Safety and efficacy of percutaneous mechanical thrombectomy in the treatment of acute medium- or high-risk pulmonary embolism: a single-center retrospective cross-sectional study

Introduction

According to literature, pulmonary embolism is one of the important causes of death from cardiovascular diseases, especially in hospitalized patients (1-3). According to the severity of the disease, pulmonary embolism can be classified into low-, medium-, and high-risk, with low-risk patients generally being treated with anticoagulation monotherapy (4-6). Numerous studies have reported fatal outcomes in high-risk patients within the first few hours, with mortality rates as high as 60% (2,3,7). Patients with acute intermediate-risk pulmonary embolism may have relatively mild symptoms at onset, but mortality rates as high as 15% to 20% within a month have been reported (8,9). These medium- and high-risk patients lead to pulmonary hypertension and right-sided heart failure.

We know that anticoagulation remains the cornerstone of pulmonary embolism treatment, but it is also important to reduce the pulmonary thromboembolic burden as early as possible for acute and high-risk pulmonary embolism. Current guidelines recommend that in addition to anticoagulant therapy, other methods such as systemic thrombolysis and surgical thrombectomy can also be used for medium- and high-risk pulmonary embolism (10,11). However, in the real world, thrombolytic therapy is contraindicated for some patients with medium- or high-risk pulmonary embolism because these patients have a history of trauma, operation, or long-term bed rest with cerebral infarction or cerebral hemorrhage. Moreover, surgical thrombectomy can only be performed in a few tertiary hospitals. Percutaneous mechanical thrombectomy (PMT) effectively enhances pulmonary flow by modifying emboli or thrombi. It is particularly valuable in situations where fibrinolysis is contraindicated and surgical embolectomy is not a viable option. PMT has demonstrated excellent results in patients with peripheral venous thrombosis and has been applied in patients with acute pulmonary embolism.

This cross-sectional study analyzed the curative effect of PMT in patients with acute intermediate-to-high-risk pulmonary embolism admitted to Taizhou Hospital of Zhejiang Province over the past 4 years and examined the 1-year postoperative follow-up and changes in preoperative and postoperative test indices. The aim of this study was to evaluate the safety and efficacy of PMT in patients with acute intermediate-to-high-risk pulmonary embolism and thus provide a clinical basis for treating these patients. We present this article in accordance with the STROBE reporting checklist (available at https://jtd.amegroups.com/article/view/10.21037/jtd-24-1690/rc).

Methods

Study design

The clinical data of patients who underwent PMT in Taizhou Hospital of Zhejiang Province from May 2018 to May 2023 due to acute medium- or high-risk pulmonary embolism were retrospectively analyzed. Patients were treated using a percutaneous aspiration device if they fulfilled all of the following criteria: (I) dyspnea, hypoxia, or hemodynamic instability; (II) evidence of pulmonary embolism by multidetector contrast-enhanced computed tomography (CT); and (III) right ventricular dysfunction by echocardiography or right-to-left ventricular dimension ratio >0.9 by CT. A total of 43 patients were enrolled, including 50 patients with high-risk pulmonary embolism and 28 patients with medium-risk pulmonary embolism. The basic data are shown in Table 1. All patients underwent primary PMT. Blood tests, vital signs, and cardiac ultrasound parameters within 48 hours before operation were compared with those within 48 hours after operation, and the incidence of perioperative complications was recorded. Telephone follow-up was performed 1 and 6 months after discharge, and outpatient follow-up was performed 12 months after discharge. The improvement of related symptoms, the reexamination of cardiac echocardiography, and the occurrence of recurrent pulmonary embolism and death were recorded. We analyzed the changes of vital signs and test indicators of patients after PMT, which included oxygen saturation, pulse, mean arterial pressure, hemoglobin, lactic acid, etc. Additionally, we followed up on patients three times, with telephone follow-up at 1 and 6 months after operation and a follow-up visit at 12 months after operation, to evaluate the overall recovery of patients.

The study was conducted in accordance with the Declaration of Helsinki (as revised in 2013). This study was approved by the ethics committee of Taizhou Hospital of Zhejiang Province (No. 2022-11-22-01). Informed consent was taken from all the patients.

