the left lower chambers. The CRT device simultaneously stimulates the left and right ventricles and restores a coordinated, or “synchronous,” squeezing pattern. This reduces the electrical delay and results in a more coordinated and effective heart beat.
Who needs the CRT?
According to the Heart Rhythm Society, the ideal candidate for a CRT device is someone with:
- Moderate to severe heart failure symptoms, despite lifestyle changes and medication
- A weakened and enlarged heart muscle
- A significant electrical delay in the lower pumping chambers.
How effective is CRT?
There have been around 8-9 clinical trials involving around 5000 patients. Clinical studies demonstrate modest improvements in exercise tolerance, heart failure severity, and quality of life in most patients. Almost two-third of the patients implanted with the device benefit in their symptomatic status and also have decrease in the number of hospitalizations over the next few years. Improvement may happen quickly, but sometimes it can take several months.
(II). Implantable Cardiac Defibrillators (ICD)
ICD is a device designed to shock the heart out of a dangerous life threatening rhythm. The device is similar to the pacemaker and is the size of a pager. It is implanted below the skin in the upper chest and is then connected to a wire (lead) which monitors the heart rhythm 24 hours. Whenever it detects a dangerous heart rhythm, it delivers an internal shock to the heart and restores the normal rhythm.
Who needs ICD? Who is at risk of developing dangerous heart rhythm?
Dangerous heart rhythms can cause Sudden Cardiac Arrest which can cause instant death. Patients most at risk are those with compromised heart function (Ejection fraction < 35%). These patients if symptomatic need to undergo an ICD implantation so as to reduce their risk of dying from sudden cardiac arrests.
How effective is ICD?
There have been around 6 clinical trials involving around 3000 patients. Clinical studies demonstrate modest reduction in the death rates due to sudden cardiac arrest and have been life-saving in the majority of the patients.
Patients with heart failure are at risk of dying from progressive heart failure and sudden cardiac arrest. This can be now corrected and treated effectively by implanting devices (namely CRT and ICD respectively). However, these patients need to be carefully evaluated and selected by the cardiologist before undergoing these procedures so as to ensure maximum benefit.