Overview of Catheter-Directed Thrombolysis of Pulmonary Embolism
Venous thromboembolism, or VTE, impacts around ten million people globally every year, leading to over half a million deaths in Europe and between 100,000 and 300,000 deaths in the US. This is a condition where blood clots form in veins, which can be life-threatening if they travel to the lungs, causing a pulmonary embolism (PE). These can be very severe; some people may not show any symptoms, while others may suddenly die from a PE. This shows how vital it is to correctly identify the severity of a PE as soon as it is detected.
Due to this, it’s really important to categorize patients according to their risk of complications from a PE so that the best treatment plan can be tailored for them. While generally, blood thinning medication is enough for those at a low risk, the benefits of actively removing blood clots, such as through a process called catheter-directed thrombolysis (CDT), is increasingly recognized for those with more severe cases.
CDT is becoming a more used treatment, especially for patients with a moderate to high risk from a PE. This treatment aims to decrease the amount of blood clots in the lung’s arteries, which might improve the functioning of the right ventricle – one of the heart’s chambers – and patient outcomes. However, applying CDT isn’t risk-free, as the chance of bleeding and other complications needs to be compared to the potential benefits of the treatment.
New forms of treatment for PEs are continually being developed and approved for use in medicine. This rapidly changing area requires a good understanding of current methods and the development of scientific evidence to direct their use in different situations.
Anatomy and Physiology of Catheter-Directed Thrombolysis of Pulmonary Embolism
The condition called Pulmonary Embolism (PE), usually starts from the deep veins in your lower body or pelvis. Sometimes, a blood clot in these veins can break free and move upwards through your veins into your lungs. This clot can get stuck in different parts of your lung blood vessels, including the main passage or smaller offshoots.
When this blood clot blocks the blood flow in your lung, it can cause strain on your heart and cut off the blood supply to the part of the lung that’s blocked. The seriousness of this situation can vary depending on the blood clot’s size and where it’s located. In severe cases, the blockage can cause so much pressure that it leads to right ventricular (RV) failure, which is a principal cause of death in these instances.
If the blood clot blocks more than 30% to 50% of the blood vessels in your lungs, it can cause increased pressure there. Chemicals released during this condition can make the blood vessels in the lungs tighten, adding to the resistance against blood flow and making it harder for the vessels to expand. This sequence of events can cause the right side of your heart to expand, which may alter how heart muscle works. It may increase the tension on the heart wall and stretch the heart cells, making the right side of your heart contract for longer. These can prompt the body to increase the heart’s pumping and beating rate.
However, the right part of your heart is not designed to withstand high pressures for an extended period. If this situation continues, it can lead to decreased stability in your blood circulation. Overdrive in the heart’s pumping and beating rate, potentially leading to inflammation of the heart muscle, and the mismatch between the oxygen demand and supply can further harm the right side of your heart.
Respiratory failure in PE mainly comes from blood flow disturbances causing mismatched airflow and blood flow in the lungs. There is also a risk that the blood clot might move to the left side of the heart through a small hole present since birth in some people, worsening the decreased oxygen level in the blood and increasing the risk of a blood clot reaching the brain and causing a stroke.
Why do People Need Catheter-Directed Thrombolysis of Pulmonary Embolism
Selecting the right patient to undergo endovascular (related to blood vessels) strategies in the treatment of pulmonary embolism (a sudden blockage in a lung artery), is very important. It involves three key considerations before deciding to proceed with catheter-directed thrombolysis (CDT – a treatment method where a tube is used to deliver a small dose of drugs to break up clot formation):
Determining the seriousness and suddenness of the disease:
– When dealing with massive pulmonary embolism, the first choice is usually systemic thrombolysis (a treatment method that dissolves clots). This choice has been shown to lower the rate of death from any cause. However, when this method fails, endovascular methods like CDT may be considered. Doctors can also consider using an artificial lung (extracorporeal membrane oxygenation – ECMO) or surgical removal of the clot (embolectomy) in situations where the patient’s life is threatened.
– Submassive pulmonary embolism: Systemic thrombolysis can offer mortality benefits, but it also increases the risk of serious bleeding, like bleeding within the brain. The American College of Cardiology (ACC) and American Heart Association (AHA) guidelines suggest considering CDT if the patient’s condition worsens or if there are signs that predict a worse outcome. The European Society of Cardiology advocates assessing the risk twice using recognized tools like the PE Severity Index, followed by imaging and biomarker (a measurable substance in an organism whose presence indicates some phenomenon such as disease, infection, or environmental exposure) assessment. If both clinical and objective assessments show a high risk, and it’s likely that the patient’s heart and lungs will worsen, CDT may be considered.
