In a recent study, factors related with venous thromboembolism (VTE) severity—including pulmonary embolism response team (PERT) referral from the intensive care unit (ICU) and right ventricular dysfunction—and elevated bleeding risk were associated with inferior vena cava (IVC) filter placement among PERT patients.
Elizabeth Weng Yan Lun (Massachusetts General Hospital, Boston, USA) and colleagues write in the Journal of Vascular Surgery: Venous and Lymphatic Disorders that, while the use of IVC filters is “controversial,” the procedure is “widely performed for secondary prophylaxis patients with severe pulmonary embolism, including those treated by a pulmonary embolism response team”. In the present study, the investigators analysed patient factors associated with the clinical decision to place an IVC filter in PERT patients.
The investigators collected data on all Massachusetts General Hospital patients who had a PERT activation from 1 October 2012 to 29 January 2019. They gathered information regarding demographics, medical history, pulmonary embolism (PE) characteristics, and treatment at the time of PERT activation, and prospectively for one year thereafter. They performed univariate and multivariable regression analyses to determine factors associated with IVC filter placement.
In this single-centre retrospective review of prospectively collected data, Lun et al identified 834 patients, of whom 91 (10.9%) had an IVC filter placed in the first seven days after PERT activation. They state that the majority of patients receiving an IVC filter were male (55/91 [60.4%], p=0.096) with a mean age of 65±15 years.
The authors detail that patients who received an IVC filter were less likely to have had a PERT referral from the emergency department (41/544 [7.5%], p<0.001) and more likely to have been referred from the ICU (24/107 [22.43%, p=0.001) compared to a floor referral.
Lun et al add that patients who presented with syncope (15/86 [17.4%], p=0.04), a history of recent trauma (12/41 [29.3%], p<0.001), intracranial haemorrhage (11/39 [28.2%], p=0.002), a recent surgery or invasive procedure (30/188 [16%], p=0.012), recent surgery (29/160 [18.1%], p=0.001), and recent hospitalisation (38/250 [15.2%], p=0.009) were more likely to have an IVC filter placed.
Furthermore, they communicate that patients receiving an IVC filter were also more likely to have evidence of right heart dysfunction on computed tomography pulmonary angiogram (CTPA) (61/359 [17%], p<0.001) and echocardiogram (26/144 [18.1%], p=0.003).
Finally, they note that, compared to patients without an IVC filter, the 30-day VTE recurrence rate was higher (4.7% vs. 11%) in patients with IVC filters (10/45 [22.2%], p=0.023).
Lun and colleagues acknowledge several limitations to the study, including its single-centre nature and their restricted data pool, comprising only PERT patients in Massachusetts General Hospital.
They also recognise that, where IVC filter patients suffered higher rates of recurrent bleeding and VTE recurrence within the first 30 days’ post PERT, “this may have been influenced by confounding by indication” and therefore “should be interpreted with caution”.
The authors detail that confounding factors included that patients who received an IVC filter were more likely to be from higher risk groups predisposed to recurrent bleeding and VTE regardless of IVC filter placement.
Finally, Lun et al note that it was “impossible to eliminate all confounding, which would have influenced outcomes results”. They recommend a future randomised controlled clinical trial to standardise pre-PERT referral patient factors and eliminate confounding for accurate outcomes results. However, they stress that the aim of their study was to clarify the clinical reasoning behind a PERT’s decision to place an IVC filter, “which will provide the foundation to guide future studies”.