With blood clots, filters may fail to save lives

For patients suffering a pulmonary embolism, filters used to block clots from passing from the legs to arteries in the lungs do not improve mortality rates in most cases. A series of three research articles on pulmonary embolism published in the American Journal of Medicine are based on a study of more than two million patients suffering from the sometimes deadly clots that travel to the lungs and block arteries. A second article finds that vena cava filters do save lives when a patient is unstable, is in shock, or in need of a ventilator. A third paper stresses it is crucial that unstable patients with a pulmonary embolism, receive clot-dissolving medications known as thrombolytic therapy. The studies provide clearer guidance on what treatments are most effective for patients, specifically in regard to vena cava filters and thrombolytic therapy, says Paul Stein, professor of osteopathic medical specialties at Michigan State University. “There has been an increase in the use of vena cava filters in the past several years for patients who arrive at a hospital suffering from a pulmonary embolism. But it appears the vast majority of filters that are placed in patients with pulmonary embolism may not reduce mortality.” For the small proportion of patients who arrive at a hospital in an unstable condition the data suggest mortality can be greatly reduced with a filter. “These studies provide strong evidence on when filters reduce mortality and when they will not,” he says. “Only a small percentage of patients suffering from a pulmonary embolism are in shock or in need of ventilation support, and therefore only a small proportion need a filter.” For unstable patients it is vital that in addition to using a filter, they receive thrombolytic therapy, which is much less of a risk than the surgical removal of a clot known as an embolectomy. “Only about a third of unstable patients receive thrombolytic therapy,” he says. “The reason may be doctors are afraid that patients will suffer from excessive bleeding. But the data show thrombolytic therapy would save lives if used more frequently.” As for an embolectormy, Stein’s team found that in most surgical centers, unless the clinicians are highly specialized and experienced, the mortality rate is high. In most hands, he says, thrombolytic therapy would save more lives. The findings were from a nationwide government database, the Nationwide Inpatient Sample, and included data on more than two million patients who suffered a pulmonary embolism between 1999 and 2008.