CTV07 - Inari Mechanical Aspiration Thrombectomy in Non-Massive PulmonaryEmbolism: A Case Study

Introduction/Purpose:
Pulmonary embolism (PE) is the third most common cause of cardiovascular mortality. It is estimated that there are 300,000 to 600,000 Americans affected by a venous thromboembolism each year, one-third of which will present with a PE (1,2). The widely accepted classifications subdivide pulmonary embolism into massive, sub-massive and low risk pulmonary embolism. A massive PE is defined as a suspected or confirmed PE with hemodynamic instability causing obstructive shock. A sub-massive PE is defined as a suspected or confirmed PE without shock but with evidence of right ventricular dysfunction, or with borderline hypotension responsive to fluids (3). For hemodynamically compensated patients with no contraindications to anticoagulation, immediate anticoagulation is indicated. For patients with massive PE thrombolysis use is preferred.



Treatment of sub-massive pulmonary embolism still represents a challenge for clinicians. One of the newer options is the FlowTriever device by Inari Medical which allows for rapid retrieval of the embolus without the use of thrombolytics. Our case demonstrates successful use of the FlowTriever on the third day of hospitalization in a symptomatic patient.

Methods or Case Description:
A 38-year-old female presented to the emergency department with a complaint of sudden onset sharp pain in the right upper abdominal quadrant and flank since the previous night. The patient reported the pain radiated to the right scapular region and was worse with deep respiration. She was noted to be obese with BMI of 31.9. Medications the patient was on at the time of presentation included OCPs and vitamins. Social history included social alcohol use with current quarter pack-per-day tobacco use. Patient had cholecystectomy 2 years prior, and subsequent ERCP with sphincterotomy due to retained stones. Due to the significant history as well as acute presentation, the patient underwent CT of abdomen and pelvis to rule out an acute intra-abdominal process. While the imaging did not show any acute process of the abdomen, it did demonstrate bilateral pulmonary emboli in the inferior portions of lung vasculature.



Dedicated CT angiography of the chest revealed a saddle pulmonary embolus bridging the main pulmonary arteries, with additional significant emboli extending into the bilateral lower lobes. The radiology report indicated presence of right ventricular strain. A high sensitivity troponin and brain-natriuretic peptide were obtained, both within normal limits. The patient was started on a continuous heparin drip, pain control, and had bilateral venous duplex ultrasound which showed deep vein thrombosis in the left gastrocnemius vein, with no DVT in other veins. A transthoracic echocardiogram demonstrated normal right ventricular size and function, suggesting that the saddle embolus was not compromising the patient hemodynamically.



Early the next morning, the patient reported worsening of pain and dyspnea. The patient was placed on 3L of oxygen by nasal cannula which brought the saturation up to 98%. Additional clot burden was presumed, and CT imaging incidentally showed development of large right pleural effusion.



Consultation by interventional cardiology was done and the patient refused any intervention, stating she would reconsider if she continued to have significant symptoms the following day.







Figures 1A-D: Depict the CT Angiogram imaging of the patient’s pulmonary vessels and the large saddle embolus within. (A-C). Image D shows the right ventricle from the same CTA study.


On the second day of admission, the patient’s significant pleuritic pain persisted but she continued to defer any surgical intervention despite extensive discussion with her medical team. Throughout the day the patient’s pain progressed in severity, and she developed worsening dyspnea on exertion, limiting ability to ambulate and needed an elevated O2 requirement. The patient received opioids for pleuritic chest pain and after further discussion with the medical team that evening, and review of treatment options, the patient ultimately agreed to undergo catheter-based treatment the following day. The patient underwent transcatheterremoval of the pulmonary embolus via INARI FlowTriever on her third day of admission. Findings during the procedure demonstrated pulmonary hypertension due to clot burden. The clot was successfully removed and there were no complications during the procedure. The following day the patient was ambulating pain-free, without supplemental oxygen, and was able to be taken off IV pain control entirely within 12 hours of the procedure. She was then switched to oral anticoagulation and discharged.








Figure 2A and 2B (left and right, respectively): Demonstration of before and after images of the patient’s saddle embolus of the right lung, shown prominently against the contrast during inari thrombectomy. Pronounced filling defect is easily visualized, and greatly reduced immediately after clot removal.




