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Catching a Killer

Report: initial. Enemy involvement: none. Name: Bloom, David. Military unit: civilian. Status: deceased.

As a gritty journalist reporting the front-line action of the 3rd Infantry Division during the war with Iraq, the sudden death of 39-year old reporter and news anchor David Bloom was an unexpected tragedy that left many asking, "Why?"

During the last few weeks of his life, Bloom had been traveling in an armored military-recovery vehicle through the Iraqi desert. His broadcasts took viewers on a virtual-reality ride with the troops, complete with sand storms, whizzing bullets and false alarms. On April 6, just 25 miles south of Baghdad, Bloom collapsed. He was airlifted to a nearby field medical unit where he was pronounced dead. Bloom's coworkers at NBC and colleagues from competing networks all relayed the news with respect for the loss of a fellow journalist and sadness for the loss of a friend.

The cause: pulmonary embolism.

Lying in Wait

A pulmonary embolism originates, usually in the lower extremities, as a deep vein thrombosis (DVT) - a blood clot that is formed in the deep vein system. Sometimes, if the body cannot efficiently break up the clot, it dislodges and travels through the venous system to the heart where it is pumped into the lungs where it can be fatal. "When you have a DVT, a vein gets blocked with a blood clot. Why does the blood clot form, especially in a young, healthy guy like David Bloom?" asks Craig Greben, MD, chief of vascular and interventional radiology at North Shore University Hospital, Manhasset, N.Y. "Basically, there has to be a 'perfect storm' in which three things happen: There has to be some slow blood flow; there has to be some type of injury to the blood vessel; and there has to be some kind of hypercoagulability, meaning the patient clots too well."

Tragically, it may have been the on-the-move reporting style he loved so much that caused Bloom's death. Battlefield conditions frequently include cramped conditions and immobility for extensive periods of time. Anthony Venbrux, MD, director of interventional radiology at the Cardiovascular Center at the George Washington University Hospital, Washington, D.C., says that's the perfect environment in which to develop a DVT. "Patients who have been immobile, for whatever reason, are at the greatest risk to develop this thromboembolitic disease," he says. "Because they're not moving around, blood tends to be more sluggish and spontaneously clots. So long car rides and transcontinental flights also pose a risk."

Reportedly, Bloom slept many nights with his knees curled to his chest. And in the hot desert sun, the journalist may have been experiencing some level of dehydration - another contributing factor. Several days before his death, Bloom complained of cramps behind his knee. Military physicians suspected DVT and advised him to seek medical attention, but Bloom brushed off his symptom as just a cramp and no need for concern. Although symptoms of DVT often never surface, understanding the risk factors can help aid in early detection.

Along with prolonged immobilization (from trauma, surgery and long plane and car rides) recent pregnancy, oral contraception and disorders of the coagulation system also pose a threat of developing DVT. But perhaps radiologic technologists (RTs) should be especially aware of potential DVT cases, since cancer is one of the biggest risks. DVT and pulmonary embolism are two disorders with which many are not familiar. In order to protect patients who may fail to recognize the symptoms of DVT, radiology professionals should be educated to help improve detection rates, due especially to the fact that symptoms are not reliable.

Oftentimes, those suffering from malignancies present with hypercoagulability. Some experts believe proteins emanating from the tumor increase the blood's ability to clot. Regardless of the reason, Venbrux says, "Many cancer patients, particularly oncology patients, are very prone to getting DVT."

Barry Katzen, MD, FACR, FACC, founder and director at the Miami Cardiac and Vascular Institute, Fla., says immediacy is key. "The main thing radiology professionals should know is that cancer patients are at a greater risk, and if symptoms develop, the cause must be diagnosed as quickly as possible," he says. Symptoms, when they occur, include a painful, swollen leg, typically only one leg, which is often tender and warm to the touch. If conditions progress, pulmonary embolism can show symptoms of sudden apprehension, shortness of breath and chest pains, rapid pulse, sweating, cough with bloody sputum or fainting.