– For low-risk pulmonary embolism, endovascular interventions aren’t usually recommended since the conditions aren’t life-threatening. The exception might be in the case of large “saddle emboli” (a blood clot lodged at the division of the main artery of the lung) without any sign of overload on the right side of the heart.
Mitigating the risk of major adverse bleeding:
– It’s really important to balance the possible benefits of CDT with the individual risk of bleeding. The doctor needs to be mindful of other diseases and past instances of bleeding.
Patient-centric considerations:
– It’s important to respect the values, preferences, and goals of the patient in making treatment decisions. This is called “shared decision-making” and helps ensure that the chosen treatment suits the individual patient’s specific circumstances and needs.
When a Person Should Avoid Catheter-Directed Thrombolysis of Pulmonary Embolism
During Catheter-Directed Thrombolysis (CDT), a medicine is used to dissolve clots in the blood vessels. However, this treatment can pose its own health risks, including bleeding complications, as the medication can spread throughout the body. Before a doctor considers thrombolytic therapy, they need to thoroughly review the patient’s health history.
This review helps the doctor to understand whether it would be dangerous to administer the therapy based on several contraindications (medical reasons to not use the treatment).
According to guidelines, some absolute contraindications (when the treatment should definitely not be used) are:
* Diseases in the structure of the brain
* Bleeding inside the skull
* Stroke within the last 3 months
* Active bleeding (anywhere in the body)
* Recent surgery on the brain or spine
* Recent head injury involving a fractured skull or brain injury
* Blood disorders that can lead to excessive bleeding
In addition, there are relative contraindications (situations where the treatment should be used with caution). These include:
* Very high blood pressure
* Recent non-brain related bleeding
* Recent other surgery or procedure
* Stroke more than 3 months ago
* Blood thinning medication usage
* History of forceful Cardio-Pulmonary Resuscitation (CPR)
* Inflammation or fluid in the sac surrounding the heart
* Eye disease caused by diabetes (diabetic retinopathy)
* Pregnancy
* Age above 65
* Low body weight
* Being female
* Being of Black ethnicity
Thus, doctors should consider all these factors before deciding on thrombolytic therapy to make the treatment as safe and effective as possible.
Equipment used for Catheter-Directed Thrombolysis of Pulmonary Embolism
The standard way of treating an acute pulmonary embolism (PE) – a sudden blockage in a lung artery, usually due to a blood clot – has its limitations. It poses significant bleeding risks, especially for high-risk patients. Also, the medication may not effectively reach and dissolve the blood clot, limiting how well it works.
Catheter-Directed Thrombolysis (CDT) is a promising new approach. This technique directly administers medication to dissolve the blood clot through a tube inserted into the body. It competently targets the embolism and reduces the chance of bleeding compared to the traditional method. However, the best way to use CDT is still a matter of ongoing research and varies based on individual patient’s condition and severity of PE.
Though research on CDT’s effectiveness is ongoing, the future looks promising. Current clinical trials are trying to understand how well it can be applied to different patient groups. Still, more research is needed to pinpoint its role and formulate the best treatment plans.
Different trials have been conducted using different types of catheters to deliver the medication, at different doses, over varying periods. One type of catheter known as “Cragg-McNamara” has shown to improve the condition after three months of treatment compared to anticoagulation therapy. Other catheters like “EKOSonic” and “Bashir Endovascular Catheter” have also shown efficiency in treatment with a decreased ratio of right ventricular to the left ventricular diameter, which signifies improved heart function.
There are several types of catheters available to perform CTD, each with its unique mechanism. These include the EKOS Intelligent Drug Delivery System and the Bashir Endovascular Catheter. Both of these devices come equipped with special tools to break down PE clots.
The EKOS system allows for the delivery of medication and a saline coolant directly to the clot. It also uses targeted low-frequency sonic waves to break up the clot and enhance the penetration of the drug into the clot. This system also monitors vital parameters like pulmonary artery pressure and heart output for patient safety during the procedure.
The Bashir Endovascular Catheter has a unique expandable “basket” feature with 48 openings, which allows for strategic deployment and better interaction between the clot and the drug. It uses a controlled “pulse spray” to create tiny cracks in the clot, followed by a steady pumping of the drug to ensure sustained breakdown of the clot. This system also uses real-time imaging to guide the placement of the catheter.
