Overview of Orbital Atherectomy
Orbital atherectomy (OA) is a special technique used during heart surgeries to prepare hard, chalky plaques in the heart’s arteries before the actual surgery starts. Using OA, doctors can change the structure of these tough plaques to make the arteries more pliable. This then allows for successful insertion and expansion of balloons and stents, which are small tubes used to keep the arteries open, especially for those arteries that have heavy plaque build-ups.
Coronary artery disease (CAD) is a common heart problem that is becoming increasingly common in the U.S. It greatly impacts health and lifestyle. According to the American Heart Association, more than 15.5 million individuals over the age of 20 suffer from significant CAD. Moreover, deaths due to heart diseases have been rising since 1990. Shockingly, nearly 650,000 people died due to heart diseases in 2019 alone.
In patients with severe CAD, coronary artery calcification (CAC) occurs, which is the hardening or calcification of the heart’s arteries. This condition is linked with increased fatty deposit build-up and a higher risk for future heart issues.
Interestingly, CAC seems to depend on both gender and age. For individuals over the age of 70, it’s estimated that more than 90% of men and 67% of women experience some degree of CAC. Advanced imaging techniques, like intravascular ultrasound (IVUS) or optical coherence tomography (OCT), are more effective in detecting CAC than traditional heart X-rays, also called coronary angiography.
As CAD becomes more common, the number of people with CAC is also increasing. Past studies have shown that patients with severe CAC often face worse outcomes when undergoing heart surgeries than those with mild CAC. Moreover, it is more difficult to do surgery on patients with severe CAC. Research also reveals that high levels of artery calcification are linked with less effective heart surgery and increased risks for death, heart attack, and repeat surgeries.
To reduce complications and improve successful stent insertion in patients with severe CAC, OA can be a significant help. This article reviews OA, how the available devices work, reasons for using it, possible complications, contraindications (situations where it should not be used), and clinical trial outcomes based on the most recent data.
Anatomy and Physiology of Orbital Atherectomy
When your heart’s arteries become hardened with calcified plaques, it can make it difficult to successfully carry out a procedure called PCI. This procedure is used to put a stent, a small tube, into your artery to keep it open. If the stent can’t open fully because of these plaques, it can lead to poorer health outcomes in the long run. It’s known that this calcification can negatively affect the shape and function of your arteries, making them stiffer, less responsive to normal body signals, and unable to efficiently supply oxygen to your heart muscle.
The process of vascular calcification, which is the hardening of arteries, is complex and not fully understood yet. Earlier theories suggested that imbalances in calcium/phosphate, specific harmful complexes in the blood, programmed cell death, and bone formation might play a part in this process. More recent research suggests tiny molecules called microRNAs, which control the behavior of the cells forming the walls of arteries, may also be involved.
While the exact cause of artery calcification is still a mystery, certain risk factors are known to be connected with more severe and advanced cases. The hardening can occur in different layers of the artery wall and hardening in one layer, the tunica media, is believed to be more linked with heart events.
Common risk factors for artery calcification include smoking, obesity, high blood pressure, diabetes, advancing age, chronic kidney disease, being male, and being Caucasian. These risk factors are becoming more common in the United States according to the Heart Disease and Stroke Statistics-2019 Update.
Why do People Need Orbital Atherectomy
Orbital atherectomy (OA) is a procedure used to help place a stent, a small mesh tube that helps keep narrow or weak arteries open, specifically in people with severely hardened (calcified) coronary artery lesions. The coronary arteries are major blood vessels that supply the heart with blood, oxygen, and nutrients. Therefore, when they get severely calcified, it requires a procedure like OA, which is approved by the Food and Drug Administration (FDA).
Whether OA should be used depends on how thick and severe the calcification is. Past studies suggest that lesions – damaged or abnormal areas – with a thickness of less than 0.24 mm are likely to crack and can be treated with something called balloon angioplasty. This is a procedure where a small balloon is inflated inside the artery to widen it and improve blood flow before a stent is placed. Similarly, lesions with a high calcium score may cause the stent not to expand properly. In these cases, using OA before placing a stent could be beneficial.
Although the maker of the device used for OA hasn’t suggested any more uses, some doctors might find it useful in other situations due to its adjustability. They might use it for people with hardened lesions in more than one artery, preparing a lesion for a bioresorbable scaffold placement (a newer type of stent that gets absorbed by the body over time), treating a disease of the left main coronary artery when there is no other artery bypassing the blockage, treating lesions near the start of an artery, and dealing with chronic total occlusions, which are complete blockages of an artery.
More studies and data are needed to determine other clinical uses and situations where OA might be a suitable treatment option.
When a Person Should Avoid Orbital Atherectomy
Orbital atherectomy, a procedure to remove plaque from your blood vessels, may not be recommended if you fall under certain categories:
- Firstly, if it’s impossible for a thin, flexible medical wire (guidewire) to cross an area of clogged blood vessel.
