Whether your program is primarily 9-1-1, interfacility transport (IFT), or a combination of both, the likelihood of being responsible for the safe and expeditious transport of a STEMI patient is high for anyone in the out-of-hospital care setting. Minutes matter with critical interventions such as percutaneous intervention (PCI), and when time is of the essence for these patients, there are a few things that are probably not in your protocol that you can do to save time during handoff to the Cath Lab. Understanding the anatomy of cardiac catheterization will make all these recommendations make sense.
“If I have seen further, it is by standing upon the shoulders of giants.” -Sir Isaac Newton.
Things have changed significantly since the first right heart self-catheterization in 1929, with the advent of percutaneous transluminal coronary angiography (PTCA) in 1977. For decades since, the femoral approach was the industry standard. In 1995, the first angioplasty was performed via the transradial (TR) approach. If the femoral approach worked for so long, why did the radial approach grow in popularity? To understand that better, let’s review the anatomy of the cardiovascular system specific to percutaneous intervention.
Anatomy
Going against the flow of blood, the femoral approach relies on the catheter transcending the femoral artery into the common iliac (Fig.1a), through the abdominal aorta, past the descending aorta, aortic arch, and ascending aorta until it finds its way to the aortic root, just above the cusps of the aortic valve. There, in an anatomically “normal” patient (for the sake of this blog, we are assuming everything is “normal.”), There, we would find two coronary ostias, left and right. The left leads into the left main artery (LMA), which (typically) bifurcates into the left anterior descending (LAD) and left circumflex (LCx) artery. (Fig.1b) An uncommon anatomic finding would be a third branch, causing a trifurcation called the Ramus artery. That’s irrelevant to this conversation. The right coronary artery has its own ostia that is engaged independently of the left.
Access
While this is not intended to be all-encompassing or a comprehensive review, we can at least understand the roadmap the catheter follows to the aortic root via femoral or radial access. However, getting the catheter into the body requires using a series of Seldinger (catheter over the wire) techniques, where a wire is advanced before the catheter (think Bougie and ETT).
TL;DR
Local anesthetic -> needle in -> tiny wire in -> needle out -> sheath/introducer over tiny wire -> tiny wire and introducer out -> bigger wire in -> catheter in -> bigger wire out -> engage coronaries
Long Version:
The start of the procedure is a local anesthetic delivered into the area of needle insertion. Then, recommended under ultrasound guidance, a needle is introduced into the artery, a small (0.014-0.018-inch) wire is then advanced through the needle. An angiogram is performed to confirm the wire is in the common iliac. The needle is removed, leaving the wire in place and holding direct pressure on the artery, and a sheath (usually 5F or 6F) is advanced over the wire. This is when the smaller wire (0.018-inch) is removed, and a larger (0.035-inch) is placed into the sheath and advanced up the aorta, then a catheter is introduced over the wire through the sheath and advanced along with the wire. This approach is similar for both femoral and transradial, with the most significant difference being in the specific equipment used and the introduction of vasodilators in radial access to prevent vessel spasms on the sheath/wire/catheter (this may have been specific to the program I worked in; I am unsure if that is the industry standard).
In either case, when the wire goes over the arch, it will usually loop back after deflecting off of the aortic valve. When the catheter gets to the aortic root, the wire is withdrawn from the catheter, and the catheter is connected to a manifold, which can read an aortic pressure and inject contrast dye. At this point, the catheters “engage” the coronary ostia, and angiograms are taken to assess the vessels.
Intervention
If the patient requires intervention, a guide catheter would then be exchanged, allowing a little more structure, limiting the ability to lose its shape as the catheter warms up in the body compared to a diagnostic catheter, and it is reinforced by design to put balloons and catheters through it and support the manipulation of the devices. After the guide catheter is seated, an intervention wire is introduced past the lesion, a balloon is placed on the wire that’s already in the vessel and advanced within the same guide catheter until it is in the lesion. The balloon is then injected with a mix of heparinized saline and contrast dye to dilate the lesion. Once the dilation of the balloon is complete (angioplasty), a stent can be introduced, which is compressed over a balloon. The balloon catheter is removed, and a stent balloon is then inserted and advanced to the area of the lesion, inflated for a determined amount of time and at a specific pressure, and then deflated, leaving the stent opposed to the vessel's walls. Badda-bing, badda-boom! Take some pictures of the new, juicy vessels and remove all the equipment.
