BackTable Article

Pulmonary Embolism Interventions

Quynh-Anh Dang • Aug 24, 2021

Pulmonary embolism interventions such as catheter directed thrombolysis and mechanical thrombectomy are alternative treatments for patients who do not respond well to systemic anticoagulation. Dr. Eric Secemsky describes patient selection for each type of intervention, his team’s thrombolysis technique, and thrombectomy devices. This is the second installation of a three-part article series over diagnosis and interventions for pulmonary embolisms from the BackTable Podcast.

We’ve provided the highlight reel in this article, but you can listen to the full podcast below.

The BackTable Brief

• After initial administration of heparin, Dr. Secemsky transitions his patients to Lovenox, which is more easily managed and more compatible with subsequent interventional therapies, if they are needed.

• Dr. Secemsky prefers catheter directed thrombolysis for cases involving distal clot, mixed thrombus, and subacute thrombus. He prefers mechanical thrombectomy for cases involving proximal clot, saddle embolus, or any PE with thrombus.

• For catheter directed thrombolysis, Dr. Secemsky cites patient comfort as a reason to opt for femoral access and conscious sedation.

• Although minimally invasive pulmonary embolism interventions are advancing, surgical embolectomy still plays a role in treating high-risk PE cases that involve severe shock, intra-atrial shunts, or clots in transit.

Table of Contents

Systemic Therapies: Anticoagulants and Thrombolytics for PE

Catheter Directed Thrombolysis for PE: Sedation, Imaging, and Devices

Current Data for Catheter Directed Thrombolysis and Mechanical Thrombectomy

The Role of Surgical Embolectomy

Mechanical thrombectomy is a pulmonary embolism intervention that allows for rapid clot extraction

Systemic Therapies: Anticoagulants and Thrombolytics for PE

Dr. Secemsky describes systemic therapies for pulmonary embolisms. The systemic thrombolytic tPA is administered for massive PEs that are too unstable to transport to the lab. For anticoagulants in non-massive PEs, patients will first receive heparin and then transition to Lovenox. Lovenox is more favorable because its dosage can be calculated based on patient weight and it requires less close monitoring. Lovenox is also compatible with further interventions such as catheter directed thrombolysis. If no further interventions are needed, the patient will transition to direct oral anticoagulants (DOACs) or novel oral anticoagulants (NOACs).

[Dr. Sabeen Dhand]
What kind of systemic therapies are your patients getting, in terms of thrombolytics and anticoagulants? Are your patients getting tPA, or are you holding off on tPA and taking them to the lab?

[Dr. Eric Secemsky]
The majority of our lytics go to massive PEs that are unstable in the emergency room and we don't think we could get them on ECMO or to the lab. If there is someone who arrested with either a documented PE or high suspicion for PE, we'll lyse with tPA.

We've had some situations where they are not technically massive, but the patients are particularly sick or have other comorbidities. In these cases, if we don't think that mobilizing them or bringing them to an interventional suite makes sense, we will give them half-dose lytics.

Most of the time, everything that we do is decided in the lab. We will bring them to the lab where the only systemic therapy that we do is heparin. We used to keep people on systemic heparin and then transition them to Lovenox, once there was no plan to go for aggressive invasive therapy.

[Dr. Sabeen Dhand]
Lovenox, no oral anticoagulation?

[Dr. Eric Secemsky]
We move to oral anticoagulation. Heparin is unpredictable. It depends on how attentive the nurses are, and there are always some patient care considerations that predict whether they are going to get a high dose or low dose. Lovenox is probably the right systemic agent for everyone that comes in because you get really good weight-based therapeutic anticoagulation. You can quickly check the factor Xa level. The most important thing for any PE patient is that they are systemically anticoagulated, which is better than any device or treatment you are going to do.

We don’t have a lot of procedural issues on Lovenox. We could take them to do EKOS with Lovenox already in their system. We are really trying to move people on the systemic anticoagulation right away with Lovenox and then a quick transition to a NOAC or DOAC as soon as the decision to not intervene further is made.

Catheter Directed Thrombolysis for PE: Sedation, Imaging, and Devices

Dr. Secemsky explains his team’s reasoning for choosing conscious sedation, femoral access, and pulmonary angiography, and specific dosing and duration of lysis. He also describes their use of the EKOS ultrasound-assisted catheter and adds that the decision to use an ultrasound-assisted catheter or a non-ultrasound drip catheter is a matter of familiarity, not effectiveness.

Dr. Secemsky explains his team’s reasoning for choosing conscious sedation, femoral access, and pulmonary angiography, and specific dosing and duration of lysis. He also describes their use of the EKOS ultrasound-assisted catheter and adds that the decision to use an ultrasound-assisted catheter or a non-ultrasound drip catheter is a matter of familiarity, not effectiveness.
[Dr. Sabeen Dhand]
I want to briefly talk about your catheter-directed technique. Are you using local or conscious sedation, or are you going with anesthesia?