Not only can RTs be alert to the possibility of their patients developing a DVT, they may be called on to help diagnose one if there is suspicion from physicians. And interventional radiologists need to stay abreast of the current treatments in order to provide the best options to their patients. "If we suspect a DVT, we use the least invasive test possible," says Venbrux. "The best one for screening in the legs is a duplex ultrasound study. By using a color-flow Doppler ultrasound, blood flow can be assessed in the deep veins. Ultrasound is wonderful for this type of study because it has very high sensitivity and specificity for picking up clot."

If a physician has a strong clinical suspicion, Greben says they might order a blood test. "If the results of the blood test and the ultrasound are equivocal, and there's a high suspicion, the 'gold standard' - a venography, or angiogram - is ordered," he says. This procedure requires a physician to insert a needle into the vein of the affected extremity and contrast is injected through the needle to examine the veins' filling. "If we see the filling defect or the vein doesn't fill, we call it venous thrombosis," says Greben.

And other imaging studies are also useful. Magnetic resonance angiography is a good non-invasive study for creating detailed images of the blood vessels while a computed tomography scan provides a 3-D view of body structures.

Most interventional radiologists agree the first step in therapy should usually be anticoagulants. But Venbrux says anticoagulation drugs are not a treatment. "Blood thinners do not dissolve the clot, rather they prevent propagation of more clots and allow the body to try to break down the clot itself."

Sometimes, clot-busting enzymes, known as thrombolytic agents, may also be administered to help the body fight the clot. "An interventional radiologist may choose to do catheter-directed thrombolysis," says Greben. The procedure requires a catheter to be directly embedded into the clot in the vein. "Then we drip in a very powerful clot-busting medicine in an attempt to dissolve the clot and resume blood flow," he says.

Although drug therapy is a great tool, Katzen says some patients are not good candidates for lytic therapy. If contraindications are present, such as bleeding problems, recent surgery, old age, fall risks and anticoagulation disorders like hemophilia, these drugs should be avoided.

If patients can't get these drugs safely, a vena cava filter is used to protect the body from a pulmonary embolism - something that could potentially be life-threatening. The permanent metallic device is put into the vein to protect the lungs from blood clots migrating from the leg. "It is like an umbrella," Greben says. "It will trap any large clots while allowing normal blood to go through. DVT is not a problem in and of itself - it is the risk of the clot breaking off and traveling around the body where it can be lethal that is worthy of concern."

Greben says another option, particularly effective in treating a multi-trauma patient or someone going in for surgery, is retrievable filters. Ordinarily, the filter is put into place and left there permanently. "That's not usually a problem," says Greben, "except for the fact that when you have a foreign body in the vein, there is a risk that you will thrombose or occlude the vena cava from this device." So he feels retrievable filters are very appealing. However, many people are not candidates for temporary devices. "These filters must typically be removed in 14 days, and for a lot people, that's not enough time. But for some, it's a great bridging device to help prevent the fatal outcome of pulmonary embolus in very critical times."

And perhaps the most recent development in the treatment of DVT comes from a new evolution - the Resolution¨ System from OmniSonics Medical Technologies Inc., Wilmington, Mass. The product (which is not yet commercially available in the United States) consists of a thin, titanium wire that is placed into a clogged artery or vein to deliver low power acoustic energy 360 degrees around the active wire to accelerate the dissolution of clot. It reduces both fresh and organized thrombus to micro-fragments while avoiding healthy tissue. Katzen has been exploring the possibilities of the new technology and says the greatest advantage is speed. "By putting a wire in the occlusion, we have the opportunity to do clot-busting very quickly, and that's the key difference," he says.

If a DVT cannot be completely resolved, the patient will likely endure long-term problems, including recurrent blood clots, leg swelling and pain, which keeps the patient at risk for a pulmonary embolism.

"DVT patients should be managed much more aggressively than they currently are," says Katzen. "There are two issues we are concerned about from a medical point of view: one is early diagnosis and two is aggressive therapy. The incidence of delayed complications will end in much higher incidence with serious secondary problems."

"The thing that tends to kill patients is clots generally above the knee, in the pelvis and in the inferior vena cava because they tend to be large chunks in those locations and a break-off can be devastating," says Venbrux. "If an RT sees a large clot, they should report it immediately to the attending physician. And interventional radiologists need to be more aggressive in getting rid of the clot - especially in young patients."