TR vs. Femoral Access
Why one over the other? Femoral access is still the default for some interventionalists. Reserving TR for diagnostic cases only. There is a risk when accessing the femoral artery in that it’s big, and with big arteries comes increased bleeding complications. In rare cases, patients can bleed retroperitoneally and require transfusion (worst case). Less severe, the patient is bed-bound for 4-6 hours, sometimes longer, and a lot of pressure is needed to ensure a good clot has sealed off that vessel. Some interventionalists will also use closure devices, such as a collagen plug or a small stitch, to close the vessel, reducing complications from errors in holding manual pressure.
With TR access, the patient gets a TR band, which has a small pocket inflated just above the puncture site of the needle as the sheath is getting pulled. That band stays on their wrist for several hours (sometimes less), relieving air at regimented timeframes. During this, the patient cannot use their hand or put pressure on their wrist, but they can stand right up from the table in the lab and walk to the bathroom. They are not limited to mobility, just the use of their hand. Making the patient experience a little better overall. It is also cheaper for the hospital as the patient doesn’t require as long of a stay, and reduced rates of complications mean decreased morbidity and mortality. It’s just better for patients if it can be done. Sometimes, the patient’s anatomy or previous plumbing work on the patient’s cardiovascular system can make it a less optimal option- introducing more opportunities for time delays to intervention and complications. Therefore, there is not only one way to skin a cat; they both still have their place.
CABG – Coronary Artery Bypass Grafts
We can’t talk about cardiac catheterization without at least touching on CABG. Specifically, patients with a Left Internal Mammary Artery graft (LIMA). They will have a takeoff from the left subclavian artery that is marked on an X-ray with rings they place during the bypass surgery. Jokingly, and sometimes not so jokingly, I would say that CT surgeons would troll the interventionalists by putting the markers nowhere near the graft takeoffs. It always made me chuckle as the cardiologist got frustrated trying to find the bypass graft and thought of this alternate reality. This graft takeoff is always easier to access through the left radial approach. This is more reserved for diagnostic cases, as STEMIs usually get a femoral approach to make it easier. It's not so relevant, but I find it interesting.
Scenario
You have a 54-year-old male who woke up with crushing chest pain, jaw pain, and left arm numbness and tingling, nauseated and diaphoretic. You arrive on scene and quickly get a 12-lead revealing S-T segment elevation and reciprocal S-T depression.
You activate your local PCI center’s Cath Lab via phone and begin treatment. You give the patient aspirin, waste time giving them nitro (but you want to avoid that QA flag, we get it), oxygen, because their RA sat, was 89%, and some fentanyl for the pain. You’re enroute to the hospital and the patient says he’s feeling better, leaving you not much else to do. What else could we do to make the handoff to Cath Lab better and ensure the patient receives PCI faster?
Standards
The gold standard of STEMI care looks at the door-to-balloon (D2B) time. Simply put, from when the patient crosses the threshold of the hospital until the first balloon angioplasty. Now when the patient calls 9-1-1, this is measured as first medical contact-balloon time (FMC2B). Either way, the goal is 90 minutes (30 prehospital – 30 in the ED – 30 in the cath lab). If the patient requires transfer from an outside facility, the goal is 120 minutes. 30 minutes prehospital is not a long time when you consider contact, assessment, movement, interventions, and transport time. In some rural areas, 30 minutes is impossible. Finding areas where we can trim down time can improve patient outcomes. Going directly from the field to the cath lab should be the gold standard when it comes to STEMI and PCI. However, some facilities still struggle to meet this metric. So, how else can we reduce handoff times? Here are my top 5 recommendations to add to your STEMI bundle of care.
