Overview of Percutaneously Inserted Ventricular Assist Device
Devices like the Intra-Aortic Balloon Pump (IABP), which are used to help support the heart’s pumping mechanism, have been in use since the 1960s. The IABP was relatively small and easy to insert, but it only increased the heart’s pumping capacity (cardiac output) by about 0.5 liters per minute, which isn’t a large increase.
Since then, we have seen the development of the percutaneously inserted Ventricular Assist Device (LVD), which is a pump that is inserted into a person’s body without the need for large surgical incisions. This device helps pump blood from the left ventricle (large chamber in the heart that pushes blood into circulation) towards the aorta (the big blood vessel that distributes oxygenated blood from the heart to the rest of the body). There are several types of these devices, with different capabilities, ranging from providing a little bit of support to replacing the heart’s pumping action completely.
The LVDs have shown promising results in reducing the strain on the heart and decreasing the heart’s oxygen requirements, which in turn improves blood flow (cardiac output). They reduce the pressure inside the heart (end-diastolic pressure), which can lead to better blood flow to the heart muscle (coronary perfusion) and to the rest of the body (systemic mean arterial pressure). Moreover, they also decrease pressure in the left atrium (the upper chamber on the left-hand side of the heart that receives oxygenated blood from the lungs), which indirectly reduces the strain on the right side of the heart.
Apart from these, devices designed to provide right-sided heart support, like the right ventricle assist device (RVD), are under development. These are devices that are inserted via a vein in the leg (femoral venous access) to aid the working of the right side of the heart. These can help manage right-side heart failure by supporting up to 4 liters per minute of blood flow.
Anatomy and Physiology of Percutaneously Inserted Ventricular Assist Device
Using one small incision in the large blood vessel of the thigh (femoral artery), a device called the LVD (Left Ventricular Device) is inserted. This device moves in a backward direction through the heart, crossing the aortic valve (the gateway between the heart and the large artery, aorta). One part of the device is placed in the left ventricle (the main pumping chamber of the heart), while the other part is placed in the ascending aorta (the part of the aorta that carries oxygenated blood to the rest of the body).
On the other hand, the device named the RVD (Right Ventricular Device), that assists the right side of your heart, is inserted through a small cut in the femoral vein (the major vein in the thigh). This device passes through the tricuspid and pulmonary valves and helps to push blood from the large vein that carries deoxygenated blood (inferior vena cava) to the pulmonary artery, which then carries the blood to the lungs to be filled with oxygen.
Why do People Need Percutaneously Inserted Ventricular Assist Device
Medical procedures like percutaneous coronary intervention (PCI, a procedure to open blocked arteries) can sometimes be high-risk. This procedure can be more risky if the patient has certain health issues, such as a weakened heart (impaired LV function), blockage of the main artery supplying the heart (left main stenosis), the start of blockages (ostial stenosis), hardened and narrowed arteries due to calcium build-up (heavily calcified lesions), and a severe form of heart failure (cardiogenic shock).
Patients with acute myocardial infarction, more commonly known as heart attack, might find it beneficial to have circulatory support. This helps to lighten the load on the heart and improve blood flow. Two types of heart attacks are ST-Elevation Myocardial Infarction (STEMI) and Non-ST-elevation myocardial infarction (NSTEMI). However, there is currently no evidence to suggest that this circulatory support helps to decrease the damage to the heart during an episode of acute blockage.
Patients who are critically ill from severe heart failure or cardiogenic shock, might also benefit from stabilization methods. These methods act as a holding measure to keep the patient stable until they recover, or until they can receive surgical or mechanical circulatory support, or a transplant.
In certain cases, patients who need percutaneous aortic valvuloplasty or aortic valve replacement might also need additional procedures. These include patients with severe heart weakness or those undergoing certain types of procedures which look into the heart’s electrical system. This is because these patients might not be able to tolerate long-lasting irregular heart rhythms during the procedure. Right ventricular failure can also be treated using a device that is inserted through the skin. A clinical trial named RECOVER RIGHT has shown that this treatment is safe and can help stabilize patients with sudden onset of right heart failure.
When a Person Should Avoid Percutaneously Inserted Ventricular Assist Device
There are a few reasons a person might not be able to undergo a certain type of heart support procedure. This includes the following situations:
If a person has serious issues with the blood vessels around their heart, a condition known as peripheral vascular disease, they may not be able to have this procedure. This condition can block the blood supply to the heart, making it difficult or risky to perform a heart procedure.
Aortic stenosis is another condition that could prevent this treatment. This is when the main door out of the heart, called the aorta, is narrowed and has less than 1.5 cm of space for the blood to flow through. Similarly, aortic insufficiency, when the aorta can’t properly close, can also make this procedure impractical.
A ventricular septal defect could also be a significant roadblock. This condition is basically a hole in the wall separating the two lower chambers of the heart and can worsen if a certain type of pump, called a percutaneously inserted Left Ventricular Device (LVD), is used for treatment.
Finally, if a blood clot develops in the left side of the heart, known as a left ventricular thrombus, it’s not safe to have this procedure.
If a person has one or more of these medical conditions, doctors will need to think about using a different type of heart support treatment.
Equipment used for Percutaneously Inserted Ventricular Assist Device
The medical procedure being discussed involves utilizing a medical device called the LVD. It’s attached to what’s referred to as a “9 Fr catheter.” If you’re unfamiliar with the term, a catheter is a thin tube that is placed in the body to administer medication or drain fluid. The size of the catheter is measured in Fr (French units), the higher the number, the larger the catheter.
