Acute Treatment of a Saddle Embolism With the EKOS Catheter When Systemic Lysis is Contraindicated

An acute pulmonary embolism (PE) is on the differential diagnosis for syncope, particularly in individuals with underlying malignancy. Many physicians dichotomize treatment of a PE into those with massive embolic burden that require systemic thrombolytics¹ or those with non massive emboli who are given systemic anticoagulation. However, each treatment has its limitations. Thrombolysis has many exclusion criteria, due to the risk of major bleeding, which frequently limits its use. Conversely, anticoagulation has high rates of treatment failure, resulting in persistent dyspnea, right ventricular dysfunction and chronic thrombo-embolic pulmonary hypertension (CTEPH). However, there have been technological advancements that provide alternative therapeutic options, including the EkoSonic (EKOS) endovascular catheter, which is an FDA-approved device for submassive PE. It provides a more rapid, directed lysis of thrombus than traditional means while limiting the risks of major bleeding.² 

 

We present a case where the EKOS catheter is utilized in the acute setting for an individual with a contraindication for systemic thrombolysis. Use of the catheter resulted in rapid clinical improvement and resolution of right ventricular (RV) failure. Similar to advancements in the treatment of acute myocardial infarction, we believe that treatment of acute pulmonary emboli is likely to trend towards catheter-directed therapies that limit systemic side effects.

 

 

This patient is a 37-year-old male with a history of metastatic colon cancer. He presented to an outlying hospital following a syncopal event while at work. There was a brief period of palpitations and dyspnea before finally losing consciousness while ambulating. He was found to be in atrial fibrillation with rapid ventricular response, and given his history of malignancy, a computed tomography (CT) chest angiogram was performed. Angiography revealed the presence of large emboli in both main pulmonary arteries, and the patient was transferred to Medical City of Fort Worth for a higher level of care.

 

His arrhythmia had converted to sinus rhythm following administration of a calcium channel blocker, but he still had signs of accessory muscle use while on supplemental oxygen via facemask. Blood pressure was acceptable at 129/74 and an urgent echo revealed severe right ventricular (RV) hypokinesis and dilation (Figures 1-2). Conventional guidelines require the presence of hypotension, defined as either systolic blood pressure (SBP) <90 mmHg or a drop in SBP >40 mmHg from baseline, to diagnose an individual with a massive embolism. This is the strongest recommendation for administration of thrombolytics. Although our patient did not meet these criteria, his presenting symptom of syncope suggested he was at high risk for decompensation and therefore, we pursued more urgent reperfusion therapy. A head CT was performed that revealed the presence of brain metastasis and this excluded him from receiving intravenous tPA. An interventional radiology consultation was requested, and within 12 hours of symptom onset, directed thrombolytic infusion with ultrasonic enhancement using the EKOS catheter was performed (Figure 3).

 

Over the next 12 hours, low-dose tPA was infused directly into the thrombus in both pulmonary arteries. A rapid improvement in symptoms and oxygen requirements was noted over the course of two days. The patient was no longer dependent on oxygen and a repeat echocardiogram showed resolution of RV failure (Figure 4). Within four days of presentation, the patient was discharged in his baseline state of health without any major bleeding issues.

 

 

Massive and submassive pulmonary emboli are life-threatening entities that only differ due to the presence of hypotension. Although the strength of recommendation is weaker for submassive PE, both diagnoses have indications for administering thrombolytics due to the high risk of adverse outcome. Our patient exhibited signs that he required acute therapy, but he had a strict contraindication for systemic lysis due to his intracranial metastasis. Many similar patients may receive systemic anticoagulation which may take weeks to improve symptoms and is often associated with high rates of treatment failure. Some studies suggest that as many 35% of individuals with significant pulmonary emboli have residual RV dysfunction after 6 months of therapy.³ This has a significant effect on long-term morbidity and mortality, and many hospitals have developed PE response teams and PE protocols to help facilitate the speed at which diagnosis and treatment decision are made.

 

With advancements in technology, more studies are being done to evaluate the efficacy of new therapeutic options. The SEATTLE II trial treated individuals with massive or submassive PE using ultrasound-facilitated, catheter-directed, low-dose fibrinolysis via the EKOS catheter and found that this was effective in reducing pulmonary hypertension while minimizing intracranial bleeding.⁴ After the safety of this method was proven, the ULTIMA trial compared individuals receiving catheter-directed therapy to systemic anticoagulation. The EKOS catheter was found to be superior to heparin alone in regards to resolution of RV dysfunction without increasing bleeding complications.² A similar benefit was also demonstrated by our patient, as localized fibrinolytic therapy was successful in reducing embolic burden, demonstrated on serial echocardiography. More importantly, this aggressive treatment was administered with any adverse outcomes despite his high risk of intracranial bleeding.

 

Currently, there are multiple types of catheters for the treatment of PE, but head-to-head comparisons are limited and only small, retrospective studies exist. Lin et al evaluated 33 patients with massive PE who received either ultrasound-enhanced lysis with the EKOS catheter or traditional catheter-directed lysis. Those who underwent low-dose, catheter-directed thrombolysis had a similar treatment efficacy but lower treatment-related complications.⁵ Another study by Parikh et al showed lower rates of bleeding and higher rates of thrombus when compared with national standards in the setting of deep vein thrombosis (DVT).⁶ However, standardization in technique and timing of the intervention still needs to be investigated further.

 

In acute myocardial infarction (MI), research has shown that catheter-directed therapy is associated with improved outcomes and less risk of adverse events when compared to systemic thrombolysis. In this clinical scenario, we describe an individual with submassive pulmonary emboli and an absolute contraindication to thrombolytics. We opted to pursue aggressive localized therapy to best improve his outcome. This was effective not only as demonstrated by his clinical improvement, but also in a dramatically reduced length of stay. As compared to treatment of acute MI,  treatment of PE holds the same potential for higher benefit and lower systemic risk, and we believe that in the future, catheter-directed therapy will become the treatment of choice for acute pulmonary embolism. 

 

 

The authors can be contacted via Dr. Mark Chou at markjchou@icloud.com, or at:

Belemo Ekpete, DO, bekepete@atsu.com
Senthil Thambidorai, MD, senthil.thambidorai@medicalcityhealth.com
Iyamu Ikponmwosa, MD, iiyamu@radntx.com
Ranjit Nair, MD, yranjity@gmail.com