Indications for operation

All patients were diagnosed with acute pulmonary embolism according to their medical history and pulmonary computed tomography angiography (CTA) before operation. According to the data related to preoperative cardiac ultrasound and vital sign monitoring, the patients were confirmed to have intermediate-to-high-risk pulmonary embolism. Furthermore, we received patients’ agreement to undergo PMT after repeated communication with them or their family members before the operation. All the procedures were done by our vascular surgery team.

Surgery procedure

All hospitalized patients or patients in the emergency department who were suspected of having acute pulmonary embolism were immediately diagnosed with pulmonary CTA. Additionally, necessary life support treatment and even extracorporeal membrane oxygenation were administered according to the patient’s vital signs, and emergency surgery was performed immediately after informed consent was obtained from the patient. Without special circumstances, 5-F vascular sheath (Terumo, Tokyo, Japan) was placed via a right femoral vein puncture approach. If patients had peripheral venous thrombosis before surgery, an inferior vena cava filter (Lifetech Scientific, Shenzhen, China) was first implanted. An 8-F, 700 cm-long Fustar vascular sheath was substituted, and a 5-F pigtail catheter (Terumo) with a loach guide wire (Cordis, Miami Lakes, FL, USA) was passed through the femoral vein puncture site, inferior vena cava, right atrium, and right ventricle to the main pulmonary artery. Angiography was performed again to confirm the diagnosis (Figure 1). In some patients, a pigtail catheter was used to rotate at the embolization site in order to achieve thrombus fragmentation, and a 6-F multipurpose angiographic (MPA) catheter was used to manually aspirate the thrombus. In some patients, an Amplatz super stiff wire (Boston Scientific, Marlborough, MA, USA) was exchanged after the pig tail catheter angiography was confirmed. An AngioJet (Boston Scientific) or AcoStream (Acotec, Beijing, China) thrombus aspiration catheter device was introduced to the thromboembolic site for thrombus aspiration (Figure 2), and the number of aspirations was generally not more than three. Some patients were administered local thrombolytic therapy with varying doses of urokinase from 100,000 to 300,000 U according to the risk of bleeding. Another angiography scan was performed 10 minutes later to confirm the presence or absence of blood flow at the distal end of the corresponding main pulmonary artery. The vital signs of the patients were observed during the period. After surgery, patients were returned to the general ward or intensive care unit for further treatment according to their condition.

Figure 1 Mark the location of the embolization seen by angiography. Arrows are used to mark the location of thromboembolism.

Figure 2 Mark the location of the suction catheter. Arrow is used to mark the position of the suction tube.

Follow-up

All patients were followed up by telephone at 1 month and 6 months after discharge (Figure 3). The patients were mainly asked whether they had a cough, chest tightness, or other symptoms. After 12 months, the patients attended the hospital for follow-up and reexamination of cardiac ultrasound, and changes in cardiac function were observed.

Figure 3 CTA results of follow up one month after surgery. The thrombus disappeared at the original embolic site. Arrows are used to mark the removal of thrombus at the site of preoperative embolization. CTA, computed tomography angiography.

Endpoints events and definitions

Endpoints events were defined as death from pulmonary embolism or recurrent pulmonary embolism during the perioperative period and 12-month follow-up. According to the American College of Chest Physicians (ACCP) criteria, high-risk pulmonary embolism is defined as cardiogenic shock or hypotension excluding other causes, which has poor systemic attention or the need for a vasopressor to maintain blood pressure. When patients need vasopressor, the systolic blood pressure is less than 90 mmHg for more than 15 minutes or drops more than 40 mmHg. Medium-risk pulmonary embolism is also known as “submassive pulmonary embolism”. Blood pressure is usually in the normal range, but right-sided heart insufficiency or myocardial damage may occur in submassive pulmonary embolism. Therefore, we included submassive pulmonary embolism in the treatment group. Successful surgery was defined as patency of blood flow in at least two lobes on pulmonary angiography before the end of surgery, improvement of vital signs within 48 hours after surgery, and a lack of need for a vasopressor to maintain blood pressure.

