Pulmonary embolisms occur when a blood clot that has formed in a vein in the leg breaks free, travels through the heart and lodges in a lung artery. There are minor embolisms that don’t alter heart function, and more serious “sub-massive” embolisms that can harm the heart, but don’t affect blood pressure.
But in about 5 percent of cases, patients have very low blood pressure. These “massive” pulmonary embolisms are fatal 30 to 50 percent of the time.
A team of vascular surgeons and critical care specialists at The University of New Mexico Hospital has shown that prompt intervention with a portable heart-lung machine known as veno-arterial extracorporeal membrane oxygenation (ECMO) dramatically improves outcomes for these patients.
A new paper published in the Journal of Vascular Surgery reports that 13 out of 17 patients with massive pulmonary embolisms survived when they were placed on ECMO soon after arriving at the hospital.
“We did the first few and people did very well,” says lead author Sundeep Guliani, MD, a vascular surgeon and intensivist. The protocol was then refined to ensure that patients were started on ECMO more quickly.
“It was figuring out how to do things more rapidly,” he says. “They may arrive in the ER in a near-death state. You don’t have four hours to figure out what’s going on.”
Clots in the legs may occur when someone sits in a car or on a plane for long hours at a time, Guliani says. People who have suffered a trauma or undergone surgery are also more likely to experience clotting, he adds.
When a clot travels to the lung and triggers an embolism, it “becomes like a clogged toilet for the heart,” Guliani says. “The heart can’t pump effectively, so the heart begins to fail. The clot obstructs the heart pumping blood through the lungs and to the rest of the body.”
A failing heart might pump at only 20 percent of its normal capacity, he says. The ECMO machine draws blood from a vein in the leg, adds oxygen and returns it to the body through a leg artery, temporarily taking over for the heart and lung.
“After a couple days on the heart-lung machine and blood thinners we assess how the heart is doing,” Guliani says. Blood thinners often can dissolve a clot, restoring normal circulation, but if they don’t do the trick, vascular surgeons can perform additional procedures to clear the artery.
Prior to the new protocol, ECMO was usually only employed as a last resort, when other medical treatments had failed, but mortality rates remained high. “It was 80 percent mortality in the hospital,” Guliani says, “and that was even with people having these pulmonary embolisms while they were in the hospital.”
Now, with an “ECMO-first” approach, the team is saving close to 80 percent of people who suffer a pulmonary embolism at home.
“It has made a tremendous difference,” Guliani says. “If I was anywhere in the state I would want them to transfer me to UNM for management of pulmonary embolism.”