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Pulmonary Embolisms May Recur in Patients with Sleep Apnea

Venous thromboembolism (VTE) often comes with the risk of pulmonary embolism (PE), which can be fatal.  Blood clots are common in people who live sedentary lifestyles, are obese, and/or are advanced in age; however, recent research indicates that obstructive sleep apnea (OSA) may also be contributing to blood clots that lead to PE.  VTE is a chronic disease marked by recurring episodes of PE, but scientists wanted to review the OSA risk of developing PE.  Findings show that after initial PE, patients with OSA are at increased risk of developing another.

This study is published in the December issue of CHEST.

Recurrent PE comes with a 9% chance of mortality, and patients who have had one PE are 30% more likely to have another.  Generally, anticoagulant medications can help prevent the recurrence of PE, but they also come with a higher risk of bleeding.  The need for blood thinners can be reduced by properly identifying risk factors and making changes as a preventative measure.  One of the biggest risk factors is sleep apnea, which shares many other risk factors with PE like obesity, decreased physical activity, and advancing age.

Lead investigator, Alberto Alonso-Fernandez, MD, PhD, from Hospital Universitario Son Espases in Spain notes that the evidence in longitudinal and cross-sectional studies shows that there is a link between PE and OSA.  The link indicates there is a major health burden, especially since both disorders are prevalent and there is a high fatality rate for PE.  To their knowledge, there are no studies to investigate how OSA contributes to recurrent thromboembolisms.

The current research trailed 120 people for five to eight years post PE initial occurrence.  Scientists monitored sleep to determine if there were any signs or symptoms of OSA.  It was noted that 19 patients had recurrent episodes of PE, and 16 of those 19 patients had OSA.

The primary finding is that patients who had an initial PE and an OSA diagnosis were at increased risk of experiencing a recurrent PE than those who did not have OSA.  Furthermore, even without an OSA diagnosis, patients whose oxygen saturations consistently stayed below 90% were also at risk for PE recurrence.  Many of these patients were started on anticoagulation due to new blood clot formation.

Dr. Alonso-Fernandez is working to determine how OSA contributes the susceptibility of a repeat PE event.  He believes OSA may affect the three components of Vichow’s risk triad: vascular endothelial impairment, blood flow stasis, and/or higher ability to coagulate.  There is an increased inflammatory response and oxidative stress when hypoxia is present, both of which impair endothelial function.  OSA may slow intravenous flow with sedentary position and hemodynamic alternations.  Finally, it is possible that OSA patients have increased coagulability, decreased fibrinolytic capacity, and better platelet activity, which are often improved with the use of CPAP.

A lot of research has been dedicated to determining the origin of PE, there are only a few known factors identified in recurrent PE, including things like continued use of estrogen, vena cava filters, high D-dimer after anticoagulation, cancer, obesity, and male gender.  OSA is now labeled as an independent risk factor for experiencing another PE, even after researchers adjusted for factors like BMI and gender.  OSA is more prevalent in obese men, so researchers believe that the higher risk of recurrent PE in obese patients is likely related to OSA as well.

It is notable that obesity is directly linked to a sedentary lifestyle, as well as venous stasis; however, there is also research connecting obesity to higher concentrations of clotting factors, putting an individual in a prothrombotic state and increasing his or her risk of clots because of the increased estrogen and inflammation that are associated with obesity.

These findings will help physicians determine better treatment interventions for those who have had PE and a history of OSA.  CPAP is the usual treatment for OSA, and these patients may also need longer-term anticoagulation to reduce PE risk.  Given the prevalence of OSA in patients with thromboembolic events, further study circling around procoagulability states caused by hypoxia and treated with CPAP would be greatly beneficial for further interventions.

Reference:  https://www.eurekalert.org/pub_releases/2016-12/ehs-sac120716.php

Rachael Herman is a professional writer with an extensive background in medical writing, research, and language development. Her hobbies include hiking in the Rockies, cooking, and reading.

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