- If the area with the blockage is inside a graft or stent, which are devices used to prop open your blood vessels.
- If you’re not eligible for methods such as atherectomy (plaque removal), coronary angioplasty (widening blocked or narrowed coronary arteries), or bypass surgery.
- Orbital atherectomy may also not be suitable if a clot is visible on your angiography, a type of X-ray used to check your blood vessels.
- If you have multiple blocked vessels but only one is open, this treatment might not be for you.
- If an angiogram, a specific type of X-ray, shows that your coronary artery is tearing or splitting (coronary dissection).
- If you are pregnant or a child, you are also advised not to go through with the procedure.
Additionally, there are several factors to consider before choosing orbital atherectomy:
- It may not be suitable for very twisted blood vessels, which are at higher risk of being damaged.
- Treating areas in the right coronary or left circular areas of the heart increases the risk of heart block, a condition where the heart beats more slowly or skips beats and may need a temporary pacemaker to manage.
- If heart surgery is required, ensure a team of heart surgeons is readily available at your location.
- Lastly, if you have heart failure and your heart’s pumping ability (ejection fraction) is less than 25%, this procedure may not be advised.
Equipment used for Orbital Atherectomy
The orbital atherectomy system (OAS) is made up of a few key pieces: a coronary orbital atherectomy device (OAD), a special pump for the system, a coronary guidewire, and a lubricant. The OAD is built with a protective cover over the drive shaft, a small crown (1.25/1.50 mm in size) that fits over the VIPERWIRE coronary guidewire, a knob for moving the crown forward, and a connection for saline tubing to the pump. There’s also a machine or motor handle that can be operated from the tableside in the surgery room, which is responsible for controlling how fast the crown rotates, directing the crown’s movement, and includes the braking system for the guidewire.
The OAS system requires a minimum size 6 french guide or larger. The lubricant, which gets mixed with saline, needs to be attached to the pump and needs to be used throughout the procedure. The purpose of this is to reduce the risk of overheating damage and potentially blockage affecting the heart. The flow rate of the saline is controlled by the pump and is typically around 18 ml/min, but it can be boosted up during the procedure as required. The whole device is easy to assemble and an experienced operator can get it up and running in just a few minutes.
Who is needed to perform Orbital Atherectomy?
When you’re undergoing an operation called orbital atherectomy (OA), a team of heart specialists will be there to ensure everything goes smoothly. This team is made up of special heart doctors called interventional cardiologists, cath lab technicians, and nurse practitioners or provider assistants, as well as heart catheterization laboratory personnel.
All these people play unique roles: they help in checking in patients, doing lab tests, monitoring your vital signs during the procedure, and evaluating you after the procedure for new symptoms or signs of instability or complications.
The OA procedure is done by an interventional cardiologist, who is a doctor specialized in treating heart conditions with minimally invasive procedures. They perform the operation using a particular technique where they are the primary operator. Before they can use the specific tool for this operation, known as the coronary orbital atherectomy system (OAS), in the United States, they need to be certified.
Earning this certification involves completing online education modules and doing a minimum of six supervised cases. Depending on their experience, they might also have to complete a special training course beforehand.
Preparing for Orbital Atherectomy
Before a heart procedure, it’s crucial for the doctor to have a complete understanding of the patient’s medical and surgical history, current medications, and any allergies. This helps to ensure the best possible results. The doctor will closely examine any previous heart scans and tests – like electrocardiograms (which monitor the heart’s electric activity), echocardiograms (ultrasounds of the heart), stress tests (tests that measure how the heart functions while under physical strain), and angiograms (X-rays of the blood vessels) – to help plan the procedure as accurately and effectively as possible.
Understanding any previous heart procedures the patient has undergone is also very important to help the doctor plan accordingly for the upcoming procedure. The doctor will decide on the best site to insert the catheter (a thin, flexible tube) based on the specific characteristics of the patient’s blood vessels and their own personal preference.
Everyone involved in the procedure must carefully wash and sterilize their hands to maintain a clean environment and minimize the risk of infection. Once everyone is properly dressed in sterile clothing and gloves, they will take a moment to double-check everything before the procedure – this is called a “time-out”. Only after all these steps are complete can the procedure, known as an “orbital atherectomy”, commence. This is a type of procedure used to treat heart disease by removing plaque (a buildup of fat, cholesterol, and other substances) from the coronary arteries, which supply oxygen-rich blood to the heart.
How is Orbital Atherectomy performed
Before starting a procedure known as coronary orbital atherectomy, the team needs to prepare all the necessary equipment. This includes a special system called coronary orbital atherectomy system, a guide catheter (a thin tube used to perform procedures), an IV pole (a stand used to hang bags of fluid or medicine), normal saline (a solution of salt in water), and fluoroscopy imaging equipment (a kind of X-ray machine).
When everything is ready, the team can start the procedure. They begin by getting access to the blood vessels in your body through a small cut in your skin. This can be achieved using a method preferred by your doctor. Once they have access, they will use a guide catheter and special imaging technologies to locate and assess the problem area (called the ‘lesion’).