Statistical analysis

SPSS 19 (IBM Corp., Armonk, NY, USA) was used for statistical analysis. All quantitative data with a normal distribution are expressed as the mean ± standard deviation (SD), data with a nonnormal distribution are expressed as the median and interquartile range (IQR), and dichotomous variables are expressed as percentages. A paired sample t-test was used for comparison of means. A P value <0.05 was considered statistically significant.

Results

A total of 43 patients with a mean age of 62.51±15.54 years and a mean hospital length of stay of 9.98±8.08 days were included in this study. Among these patients, 23 cases were male (53.5%) and 20 cases were female (46.5%). In terms of basic diseases, 21 cases were complicated with hypertension (48.8%), eight cases were complicated with diabetes (18.6%) and 3 cases were complicated with chronic obstructive pulmonary disorder (7.0%). There were 38 cases of peripheral deep vein thrombosis, 18 cases of peripheral thrombosis, and 20 cases of mixed type; in another five cases, deep vein thrombosis of the lower extremity was not found by B-ultrasound before operation, one case experienced pulmonary embolism after sclerotherapy of superficial vein flexure in other hospital, and one case experienced pulmonary embolism after vertebroplasty using bone cement. In terms of bleeding risk, 38 patients were assessed as having different degrees of bleeding risk according to the venous thromboembolism risk assessment table of inpatients in Taizhou Hospital of Zhejiang Province, and five patients had no bleeding risk. Of these five patients, two were young patients in their 20s with pulmonary embolism secondary to unexplained deep vein thrombosis of the lower extremities. In terms of treatment options, 38 cases of patients underwent inferior vena cava filter implantation, and five patients without peripheral venous thrombosis did not receive inferior vena cava filter implantation. Only one patient refused to undergo inferior vena cava filter implantation. All patients used different thrombus removal devices. Twenty-two were treated by thrombus fragmentation via a pigtail catheter and aspiration with a 6-F MPA catheter, 11 cases were treated with the AngioJet thrombus aspiration catheter device, and 10 cases were treated with the AcoStream thrombus aspiration catheter device. All patients were treated with low molecular weight heparin anticoagulation before surgery. After discharge, 40 patients were treated with rivaroxaban for continued anticoagulation, and three patients were treated with warfarin (Table 1).

All the 41 patients achieved technical success. Blood tests, vital signs, and cardiac ultrasound from 48 hours before operation were compared with those from 48 hours after operation; blood tests showed significant differences between these time points in terms of hemoglobin level (mean ± SD: 130.05±17.29 vs. 119.47±18.62 g/L; P=0.008), oxygen partial pressure {median [IQR]: 73 [66, 77] vs. 90 [87.5, 92] mmHg; P<0.001}, and lactate level of mmol/L {median [IQR]: 1.8 [1.2, 2.6] vs. 1.1 [0.9, 1.3] mmHg; P<0.001}. There were no significant differences in the partial pressure of carbon dioxide or creatinine levels. In terms of vital signs, there were significant differences in preoperative and postoperative oxygen saturation {median [IQR]: 92% [90.5%, 94%] vs. 97% [96%, 98%]; P<0.001}, pulse {median [IQR]: 106 [87, 114] vs. 87 [81, 96.5] bpm; P=0.003}, mean arterial pressure (mean ± SD: 91.14±15.36 vs. 112.95±10.68 mmHg; P<0.001), and cardiac index {median [IQR]: 2 [1.9, 2.2] vs. 2.6 [2.4, 2.7]; P<0.001}. Finally, there were significant differences in the echocardiography measures of peak arterial pressure (PAP) {median [IQR]: 66 [58.0, 70.5] vs. 42 [39.5, 44.0] mmHg; P<0.001} and right atrial diameter (mean ± SD: 44.91±3.10 vs. 39.44±2.87 mm; P<0.001) (Figure 4).

Figure 4 Trend chart of clinical indicators before and after thrombectomy. Hb, hemoglobin (g/L); PO₂, partial pressure of oxygen (mmHg); SaO₂, oxygen saturation (%); PCO₂, partial pressure of carbon dioxide (mmHg); CREA, creatinine (µmol/L); Lac, lactate (mmol/L); CI, cardiac index (min·m²); MAP, mean arterial pressure (mmHg); PAP, pulmonary arterial pressure (mmHg); RCD, right chamber diameter (mm).