Both these procedures need initial venous access, typically achieved using a micropuncture needle. A guidewire helps navigate the catheters to the blood clot within the lung artery. Anticoagulant therapy also plays a crucial role in both techniques, preventing further clot formation and maintaining the openness of the blood vessels during the procedure.
Who is needed to perform Catheter-Directed Thrombolysis of Pulmonary Embolism?
New guidelines in healthcare recommend using a team called a PERT to diagnose and manage blood clots in the lungs, also known as ‘acute PE’. A PERT is made up of experts from different fields of medicine who work together to give their patients the best possible care. PERT teams often deal with serious cases of lung clots, but they can also help patients who can’t take standard blood thinners because of potentially dangerous side effects, such as serious brain bleeds.
Here are some things to remember about a PERT team:
- Starting blood thinners is crucial and should not be delayed unless it’s too risky.
- Starting the PERT team should happen at the same time as the treatment.
- Every hospital has a different PERT team. The team could include doctors who focus on care in high-risk situations, lung diseases, heart conditions, using images to diagnose and treat illness, and more.
Each team member has a specific job, whether that’s diagnosing the patient, deciding who’s most at risk, performing medical procedures, or managing medications.
The PERT team follows a certain set of steps in order to manage lung clots. However, this could change depending on the hospital’s rules or the patient’s individual needs. Here are the main steps:
- Patient identification: Identify patients who are suspected to have or confirmed to have lung clots, especially in serious cases. This also includes patients at low risk of lung clots who can’t take blood thinners due to other health risks.
- Activate PERT: Start the PERT team based on certain criteria like the severity of the clot and the patient’s other health conditions. Make sure there’s a clear way to let the team know about new cases.
- Initial assessment: The first medical team that sees the patient will evaluate them and make a diagnosis. They gather important information like the patient’s symptoms, risk factors, vital signs, and results from lab work and picture tests.
- Consultation: The PERT team meets to talk about the case and possible treatments. Each specialty has a possible role to play, whether it’s managing the patient’s vital signs, providing breathing assistance, diagnosing the condition, managing medications, using picture tests to help with treatment, surgically removing the clot if needed, or managing blood thinners and checking for clotting disorders.
- Treatment decision: The PERT team decides together on the best treatment approach based on the patient’s individual factors and the available resources. Options could include blood thinners alone, clot dissolving medication, mechanically removing the clot with a catheter or with surgery, or combining these treatments.
- Ongoing management: The PERT team continues to monitor the patient’s condition and adjust the treatment as necessary. It could include interventions like extra oxygen and monitoring vital signs. The team regularly checks the patient and watches for any complications to make sure the patient gets the best outcome.
The PERT team approach aims to better coordinate how we care for patients with lung clots. By bringing together experts for quick consultations and joint decisions, it helps improve communication and make treatment more efficient. Studies show it’s possible to create these teams, and a combined effort is gathering data to see how much these teams help. This can give us valuable insights into how well PERT teams help patients, how well they carry out patient care, if they save money, and how much they know about treating lung clots.
Preparing for Catheter-Directed Thrombolysis of Pulmonary Embolism
Before starting the procedure, the doctor needs to check the delivery system for the thrombolysis catheter, which is a tube used to deliver medicine, to make sure everything is in place. This procedure needs to be done in a fully functioning laboratory equipped for catheterization. Catheterization is a process where a thin tube is put into a large blood vessel. It’s important for the healthcare team to follow all sanitary rules for this procedure. This means they need to use things like clean sheets, gloves, and surgical gowns.
How is Catheter-Directed Thrombolysis of Pulmonary Embolism performed
The EKOS system is a special kind of medical equipment that uses low-frequency sound waves, or ultrasound, sent through a unique tube or catheter. The sound waves help break up clot forming components within a blood clot, making it easier for medications that dissolve clots (thrombolytic agents) like rt-PA to work. The ultrasound energy also creates a ‘microstreaming’ effect that helps the medication reach deeper parts of the clot. The treatment process using this system has to be done carefully step-by-step.
Getting Ready for the Procedure
Selecting the right patient is very important for a good outcome. Your doctor will consider your individual risk factors and will use some specific selection criteria before they can decide to use EKOS. You must sign a consent form after the doctor explains the procedure, including any risks. Before the procedure, you may also need to have some imaging tests like an echo test (echocardiogram).
