Retrieve to Relieve: Novel Percutaneous Thrombectomy Device in Select Patients With Pulmonary Embolism

We describe two cases of submassive pulmonary embolism (PE) managed with percutaneous thrombectomy with the novel FlowTriever Retrieval/Aspiration system (Inari Medical). These cases illustrate catheter-directed mechanical thrombectomy for pulmonary embolism, and highlight potential advantages over protocols that require fibrinolytic agents.

In-hospital mortality among those admitted with the primary diagnosis of PE has been estimated between 8 and 10%.¹ In addition to anticoagulation, catheter-based therapies for pulmonary embolism have been established to expedite thrombus resolution and in part to mitigate complications observed with systemic fibrinolysis.² Among these, ultrasound-assisted fibrinolysis (EKOS) has emerged as an acceptable alternative among patients with submassive PE.³ Other studies have suggested that thrombus fragmentation and aspiration may help stabilize patients with massive PE, especially when fibrinolysis is contraindicated or ineffective.⁴ Although there are no commercially available and approved devices for thrombus aspiration in the specific setting of PE, a novel thrombectomy system has been developed. 

The FlowTriever Retrieval/Aspiration system has FDA 510(k) approval for removal of emboli and thrombi from blood vessels. It is a catheter-based mechanical thrombectomy device for percutaneous endovascular retrieval of emboli from the peripheral vasculature and is intended for use in the proximal pulmonary arterial system. It requires a 20 French (Fr) venous sheath and consists of 3 parts: (1) the flow restoration catheter, which is made up of 3 self-expanding nitinol disks; (2) the aspiration guide catheter; and (3) the retraction aspirator device. The FlowTriever device is advanced over an .035-inch guidewire (e.g. Amplatz Super Stiff or Rosen wire) and into the thrombus, where the expandable disks are deployed using a pin and pull method. The disks and disrupted thrombus are then retracted and removed through the aspiration catheter. We present 2 cases of successful mechanical thrombectomy, one with clinical deterioration after fibrinolysis, and another in the setting of contraindications to fibrinolysis.

Case 1

A 47-year-old male with a past medical history of bronchiolitis obliterans organizing pneumonia (on 2L oxygen at home) presented with acute onset of shortness of breath. A computed tomography (CT) scan demonstrated bilateral PE and evidence of right ventricular enlargement (Figure 1). He was initially treated with ultrasound-assisted fibrinolysis (EKOS); however, his dyspnea persisted and repeat CT showed significant residual thrombus (Figure 2A-B). A multidisciplinary discussion ensued, and percutaneous thrombectomy was offered. The FlowTriever Retrieval/Aspiration system (Figure 3A-B) was advanced into the main pulmonary arteries, and two aspiration runs were performed in each, with the explant of rather organized thrombus (Figure 4A-C). Final angiography showed a reduction in thrombus burden (Figure 5A-B) and the patient’s clinical status improved (he was weaned from 4L of oxygen to baseline of 2L). He was later discharged in stable condition to home. 

Case 2

A 59-year-old woman with remote breast cancer presented with syncope referable to a massive, saddle PE. Her fall was complicated by a subdural hematoma, and accordingly, she was deemed a poor candidate for fibrinolysis or surgical embolectomy. Low doses of norepinephrine were required to maintain a systolic blood pressure >90 mm Hg. An echocardiogram revealed moderate to severe right ventricular dilation and moderate to severe right ventricular dysfunction with echocardiographic McConnell’s sign (Figure 6). Labs showed elevated Troponin I and brain natriuretic peptide (0.22 ng/ml, and 221 pg/ml, respectively). With continued pressor dependence, we elected to offer percutaneous thrombectomy. The FlowTriever Retrieval/Aspiration system was advanced into the right and left pulmonary arteries, and two runs were performed in each vessel. Immediately after thrombus extraction, systemic blood pressure improved, and her pulmonary artery pressures nearly normalized (pre-intervention 56/21 mm Hg, post-intervention 30/15 mm Hg). Within 3 hours, her oxygen requirement improved (12 L/min to 3 L/min), and vasopressors were discontinued.

Discussion

With the recent availability of device-based therapies to alleviate thrombotic burden, many institutions have established multidisciplinary teams for the triage of patients with pulmonary embolism.^5,6 Randomized clinical trials have established more rapid clinical improvement with catheter-assisted thrombolysis, and one device has been FDA approved for this purpose.⁷ More recently, the FlowTriever has received FDA 510(k) clearance for use in the pulmonary arteries, and a clinical trial has been initiated to evaluate safety and efficacy in patients with submassive pulmonary embolism.⁸ 

The cases presented herein illustrate thrombus extraction and clinical improvement in a submassive and massive pulmonary embolism. Each of these cases represents distinct situations where the utilization of thrombectomy, rather than fibrinolysis, was preferred. These cases demostrate that the FlowTriever Retrieval/Aspiration system can be utilized for thrombus reduction in cases of pulmonary embolism after failure of fibrinolysis or when fibrinolysis is contraindicated. It may also be useful for individuals that are high risk for surgical embolectomy.⁹ Whether or not the FlowTriever device is effective in place of catheter-directed thrombolysis will be partly addressed by the forthcoming FlowTriever Pulmonary Embolectomy Clinical Study (FLARE).

References

1. De Miguel-Diez J, Jiménez-Garcia R, Jiménez D, et al. Trends in hospital admissions for pulmonary embolism in Spain from 2002 to 2011. Eur Respir J. 2014; 44: 942-950.
2. Fuller TJ, Paprzycki CM, Zubair MH, Hussain LR, Kuhn BA, Recht MH, Muck PE. Initial experiences with endovascular management of submassive pulmonary embolism: is it safe? Ann Vasc Surg. 2016 Sep 22. pii: S0890-5096(16)30815-9.
3. Jaber WA, Fong PP, Weisz G, Lattouf O, Jenkins J, Rosenfield K, Rab T, Ramee S. Acute pulmonary embolism: with an emphasis on an interventional approach. J Am Coll Cardiol. 2016 Mar 1; 67(8): 991-1002.
4. Provias T, Dudzinski DM, Jaff MR, et al. The Massachusetts General Hospital Pulmonary Embolism Response Team (MGH PERT): creation of a multidisciplinary program to improve care of patients with massive and submassive pulmonary embolism. Hosp Pract (1995). 2014; 42: 31-37.
5. Kabrhel C, Jaff MR, Channick RN, et al. A multidisciplinary pulmonary embolism response team. Chest. 2013; 144: 1738-1739.
6. Keller K, Beule J, Balzer JO, Dippold W. Syncope and collapse in acute pulmonary embolism. Am J Emerg Med. 2016 Jul; 34(7): 1251-1257.
7. Piazza G, Hohlfelder B, Jaff MR, et al. A prospective, single-arm, multicenter trial of ultrasound-facilitated, catheter-directed, low-dose fibrinolysis for acute massive and submassive pulmonary embolism: the SEATTLE II Study. JACC Cardiovasc Interv. 2015; 8: 1382-1392. 
8. FLARE trial (ClinicalTrials.gov ID: NCT02692586)
9. Donaldson CW, Baker JN, Narayan RL, et al. Thrombectomy using suction filtration and veno-venous bypass: single center experience with a novel device. Catheter Cardiovasc Interv. 2015; 86: E81-E87.

Disclosures: The authors report no conflicts of interest regarding the content herein.

The authors can be contacted via Scott M. Lilly, MD, PhD, Assistant Professor at The Ohio State University Wexner Medical Center/Division of Cardiovascular Medicine and Interventional Cardiology. Phone: (614) 293-4967. Email: Scott.Lilly@osumc.edu