Introduction

Pulmonary embolism (PE) is a life-threatening condition that occurs when a blood clot originating from another part of the body, most commonly from the deep veins of the legs, obstructs the pulmonary arteries. This leads to dyspnea, pleuritic chest pain, syncope, hemodynamic instability, right ventricular (RV) failure, and, in severe cases, cardiac arrest. The presence of hemodynamic instability is crucial for classifying PE and identifying high-risk PE. Patients with systolic blood pressure less than 90 mmHg for more than 15 min in the absence of hypovolemia, sepsis, or arrhythmia, and those requiring inotropes or vasopressors to maintain hemodynamic stability are considered to have massive or high-risk PE with an increased likelihood of death from obstructive shock [1].

Acute PE has a higher incidence in males compared with females [2] and carries a high mortality rate, causing approximately 100,000 deaths annually in the United States [2, 3]. It is the third leading cause of cardiovascular-related death in the country [4]. Acute massive PE can result in RV failure; therefore, it is crucial for clinicians to identify impending RV strain and shock in patients with PE who develop bradycardia or a new broad complex tachycardia with right bundle branch block [2, 5].

PE can be classified into five risk categories using the PE severity index (PESI) score, which is based on 11 clinical variables that estimate 30-day mortality and guide management. According to this scoring system, patients identified as very low or low risk may be appropriate for outpatient treatment or early discharge with oral anticoagulants [6–9], whereas those at intermediate or high risk can benefit from endovascular therapies in conjunction with medical therapy [10].

In the past, patients with PE were commonly treated with systemic thrombolysis; however, this approach is associated with an increased risk of bleeding [11]. Consequently, endovascular treatment modalities are becoming increasingly popular and are broadly classified into mechanical thrombectomy and catheter-directed thrombolysis (CDT) [12].

One example of CDT is the EkoSonic Endovascular System (EKOS), which treats PE using small catheters placed in the pulmonary arteries through a vein. It delivers ultrasound waves that enhance the binding of tissue plasminogen activator (tPA) to the clot, accelerating thrombolysis. Mechanical thrombectomy devices include the FlowTriever System (Inari Medical), Indigo Thrombectomy System (Penumbra, Inc.), and AngioVac or AlphaVac (Angiodynamics, Inc.) [12].

Our case report and literature review demonstrate the value of escalating management from EKOS to thrombectomy for persistent clot burden following initial thrombolysis, supported by a brief review of published case reports on both modalities.

Timeline

Timeline mentioned in Table 1.

Narrative

A 49-year-old female with class III obesity and a history of recent left ankle surgery three weeks prior presented with acute shortness of breath, palpitations, and a syncopal episode while ambulating. She had been non-weight-bearing in a cast and reported new-onset left lower extremity pain four days earlier, which she initially attributed to cramping from immobility. On examination, the patient was tachycardic, hypotensive, afebrile, and tachypneic. She appeared acutely ill and diaphoretic, with cool, clammy skin, weak peripheral pulses, and delayed capillary refill. Breath sounds were clear bilaterally.

Initial labs were performed. The chest X-ray was unremarkable, and the electrocardiogram (EKG) showed an S₁Q₃T₃ pattern, raising suspicion for PE. Computed tomography angiography (CTA) confirmed a large saddle embolus with extensive bilateral clot burden and right heart strain. After EKOS therapy, a limited echocardiogram showed improved but persistent RV dilation. During her second hospitalization, labs showed pro-BNP 3,554 pg/mL and troponin 30 ng/L. Repeat CTA revealed residual thrombus with right heart strain (RV to left ventricular, RV/LV 1.15) and McConnell’s sign on echocardiography. Her PESI score was 90 points, corresponding to intermediate risk (Class III) and a 30-day mortality risk of 3.2–7.1%, guiding the decision for further intervention.

The patient was initiated on an intravenous heparin bolus followed by continuous infusion. Due to the extensive clot burden and hemodynamic instability, interventional cardiology was consulted, and she underwent CDT (EKOS). Systemic thrombolysis was deferred after shared decision-making because of increased bleeding risk. The patient’s symptoms improved markedly, and her tachycardia resolved shortly after the procedure. She transitioned to oral apixaban (Eliquis) for continued anticoagulation. Follow-up echocardiography demonstrated improved RV function, and she continued to recover with physical therapy support. She was discharged on a three-month course of apixaban and home oxygen (2 L/min) for persistent hypoxia.

During her second hospitalization, intravenous heparin was restarted after imaging confirmed residual thrombus. Following multidisciplinary discussion and informed consent, she underwent INARI mechanical thrombectomy, during which a large thrombus was successfully extracted (Figure 1). Post-procedure, she was monitored in the intensive care unit (ICU), showing rapid clinical improvement with resolution of tachycardia and dyspnea. On day five, she was discharged on apixaban for three months and arranged for outpatient cardiology follow-up.

Display full size

Figure 1. Extracted thrombus burden using INARI thrombectomy during 2nd hospitalization.