Outcomes:
Pulmonary emboli are a common and potentially life-threatening issue that occur in patients of all ages. If untreated the mortality rate is estimated to be as high as 30%, while diagnosis and treatment bring that number down closer to 8% (4). Implementation of pulmonary embolism response teams (PERT) have shown improvement in our management of pulmonary emboli in the hospital. (5,6) However, the guidelines for management of sub-massive pulmonary embolism are still not well defined. (7,8,9) There have been studies that recommend using low dose thrombolytic therapy in patients with sub-massive PE such as the MOPETT study. This study showed immediate reduction of pulmonary hypertension with use of low dose thrombolytics and anticoagulation in comparison to anticoagulation alone. But, despite the positive results there was no significant difference in rate of individual outcomes of death or recurrent PE. (10) A similar study was conducted in which fibrinolytic therapy with Tenecteplase, and heparin was compared to heparin and placebo in patients with sub-massive PE. The study showed that while, use of fibrinolytics prevented hemodynamic compensation, it did so with a six-fold increase in risk of major hemorrhage and stroke (11). The results of these 2 trials are just a few examples of the reason that thrombolysis is not the standard of care for sub-massive PE. Thrombolysis comes with significant limitations, with intracranial hemorrhage being the most significant.





Newer options for treatment of pulmonary embolism are catheter-based therapies. The Inari FlowTriever is a device created to remove clots through mechanical aspiration by deploying ninitol discs to capture the thrombus. The clot removal via this process has already shown promising results in terms of its safety and efficacy. (5,12,13,14,15) Our case supports the assertion that even in a patient that has no contraindications to thrombolytic therapy, it may be efficacious in a hemodynamically stable patient with right-heart strain to have a mechanical thrombectomy rather than thrombolytic therapy. Given the advances in technology, and many new catheter-based devices, it could be time to review and expand the current indications for mechanical clot retrieval (16,17).



Most cases of PE do not warrant catheter based chemical or mechanical therapy in hemodynamically stable patients, with some exceptions: patients with a large clot burden, right ventricular strain despite normal heart rate or blood pressure or decreasing oxygen. (18,19,20) For many large clots or more distal emboli, systemic or catheter directed thrombolysis will likely remain superior. (18,21). In our patient, studies were indicative of proximal clot location and RV strain based on CT criteria. Increasing right-sided chest pain and dyspnea along with development of pleural effusion, indicated considerable clot burden. Prior to the procedure, our patient was requiring IV opioids in addition to an oral opioid regimen. Her pain and dyspnea remained significant despite continuous anticoagulation. Our patient required an average of 57.3mg/day of IV morphine equivalents, as calculated using standard conversions of the PO oxycodone, IV morphine, and IV Dilaudid she received over the first 72 hours leading up to the procedure. Following the procedure, the patient had her last dose of IV pain medication within 12 hours and was able to tolerate walking >150ft on a purely PO pain regimen, without complaints of pain. Her calculated average opioid use following procedure was 24mg/day of IV morphine equivalents, which only consisted of 1mg total IV Dilaudid, and with the rest being PO oxycodone. These findings indicate over 56% reduction in opioid use, and marked increase in functional status, within 24 hours of procedure.



Percutaneous mechanical thrombectomy with the Inari FlowTriever has shown to be safe and effective for patients with submassive PE with significant improvement of symptoms and RV function as well as absence of the complications associated with thrombolytic therapy. The procedure also was shown to reduce ICU stay for the patient, as well as hospital stay (12).Mechanical thrombectomy numbers as a percentage of total treatment cases have been increasing over the past 20 years, and the data show promising results for their safety and efficacy. (6, 22)

Conclusion:
Our case demonstrates that for- submassive PE with more proximal clot location, use of Inari FlowTriever can be beneficial. The benefits we were able to document included pain reduction, decreased oxygen demand, increased ambulation, and decreased hospital stay. Moreover, to the best of our knowledge this is the first case showing additional benefit of Inari FlowTriever thrombectomy despite of three days continuous anticoagulation treatment. In patient with submassive pulmonary embolism who remain symptomatic and hypoxic, Inari FlowTriever thrombectomy may be beneficial even later in the course of treatment.