In terms of surgery-related complications, no serious adverse events such as surgery-related major bleeding, infection, or intraoperative heart rupture occurred in any of the 43 patients in this study. Among the patients, seven patients had local hematoma at the puncture site after operation, and three patients had local infection at the puncture site, all of whom improved after treatment. Moreover, nine patients had transient arrhythmia during operation, which manifest as cardiac arrest, and the operation was suspended, with the heartbeat being restored immediately. AngioJet catheters were used in seven of the nine patients, and pigtail catheters combined with 6-F MPA catheters and AcoStream catheters were used in one patient. In addition, one patient developed systemic sepsis after surgery, but this patient had received extracorporeal membrane oxygenation support treatment before surgery due to his serious condition. One patient abandoned treatment and died after discharge due to his older age and aggravated pulmonary infection during hospitalization.

During the follow-up period, two patients developed post-activity chest tightness after automatic withdrawal of anticoagulant drugs 6 months later. Outpatient pulmonary CTA showed that pulmonary thrombosis was worse than that during postoperative angiography, and pulmonary embolism recurrence was considered, but the patient was not further hospitalized. The other 21 patients were followed up at 1, 6, and 12 months. Five patients still had chest tightness and discomfort after activity, the other patients were normal, and the cardiac indicators also improved significantly (Figure 5).

Figure 5 Clinical status of postoperative follow up. PE, pulmonary embolism.

Discussion

In recent years, acute medium-to-high risk pulmonary embolism has been a considerable concern due to its high mortality (10). We conducted a single-center retrospective study with a small sample size, but the results are reassuring, demonstrating the moderate efficacy and safety of PMT in patients with acute or high-risk pulmonary embolism. We know that anticoagulation is the cornerstone of treatment in pulmonary embolism, but for patients with medium-to-high-risk pulmonary embolism, especially those with cardiogenic shock or hemodynamic instability, the current guidelines, both in the United States and Europe, recommend systemic thrombolytic therapy or surgical thrombectomy (10-12). A perioperative mortality of 6% or less has been reported in cases where early embolectomy was performed before hemodynamic failure (13,14). However, surgical thrombectomy can only be carried out in a small number of large hospitals, and operations of long duration may adversely affect the prognosis of patients. In addition, most patients with pulmonary embolism have some degree of bleeding risk. In a 90-day study, patients with intermediate-to-high pulmonary embolism who received anticoagulation alone had a similar mortality rate as did those who received thrombolytic therapy (46.3% vs. 55.1%; P=0.44), and there was no reduction in pulmonary embolism recurrence in the thrombolytic group (12% vs. 12%) (15). In a retrospective study by Hamel et al., 64 patients who received thrombolytic therapy and 64 patients who received heparin had a matched right/left ventricular diastolic diameter ratio, but the thrombolytic group had a higher improvement in lung perfusion scans than did the heparin group. Moreover, the in-hospital mortality was 6.25% in the thrombolytic group and 0.0% in the heparin group. The recurrence rate of pulmonary embolism was the same in both groups (16).