The procedure also utilizes a console, which is used to control how the device operates. It also displays the difference, or gradient, between the incoming and outgoing pressure. This information helps the medical team to ensure the device is operating correctly and safely.
A vital part of this procedure involves the use of a “purge solution”. It is introduced into the body through a sidearm at the far end of the 9 Fr catheter. This solution helps to clean the device and ensure its functionality.
Lastly, pressure monitoring tubing is also used in this procedure. This tubing allows the healthcare team to keep an eagle eye on the pressure levels within the patient’s body or the device being used.
Who is needed to perform Percutaneously Inserted Ventricular Assist Device?
Heart doctors, known as interventional cardiologists, insert devices called “low flow” and “intermediate flow assist devices” into the body. They do this through a procedure called percutaneous placement, which means they use a small needle or tube and insert it into your body. They use a tool called a fluoroscope, which is like a special X-ray, to guide them during the procedure.
There are also “high flow assist devices,” but these require a more involved surgical procedure to place them in the body. Because of the complexity, cardiothoracic surgeons, who are specialized heart surgeons, take care of positioning these devices. They ensure the procedure is done correctly and safely.
How is Percutaneously Inserted Ventricular Assist Device performed
The low flow Left Ventricular Device (LVD) (2.5 L/min) is a small pump that’s mounted on a thin tube called a catheter, and it’s inserted into your body through the femoral artery, a large blood vessel in your upper thigh. With the help of an X-ray technique called fluoroscopy, doctors can guide it and place it across the aortic valve in your heart.
The high flow LVD (which moves 5.0 L/min) is a larger pump of the same kind, that’s mounted on the same thin tube, the catheter. However, due to its larger size, doctors need to make a surgical incision in the axillary (armpit area) or femoral artery to put it in place.
The catheter tube has additional channels, one is for the purge (cleaning solution) and another one is for monitoring blood pressure. At the top or ‘proximal end’ of the catheter, there’s a hub, a part where different pipes can connect. It’s here that the cable attachment for the device console and the tubing for the cleaning solution and blood pressure monitoring is connected.
The console is like the control panel for our left ventricular device. It allows doctors to control the speed of the pump and shows the difference in pressure between where the blood is coming in (inflow) and going out (outflow) of the pump.
While inserting and setting up the device, doctors recommend the use of intravenous heparin – a medication that thins the blood and prevents clots. The clotting time of the blood, which refers to how fast it forms clots, is closely watched. During the insertion of the device, doctors aim for a clotting time of 250 to 500 seconds, and after its placement, an ideal clotting time between 160 to 180 seconds is maintained to ensure the right balance and prevent clot formation.
Possible Complications of Percutaneously Inserted Ventricular Assist Device
There are several possible complications that can occur due to certain medical treatments or procedures. These include:
– Hemolysis: which means the breaking down of red blood cells. This could happen due to mechanical shearing – or the forceful tearing or cutting action by medical devices.
– Acute kidney injury: which is a sudden episode of kidney failure or kidney damage that happens within a few hours or a few days. This can happen because of hemolysis, or the destruction of red blood cells, which can negatively affect the kidneys.
– Limb ischemia: which is a serious condition that occurs when there is an inadequate supply of blood flow to a part of the body, typically the legs.
– Vascular injury: This could include complications like hematomas which are a type of swelling filled with blood, pseudoaneurysms which are false aneurysms, a condition where the blood escapes from an artery and is trapped by the surrounding tissue, fistulas, which are abnormal connections between two parts of your body, and retroperitoneal hemorrhage, which is bleeding in the space surrounding the kidneys and other abdominal organs.
– Bleeding requiring blood transfusion: This is when a person loses so much blood from an injury that they need a blood transfusion to replace the lost blood.
– Pericardial tamponade: This is a serious medical condition in which the covering of the heart, known as the pericardium, fills up with too much fluid and places extreme pressure on your heart. This can lead to the heart not being able to pump out enough blood, leading to a life-threatening situation.
What Else Should I Know About Percutaneously Inserted Ventricular Assist Device?
The ISAR-SHOCK trial and PROTECT II were studies conducted to compare the effectiveness of two different heart devices: the percutaneously inserted Left Ventricular Device (LVD) and the Intra-Aortic Balloon Pump (IABP). These devices help the heart pump blood.
In the ISAR-SHOCK trial, 25 patients with heart attacks and severe heart weakness were assigned randomly to try either the LVD or the IABP. After 30 minutes of using each device, the LVD performed better by pumping more blood. However, the patients’ survival rate after 30 days was the same for both devices.
In the PROTECT II study, 448 high-risk patients receiving a heart procedure were randomly assigned to use either the IABP or the LVD. This study was stopped early. They found that after 30 days, there was no difference in the number of serious negative events for patients using either device. However, when they followed the plan of the study, the LVD was found to have better results after 90 days. This was mainly because fewer patients needed another heart operation.
The RECOVER RIGHT trial was another study that focused on 30 patients with severe Right Ventricular (RV) failure, a condition where the right side of your heart can’t pump blood efficiently. Twelve patients had heart attacks, and 18 had heart surgery. This trial showed that the Right Ventricular Device (RVD), a similar device to LVD but for the right heart, was safe and effective. It was helpful in enhancing the function of the heart right after activation. Also, the overall survival rate was about 73.3% after 30 days for patients in this trial.
All these findings help doctors understand which devices can effectively support patients with different heart conditions.