[Dr. Eric Secemsky]
In our cath lab, everything is usually under conscious sedation. Most people get our usual protocol of some fentanyl or Versed. We do access mainly from the groin. I think the groin access is more straightforward and easier, especially when people aren't intubated. Patients don't love large catheters in their necks. People have shown that you can do EKOS from brachial arm veins and the antecubital fossa, which is great.

I do everything with femoral ultrasound access, and we usually will do some kind of pre-close with the Perclose or mattress sutures upfront if it is going to be the large bore access like for the Inari device. For EKOS, you know we just pull and hold so that is easy.

[Dr. Sabeen Dhand]
Do you do pulmonary angio? Do you worry about increasing pressures or, if you do, then what rate do you use to get decent pictures?

[Dr. Eric Secemsky]
Yes. I haven't seen the angiogram causing any issues with the clot. I don't do them upfront if the patient came straight from the scanner and I already have an idea of where things lie. Sometimes, if we are doing the Inari device or clot extraction, we'll take some puffs through the catheter (the large bore sheath).

[Dr. Sabeen Dhand]
Do you have to use EKOS? Or is it okay to use an infusion catheter without the ultrasound in it? Do you have any opinions on either of the two?

[Dr. Eric Secemsky]
We have a lot of experience with EKOS, so we tend to use EKOS.

There was a recent study called "SUNSET sPE” that didn't show any difference between catheter types. I'm still a believer in EKOS and I'm familiar with the device, so I tend to use it. But, my other colleagues have sometimes wanted to put in a non-ultrasound drip catheter and that's totally fine with me.

[Dr. Sabeen Dhand]
Regarding the dose and duration, what do you use if you are doing a short-term or long-term lysis?

[Dr. Eric Secemsky]
Our standard has always been 12 hours. This may vary depending on when we put in the catheters and then also with COVID, how long we want them to be sitting in the ICU with them infusing.

You can go as short as 2 to 4 hour protocols. The traditional ones are 12 or 15 hour protocols. Usually we'll do 12 hours, a milligram per hour per catheter, so no more than 24 mg of tPA. Sometimes we will do a shorter course. If we were a little bit more on the fence about the benefits of therapy and/or concerned about any risk of tPA, we will want to limit how much tPA we give, so we will go down to a 4 hour protocol and just give a milligram per hour for 4 hours.

[Dr. Sabeen Dhand]
What's your endpoint? Are you measuring pressures at bedside through the sheath or are you bringing them back down?

[Dr. Eric Secemsky]
My training and teaching was always that, you complete the course and you're done. As long as they're bad, which they almost always are, there is really no value at that point of doing anything more invasive. I think we got a little bit used to (with the Inari device) checking pressures before and after clot extractions. It is always nice to have that data.

If it is someone with shock with PE, we'll leave a right heart cath PA line in there to manage them after they leave the lab, just to watch. This is a really benign thing to do and it can be helpful. Otherwise, we'll go back to an echo and use that to measure pressures and RV function, which is the long term protocol.

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Current Data for Catheter Directed Thrombolysis and Mechanical Thrombectomy

Dr. Secemsky describes the proportions of his patient population that fall into the massive and submassive PE classifications, which require more aggressive pulmonary embolism interventions. He gives an overview of current data over catheter directed thrombolysis and the upcoming HI-PEITHO trial. With mechanical thrombectomy, Dr. Secemsky emphasizes that the current research focuses on the RV/LV ratio at the expense of data over other clinical outcomes, and more data is needed to determine the effectiveness of thrombectomy devices. Dr. Secemsky describes the cases in which he prefers catheter directed thrombolysis versus mechanical thrombectomy.

[Dr. Eric Secemsky]
If we see a lot of proximal clot, saddle embolus, or any PE that's got thrombus, we tend to favor a mechanical thrombectomy. On the other hand, when we see a little more distal clot bilaterally and not as much central clot, we'll move more towards the EKOS catheter. Also, if we think that there is more subacute thrombus, we've felt that the clot retrieval devices haven't been as easy to function when there is a mixed thrombus. So in those situations, we will tend to use EKOS.
[Dr. Sabeen Dhand]
In your current practice, how many patients are going for catheter directed thrombolysis versus this newer mechanical thrombectomy?

[Dr. Eric Secemsky]
There are 600 thousand to a million PEs each year. About 45% of them are going to be massive or submassive PEs, which are the ones that will be hospitalized. Out of those, 5% are going to be massive and need either surgery or systemic lysis for intervention. Then, the leftover 40% are submassive PE. If you look at this specific group, probably about 5%-10% are going to get aggressive therapy at our institution.