The ACCP recommends PMT be used only in patients for whom thrombolysis is contraindicated (11). Although the treatment used in this study was not the first treatment recommended by the guidelines, the experience of some researchers has suggested that PMT in patients with acute high-risk pulmonary embolism can be effective. Therefore, for some experienced clinical teams, direct catheter thrombolysis has a certain risk of bleeding and more complications and PMT is considered the surgical method of choice, although systemic thrombolysis and surgical embolectomy still play an important role (17-20). Bunc et al. reported 25 patients with high-risk pulmonary embolism with concomitant thrombolysis, all of whom were treated with PMT. The technical success rate was 80%, and the discharge survival rate was 68% (21). The higher overall technical success rate in this report may be related to the more mature development of interventional techniques in recent years. In addition, the higher discharge survival rate may be related to the inclusion of medium-risk pulmonary embolism population in this study. The purpose of interventional therapy is to open embolic vessels as early as possible and improve pulmonary blood flow. A study has shown that right-sided heart failure due to a sharp increase in pulmonary artery pressure is the leading cause of death in patients with pulmonary embolism (21). In some emergencies, opening even a small section of the embolized vessel can save the patient’s life. PMT can not only restore partial blood flow in pulmonary artery in a short time, but also increase the contact area between urokinase and embolus, and then accelerate thrombolysis, thus improving the therapeutic effect (22). Our study showed a significant improvement in all indicators within 48 hours after PMT, which serves as a good indirect evidence of advantages of PMT. In a meta-analysis of CT prediction of short-term pulmonary embolism outcomes among 13,162 patients with acute pulmonary embolism across 49 studies, the right ventricle/left ventricle diameter ratio was found to be the strongest predictor of short-term mortality and adverse outcomes (stronger than thrombus burden and pulmonary embolism location, which were not significantly predictive) (23). In addition, a significant reduction in pulmonary hypertension was reported to greatly reduce right-sided heart load, and there is evidence to support a relationship between PAP reduction and remission of right ventricular dysfunction (24). In this study, the significant improvement of these two important indicators before and after surgery also supports the effectiveness of PMT in patients with acute intermediate-to-high-risk pulmonary embolism. In addition, the significant difference in hemoglobin before and after surgery is considered to be caused by the destruction of a large number of red blood cells during PMT, but this does not affect the overall prognosis of patients. However, in the future, PMT should be used more cautiously for some patients with pulmonary embolism and severe anemia before surgery. However, in this study, the catheter thrombolysis group and AngioJet group were not further divided for subgroup analysis, mainly due to the small sample size.

There are also complications associated with interventional surgery. In our study, there were no such serious bleeding or serious catheter-related related complications such as cardiac rupture; however, there were seven cases of local hematoma in the puncture point and three cases of local infection. After simple treatment, these complications were completely resolved. One patient had sepsis that was considered to be related to ECOM support during hospitalization. Moreover, arrhythmia caused by intraoperative procedures should be a future point of concern. Several authors have reported arrhythmias associated with the use of the AngioJet system (24), while other authors have attributed to this to hyperkalemia associated with hemolysis, adenosine, or arterial spasm caused by nitric oxide trapped in the pulmonary circulation (25,26). In our study, seven of the nine patients with intraoperative arrhythmia were in the AngioJet group. We speculate that the AngioJet aspiration catheter greatly stimulated pulmonary blood during thrombus aspiration and then triggered a vagal reflex, leading to transient cardiac arrest, and this process may be related to the working principle of aspiration catheter itself. Although a patient can recover heartbeat autonomously after suspension of the operation, the risk of such complications is high, and should thus be a concern for surgeons.

During the follow-up, we found that the symptoms of five patients did not improve significantly. One of these patients experienced pulmonary embolism secondary to superficial vein sclerosis injection in another hospital. Another patient had a cement embolism. Although the pulmonary blood flow was partially opened at that time, there was a difference between such embolic foreign bodies and common thrombus emboli, which could not be dissolved by urokinase or the antifibrinolytic system, which ultimately caused persistent postoperative symptoms. We believe that elective open thrombectomy may be the best treatment for these patients after early vital signs are stabilized. The symptoms of the remaining patients and the 12-month echocardiography indicated that the midterm outcome of patients after PMT was also satisfactory.

This study had several limitations. First, we employed a single-center, retrospective design with a small sample size. Second, most of these patients were emergency surgery patients, and most of the preoperative and postoperative cardiac ultrasound examinations within 48 hours were performed with a bedside simple B-ultrasound device; thus, some indicators may be biased; moreover, a portion of the patient data were missing.

Conclusions

PMT can be used as a safe and effective treatment option for acute medium- or high-risk pulmonary embolism.

Acknowledgments

Funding: None.

Footnote

Reporting Checklist: The authors have completed the STROBE reporting checklist. Available at https://jtd.amegroups.com/article/view/10.21037/jtd-24-1690/rc

Data Sharing Statement: Available at https://jtd.amegroups.com/article/view/10.21037/jtd-24-1690/dss

Peer Review File: Available at https://jtd.amegroups.com/article/view/10.21037/jtd-24-1690/prf

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://jtd.amegroups.com/article/view/10.21037/jtd-24-1690/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki (as revised in 2013). The study was approved by the ethics committee of Taizhou Hospital of Zhejiang Province (No. 2022-11-22-01). Informed consent was taken from all the patients.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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