Overview of Left Ventricular Assist Devices
Heart failure (HF) is a common reason for people needing to stay in the hospital. According to a study in 1993, factors that can increase the risk of heart failure were identified and it revealed that the chances of dying within five years was high – 25% for men and 38% for women. By 2006, the American Heart Association reported that over 5 million people in the U.S. had heart failure, with 23 million people suffering from it globally.
Heart failure can be divided into two types depending on how well the left part of the heart pumps out blood. If the left ventricle (the heart’s main pumping chamber) pushes out 40% or less of the blood it contains, it’s called heart failure with reduced ejection fraction (HFrEF), or ‘systolic’. If it can push out more than 40%, it’s called heart failure with preserved ejection fraction (HFpEF).
There are many ways to treat heart failure. These include changes to your lifestyle, such as diet and exercise, medication, and even devices that can help to regulate the heart’s beat like the implantable cardioverter-defibrillator (ICD) and cardiac resynchronization therapy (CRT). Sometimes, in severe cases, temporary mechanical support like an intra-aortic balloon pump (IABP) or extracorporeal membrane oxygenation (ECMO) may be needed to help the heart pump blood.
However, even with these treatments, many people continue to suffer from severe heart failure and their hearts become worse at pumping blood. For these people, a device called a left ventricular assist device (LVAD) can be used. This device helps the heart pump blood to the rest of the body. A notable trial found that LVADs can cut the risk of dying from any cause by 48% and significantly increase survival rates after one and two years compared to standard medication treatment. The ideal treatment for severe heart failure is a heart transplant. But since there are not enough donor hearts available, left ventricular assist devices (LVADs) offer a vital lifeline.
Anatomy and Physiology of Left Ventricular Assist Devices
Left ventricular assist devices (LVADs) are a type of mechanical pump that help the heart pump blood throughout your body. The basic setup of LVADs has remained relatively unchanged since they were first introduced. Generally, a tube (known as a cannula) is inserted into the lower part of the left side of your heart, which is the left ventricle. The blood from your heart enters the pump and then is sent back to your body via another tube that’s connected to your aorta, which is a major blood vessel in your body.
The initial LVADs were approved for clinical use in 1994 by The United States Food and Drug Administration (FDA). These first-generation LVADs had a pulsing flow and were primarily used for people waiting for heart transplants. Second and third-generation LVADs have been improved to be more durable and have a steady, continuous flow. They are now also used as a long-term treatment for people who can’t have heart transplants. These improved LVADs have shown great results, with more than 80% of users surviving at least one year and more than 70% surviving at least two years after starting to use the device.
First-generation LVADs were pumps that mimicked the natural pulsing of the heart. They went through many modifications, but are no longer in use due to issues like high risk of infection, discomfort from the noise they made, and the extensive surgery required for their placement.
Second-generation LVADs use continuous flow pumps and are generally more durable and easier to implant. They’re quieter and have a lower risk of infections compared with first-generation devices. These versions are currently the most commonly used devices.
Third-generation LVADs are also continuous flow pumps, but they are designed to be even more durable, lasting up to 10 years. They are designed to be easily implanted with a lower risk of blood cell damage or blood clotting.
There is also a device known as a Biventricular Assist Device (BiVAD) that is used for people with failure in both sides of the heart or failure in the right side of the heart associated with disease in the left side. The total artificial heart (TAH) has become a significant development in this area, with the SynCardia TAH being the most commonly used and benefiting over 1600 patients.
Why do People Need Left Ventricular Assist Devices
“Bridge-to-Transplantation” is a term for a method used to sustain people who have severe heart failure but are eligible for a heart transplant until a suitable donor heart can be found. The aim is to support the blood circulation in their body during this waiting period.
On the other hand, “Destination therapy” is a term used for individuals who have heart failure, but unfortunately, can’t have a heart transplant. In such cases, newer medical devices are used to help their weakened hearts. These devices have been shown to extend the lives of these patients.
“Bridge-to-the-Decision” is another term we use if a patient has severe organ illness due to heart failure but isn’t currently eligible for a heart transplant. In such situations, a device called a Left Ventricular Assist Device (LVAD) could be used temporarily. This device helps to stabilize their blood flow and in turn, can improve kidney function, nutritional status, and decrease high blood pressure in their lungs, which can potentially make them eligible for a transplant.
“Bridge-to-Recovery” is a temporary form of treatment used in certain heart failure patients. This method helps support the patient’s heart function and has been seen to assist the heart in recovering its functions.
There are some specific circumstances when these types of therapies could be suggested. Any patient whose condition falls under the parameters given below might be considered for either Bridge-to-Transplant, Destination Therapy, or Bridge-to-Recovery:
- Being categorized as Class IV by the New York Heart Association for 60 to 90 days.
- Being on the maximum tolerated heart medication and approved breathing therapy/having an implantable heart shock device if required.