Placing the Catheter
For this procedure, a medical professional will insert a hollow tube into a vein in your groin, which is called the common femoral vein. A long wire and a tube for imaging is then passed through this tube to reach the clot in the blood vessels of your lung, also called the pulmonary artery. The EKOS catheter, which is a special tube with ultrasound machines built in, replaces the imaging tube and is carefully positioned in the clot.
Delivering the Treatment
Your doctor will start an infusion of rt-PA (the clot-busting medication) and a liquid coolant through the EKOS catheter at calculated rates. These rates can be adjusted based on factors like your weight and other health conditions to make the treatment work well and avoid problems. At the same time, the sound waves from the ultrasound are sent through the EKOS catheter. Throughout the procedure, your doctor does a check-up to make sure you are safe and the treatment is working.
Typically, the treatment lasts between 12 to 24 hours, but it can be altered according to the hospital’s rules and your condition. To tailor the treatment, your doctor may need to adjust the dose of the medication or the ultrasound. It’s important for doctors to watch for any signs of problems like excessive bleeding or swelling of tissues during the procedure. At the end of the procedure, the EKOS devices are removed carefully. Your doctor will perform another imaging test like a CT scan to evaluate the success of the treatment and look for any leftover clots. You will continue to receive other standard treatments to prevent blood clots and monitored closely.
The Bashir Endovascular Catheter (BEC) is another device used to treat blood clots in the lungs. This device has a unique “basket” shape with 48 holes and helps break down clots by allowing increased blood flow. This also helps the clot-dissolving medications to work better.
At the start of the procedure with BEC, a doctor will insert a tube in a vein in the groin or neck. The BEC is then guided over this wire and placed into the clot in your lung. The device releases an initial high dose of clot-dissolving medication followed by a continued lower dose over several hours for the maximum effect. Throughout the procedure, a doctor will monitor your health closely to ensure your safety. At the end of the procedure, the BEC device is removed under careful supervision.
Possible Complications of Catheter-Directed Thrombolysis of Pulmonary Embolism
When someone gets catheter-directed therapy (CDT) for a pulmonary embolism (PE), which is a blood clot in the lungs, there can be potential side effects. Many of these are related to an increased chance of bleeding. However, this treatment tends to have a lower risk of severe bleeding compared to other treatments like systemic lytic therapy, which is a type of medication that helps break down clots in your body. For instance, systemic lytic therapy can lead to serious bleeding in up to 20% of people, while with CDT, the chance of severe bleeding is about 1.4% in people at intermediate risk and about 6.7% in those at a high risk.
One of the most alarming complications from CDT is a type of stroke called a hemorrhagic stroke, which can be very serious. Other common side effects include injuries at the place where the catheter was inserted, like a hematoma (a buildup of blood outside of the vessels), bleeding inside the lungs or in the area behind the lower abdomen, complications related to the heart like an irregular heart rhythm or a condition called pericardial tamponade that affects the fluid around the heart, and damage to the kidneys caused by the contrast dye used in the procedure.
What Else Should I Know About Catheter-Directed Thrombolysis of Pulmonary Embolism?
Systemic thrombolysis is a standard treatment for severe acute pulmonary embolism (PE), which is a sudden blockage in a lung artery. But, this treatment carries a risk of bleeding, particularly for the elderly. The right treatment is still indecisive for those with a moderately high-risk PE and right ventricular dysfunction (RVD), which is a condition affecting the right side of the heart.
Therapies using catheter-directed thrombolysis (CDT) are emerging as a promising solution. This approach directly delivers medication to dissolve the blood clot, potentially reducing bleeding by lowering the dose of the clot-dissolving drug. This makes it a beneficial choice for patients at high risk of PE who can’t safely undergo systemic thrombolysis. Early research reviews, although mainly observational, show promise. CDT reduces right ventricular dysfunction, which is a crucial mortality indicator in PE patients, and shows potential in improving short-term functional limitations and measures of blood flow.
However, we still need more evidence from ongoing studies like PE-TRACT and HI-PEITHO, which compare CDT to standard treatments in patients with moderately high-risk PE.
Until then, seasoned heart doctors will have to rely on personalized patient evaluations and make collaborative decisions within PE response teams. These teams, backed by local protocols and resources, can customize the therapy to fit each patient’s needs. Establishing PE response teams and promoting participation in clinical trials are essential to fully realizing CDT’s full potential and improving the outlook for these high-risk patients.
