NEW YORK (Reuters Health) – Inferior vena cava filters were associated with significantly lower all-cause mortality in unstable adults with pulmonary embolism (PE), whether patients received thrombolytic therapy or not, researchers say.
The benefit was most marked in those over 80 years of age, they found.
The results, from a review of the Nationwide Inpatient Sample (NIS) by investigators from the Michigan State University College of Osteopathic Medicine, were reported online in the American Journal of Medicine.
Lead author Dr. Paul D. Stein told Reuters Health he thinks “all unstable patients with pulmonary embolism should receive a filter.”
His group looked at data from 1999 to 2008, on unstable adults age 21 and over with PE. Criteria for “unstable” were ICD-9-CM codes for shock or mechanical ventilation.
Patients were stratified by age in 10-year increments and whether they received thrombolytic therapy or not.
Of the more than two million patients with PE in the NIS database, 71,305 (3.4%) were unstable – and of that group, “only 19,480 (27%) received a vena cava filter,” said Dr. Stein.
Thrombolytic therapy was administered to 21,095 patients. The all-cause fatality rate for every age group was significantly lower for patients who received a vena cava filter, with p values ranging from 0.0012 to <0.0001 for all age groups.
For the 50,210 patients who did not receive thrombolytic therapy, the all-cause fatality rate was also significantly lower when vena cava filters were placed (p<0.0001 for all age groups).
Patients aged 81 or older had the largest risk reduction with the filters, whether they received thrombolytics (absolute risk reduction, 19.3%) or not (27.7%).
Of the more than 70% of patients who did not receive thrombolytic therapy, Dr. Stein said, “I assume that the attending physicians thought that the risk of bleeding was too high.”
Earlier this year, his group reported that unstable patients had lower case fatality rates with thrombolytic therapy regardless of age or associated comorbidities. (The abstract for that paper appears here: http://bit.ly/1bLfXzN.)
But in email to Reuters Health, Dr. Philippe Girard of the Département Thoracique at the Institut Mutualiste Montsouris in Paris, France pointed out that “a statistical link certainly does not prove a causal relationship outside of a randomized trial.”
He thinks the likeliest explanation for the difference in this study is that patients who survived the first hours or days after the acute event could receive a filter, those who died early, whatever the cause, could not.
“For this to be true, 42% of all deaths in unstable patients who did not receive a filter would have had to be in the first hours before filter could be inserted,” said Dr. Stein. “This seems unlikely, but I am not sure how quickly unstable patients succumb.”
The authors acknowledged that the study was limited by possible selection bias of the NIS, possible coding imperfections, and the inability to adjust for confounding variables.
Some of those variables, Dr. Girard said, are co-morbidities, date of filter insertion, date of death, and cause of death.
Dr. Girard also cited the randomized PREPIC 2 study, which involves 399 patients at high-risk for recurrent PE. Data from that study, presented at a meeting this past July, “failed to show any protective effect of filters at 3 months,” he said. (The abstract appears here: http://bit.ly/1c7F0j4.)
According to Dr. Stein, “This is compatible with our observation of no lower case fatality rates in stable patients with PE.” In a 2013 paper in Thrombosis and Haemostatis, his group reported a lower case fatality rate in stable elderly patients with COPD who received thrombolytic therapy and a filter (http://bit.ly/1c7F2Yl). “It does not seem that there were enough patients to examine such subcategories in PREPIC 2,” he said.
Dr. Girard says the new study should be interpreted with caution. “I fear that Dr Stein’s paper will further increase a filter insertion rate that is already incredibly high in the US–about 15% of all patients with venous thromboembolism, vs. about 2% in a mainly European prospective registry,” he said. “Such an increase, if it occurs, will be based on extremely fragile–I would even say: unsound–evidence, and without any mention of consequences in terms of costs and potential harms.”
But the authors, based on their findings, think vena cava filters are under-utilized in unstable patients. They conclude: “In-hospital all-cause case fatality rate in unstable adults with acute pulmonary embolism was lower in those who received a vena cava filter, irrespective of age.”
Am J Med 2013.