- Long-term reliance on medications that stimulate the heart.
- Having a Left Ventricular Ejection Fraction (LVEF) of less than 25%. The LVEF is the measurement of how much blood is being pumped out of the left side of your heart.
- Having a Pulmonary Capillary Wedge Pressure (PCWP) greater than or equal to 20 mmHg. PCWP is a measure of the pressure in your heart.
- Having a Systolic Blood Pressure of 80 to 90 mmHg or less or having a Cardiac Index less than or equal to 2 L/min/m2, with signs of worsening kidney or right heart function. The Cardiac Index is a measure of your heart’s pumping capacity.
When a Person Should Avoid Left Ventricular Assist Devices
Certain conditions might prevent a person from being able to have a device known as a Left Ventricular Assist Device (LVAD) placed in their heart. This device, which helps the heart pump blood throughout the body, might not be appropriate in these situations:
If the right side of the heart isn’t working properly, the left side of the heart doesn’t get enough blood, and the Left Ventricular Assist Device might malfunction.
If a person is having an acute heart attack and has been affected mentally by it, placing a LVAD is generally not recommended, as it could worsen the person’s overall health and quality of life.
If a person has severe end-stage diseases such as kidney, lung, liver, or nerve diseases, or has advanced cancer that has spread to other parts of the body, a LVAD might not be a good option.
Bleeding issues: If a person has active bleeding or has a low platelet count (platelets are cells that help our blood to clot), or if they react negatively to a common anticoagulant drug called heparin, an LVAD can’t be used. This is also the case if a person can’t take medicines that stop the blood from clotting.
Anatomical problems: If a person’s heart muscle is abnormally thick, known as hypertrophic cardiomyopathy, or if they have a large hole in the wall separating the two chambers of the heart, known as a ventricular septal defect, their heart may not be able to accommodate the LVAD.
Technical limitations: If a person’s body surface area is less than 1.2 to 1.5 m2 or any other factors, they may not be suitable for LVAD placement.
Social considerations: Having an LVAD requires the individual to stick closely to their medicines and device upkeep. The person’s family also must be educated about how to interpret the device’s basic functions and alerts. If these conditions can’t be met, an LVAD may not be a good option.
Possible Complications of Left Ventricular Assist Devices
After having a left ventricular assist device (LVAD) – a pump that helps circulate blood in people with weakened hearts – installed, some complications could arise.
The most common issue is bleeding, which may happen during or after the surgery. This can be caused by changes to the way your blood clots during heart bypass surgery, or because of a temporary bleeding disorder that can develop after getting an LVAD. If there’s a leak in the pump, or in the tubes connecting it to your heart, you might also bleed from those spots. In addition, some people might bleed internally in the gut or brain.
Another problem is the formation of blood clots (thrombosis). This could be in the pump itself, or it could cause stroke or other issues. Poor control of blood thinners, irregular heart rhythms, or infections can make clot formation more likely.
In some cases, a technical issue with the pump design or its position can cause the destruction of red blood cells (hemolysis).
Besides blood problems, an LVAD changes your heart physically. Installing it shifts parts of your heart, which could lead to failure of the right part of the heart. If you already had chronic heart failure, you may have a higher risk of this happening. Some medications might be used to ease the pressure on the right side of your heart, or in some cases, mechanical support might be used.
Infections are another potential complication and could occur at the pump site, inside the pump pocket that holds the device, or along the power cord. These infections typically cause redness and warmth at the pump site, fever, and an increase of white blood cells, our body’s defense against infection. Ultrasounds can help doctors spot these infections, and samples can guide treatment. Usually, infections are caused by bacteria commonly found on the skin or in the gut and will need strong antibiotics to treat, maybe even requiring pump replacement or surgery.
There’s also the risk of strokes, which are usually because of blood clots and might be more likely if blood thinners are not controlled well. Balancing the right amount of blood thinners is important since they can also cause bleeding strokes.
Finally, you may experience irregular heart rhythms (arrhythmias) after the procedure. This might be due to the placement of the tubes that connect your heart to the pump, changes in weight, or scar tissue. Adjusting the pump settings or medications can usually manage these arrhythmias.
What Else Should I Know About Left Ventricular Assist Devices?
LVADs, or Left Ventricular Assist Devices, can be a game-changer for people with severe heart disease. They work by helping the heart pump blood to the rest of the body, providing a medium to long-term treatment option for people with Heart Failure with Reduced Ejection Fraction (HFrEF), a condition where the heart muscle doesn’t contract effectively and can’t pump enough blood into the body.
These devices are typically used either as a Bridge to Transplant (BTT), meaning they help keep the patient stable until a heart transplant can be performed, or as Destination Therapy (DT), meaning they are a long-term solution for people who aren’t transplant candidates.
Over the years, the designs and functions of LVADs have improved greatly, and these advancements are expected to continue. The hope is that these developments will further decrease the number of deaths caused by severe heart failure.