Advanced therapies have shown, in clinical practice and in trials, that we can make people feel better and stabilize them hemodynamically or from an oxygenation standpoint, much quicker than systemic anticoagulation therapy alone. However, we haven't proven what happens after hospitalization.

We don't have data to say that upfront clot debulking predicts that the patient would be a more functional person with less dyspnea in six months. The data that we have is six month follow-up data and long term follow-up data from PEITHO, which was studying tPA versus anticoagulation for submassive PE. People who received full-dose tPA had the same echo characteristics as those who received anticoagulants at six months and beyond. Getting upfront clot debulking or systemic lytics didn't predict that you were going to function better long-term.

[Dr. Sabeen Dhand]
It’s a whole different game when you are taking out the clot. You're taking out a physiologic part, versus systemically breaking it up. Do you know of any upcoming data that will help answer that question for us?

[Dr. Eric Secemsky]
The best data will come from HI-PEITHO, a randomized trial sponsored by Boston Scientific and the PERT Consortium. They will randomize people with intermediate high risk PEs to EKOS versus systemic anticoagulation. The primary endpoint at 7 days post-discharge will evaluate for death, deterioration, re-escalation of care, and repeat VT or pulmonary embolus. They're going to have long-term data as well. Hopefully we will get a more contemporary picture of the effects of upfront EKOS.

For mechanical thrombectomy, I don't know of any prospective randomized trial data that are currently public. They are still new and the FDA has given these thrombectomy devices a faster pathway onto approval, which has created issues with us having all the data we need. Most trials are single-arm trials and the primary endpoint is reduction in the RV/LV ratio within 48 hours.

Historically, there is data that said, “An RV/LV ratio greater than 0.9 or 1 predicted 30-day mortality, so let's not worry about 30-day mortality, let's just look at the RV/LV ratio on the CT scan.” In reality, we should have been focusing a little bit more on a hard clinical endpoint because we don't check follow-up RV/LV ratios.

[Dr. Sabeen Dhand]
Is your practice for PE intervention mostly doing lysis right now?

[Dr. Eric Secemsky]
Out of those 40% of patients with submassive PE, we end up taking 5% to 10% of the intermediate high-risk cases. We were doing more EKOS to start, but we now have gotten into thrombectomy because we get pretty quick clinical improvement and we can limit the time in the ICU.

If we see a lot of proximal clot, saddle embolus, or any PE that's got thrombus, we tend to favor a mechanical thrombectomy. On the other hand, when we see a little more distal clot bilaterally and not as much central clot, we'll move towards the EKOS catheter. Also, if we think that there is more subacute thrombus, anecdotally, we've felt that the clot retrieval devices haven't been as easy to function when there is a mixed thrombus. So in those situations, we tend to use EKOS.

The Role of Surgical Embolectomy

Minimally invasive interventions for pulmonary embolism can present patients with more treatment options, but they may not be ideal for all patients. Dr. Secemsky comments on the role of surgical embolectomy in these high-risk cases.

[Dr. Sabeen Dhand]
You've mentioned these patients in shock and you even have devices to treat these patients. Is surgical embolectomy even necessary now?

[Dr. Eric Secemsky]
I don't think it's never going to have a role, but I definitely think that is changing a lot.

There are always situations that require surgical embolectomy, like if they are particularly young, in severe shock, and they have a really central clot. Also sometimes, if there is a clot in transit, particularly if there is a PFO or any type of intra-atrial shunt where the clot can cross over and cause arterial embolism, we'll bring them to the OR. But even treatments for intracardiac clots and clots in transit will change. Inari got approval for clot in transit, and I think that the less that we need to send people for surgery, the better. It's a good time in this space, because we've got a lot of development going on at the same time and they are very complementary.

Podcast Contributors

Dr. Eric Secemsky

Dr. Eric A. Secemsky, MD, MSc, RPVI, FACC, FSCAI, FSVM is the Director of Vascular Intervention and an Interventional Cardiologist within the CardioVascular Institute at Beth Israel Deaconess Medical Center (BIDMC).

Dr. Sabeen Dhand

Host Dr. Sabeen Dhand is a practicing interventional radiologist with PIH Health in Los Angeles.

Cite This Podcast

BackTable, LLC (Producer). (2021, April 12). Ep. 120 – Pulmonary Embolization Interventions & Response Teams [Audio podcast]. Retrieved from https://www.backtable.com/podcasts

Medical Disclaimer

The Materials available on BackTable.com are for informational and educational purposes only and are not a substitute for the professional judgment of a healthcare professional in diagnosing and treating patients. The opinions expressed by participants of the BackTable Podcast belong solely to the participants, and do not necessarily reflect the views of BackTable.