Pulmonary Embolism Interventions

[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 the EKOS catheter 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.

[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 the EKOS catheter.

[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 anticoagulation versus tPA for submassive pulmonary embolisms. People who received full-dose tPA for pulmonary embolisms 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 pulmonary embolism 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.