Tip #1 - Sites
To access the radial artery, you must tape the patient’s hand anatomically positioned, slightly bent posteriorly, and then sterile drape around the radial artery. For this reason, we should avoid the right hand and wrist for IV access. Should anything happen with that IV after the patient has been draped, it will most likely go unnoticed until the patient is not anymore sedated after receiving 5 of Versed and 100 of Fentanyl because it all just dripped on the floor... ASK ME HOW I KNOW.
In a perfect world, STEMI patients will have bilateral access to prevent this. However, it’s understandable when you only have one good site of access. I have seen a femoral vein be accessed because there were no peripheral options. However, that is reserved for the most extremes of cases. If possible, go left, but either way, go high. If you must go right, ensure the IV line is secured to the arm proximal to the venipuncture site to come off from the shoulder. This is a loophole in the drape where there is more line to troubleshoot problems.
In preparation for access, let’s remove your clippers from the monitor and give either side of the groin a good shave and your right wrist. Feel for the artery; envision a small 2-3” circumference around where you can palpate. Give that area as close of a shave as you can. This area will get prepped with chloraprep just prior to draping the patient. This allows some of the pores to close from the shock of shaving before they feel a burning sensation. Imagine shaving and immediately putting isopropyl alcohol on there or shaving and waiting 10-15 minutes and then doing it. It will make your patient a little more comfortable in the long run and shave time off the clock (pun intended) once they’re in the Cath Lab.
Tip #2 – Take Off Their Clothes
The patient should be naked under your blanket, with a towel vertically covering their nether regions. The number of times patients would come in 30 minutes out from the facility just to be fully clothed was too many to count, and that adds minutes to get the patient on the bed and ready to be prepped. This is the easiest and most appreciated thing you can do for your Cath Lab. Clothes off, every time.
Tip #3 – Electrodes
Understanding that a STEMI patient can go from uncomfortable to unstable very quickly should clue us all into having defib pads placed on our patients. The Cath Lab uses radiopaque pads so as not to interfere with the angiograms. With this in mind, they tend to put the wire side superiorly in A/P placement so the wires are out of the way of most views. With that in mind, if your Cath Lab gives you specific pads to place on STEMI patients, awesome! That’s leading edge. If they don’t, consider anterior placement as to leave the anterior chest open for their pads. Then, during the transition, the patient will always be on someone’s monitor should they go into a lethal arrhythmia.
Tip #4 – Mark Pulses
With their clothes off and seeing as you’re close to the legs and feet already, go ahead and palpate the dorsalis pedal pulse and mark the spot with your sharpie. The staff will look for that before and after the procedure to ensure it’s still present after femoral access.
Tip #5 – Immune Response
Ask your patient if they have ever received IV contrast dye and had a reaction. If they have, it is worth contacting the receiving hospital to see if the interventionalist would like you to give an antihistamine and steroid, maybe even a fluid bolus, before arrival.
Working as a medic and then in the Cath Lab, I tried to take every opportunity I could to help transform my care of STEMI patients. These five changes are the biggest takeaways that you can implement tomorrow that will reduce time once in the lab until the patient gets access and that first balloon inflates. None of these interventions should be prioritized over protocols or best practice. However, if you find yourself sitting in the back with a few minutes to spare, consider these tips to make your STEMI care stand out from everyone else, and have the Cath Lab love you.
References
Morris JB, Schirmer WJ. The “Right Stuff”: Five Nobel Prize–winning surgeons. Br J Surg. 1990;77(8):944-53. https://doi.org/10.1002/bjs.1800770833.
Kiemeneij F, Laarman GJ, de Melker E. Transradial artery coronary angioplasty. Am Heart J. 1995 Jan;129(1):1-7. doi: 10.1016/0002-8703(95)90034-9. PMID: 7817902.
Mueller RL, Sanborn TA. The history of interventional cardiology: cardiac catheterization, angioplasty, and related interventions. Am Heart J. 1995 Jan;129(1):146-72. doi: 10.1016/0002-8703(95)90055-1. PMID: 7817908.