After discharge from her second hospitalization, the patient experienced no unanticipated events or complications. She achieved full clinical recovery with complete resolution of her symptoms. On follow-up visits with her primary care physician at one week and two months, she reported no dyspnea, palpitations, or functional limitations and remained hemodynamically stable.

Diagnostics

Initial laboratory values are summarized in Table 2. The chest X-ray was unremarkable. The EKG demonstrated an S₁Q₃T₃ pattern, raising suspicion for PE. CTA confirmed a large saddle PE with extensive clot burden involving the bilateral lobar pulmonary arteries, accompanied by signs of right heart strain, including septal straightening and an elevated RV/LV ratio. Following treatment with CDT (EKOS), a limited echocardiogram performed on day four continued to show evidence of right heart strain but with improved RV size and function, consistent with partial recovery.

During her second hospitalization, pertinent laboratory findings included a pro-BNP of 3,554 pg/mL and troponin of 30 ng/L. Repeat CTA (Figure 2) again revealed persistent thrombus within the segmental and subsegmental pulmonary arteries, with right heart strain evidenced by right atrial and ventricular enlargement and an RV/LV ratio of 1.15. A limited echocardiogram demonstrated McConnell’s sign with dilated right-sided chambers, confirming ongoing right heart strain. Her PESI score was 90 points, corresponding to intermediate risk (Class III) with an estimated 30-day mortality risk of 3.2–7.1%, which guided the decision for further intervention.

Display full size

Figure 2. Persistent pulmonary embolism during 2nd hospitalization, seen on computed tomography angiogram as filling defect (shown by red arrows).

Patient perspective

The patient expressed satisfaction with her care and overall outcome, noting significant improvement in her symptoms.

Discussion

We present 17 case reports on EKOS and 16 case reports on INARI thrombectomy for the removal of clot burden in patients with PE, as part of a comprehensive literature review. This compilation allows for a clearer understanding of the applications of these interventions. By systematically listing indications and outcomes, this review aims to identify patterns in patient selection, efficacy, and safety, thereby assisting in refining clinical decision-making in the management of PE.

In patients who were treated with EKOS, the age ranged from 38 to 86 years, as shown in Table 3. This review highlights the efficacy of EKOS as a treatment modality. The majority of studies demonstrated a decrease or resolution of clot burden, a reduction in RV pressure with improvement in the RV/LV ratio, and subsequent recovery of RV function [13–22]. Das Gupta et al. [17] describe a case series in which EKOS was discontinued in all patients within 24 to 30 hours, and the patients were discharged within 24 hours after undergoing the procedure.

The most common complication of EKOS was bleeding, as seen in case reports published by Ganatra et al. [25] and Lauren Lindsey et al. [20]. EKOS failure was observed in a case report by Tirthani et al. [24], where the patient was subsequently treated with systemic thrombolysis. Lauren Lindsey et al. [20] and Patel et al. [26] shed light on the use of mechanical circulatory support (MCS) via extracorporeal membrane oxygenation (ECMO) for stabilizing and supporting patients hemodynamically.

This review also provides insight into less common causes of PE successfully treated with EKOS. The patient described by Cetingok et al. [15] had a prior COVID infection and subsequently developed PE and superior mesenteric artery thrombosis about two months later, highlighting a post COVID thrombotic state as the likely culprit. Khan and Besis [23] documented a case of PE treated with EKOS in a patient with JAK2 kinase positivity, while Rahman et al. [16] reported a case involving a patient with Prader-Willi syndrome. According to the latter, there is a higher prevalence of PE in patients with Prader-Willi syndrome.

The patients treated with INARI had an age range from 32 to 88 years, as shown in Table 4. The majority of cases demonstrated a reduction in pulmonary arterial pressure, improvement in RV function, and resolution of clot burden following the procedure, highlighting the efficacy of INARI as a treatment modality [26–38]. None of the studies reported procedural failure.

This review also highlights the use of different types of MCS with INARI. MCS support with ECMO was utilized in the case reports provided by Patel et al. [26], Stadler et al. [34], Pham et al. [36], and Mahmudlu et al. [38], whereas Agarwal et al. [31] described a case in which MCS was established using the Impella device.

Several rare and unique cases were also reported. Jones et al. [30] described a distinctive case where a suspected clot within the pulmonary vasculature was later identified as a fibroelastoma. Saricilar et al. [33] reported a patient who developed fat embolism during right hip arthroplasty, in whom CT pulmonary angiography demonstrated multiple fat attenuation filling defects. Pham et al. [36] described a case in which tPA was injected into the right pulmonary artery because the clot size was too large to be aspirated. Stadler et al. [34] described the first reported case of PE with acute heart failure treated with INARI outside the United States.

Conclusions

This case highlights the importance of individualized escalation in PE management when initial thrombolysis fails. Suction thrombectomy can provide rapid hemodynamic improvement and RV recovery. Equally crucial is post-procedure imaging to confirm clot resolution, assess RV function, and guide anticoagulation and follow-up strategies for optimal long-term outcomes.