Upon locating the lesion, the team will use a special wire to cross the lesion. They will then connect a device known as an Orbital Atherectomy Device (OAD) to the atherectomy system and prepare it for use. Then the OAD is inserted into the blood vessel over the wire while being guided by the fluoroscopy machine.
Once the OAD is close to the lesion, it will start rotating slowly at 80,000 rotations per minute which can be verified with an LED light on the OAD. This rotation helps in breaking down the plaque in the blood vessels.
Using the advancer knob, they advance the rotating device slowly through the lesion, taking care not to leave the device in one spot for too long as it could injure the blood vessel. To ensure safe operation, the device is moved back and forth across the lesion in short intervals, separated by rest periods.
If the plaque isn’t sufficiently cleared at slow speed, the speed may be increased to 120,000 rotations per minute, provided the blood vessel is of adequate size and there are no bends in it. The maximum time recommended for treatment with one device is 5 minutes. This duration must be manually timed by a team member as the device does not track the time.
Upon removing the device, the treated area is checked using a balloon to see how well it expands. If it doesn’t expand adequately, more treatment may be needed. Imaging can be used to further assess the treated area before a stent (a small mesh tube) is placed. It’s also important to have a bag of saline and lubricant ready, in case it’s needed during the procedure.
Possible Complications of Orbital Atherectomy
Orbital atherectomy is a procedure that has been proven to be a safe and effective treatment in several studies. It involves a special device that helps to open up blocked blood vessels in the heart. This procedure has shown to have a low rate of complications even in high-risk patients. These may include women, older adults, those with diabetes, chronic kidney disease, low heart function, or people who have had previous heart bypass surgeries.
However, like any procedure, there can be complications. The most commonly reported ones include dissections (small tears in the artery wall), slow or no blood flow, and perforations (holes in the blood vessel). There have been two major studies, ORBIT I and ORBIT II. In the ORBIT I study, out of 50 patients, there were six instances of dissections and only one of perforation. No cases of slow blood flow were reported. In the larger ORBIT II study, which included 443 patients, the rates for dissection, perforation, and no blood flow were 3.4%, 1.8%, and 0% respectively.
In some rare cases, patients can experience a slow heart rate (bradycardia) during the procedure. In a 2017 study, 4% of the 50 patients had this side effect. However, none of them required a pacemaker to help control their heart rate.
Very rare complications include a Pseudoaneurysm (a false aneurysm, which is a blood-filled sac that forms due to a leak in the artery wall) and a dislodged microtip (a small piece of the device becoming detached). In some cases, parts of the device can get detached or damaged. These may include the head, body, and tip of the device’s guidewire (the thin wire that guides the device into place), as well as the tip and body of the driveshaft (the part that powers the rotation of the device in the body).
What Else Should I Know About Orbital Atherectomy?
The use of a procedure called atherectomy, which treats heavily hardened or calcified heart lesions, is gradually becoming more common. The first human study, named ORBIT I, worked with 50 patients to explore the safety and effectiveness of a particular type of atherectomy, called orbital atherectomy (OA). The success rate of the operation in this study was 94%.
This first trial was followed by another, larger trial called ORBIT II. It involved 443 patients but did not compare OA with any other treatment because no other alternative had gained FDA approval at that time. The main measure of success in this trial was the frequency of significant harmful heart events – or MACE – in the 30 days following treatment. Nearly 90% of patients were free from such events during that period. MACE rates at various times after hospital discharge were also recorded; the frequency of these harmful heart events were close to 10%, 16%, and 24% at the time of discharge, after one year, and after three years, respectively. These results led to the FDA approving OA in 2013.
Some patient groups that are considered to be at high risk were not included in the ORBIT II study. These neglected groups include patients with disease in the principal artery supplying the left side of the heart, and patients with what is known as an ‘ejection fraction’ of less than 25% – essentially, their hearts are less effective at pumping blood. These high-risk patients were included in a study carried out in 2018, which suggested that OA could be a valid treatment option even for patients with severely hardened heart lesions.
In terms of cost, an analysis was conducted that compared ORBIT II data with data from other sources. The average cost per patient was found to be roughly $3,590 lower for those in the ORBIT II trial. This discrepancy was attributed to shorter hospital stays for the patients in ORBIT II (an average of about 1.8 days compared to roughly 4.24 days according to other data). ORBIT II patients also had a lower rate of hospital readmission for heart bypass surgery in the month following the procedure, which was calculated to reduce costs by approximately another $704. In total, the cost saving per patient from using OA was found to be around $4,294.
A primary goal moving forward is to carry out larger trials that evaluate how useful OA is for patients with severe heart calcification. One such larger trial, named the ECLIPSE trial, has been ongoing since 2017 and is expected to finish in February 2022. The parameters being studied include the minimum area inside the stent after the procedure and whether the treated vessel fails.
