Heart failure is a condition where the heart struggles to pump blood effectively throughout the body, often leading to symptoms such as fatigue and shortness of breath. A key measurement used to assess the heart’s pumping ability is the ejection fraction. For individuals with certain types of heart failure, Cardiac Resynchronization Therapy (CRT) offers an advanced treatment option aimed at improving the heart’s efficiency.
Understanding Ejection Fraction and Heart Failure
Ejection fraction (EF) is a percentage that indicates how much blood the left ventricle, the heart’s main pumping chamber, pushes out with each beat. It serves as a crucial indicator of the heart’s pumping efficiency. A normal ejection fraction typically ranges between 50% and 70%, meaning that 50% to 70% of the blood in the left ventricle is ejected with each contraction.
A reduced ejection fraction signifies that the heart is not pumping enough blood to meet the body’s demands. An EF of 40% or less usually indicates heart failure. When the heart’s pumping action is weakened, blood can back up, causing fluid buildup in the lungs and other areas like the legs, leading to symptoms such as shortness of breath, fatigue, and swelling.
Cardiac Resynchronization Therapy Explained
Cardiac Resynchronization Therapy (CRT) involves implanting a small electronic device, similar to a pacemaker, to help the heart’s lower chambers contract in a more coordinated manner. This device, also known as a biventricular pacemaker, is designed to correct irregular heart signaling that can cause the ventricles to beat out of sync.
The CRT system consists of a pulse generator, implanted under the skin, and typically three thin, insulated wires called leads. One lead is placed in the right ventricle, another in the right atrium, and a third lead is specifically positioned on the left ventricle. These leads deliver precisely timed electrical impulses to both ventricles, ensuring they pump together more efficiently.
How CRT Impacts Ejection Fraction
CRT directly addresses the issue of uncoordinated heartbeats, known as dyssynchrony, which often contributes to a reduced ejection fraction in heart failure. By delivering electrical impulses to both ventricles simultaneously, CRT helps them contract in a synchronized fashion. This coordinated pumping action allows the heart to eject a greater volume of blood with each beat, thereby improving the ejection fraction.
The improved coordination leads to several physiological benefits. It can increase the stroke volume, which is the amount of blood pumped out by the ventricle per beat. Furthermore, CRT has been shown to reduce functional mitral regurgitation, a condition where the mitral valve leaks blood backward into the heart, further enhancing pumping efficiency. Clinical studies have consistently demonstrated that CRT can significantly improve ejection fraction for many patients, alongside alleviating symptoms and enhancing their overall quality of life.
Who Benefits from CRT
Cardiac Resynchronization Therapy is not suitable for all heart failure patients and requires careful evaluation by a cardiologist. It is primarily considered for individuals with moderate to severe heart failure symptoms despite optimal medical therapy. A key criterion is a significantly reduced left ventricular ejection fraction, typically at or below 35%.
Patients must also exhibit a specific type of electrical conduction delay in the heart, which causes the ventricles to beat out of sync. This is often identified by an electrocardiogram (ECG) showing a wide QRS complex, particularly a left bundle branch block. The presence of this electrical dyssynchrony indicates that CRT has a higher likelihood of effectively resynchronizing the heart’s pumping action.
The CRT Procedure and What to Expect
The implantation of a CRT device is a minimally invasive procedure, typically performed under local anesthesia, though sedation may also be administered. A small incision is made in the upper chest, and three thin leads are guided through a vein into the heart’s chambers. Once positioned, the leads are connected to the CRT device, which is then inserted beneath the skin. Patients typically remain in the hospital for a few hours or overnight, with recovery involving avoiding vigorous arm movements for a few days to a week. Normal activities can resume within days to weeks, followed by regular follow-up appointments to check device function, battery life, and lead integrity.